I just bought a 89 RS TBI 5spd for a project car that I'm building an engine for. I'm trying to get it running properly with the stock engine. The guy i bought it from said it ran fine up until 3 months ago and suspects a bad fuel pump. I got it started after replacing the battery and keeping my foot on the gas. At first i thought it was as ignition problem since it seems like it runs on fewer than 8 cylinders, barely moves under load, and smells rich. After it warmed up it seemed to get a little better. I drove it home hoping the symptoms would change and they didn't. Anyway, the car will either not idle, or it will jump up and down between ~400-~2000rpm. When i try to get it going it bucks and stumbles really bad. It has an extremely hard time revving past about 2700rpm. If you keep it floored it will pop and buck and eventually get to 4k but only in 1st and 2nd. I am pretty sure that the iginition is ok and i'm suspecting MAF relay trouble. Althought, i'm a bit confused. I searched and noticed that most people here talk about there being two maf relays one power and one burn off. My car only has 2 relays in that spot and not 3. I'm assuming one is for the fuel pump and the the other is for the MAF. I noticed that the relay closet to the fender was broken off of at the bracket and resting on the fender well. I looked at the socket and saw that three of the wires, green/white, tan/white and black were missing about an inch of insulation at the bottom of the socket and were all touching. (See pics) Can someone help me out here? I'm pretty sure the fuel pump is fine. I'd like to get the car running for the weekend.

 

Here is a close up of the relay/socket.

 

Your car doesn't have a MAF sensor. Just the TPI's have that. Your car is speed density and uses a MAP sensor. I'm not sure what that relay goes to. A wiring diagram would be helpfull here.

To me it sounds like it is your fuel pump. Backfireing and bucking are indications of a lean condition. The fact that it runs better once warmed up shows that once your demand for fuel is reduced the car runs better (pump can keep up). I'd almost lay a 20$ bill down that it's the pump. Might try to get your hands on a fuel pressure guage.

 

I thought it ran better when it warmed up but it doesnt. As i said, it smells like its running super rich, not lean.

 

Hey there! Welcome to TGO.

You are likely one of those guys who can do work on cars yourself but it just so happens I know an ASE master mechanic in McAllen. If you are interested, I can shoot you his contact information so long as he still does work on the side and you are interested.

Cheers,

~C

 

the relay on the left is for the cooling fan the relay on the right is for the cooling fan or the reverse. If the map sensor is real bad it would run super rich...... but if your o2 sensor is out it would do the same thing. You should jump out the computer and see if she's throwing any codes....... also if the tps is messing up the idle might jump up and down also check the iac it may be stuck or frozen..................... these are the two components on the tbi
what condition are the plugs,cap, rotor and wires...............

Kenny

 

There are no codes. You have my confused on the relays. As far as the iginition goes, everything looks good and new. haven't pulled the plugs yet though. It wouldnt be the 02 since it does it all of the time cold or hot.

 

very simple one is the electric fan relay and one is the fuel pump relay trust me I had to change both and trace out both circuits the box looking one is for the fuel pump.............
kenny

 

Ok, i can't figure this one out. Replaced the computer, still no codes, checked ignition module and coil, replace fuel filter, played with timing. Still runs like crap. Maybe even a little worse.

 

I'll admit I'm new to GM and TBI, but did you think about the CTS.
It is a big problem on Fords with all the symptoms, and no check engine light. Just a thought.

 

did you do a compression test? check your firing order? check for burnt wires etc............ just my 2 cents maybe check your fuel pressure as well if you still think you are having a fuel issue


Kenny

 

calso check your egr valve thhat can cause a vacuum leak and produce some of those symptoms..with carbon build up and such...just disconnect the vacuum line and plug it then start it and try that to troubleshoot a little....mine was having similar probs so i blocked off my egr and removed smog equip..you may be able to replace yours and have a simple fix...good luck