At the March club meeting, Marcel and Clynt and Blair and I were discussing how long the fuel system should maintain pressure when the engine is turned off. The discussion originally started last month when Clynt and I were chatting about checking for leaking fuel injectors.

Anyway, there was something that was mentioned last month that I asked about at Pennock's. I thought it might be informative for anyone wondering about this stuff. The question I asked and the subsequent response can be found http://www.fiero.nl/forum/Forum2/HTML/098712.html#p8 - Here .

Comments, questions? Agree, disagree?

[EDIT] Well, this is interesting. After re-reading JazzMan's response to my question, I realize he must've misunderstood what I was asking about and I misunderstood his response.

I'm now more confused than ever, and I'm sure I've confused everyone else as well in the process.

It shouldn't be that confusing....

When the pump turns off  (However that relates to the engine stopping) the regulator should trap pressure in the fuel rail. The injectors won't be firing, and the cold start injector better not be on. Therfore, ideally, the pressure will be maintained.

For example, for my Jimmy with a similar setup this is what they say:

Note the fuel pressure with the pump RUNNING, it should be 41-47 psi (284-325 kPa). When the pump stops pressure may vary slightly, then should hold steady. If not, refer to the accompanying fuel system diagnosis charts.

I'll check this out soon, because I want to hook up a gauge to check my fuel pressure and then I can get some numbers for you.

Chay

Chay, I bought a fuel pressure gauge this week. Hopefully in the next few days I can try it out and then we can compare readings. Thanks.

I thought I'd better take advantage of the fact that it wasn't raining today, so...

Fuel pressure with key on/engine not running is 41 psi.

With the engine running at idle it's 33 psi.

With the system primed to 41 psi and key off/engine not running, the pressure slowly drops to 30 psi within 30 minutes.

Is this an indication of something (injectors, regulator, etc) leaking which needs attention, or is this within tolerances?

It is leaking (It has to be), but where?

I don't think it's an injector stuck open. It think it would go down much quicker than that. Keep in mind the volume is only the fuel rail after the key is off, and that 'ideally' a fluid cannot be compressed, so it doesn't take much leakage to reduce the pressure substantially (Not like air, for example).

I think it's more likely that the regulator is leaking a pinch back tot he tank. Either way, I'd view this result as a pass.

I still haven't found my gauge which is pissing me off now. As soon as I find it I'll let you know how mine acts.

Anybody out there have a permanently installed gauge which could yeild some insight?

Chay

Thanks Chay. Not that I know much about EFI, but I suspected the fuel pressure leakdown test results were probably acceptable. Nice to get some confirmation though.

Well, I still need to figure out why I'm only getting 14 mpg. The GT actually runs great, but this gas mileage sucks (literally).

The next thing I'll try is to replace the EGR tube and put back the stock ECM chip. I've had a custom "EGR delete" chip installed since last summer when I discovered the EGR tube was cracked and I blocked it off.

I also need to fix the "tick, tick, tick..." front exhaust manifold leak as I hear this can fool the O2 sensor and create a rich condition. I'm NOT looking forward to THAT job! (as I know at least one bolt was broken off in the head by the PO)

Maybe so, but it's a helluva lot easier to put the EGR system back together and swap back the stock chip than doing the other task.

Just adding a bit, I didn't totally read the entire thread as I only have a few mins.

        However a stuck injector is not the only thing that will cause fuel pressure to drop.   I have 6 BRAND NEW GM INJECTORS in my motor, I got them in a trade, and the person had paid $2400 for the injectors.  

When I shut the key off, my fuel pressure drops to Zero in less than 2 seconds.    The fuel pressure regulators can leak, rather badly.  At speed with the engine running, the fuel pump can compensate for the fuel leaked past the internal valve, however when shut off the pressure bleeds to zero in less than a few seconds.  (Remember this is fluid pressure vs air pressure and fluid pressure requires much less to bring it from 40psi to 0psi.)  Ah hell that entire last statement did not come out right, but hopefully you get what I was trying to say.   One of these days I am going to pop the regulator off and replace it.  However for the time being it still holds pressure at or above 40psi, with the vacuum removed from the MAP, the TPS held Wide open, and the idle slightly over 1500.  (Car See's no vacuum at MAP, Wide Open on TPS, it thinks you are gunning and runs the injectors at Max Programed Duty Cycle) 

Capt Fiero wrote: However for the time being it still holds pressure at or above 40psi, with the vacuum removed from the MAP, the TPS held Wide open, and the idle slightly over 1500.

Is this how you're currently driving the car?  And your gas mileage isn't terrible?

Patrick wrote: Capt Fiero wrote: However for the time being it still holds pressure at or above 40psi, with the vacuum removed from the MAP, the TPS held Wide open, and the idle slightly over 1500.  Is this how you're currently driving the car?  And your gas mileage isn't terrible?

If you mean with the pressure at 40-50psi then yes.  If you are asking do I leave the MAP unhooked and the TPS wired open.  No not a chance, most engines would drop dead and not run for more than a few seconds like that.    I only unhook the MAP and Hold the TPS to trick the car into maxing out the injectors, so I can see if the fuel pressure remains stable when the injectors are allowed to run as fast as the ECM will let them go simulating a WOT run.    Once I verify the fuel pressure stays up, I hook the map back up, release the TPS and let the idle come back down.    

      As for fuel mileage, the car did great on its first fill up in BC all the way down to Olympia, and did pretty good until I had done 2 or 3 full tanks of Oregon fuel through it.      I normally get 25-28mpg out of it if I drive it sane, and even on the Arlington Run where I had the trailer fully loaded, driving it like a MAD MAN, I think I got 24mpg out of the car.     

Capt Fiero wrote: If you are asking do I leave the MAP unhooked and the TPS wired open.  No not a chance...

Yeah, that's what I was wondering. Didn't think it would run very well set up in that manner.

Capt Fiero wrote: However for the time being it still holds pressure at or above 40psi, with the vacuum removed from the MAP, the TPS held Wide open, and the idle slightly over 1500.

Dr.Fiero wrote: Its your gas bill. Do whatever ya like.

Thanks, I plan to.

Look John, it’s all about eliminating variables. Something is totally messing with the gas mileage on the car.

This GT already had the exhaust manifold leak when I bought it last spring. The leak isn't that bad (the "tick, tick, tick..." actually almost disappears when the engine is hot) and it's gotten no worse in the time I've had the car.

I didn’t drive it much before I blocked off the cracked EGR tube and installed one of your "EGR delete" chips, but I recall I had gotten 230 to 250 KM per tankful at least once prior to the chip change. Ever since then I’ve been sucking fumes to get 200 KM per tankful if I’m lucky (and that includes situations where most of the driving was cruising on the highway).

Is it the EGR delete chip which is to blame for the crappy mileage? I don’t know.

Is it the front manifold exhaust leak which is to blame for the crappy mileage? I don’t know.

Or is it something else completely different which is to blame for the crappy mileage? I don’t know.

However, I most certainly DO know it’s a helluva lot easier to put a replacement EGR tube and stock chip back in the GT than drilling out broken manifold bolts in the head to fix the exhaust leak on the front bank.

If I do this and nothing changes, fine. You’d be right, and it wouldn’t take much for me to put it back the way it was if need be.

However, if I do this and all of a sudden the mileage improves, well...

I think one of the ways to check out what you have is to hook up Winaldl and check your BLMs. If the 02 is crapped out or the leak is causing a fake lean condition, your BLM will be way high, as the ecm is trying to compensate for a 'lean' condition.

Pull and check a few spark plugs...are they black? Check the exhaust pipe...is it black? These indicate a consistent rich condition.

If the plugs are tan coloured I suspect the problem is a heavy right foot! Ok, you probably wouldn't go to this trouble if you didn't think of that already....I know that's my problem though.

I like to do the easiest stuff first too, but there is a quote from a guy online signature which I'm lending more and more weight to,"Why is there never time to do it right the first time, but always time to do it again?"

Sometimes doing the hard thing is the right thing.

Chay

CFoss wrote: I think one of the ways to check out what you have is to hook up Winaldl and check your BLMs. If the 02 is crapped out or the leak is causing a fake lean condition, your BLM will be way high, as the ecm is trying to compensate for a 'lean' condition.

Chay, in http://www.westcoastfieros.com/forum/forum_posts.asp?TID=956&PN=1&TPN=2 - This thread  you commented on the "black magic" of interpreting WinALDL readings.  I still have that WinALDL file http://rapidshare.com/files/215476298/20081115_230029_LOG.txt.html - Here  that you had looked at back in November. Yes, I should do another test, but nothing has changed in regards to my gas mileage since that WinALDL reading was taken four months ago (although the stock 195 degree thermostat was reinstalled shortly after those readings were taken).

CFoss wrote: Pull and check a few spark plugs...are they black? Check the exhaust pipe...is it black? These indicate a consistent rich condition. If the plugs are tan coloured I suspect the problem is a heavy right foot! Ok, you probably wouldn't go to this trouble if you didn't think of that already....I know that's my problem though.

The tail pipes are definitely black and sooty. Last weekend I pulled the #5 spark plug (yes, I will pull them all to have a better look), and the ceramic tip was absolutely white. I was surprised.

The weight of my right foot is not an issue here as driving "like an old lady" has resulted in the 14-15 mpg readings.

CFoss wrote: "Why is there never time to do it right the first time, but always time to do it again?"

Well, that statement only rings true if doing a repair the first time never results in resolution. My record is better than that. I'm sure yours is as well.

CFoss wrote: Sometimes doing the hard thing is the right thing.

And sometimes it's the simple things we overlook which are actually causing the problem.

Yes, I plan on doing the "hard thing" (fixing the exhaust leak) eventually (as I don't like the sound of the "tick" when the engine is cold), but as I reported previously, my gas mileage was up to 25% higher when I first got the GT last spring. At that time it already had the exhaust leak but the EGR had not yet been "deleted". Therefore, I'm not convinced at this point that the exhaust leak is responsible for the bulk of the problem. I'm not saying it's necessarily the "deleted" EGR which is responsible either, but it's a whole lot easier checking that first than pulling the head(s) off to drill out the broken exhaust manifold bolts.

This will all get sorted out eventually.

Patrick wrote: Chay, in http://www.westcoastfieros.com/forum/forum_posts.asp?TID=956&PN=1&TPN=2 - This thread  you commented on the "black magic" of interpreting WinALDL readings.  I still have that WinALDL file http://rapidshare.com/files/215476298/20081115_230029_LOG.txt.html - Here  that you had looked at back in November. Yes, I should do another test, but nothing has changed in regards to my gas mileage since that WinALDL reading was taken four months ago (although the stock 195 degree thermostat was reinstalled shortly after those readings were taken).

Chay, I uploaded a slightly newer WinALDL file http://rapidshare.com/files/215545386/20081118_222430_LOG.txt.html - Here which was recorded after I had reinstalled the 195 degree thermostat.

Not that I understand BLM very well, but it's interesting to note that of the 810 separate measurements taken during this particular reading, 436 are at 120, whereas 33 are at 127, and 8 are at 128 (the remainder are between 121 and 126). There are NO readings over 128.

What does that indicate regarding being rich and/or lean?

Bobz0r wrote: Sounds like quite the mystery. I'm interested in hearing more about this.

It is a mystery, Rob. Stay tuned!

Patrick

Have you noticed any coolant loses????

through head gasket leakage????

Marcel

If you have a bad injector, or 2, maybe on that one cylinder, the ECM can't tell if ONE injector or 2 injectors is bad, so it just cranks the fuel up the whizoo. That is the only way I could see having a spark plug bleach white and still black tail pipes.    Bleach white plugs are simtoms of running really LEAN and heating and burning off everything in the chambers.   However jet black tail pipes is a sign of Over Rich condition.

       Not to beat my head on a wall, but when was the last time a new O2 sensor was installed.   What Brand did you install?  If its anything but Delco, I would go back and get a Delco one.   My 4.9 running NGK O2 sensors ( 2 of them) the mileage was darn near Gallons per hour.  Idling in Traffic or WIDE OPEN 200kph on the highway and it was going through the same amount of fuel per hour.  It was horrid, 29mpg on the highway, 10mpg if I was lucky in town.   The NGK ones would not switch properly in the Caddy, as soon as I put the Delco ones in, that the cars software was designed to use, everything went perfect.     The caddy motor has one sensor per bank and can set an error code on what bank of injectors has an issue.  Still not as good as single O2 per cylinder, but still decent.

marcelvdgn wrote: Have you noticed any coolant loses???? through head gasket leakage????

Marcel, are you suspecting coolant leaking into the combustion chamber and "steam cleaning" the spark plug I had a look at?

As I mentioned, I was rather surprised myself at the whiteness of the ceramic tip of the plug I had taken out. However, I've recently checked the overflow tank and the coolant level hasn't changed. The GT never overheats and steam only comes out of the tail pipes when it's first started (although lots comes out when it does).

I'm real curious now what the rest the spark plugs look like.

Eric wrote: If you have a bad injector, or 2, maybe on that one cylinder, the ECM can't tell if ONE injector or 2 injectors is bad, so it just cranks the fuel up the whizoo. That is the only way I could see having a spark plug bleach white and still black tail pipes.    Bleach white plugs are simtoms of running really LEAN and heating and burning off everything in the chambers.   However jet black tail pipes is a sign of Over Rich condition.

This is Dave, isn't it?

These spark plugs have been in since last summer. I agree, it's very strange to have such a clean spark plug when the tail pipes are black. No sign of the electrodes melting though.

Eric wrote: Not to beat my head on a wall, but when was the last time a new O2 sensor was installed.   What Brand did you install?

When all this terrible mileage started, I swapped the O2 sensor out of my Duke. When that made no difference, I put in a brand new O2 sensor. Yes, it's a Delco!  Obviously it made no difference either. WinALDL shows that it's "switching" (or whatever it's called) as it's supposed to.

As I said to Marcel, I need to have a good look at ALL the spark plugs to see if any look different. Perhaps when the latest monsoon is over I'll have a look.

         Sorry yes, I am using my dads account at the moment.  This is da Capt.  I try to pop in and read the forum before I head out for the day and again late in the evening when we get home before we hit the sack.

OK Grasping at straws here.  Chay please chime in on this one.

Black sooted up tail pipes can be normal on a Fiero due to the type of fuel injection.  Its still notable but not something to base a whole basis of an issue on.

White spark plugs should be where we look first.

There is no way to get a bleach white plug except from running lean.

Ways to run lean.  

1. Running a Fiero without an EGR Valve and having the stock chip.

2. 1/2 plugged fuel filter, at idle the fuel pressure will be fine, however at sustained higher rpms with even modest acceleration if the fuel is not getting to the fuel rail fast enough, engine will start to lean out,  then computer will attempt to increase the fuel rapidly and add a lot of fuel.  This could under the right conditions cause a Lean/Rich condition, however I don't believe that you would end up with white plugs unless it was almost torching the plugs.

#3 and #4 are going to damn near contradict each other, and would both could be true under the correct circumstances.  So read over them but don't take them as Gospel.

3. Really over advanced timing.  The ECM expects your timing to be at 10-12 degrees.  It expects a given amount of fuel to be in the tail pipe, if your timing is WAY up, it'll spark so soon, that it actually has  a great deal more, reducing the fuel left, so the O2 thinks its lean, and adds more fuel.  This would also cause hard starts due to compression and pre-ignition car would seem like it has a dead or low battery.

4. Really retarded timing, would cause too short of a burn time, and actually expel part of the flame front into the exhaust manifolds.  The computer would see all the extra unburnt O2 and Fuel in the system and try to lean it out.  Retarded timing will also cause horrible gas mileage and really low power off of idle, some automatics won't idle in gear when the timing is retarded too much.

There are a million and one things to check, if it was my car, I would also do a compression test.   One other thing to check, take a standard #2 pencil, remove the #1 spark plug, drop the pencil slowly into the hole.  If the piston won't reach, your pencil is too short.  Once you get the pencil in or other long device, turn the engine over BY HAND, NOT WITH THE STARTER.  Use a socket and ratchet.  Turn it so the pencil comes all the way up, that will have the #1 piston at TDC check your timing taps on the balancer, are they close to Zero on the timing tab?   If they are no where to be seen, rotate it 360 degrees and check the tab again, if the tabs are wrong in both positions,  you have a balancer or timing tab issue and you have probably been setting your timing wrong.  

When all the common things fail to solve the problem, you have to look at the uncommon things.   IIRC you did some changing of the balancer a year or so ago? 

Dave, I know you're bringing up info on "running lean" as a general educational guide, but I'll cover each point as it applies to my engine just to help clarify the situation I'm facing.

Eric wrote: There is no way to get a bleach white plug except from running lean. Ways to run lean.   1. Running a Fiero without an EGR Valve and having the stock chip.

My cracked EGR tube is blocked off and I have an EGR "delete" chip burned by John.

Eric wrote: 2. 1/2 plugged fuel filter, at idle the fuel pressure will be fine, however at sustained higher rpms with even modest acceleration if the fuel is not getting to the fuel rail fast enough, engine will start to lean out,  then computer will attempt to increase the fuel rapidly and add a lot of fuel.  This could under the right conditions cause a Lean/Rich condition, however I don't believe that you would end up with white plugs unless it was almost torching the plugs.

Fuel filter was replaced last summer. My fuel pressure test results are posted above in this thread. I drive VERY little at high revs around town if at all.

Eric wrote: 3. Really over advanced timing.  The ECM expects your timing to be at 10-12 degrees.  It expects a given amount of fuel to be in the tail pipe, if your timing is WAY up, it'll spark so soon, that it actually has  a great deal more, reducing the fuel left, so the O2 thinks its lean, and adds more fuel.  This would also cause hard starts due to compression and pre-ignition car would seem like it has a dead or low battery.

Ignition timing had originally been set at 12 degrees BTDC. About a month ago I increased the ignition timing and timed it "by ear" to see if it would make any difference in the gas mileage. (I'll work it out later today as my gas receipts are in the car.) The engine actually runs better with the increased timing. No rattling or pinging during hard acceleration either.

Eric wrote: 4. Really retarded timing, would cause too short of a burn time, and actually expel part of the flame front into the exhaust manifolds.  The computer would see all the extra unburnt O2 and Fuel in the system and try to lean it out.  Retarded timing will also cause horrible gas mileage and really low power off of idle, some automatics won't idle in gear when the timing is retarded too much.

I'd be VERY surprised if this engine was suffering from retarded timing.

Eric wrote: There are a million and one things to check, if it was my car, I would also do a compression test.

That's something I haven't done. I've never done a compression test on this engine.

Eric wrote: One other thing to check, take a standard #2 pencil, remove the #1 spark plug, drop the pencil slowly into the hole.  If the piston won't reach, your pencil is too short.  Once you get the pencil in or other long device, turn the engine over BY HAND, NOT WITH THE STARTER.  Use a socket and ratchet.  Turn it so the pencil comes all the way up, that will have the #1 piston at TDC check your timing taps on the balancer, are they close to Zero on the timing tab?   If they are no where to be seen, rotate it 360 degrees and check the tab again, if the tabs are wrong in both positions,  you have a balancer or timing tab issue and you have probably been setting your timing wrong.   IIRC you did some changing of the balancer a year or so ago?

Correct, I changed the harmonic balancer (as reported http://www.westcoastfieros.com/forum/forum_posts.asp?TID=874&PN=1 - Here ) when I discovered the outer ring on my original balancer had slipped due to the rubber "donut" failing. I discovered the problem by doing the procedure mentioned above to determine actual TDC. The balancer I put on was from John Carlo's old 2.8 engine which I was able to get through Blair. (Thanks guys!) I didn't do the TDC test procedure with that one on, but I could tell from where the timing marks were on it that the outer ring was still in the proper location.

I'm hoping that perhaps later today I can pull all the plugs out and have a good look if the rain holds off.

Thanks for your feedback, Dave.

I didn't pull the spark plugs today despite the fact it wasn't raining. I didn't feel like working under an open decklid for any length of time during gale force winds.

However, I did work out my gas mileage for the last couple of weeks since I set/advanced the ignition timing "by ear". I drove 272 KM and used 42 litres of gas. Works out to 15.22 MPG(US).

A little better than I was getting with factory timing, but nothing to get excited about.

I've been away for a bit, so here goes.

A blm of 120 indicates the ecm is seeing righ, and is reducing the blm number (In tis case to it's minimum of 120). This reduction reduces the duty cycle of the injectors. A high BLM indicates the ecm is seeing lean, and is increasing the duty cycle of the injectors. Just to confirm, the blm tables were cleared when the car was in closed loop (Up to temp) right? Otherwise they are useless.

Anyway, I would expect a lean or rich reading across the spectrum with a bad o2 sensor. With the ex. leak the amount of air leaking in could varry with pressure/flow/rpm.  

The white tip could be lean (overheating) or coolant leaking. The comp test is a good start, but may not catch it if it's small enough.

If it is coolant, then it's eiter head gasket or craked head. I need to know what the other plugs look like. If they are all black it's time to get serious about that cylinder. Check the injector, comp test, etc.

I don't think timing is it, but I hate to hear timing done by ear. Hopefully your ear is better than mine. I find I'm good enough to get an engine running, but not close enough for final settings.

Black tailpipes are not conclusive, but if you're rich you will definately have one.

Any white stuff around the tailpipe or steamy exhaust? I'm sure you would have said something if there was.

CFoss wrote: Just to confirm, the blm tables were cleared when the car was in closed loop (Up to temp) right? Otherwise they are useless.

Chay, I don’t know what you mean by clearing the blm tables when the car’s in closed loop.

CFoss wrote: Any white stuff around the tailpipe or steamy exhaust?

The exhaust is very steamy when the car first starts, but I’m pretty sure it’s just condensation burning off. The coolant level never drops.

CFoss wrote: I need to know what the other plugs look like. If they are all black it's time to get serious about that cylinder.

I took all the plugs out yesterday. Every plug was clean, they all looked the same. A couple of them had the tiniest bit of tan colored residue on the tips, but basically all white.

Here's two of them. #5 is the one I had taken out earlier and reported on, #6 looks basically the same (except for all the rust from being installed on the front bank!).

Dr.Fiero wrote: Too bad that's not YOUR problem though.

Unfortunately, that's the least of my problems now with the GT.

John, remember the heck of a time you had trying to remove the factory PROM from the carrier when I went to your place last summer to get the EGR delete PROM from you? Well, I guess one of the pins got cracked in the process because as I placed the factory PROM on the carrier (and before I put any pressure on it), I noticed one of the pins sort of folded over. Of course, as soon as I snapped the PROM in place the pin broke right off.

This image shows which pin broke off. X marks the spot.

Well, I had a heck of a time removing the custom PROM from the carrier as well before I tried to re-install the factory PROM. One pin broke off of it also despite being very careful. Yes, I slightly bent all pins away from the carrier so they wouldn't "grab" anymore. That damn carrier is just too tight and doesn't want to let go of any inserted PROM. 

So now I've got a dead Fiero until I track down a factory PROM for an '86 (or '87) automatic V6.

Here's all the numbers/letters on the top of my particular factory PROM:

16032500

014 B8602

Any chance you (or anyone else reading this post) might have one kicking around?

Patrick

I have an 87 2.8ltr auto ecu that might have the right chipset

But i cannot check till saturday

Marcel

marcelvdgn wrote: I have an 87 2.8ltr auto ecu that might have the right chipset But i cannot check till saturday

Thanks Marcel.  If someone else hasn't got one I can access sooner, I'd certainly be interested in the one you have. Please continue to monitor this thread to see what develops.

I would imagine with all the engine swaps that have taken place within the club, there must be a few suitable PROMs gathering dust if they weren't tossed.

Patrick wrote: So now I've got a dead Fiero until I track down a factory PROM for an '86 (or '87) automatic V6. Here's all the numbers/letters on the top of my particular factory PROM: 16032500 Delco FBA 1819 014 B8602

I was asked to talk about the blm clearing/closed loop a bit. It's actually a tip I picked up from another board on tuning.

Basically, I've been told the blm numbers can change and report when the car is not in closed loop mode. This means that the BLMs respond without the 02 sensor controlling the air fuel mixture which leads to erroneous conclusions on the part of the tuner/troubleshooter.

Before collecting BLMs, check that the closed loop flag is set on the lower square of the 'Flag Data' screen of WinALDL. Then proceed to the BLM screen and choose clear table. At this point the BLMs recorded in the tables will reflect the ecm's interpretation of the 02 signals and can be used for analysis/tuning. Most use the wide average 10 to tune with (10 Samples of the same cell, averaged).

This requires the car to be on for a while. This type of data collection/tuning is best accomplished on a long trip where a variety of rpms and loading points are seen repedatively. Alternatively, you can do shorter trips and record/coallate the results.

Chay

Sounds great, John. Thanks.

PM sent.

CFoss wrote: Basically, I've been told the blm numbers can change and report when the car is not in closed loop mode. This means that the BLMs respond without the 02 sensor controlling the air fuel mixture which leads to erroneous conclusions on the part of the tuner/troubleshooter. Before collecting BLMs, check that the closed loop flag is set on the lower square of the 'Flag Data' screen of WinALDL. Then proceed to the BLM screen and choose clear table.

Chay, thanks for the explanation. Makes good sense.

Chay, sounds like you've got more problems than I do!

I've changed the PROM in my GT back to the factory unit and the engine does appear to run differently. The first thing I noticed was that the car (an automatic) is a bit more responsive when I just barely touch the gas pedal (not that it "bogged" at all previously). I also notice the exhaust smells quite different. (I have no cat.) It's much less stinky when accelerating.

On the other hand, with the EGR connected again I now get the dreaded Code 32... EGR problem. However, I have a spare EGR solenoid to swap over which I'll be doing today.

It's too early to work out the gas mileage, but judging from the level of the gas gauge and the miles I've driven so far, I'm optimistic that there'll be a definite improvement.

Patrick wrote: On the other hand, with the EGR connected again I now get the dreaded Code 32... EGR problem. However, I have a spare EGR solenoid to swap over which I'll be doing today.

Well, swapping over the EGR solenoid did the trick. No more codes.

Just gotta put some miles on the car now to see if the MPG has changed significantly.