OK so I picked up a very nice 89 GTA a week or so ago but is was running rough. Owner said it ran great last year but this year he pulled it out of storage and now it won’t idle and when I give it gas it pops out of both the exhaust and through the intake. Won’t idle at all. Runs rough in general until I let off the gas and then it dies. Wierd thing is that every so often it will start and idle fine for a few minutes and then it starts to drop RPM and goes back to the backfiring and won’t idle. I have already replaced the MAF and the TPS. I set the TPS to .54. Is there something I need to set on the MAF or is it a plug and play?

I checked the plugs and wires - good.

Car had fuel stabilizer in the tank but he filled it with fresh no ethanol gas after he got it out of storage.

Fuel pressure is 40psi with the key on and holds 40psi after I start it.

Has an older intake set up (see previous post) but that was apparently on it for years. I did notice that it just slips over the end of the MAF so maybe there’s air getting in?

Car has an 88 5.7 TPI engine in it. The original blew up close to 20 years ago. They pulled a 5.7, complete, out of an 88 Trans Am and dropped it in. Still has the 9th injector but it’s disconnected. Trans also came out of the 88. Don’t know why they swapped the trans too other than it had less miles.

Got a good deal on the car, hoping this was something I could get fixed. All help is appreciated. Right now it’s not drivable. Don’t have anyone near me in Southern Wisconsin that’s familiar with the TPI motors so I’m on my own to figure this out.

Also - my oil sender must be bad. Gauge pegs at 60psi. Drops to zero when the car is off so the gauge isn’t stuck. Could a bad oil sender have anything to do with the rough running?

Thanks!

 

Frankenstein car.

Fuel is bad until YOU verify that it is good.

How did you verify fuel pressure while motor is running?
Did you take it on the road while monitoring fuel pressure?

Easy to to check for vacuum leaks.
Easiest methods are also most likely to start fires. Keep bucket of water handy.

EPROM chip could be from anything.
EPROM has data for some car - not necessarily the unholy beast that lurks in your garage.
Data tells motor when to fire.
If data is incorrect for that motor, not likely it will fire under all conditions in such manner as to not seem alien.

If degraded mechanical components are allowing ingress of air, or denying fuel, or over-delivering fuel, behavior will be unsatisfactory even if computer data is perfect for current components under hood.

Recommend you put a scan tool on motor to ascertain rich/lean status under various common conditions.

TunerPro for software.
Moates for hardware.

Harbor Freight to Snap-On for the tools to do fun stuff like pulling balancers to get access to timing chain and other such adventures.

Remember always, if the car doesn't fall on you while you are searching, its a good day.

Channel your inner Anthony Hopkins.

 

Used a fuel pressure gauge on the rail while just the key was on and then while I was working the pedal to keep it running.

If it’s bad fuel, not sure why it will run good every so often for a few minutes.

Forgot to mention above, aftermarket exhaust with no O2’s. Ran fine this way for the last few years though.

 

Running a computer-based fuel delivery system with no O2 sensor.

What could possibly go wrong.

That's just great.
Running on perpetual open-loop status with no data to control fuel trim.

 

My go-to diagnosis for rough running, rough idling, blah blah etc is generally Fuel Injectors. Because ethanol gas is garbage, and after 30 years stock injectors are usually pretty cruddy even if they don't have a million miles on them.

On a similar note, when fuel pumps go bad, sometimes they'll still work enough to start and idle poorly, but won't let you accelerate.

Really though, you just need to work through it. Get a copy of the GM Service Manual, and flip to the section that covers no-start/no-run and start following the charts.

 

Sorry, meant to say no catalytic converters. O2 is in the pipe after the header. It was getting late.

 

Maybe someone with a little more knowledge on this can chime in but I think in 89 there was a change in the TPI system. I always see that 89-92 parts are specified for those years. You say you have a 89 with a 88 engine. You may need a matching ECM. Not sure when they changed to MAP but if 89 was the year you may have a MAP ECM running a MAF sensor. I would not trust any info you got from the seller like it ran fine last year. I would start with checking the engine code to verify the year and then check the ECM numbers to make sure it is correct. Yhe cay being removed will have no effect in your case.

Remember Frankenstein was made up of lots of unknown parts and he did not run very well either, in fact he could barely walk.

 

Yes, I get it that it’s a Frankenstein. The price was right so I took a chance. From what I have researched, the main difference between 88 and 89 is the elimination of the 9th injector. My car has it in place but not connected. Maybe there’s more differences but I am not finding them described anywhere.

 

The 9th injector is for start up so I don't think that will matter if it is not connected. I noticed in your 1st post you did not state you checked the timing. If you havent I guess I would start there. I know that off timing definitely would cause backfire. Also there is a control module in the base of the dist. under the cap. This is connected to the ECM and controls the spark advance. I would check that also, they get alot of corrosion build up on the terminals.

 

Thanks Vinny. The timing is at 6 degrees. Good call on the ignition module. I’ll check that next. When I pulled the cap off, i did see surface rust on the base of the distributor. Thanks.

 

You have two choices.

You can keep parts-cannoning the thing, and maybe you get lucky.
Maybe not.

Or you can actually DIAGNOSE the problem.
That starts with reading the O2 sensor data (fuel trims) to figure out when it is running rich, and when it is running lean.
Then look at the reported spark advance at the time of the misbehavior.
From there, figure out which sensor is reporting in such a manner as to cause the timing changes.

There can be basic mechanical issues too. If you have a poorly-performing injector, all the ECU data in the world won't remove and replace the bad injector.

It is NOT that expensive to get the cables and gizzies to read data on these OBD1-driven cars.

Chances are you have a typical MEMCAL ECU.
Maybe the data (BIN file) on the EPROM chip in the ECU is correct for the motor currently in the car.
You can start to diagnose whether the BIN needs adjustment by examining the live-stream data that is available by plugging a suitable Moate.net cable into the ALDL port, and reading that data on a laptop loaded with Tuner Pro RT (freeware).

Or you can replace the whole fuel-delivery system, and every sensor on the car, only to finally discover that some lunkhead programmed your chip to do something really idiotic with your timing tables at a particular RPM range.

 

The entire ignition system needs to be in good mechanical condition to achieve reliable performance.

That said, these are very robust cars, and they will tolerate a lot of decay and still run better than you would expect.

I pulled this distributor out of my car (reason for pulling was just to replace the 30-year-old leaking O-ring). I discovered THIS. Car was still running pretty good with this garbage calling the shots.

 

Working on diagnosing it. There are no codes in the system - checked. I am sourcing the equipment to do the diagnostics however it is not available immediately where I am located. I am simply trying to start with the easy things first and trying to understand these touchy systems. Third car I’ve had and each ran like crap when I got them. Each had a different issue. Was just hoping for a few suggestions to start off before I tear it all apart. Spending $30 here and there to try to get to to at least idle so I can do the diagnostics, is worth it to me. If I can’t figure it out, I’ll replace the entire top end with a correct 89 set up and make it correct.

 

THAT is impressive.

I thought it was only me who usually encountered that kind of shiznit...

 

If you are chasing the easy mechanical stuff, get after the vacuum lines as first order of business.

Is the vacuum line that goes to the vacuum reservoir intact?
When I got my car, that line was rotten, and just flopping and sucking.

 

I was only one day into the car when it just shut off on me in Mississippi en route from TX to VA. Kid at the highway shop that ran the hook put a cap, coil and rotor in it. I didn't give the car much attention for several years except to fret about all the water leaks, and drive it every now and again. Ran those three new parts for a few years, and got tired of the oil puddles. Decided to keep the car, so set about dealing with the O-ring. That's when I discovered trusty rusty. Stuffed an Autozone replacement distributor in it. Parts-cannoned a few more parts. Still stuttered.

Car was throwing a code 54 (fuel pump voltage low) since the day I got it.
Drove it that way for years.

I parts cannoned a MAF, which caused the CEL to go off for just a little while, but then came back with no more code 54, but now code 42. I googled a bit and found that a bad ECU can throw a 42 (Electronic Spark Timing, etc). With emphasis on the ET CETERA. So I parts cannoned an rebuilt good ol' Cardone ECU. Put that sucker in and the CEL has been dark ever since, and not a single stutter.

Still leaks oil. Just not so bad at the distributor these days. Why would I think that the thing has ONLY ONE oil leak?

Lord only knows about that fuel thing. Fuel pumps dont just cure themselves. Like the song says, "I know a little."

Only a little.

 

Frankenstein is alive. Found a cracked vacuum line to the EGR and a bad engine ground. Not sure which did it but it started and ran well enough to get the timing light back on it and zero in the timing. Runs best at approx 8 degrees. Ran it down the road enough to find out the kick down cable end broke off the throttle. Always something. They must have cracked the plastic piece somewhere along the way. Once i get a new cable and get it installed and adjusted, I should be able to get it all fine tuned. Thanks for your suggestions.

 

Keep up the good fight.

 

dam dude. look at all the pretty colors. brown green yellow black