LuckyGen3

First time Poster...Long time reader
I recently bought a 1988 Trans Am 5.0L 5-spd from an auction.
I have owned 3 Gen3 cars:
1990 Camaro RS 5.0L TBI that I had to sell.
1988 Camaro Z-28 5.0L TPI Automatic that I lost in the 100yr flood in Washington State...I cried on that one since I had just FULLY restored it.
Now I have a 1988 Trans Am 5.0L TPI. I bought it at an auto auction because the body and interior was just too nice to pass up. I knew at the time that it was running rough under idle.
Since I bought it I have replaced some of the things that I did with my Z but not all.
I thought it might be a good idea to list the things that I have done to the T/A and the things that I did to fix the Z to get some opinions on the path that I'm on.
I'll start with what I did to the Z that had pretty much the same problem:
Replaced the Cap, Rotor, Plugs (made sure of gap), Plug wires. Ran ok before I did the tune up. Didn't start after. Adjusted the timing and it went back to running ok but not perfect. Apparently the previous owner (dealership) had to make up for crappy running by advancing the timing. After about a week I changed out the ICM. Ran good for about a month after that then would run bad and not start at all. When I tried to restart it I could not hear the fuel pump spin up. Yep, bad fuel pump.
For those of you that have your car die after some amount of time, if you have to wait before starting again, listen to the fuel pump when the key goes to the on position.

Now for the T/A:
Currently I've replaced the MAF and TPS because the code said so. Results were rather inconclusive since it stil had the hiccups if it was idle or under power. It was worse under power. I adjusted the TPS so that the RPMs were 750 under idle and warmed up conditions. It's not in any book but that should be pretty close.
Next I checked the timing with the ECS disconnected. It was WAY retarded so I adjusted it back to 6* BTDC. After that it would not start once I reconnected the ECS. I used the actual throttle to keep the care running while I readjusted the TPS. No luck. I noticed that while I was adjusting the timing that I was getting shocked when I put my had on the distributor. Pushed on the wires and 2 were loose. Pushed them down and the car now runs fine at idle, runs better at speed under load, but still stalls when I come to a stop.
I have the ICM and Plug wires on order. The timing was bouncing by 2* when idle.
I'm not as familiar with the Pontiac T/A as I am the Z-28 of the same year.
Is there anything that I'm missing?
Thanks in advance for the help.

rick121

iTrader: (1)

You've obviously gone a lot further into the whole timing issue than i did when my car did about the same thing. I replaced way too many sensors and random things before finally cracking and taking it in to the dealer for an analysis. The first thing i ever did was the timing. turns out that was the problem (probably) the whole time. When i went to the chevy dealer they said that the engine just got old and that "perfect" timing wasn't right for it anymore. Not sure how they did it, but they kept tweaking the timing until it ran its best. just never gonna right under factory settings. the MAF sensor was showing up as an error for a while but after the timing was adjusted, no error.

TPeye

You say that you adjust the TPS to get the idle to 750rpm. To adjust the idle there is a procedure to adjust the torx screw that acts as a throttle stop and get the computer to keep the recalibrated throttle opening. If you just turn the torx screw the computer will keeping bringing the idle back to where it was. You want the TPS adjusted to .54 volts at idle.