Nellsw88

Hey guys, just picked up a 95 z28 with 67k miles. I just put a new fpr and filter on and a msd cap and rotor not the whole opti. When you start the car and begin to drive it it runs like a champ but after about 15 minutes it will hesitate at wot and at idle in park it begins to stumble and rev from 600 to 1500, similar to a very bad vacuum leak but I can't find any. It also does this at red lights and the car wants to jump forward and it's a fight to keep your foot on the brake. And to top it off there's no ses light. I'm assuming it has to be a sensor because it doesn't not act up until warmed up and driven for at least 5 or 6 miles. When it starts to happen if you unplug the tps it levels out perfect but wont drive right or shift out of 2nd. Possibly iac or o2's ???

Injuneer

Was it hesitating and increasing RPM before you did the work listed above?

Any idea what brand Opti base unit is on the engine? I've seen problems with heat soak on the optical cam position sensor cause the idle surge.

Best thing to do is get the free download of Scan9495, and buy a cable from ALDLCables or Red Devil River, and run a data log on the PCM to see if the surge can be related to another PCM operating parameter or sensor.

https://www.camaroz28.com/forums/com...95-lt1-874306/

I closed your thread on the "Fuel and Ignition" forum. We ask that you post a specific problem in only one forum.

Nellsw88

I just had a hard starting issue, had to hold the key for at least 5 seconds before it fired. It ran relatively fine just a little sluggish. The P.o. had the plugs replaced about 1000 miles before I got it and had a new water pump installed.
As far as I know the opti is the original, the cap was a yellow brown color after I got all the grease and grime build up off it. I just find it odd that it only does it after its warmed up, and if I disconnect the tps it levels out.
I will order a cable tonight thanks for the advice

Nellsw88

Well I ordered the cable so while I wait for that to get delivered I decided to play around with the car. I noticed a few things.

1, when I hear the air pump come on it jumps from 600 to 1500rpm if u pull the air pump relay it only just to around 1000rpm

2, the iac after it gets warmed up is constantly opening and closing but only in park and stopped in gear, not under normal driving

3, it drives much smooter with the air pump relay pulled, it only had a little hiccup when you start to increase the throttle unlike the miss and buck when the air pump has the relay in,

Is it possible that maybe the iac is screwed or there's an issue with the air pump, I wouldn't mind deleting the air pump anyway

Injuneer

When do you hear the AIR pump turn on? It should only run for 3 or 4 minutes after you start the engine. If the AIR pump runs after the PCM goes into closed loop, it will cause the engine to run very poorly, due to causing a serious rich condition.

How did you determine the IAC is "constantly opening and closing"?