Good evening all,
I've gotta 94 Trans Am with a rather stout lt1 in it. I've put a lot of money into it and yet it still gives me problems. A little background on the engine. Had the works done to it. New pistons,rods,new valve train with 1.6 roller rockers, 575 lift comp xr cam. Throttle body has been ported to match.
Here's my problem and I couldn't seem to get any suggestions on the other forums. I've noticed what seems to be a surge while travelling at a sustained rpm range,usually 2000 rpm. It sounds like a miss or something that you would feel with a bad wire or plug or even if you have bad o2 sensors. The car has a lot of power when cool but when it reached operating temp it acts up. Its got new msd 8.5 mm wires and new plugs both less than 4 months old. Next I thought o2 sensors. Replaced both and nothing changed. It has a new map sensor so I've eliminated that as well. The ignition coil was replaced with another msd coil and the ignition control module was as well. I've checked the fuel pressure and was surprised it was set to 37 psi,i figure 30# injectors needed more than that so I adjusted it until it found a happy psi which is 44. After all this it still gives me trouble and a headache. Anyone have any ideas?

 

Have you scanned it for codes? Have you checked with the tuner, because cam surge can cause the problem you are reporting.

You shouldn't play with the fuel pressure. Whoever tuned it (who would that be?) for the cam and other mods had to know the fuel pressure and the injector size. The fuel pressure has to be measured and set with the FPR vacuum line disconnected. Did you do it that way? You want 43.5psi with the vacuum line off. The pressure will then drop into the high 30's when you reconnect the vacuum line. By increasing the pressure, all you do is force the PCM to use the long term fuel corrections to pull fuel.

 

No codes have been thrown. It was tuned at a place called PAS in Henrico,Va and until recently there's been no issue. The fuel pressure was set at 43.5 by the tuner who is one of very few who specialize in lts in the area. I put the car in another shop which apparently lowered the fuel pressure to 37 psi without saying a word to me. It was in that shop for a tune after a new maf was put in. I did some data logging and found the right bank was constantly lean yet it smelled rich. I figure the rich smell was due to the pcm trying to compensate for the lack of fuel being delievered so it was adding fuel thus loading the car and causing poor performance.
The issue isn't an ongoing thing. The car still runs strong but when I hold a constant rpm range or speed it begins to shutter during acceleration almost the same way it did when it burned a wire. I've checked the wires and they're fine and that's why I was leaning towards something in the ignition system.