My car does seem to rev up 200-400 rpm and back to normal when just sitting idling.It happens approx every 30-45sec .I wonder if this is TPS related.But it could also be the IAC motor.

 

Doesn't sound like mine. Mine is rock solid idling at about 900. The second the pedal gets pushed though the tach takes a momentary slight drop before revving and hesitating up the rpm band.

I'm hopefully going to pick up a fuel pressure gauge tonight, going to check that. I doubt it could be low fuel pressure though since the car is running so rich.

 

Hey Fastbird, sorry to hear about your problems:

1.Did you cut any material off the cam dowl? Mine was too long from Comp.
2.Did you double check all the plug wires were ran right? It's an easy mistake to make and can cause the problems your having.
3.Did you check to make sure all the rockers and pushrods are adjusted correctly? I had a bent pushrod after my timing chain break and it ran pretty rough, also like your describing....

And 1FstFormulaV8, get a new OPTI.

Brad

 

Joe Prince did the intall of my car. The cam dowel was too long from the factory, Joe cut it down, I made sure of that. I double checked it when I had my opti off and it was good to go. I double checked all the plug wires last night and even made some routing improvements. The rockers and pushrods are all fine. Everything is brand new (Comp R lifters, Comp Chromemoly Hardened Pushrods, Comp Pro Mag 1.6 rockers) and everything was fine the first time on the dyno.

At this point I'm thinking Fuel problem, EGR, TPS, or PCM.

If the car is running way too rich, then that could cause the hesitation, correct??? For whatever reason, I'm being led to believe that something is causing the car to dump too much fuel in to the mixture, which in turn in causing it to run like poop.

 

I'm not sure about that. My car is running rich (stock programming on heads/cam but it still runs fine. My money was on something mechanical so I really don't know....

Brad

 

I'm talking spitting fuel out of the exhaust burns your eyes rich.

 

Well, either you don't have spark in one or more cylinders, and the unburnt fuel is being pushed out the exaust, or it's dumping so much fuel into the cylinders they can't burn it all. It would have to be putting a hell of alot of fuel in there for that......

If your sure the ignition is proper (coil, OPTI, plugs, wires) and the computer isn't doing anything crazy then yeah fuel is the next thing to look at. Were the 30lb injectors bought used? Is the gas really old? Have you ever changed the fuel pressure from stock? Does the oil smell like gas?

 

I'm sure the ignition system is good to go. I could probably replace the plugs since they've been run so rich recently, but I HIGHLY doubt that's it.

I'm quite positive at this point that there's some anomaly in the system causing a load of extra fuel to be dumped in for some reason.

The injectors were bought brand new, the gas is relatively new (definitely not old), fuel pressure has never been changed.

I bought a pressure gauge and am going to hook that up as well as check the FPR (remove the line) and EGR (remove the vacuum hose) tonight. I'm also borrowing my buddies scanner to do a check to see what I can.

This is rather mistifying.

 

Maybe it’s a rocker adjustment problem. How far past zero lash did you go?

 

I've been expecting this. I had to get a second opinion. That's two for two. Opti is going in next week.

 

I didn't, Joe Prince did it. The rockers were adjusted prior to the problem and the valve covers have not been off since.

 

Here's what I got from the scanner:

Everything at idle:

MAP volts: 2.8x-2.9x
TPS volts: .92
Manifold Air Temperature: 70.8
Left Oxygen Sensor: 600-620 millivolts
Right Oxygen Sensor: 730-750 millivolts
Left Block Learn: 108
Right Block Learn: 108
Block Cell: 16
Left Integrator Value: 128
right Intergrator Value: 128

Showed as in closed loop.

Only thing I noticed was the O2 sensors holding a real steady millivoltage instead of the supposedly normal bouncing between 100 and 900 like I saw someone mention in the huge hesitation off idle thread.

Think that could be it since it's in closed loop???

 

I'd be suprised if it was your o2 sensors. WhenI installed my Jet-Hot LT's, I had an oil leak from the valve cover gasket that took out the O2 sensor. My Air-Fuel gauge registered the car as running exceedingly LEAN after entering open loop. When I replaced the O2 it ran richer and better.
So, if the O2's were bad I'd expect it to run too lean, not too rich.

Schantin
1997 Camaro Z28.

 

Wow, 8 pages back in one day.

FYI, for all those that had taken an interest in this thread, if you haven't seen my other one, the problem has been identified and I'm looking for the part. It was my PCM after all, most likely a Quad Driver Module failure, but the scanner didn't show it and there were no codes being thrown.

I swapped the PCM from the purple car into the black car, and that's all she wrote.

Thanks for everyone's ideas and help. I compiled a pretty good list after doing a bunch of searches on what can cause a stumble. I'm probably going to revise it then make a good post on here with my findings.

Thanks again!!!!

 

My ECM is shot , so is one of my 02 Sensors.
Same thing happened to my Formula.