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Vini's Loyal Sidekick
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Discussion Starter · #1 ·
hi! I realize it's been quite awhile, but I still try to pop in briefly from time to time. I checked the forums first, but I've yet to come across my specific issue so I'll toss it out here & cross my fingers.

Last month, I'm heading to work & my car began struggling like choking. By the time I'd entered the parking lot, she was shaking really bad & then just stalled out. I couldn't get her restarted & ended up getting pushed into a handicapped space while I ran next door to my garage to get towed out.
Next day I get the bad news: fuel pump. Okay - a few days without the old girl, at least a couple of hundred bucks poorer - it's fine.
NOT.
End of week & no call. I stop by enroute to work & get worse news: ECM fried (most likely took down fuel pump - security mentioned after they pushed me into the spot that they noticed a burnt smell from the car). After a series of delays in finding a part (because discontinued 🤦‍♀️), rebuilt ECM was FedExed to the mechanics last Thursday. I get the call that they're installing it now (supposed to be plug & play - just code the ignition keys & outta there).
BUT...
Weekend comes & goes - no call. No car. Today I stop by again...& find out that the ECM is installed, it's confirmed working & calibrated to my car - but it still won't start. It's simply not communicating with the other modules onboard. Nobody knows what the 🤬 problem is, & the mechanics are infuriated. They can't even hook up a scanner to get even one clue as to why. Everyone's at a complete loss.

Is it possible that something was overlooked in the install? Maybe the module still needs programming? Did any other modules get damaged? [Body Control Module was replaced in 2018]
I've been wracking my brain trying to figure out what could possibly be the issue, but my knowledge is limited. All I know is that I'm now going on 1 1/2 months without my car & I want her back.

Any suggestions welcome; I'll try to pop back in as soon as I can. Thanks very much in advance.

1999 3.8L
 

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3,217 Posts
Your mechanic seems to have forgotten the basics. Do a fuel pressure test. Consult 99 factory service manual at the following link to see what normal key on prime fuel pressure should be.www.mediafire.com/?40mfgeoe4ctti

Low fuel pressure will stop engine from running. Does your security light come on when you turn key to on? Then go off after several seconds? This is normal. If security light stays on, or doesn't come on at all, this indicates a problem with security system.

A problem with security system will prevent fuel injectors from spraying gas into engine. A quick test for injectors spraying is to spray starting fluid into intake. If car runs for a second or 2, the problem is not in the ignition system. But you will have to find why injectors don't open.

THe pcm in these cars is rugged & reliable. It seems like Moe, Larry, & Curly, your mechanics, are part changers & not knowledgeable in basic fuel & ignition systems.

Also check the also ( assembly line diagnostic link ) and make sure it's getting battery power when key turned on. And there are no problems with the wiring & connectors.

When aldl is repaired and can send & receive data, scan for codes. There are codes that don't light the service engine soon lamp.
 

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Vini's Loyal Sidekick
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431 Posts
Discussion Starter · #3 ·
well, as far as to what i've learned over the past month, the ECM issue wasn't discovered until after the fuel pump had been replaced - when they went to run those tests to make sure it was working properly, that was when the big problem made itself known. When they tried to scan it to find out why, the scanner would not connect.

VATS i've never had problems with...yet.

When i first broke down, i got the engine to turn over once - but once i took my foot off the gas she promptly shut down again before i could throw the gear into drive.

Something that's been bugging me, & I'm going to ask them as well (been hounding them on a near daily basis lately): the night before, i was enroute home when SES came on (P0420 nagging the crap outta me - already bookmarked a thread mentioning a similar issue); then, next day when i first turned the key she stumbled before the engine kicked in (I've had 3 starters replaced, & i'm thinking the latest one was about to be chewed up as well) - could either of these problems have anything to do with why the ECM is not communicating? I know I'm grasping at some real flimsy straws here but everyone involved is getting desperate.

I'm going to ask about the fuel pressure, VATS, battery, & even fuses - can't rule out anything anymore. Thanks for the input, very much appreciated.
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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Common problem with no scanner connect is a blown fuse for the cig lighter (#11, instrument panel block). Did they check that?

The PCM has nothing to do with "coding the ignition keys". That function is in the body control module (BCM). The BCM reads and verifies the key resistance. You only need to set that up if you change the BCM.

P0420 indicates a problem with the catalytic converter. Did they check to see if the converter is totally plugged up? A plugged catalyst might have been the cause of the engine losing power and stalling in the first place, not a problem with the fuel pump. The catalyst often fails when it overheats, and melts down. That could have caused the burning smell your security people mentioned.

In the 25 years I've been helping people with the 4th Gen F-Bodies, I have never seen an instance where the PCM "took down" the fuel pump. The PCM only interfaces with the fuel pump relay,, not the fuel pump itself.
 

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Vini's Loyal Sidekick
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431 Posts
Discussion Starter · #5 ·
Hmm, cigarette lighter was working a few nights prior to breakdown (I have an iPod adapter/transmitter I use frequently), but it's possible it could have failed. I'll add that to my list.
I had had both the O2 sensor & the cat replaced last year I believe, but even afterwards I was still getting that damned code popping up nearly every other day. I upgraded last year to an Innova scanner & the report last said my cat still needs replacing.

Thanks so much - will hopefully have some news soon.
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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14,257 Posts
An engine that is running rich can damage the cat very quickly, as the excess fuel burns on the surface of the converter substrate and melts it. Have your "mechanic" measure the back pressure in the exhaust system. Very easy to do.
 

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Vini's Loyal Sidekick
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431 Posts
Discussion Starter · #7 ·
thank you for all the advice - would have jumped back on sooner but it was crazy busy at work tonight.

I did, however, get a call - the car is running!! I'm going to pick her up in the morning.
I still plan to inquire as to everything mentioned here - I want to make sure there are no further issues down the road anytime soon; may even see if I can upload work order once i'm done looking it over.

A million thanks to Sea Dog & Injuneer for the valuable input.
 
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