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i have been an import guy my whole life. until recently when my girlfriends step dad started having me help with his firehawk and 442 repairs. the feeling of his FI cars got me wanting a powerful v8. so I got this 93 trans am a4 off a guy whose son bought it and it was having overheating issues. he explained that driving around town the car was fine but when he got on it then it would overheat. I almost knew instantly that it was bleed wrong or there was a small leak somewhere. both were right. anyways I drove the car for a week with no issues when one day at work I left for lunch and the car acted like it was out of fuel. so I added gas thinking maybe the gage broke. then it would idle fine but as soon as I went into gear it would die. got it towed home and now its been in my spot for 2 days. im getting all the necessary diagnostic tools today to do some digging. including fuel pressure gage and datamaster cable for my laptop. I have googled and I have seen fixes from letting it warm up to fix, fuel pump, fpr, opti, and so on. im new to the datamaster so im curious if anyone has a list of what the numbers should be. ill be posting later but if I cant track the issue and fix it does anyone know a reputable repair person in Houston for these cars that can tow? lol ill keep everyone updated. thanks.
 

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fuel pump, fuel filter, spark plug, spark plug wire arching on manifold/or header...?
 

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ok I just got home from picking up the tools and I replaced the fuel filter and I am getting almost 50psi when cranking and around 40psi when koeo and it holds steady. supposedly the plugs and wires were all replaced within the last month. im going to try and pull them and see if anything looks funny. I think I have eliminated fuel issues so im on to spark. I hope its not the opti.
 

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I forgot to mention the datamaster was able to pull 3 codes from the ecm. 15, 23, 26. now I have the factory service manual and it says 15 being low temp indicated. 23 is iat low temp. now for this I think the wires may be alittle frayed so im going to look them over. but the service manual says that a dtc 15 can cause a dtc 23. the hardest one to figure out is the 26 and what can cause it. its a quad driver module and from what I have read it controls a.i.r. system.
 

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15 and 23 are very important for a 93. Input from those two sensors help it run in the speed density mode 93s use.

26 is:
Quad-Driver Module (QDM) #1 circuit
applies to:
- AIR pump relay circuit
- EGR solenoid
- EVAP solenoid

None of those is particularly important as to how the engine runs. The first thing to check is the AIR pump fuse. The car being new to you, who knows if it even has an AIR pump still on it.
 

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ok so after almost 2 weeks of doing random work due to f/t job and f/t school the car now runs and almost drives. I can now take her around the block. the only code I have left is a code 26. she still falls on her face when I give it gas. the datamaster says my egr dc is at 100% when this happens. I will try to post my logs today. I have replaced fuel filter, plugs and wires, swapped a good icm/coil, checked egr with vacuum pump, replaced egr solenoid, and cut out the cat. im going to try and reset the code and see if it comes back but im trying to get ideas of something im missing here.
 

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Check your throttle body gasket and air intake.
 

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Also make sure that your air intake Elbow is properly attached. Since the car is new to yu check ur MAF to make sure the last owner didnt de screen. I hear about nothing but probs from doing that 1 horsepower headache gaining mod.
 

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...Since the car is new to yu check ur MAF to make sure the last owner didnt de screen....
workman i know you're trying to help, but don't confuse him, his car is different from yours and doesn't have a maf (it's a 93), and would run alright even with the intake elbow missing.

shbox is right, that code 26 shouldn't affect how the car runs in a big way, not so much it'd make it fall on its face. dont focus on stuff related to egr, air, etc. you can fix that after you figure out why it's running like crap.

it is great you have datamaster, how's about you do a datalogging run for us, from cold start right up to operating temperature, and make it 'fall on its face' several times. then post it, i bet we can narrow it down a bit for you..

besides that, you need to check some more basics, first off confirm that you have good fuel pressure while running.

i'd also reccommend you check for spark at the plugs with a proper spark tester. you could have a worn cap/rotor @ the opti. plug wires, coil, and icm dont fix that stuff, but a spark tester will give you a good idea. failures in the high voltage part of your ignition system will NOT throw codes.
 

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yeah I can recheck fuel pressure when I do the log. I know shbox is one of the greatest minds for this community and I will hands down follow any path he recommended but when I googled dtc 26 and egr issues there were quite a few that had the same symptoms of mine that was fixed when they fixed the egr issue. I will definitely post the one log I do have from yesterday and I will create another log today and try to make it all the way till it is warmed up. thank you all for your help.
 

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last question how can I upload the uni file?
 

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@ steveo Gosh dude i did it AGAIN! I keep forgetting 93's dont have that-.-
Thanks for the save man!
 

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anyone for the log?
 

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Hey bud i cant see it through that link. I dont have access to a computer so it might just be my phone.
Im still watchin this thread tho to help u any way i can. Did u get a chance to check those gaskets? And the reason i say that is bcuz it can idle with those gaskets cracked and leaking but once u put it in drive there's alot more goin on so it can cause it to bogg down and cut off.
 

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only if it's stuck way open would it do that. you can kinda confirm if it's jammed open without removing it from the car, by applying vacuum to it while monitoring intake vacuum at idle. an egr that's closing properly will produce a noticeable change in intake vacuum, one that's stuck open, not so much.
 

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i'm looking at your log now

your egr definitely seems wacky (although im not sure exactly how they're supposed to behave on a '93). i would unplug your EGR solenoid for the moment, for testing purposes

i dont know what the hell happened around record 1900-1960. that's really messed up. it looks like you're revving the piss out of it by your TPS, and your MAP seems to match the load, but the rpm just kind of... climbs slowly

can you confirm you were actually blipping the throttle like that, during that log event? what was going on there?

if it wasn't for the TPS following MAP, it'd look like a really hard stumble.
 

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woah woah wait a minute here

check your battery terminals and all ground points

you have major electrical issues going on here. you only have 12.5 volts full running, and near the end your volt ref. drops hard, 7 volts and stuff
 
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