Hello everyone, new to the board and was looking for some help. I just bought an 89 Iroc 5.7 off ebay. The motor has just recently been rebuilt by a professional company. The gentlemen selling the car owns a shop that works on nothing but F-bodies. He had stated to me, at purchase time, that the timing may need to be reset when it arrived to me. He had just sent another car to Tennessee and the guy complained it ran horrible. He reset the timing and said it was perfect. The seller is in Southern California and I am in Ohio. I thought with the fuel injection and computer, that the timing/air/fuel would correct itself. Heres the problem that I am having. The car was running pretty rough (like the timing was off). Tied to this, it had starting issues if you turned it off and right back on. It wouldnt start for a couple of minutes. Motor doesnt sound as strong as I thought it should going down the road, but it too sounds similar to a car out of time. You could drop the hammer on it from a stop and get a decent 2 wheel burnout for about 20 foot. The wife thought that was great, but I remember how they actually ran new. They would pop tires before they would quit spinning. Final twist to the story. Today, the car seems to be a little better. Still rough idle, but after a day of off and on and driving and it seems to start better and at least run smoother on the road. Any thoughts would be greatly appreciated. Been a long time since Ive been in an F-Body. Have a new GTO, but glad to be back!

Thanks
Bob

 

I'd start with the usual suspects. Spark plugs can tell a very good story about the engine, the fuel mix, and sometimes timing. The distributor cap, rotor, and plug wires can all affect the operation and how the plugs will appear after some use. A good visual inspection of the ignition components and resistance test of the wires would be prudent.

Make sure there are no significant vacuum leaks, including the EGR, PCV valve, all hoses, power brake booster, etcetera.

The ECM controls the overall timing, but it relies on the BASE timing setting as its reference point. The correct base timing should be 6° BTC, where the ECM presumes it would be so timing can be controlled correctly.

If the car has been sitting and stored for some time, you may have injectors that are sluggish, have deposits, or poor spray patterns. After verifying a good ignition system, correct tune, and good compression, that would be an item to check. Of course, fuel pressure needs to be correct for the injectors to operate as designed.

It's likely that you'll find something before even getting that far. Good luck.

 

Vader, Looks like I was heading down the right path as far as the basic tune up. I greatly appreciate the info on the "base" timing. Will be headed home tonight and see if I can get this straightened out. I know the great power and torque that these things had. Now I just got to find where its hiding

Thanks again
Bob