(This is a duplicate of my post in the General Tech Area, wanted to ask the 3rd Gen guys directly)

1992 Camaro RS 305ci TBI
60,000 Miles

The issue I am having is very odd...

The engine at Wide Open Throttle (WOT) will not rev past about 3000rpm. I can nurse the throttle up to redline if I do it very carefully and lightly on the peddle.

http://www.youtube.com/watch?v=te9AH2DgqXs
(Video is mirrored, I apologize)

Have replaced the Fuel Filter
Have checked the TPS and MAP with a voltmeter
Idles Good


SOMEONE PLEASE HELP!!

 

Looking at the position & direction of the gauges, and the steering wheel being on the wrong side, I'd say the problem is the car's upside-down.

 

Hahaha, yeah I can't figure out why the video turned out like that... much like I can't figure out what's wrong with my camaro.

 

Does it cut out like that while driving too, or just while revving it in neutral?
First thought is fuel or air starvation.
Your fuel pump could be on it's way out and not able to keep up with the greater demand as the engine speeds up.
Pop the air cleaner lid off and see if that helps, and check the filter while there.
Maybe the inlet horn isn't opening up, there's a flapper valve to bring in exhaust manifold heat when the engine is cold, then opens to bring in outside air.
I hear your exhaust sputtering, so another possibility is a plugged cat converter not letting the engine breathe.
Have you checked for error codes yet? You could have ones stored even though your SES light may not be on.

 

based on the response to the throttle (meaning how fast it gets to 3k), id say its not a clogged cat or dying fuel pump. it looks and sounds like there is an ignition retard to prevent over rev when its not in gear. how does it rev driving? will it go to 4500-5k before shifting? there is always a possiblity someone added something

 

^ I thought about an added rev limiter too, as I have one on my MSD box. But it wouldn't make sense on an engine like that.
The 305's performance is so restricted, it already acts as it's own rev limiter.

 

Here is what makes the problem confusing: Cannot redline at WOT, but can redline if the throttle is lightly eased on..

The vehicle while in gear and driving will not go over 3K rpm, the engine will not rev-match when downshifting. There is no aftermarket rev limiter on the vehicle.

If I am very easy on the throttle, give it like 1/4 throttle, then ease to 1/2 throttle, I can get it to redline in neutral, (not in gear)...once I ease it to redline, if I WOT it, it bogs back down like in the video. (I think ill make a video of this tomorrow)

Paperclip trick gave me a code for lean exhaust gases.

I heard that if you remove an o2 sensor, and the problem lessens, it may be a plugged Cat (open o2 sensor hole relieves pressure) would this test eliminate the possibility of it being the cat? Previous owner used to run leaded gasoline, so a Cat would be no surprise to me.

A sensor sounds most likely to me, but a voltmeter showed the TPS and MAP were working fine. Could it be a vacuum line?

Not the air filter, open air cleaner changes nothing.
Not the fuel filter, that was my first guess and replaced it.
Drained the tank thinking it may be bad gas.



Question 1: If the problem were a cat, would I still be able to ease the throttle to redline?
Question 2: Is it possible that even with the voltmeter test method on the TPS and MAP they could still be the problem?
Question 3: Could it be a vacuum leak? My brakes have been very touchy...?
Question 4: Will removing the o2 sensor to relieve exhaust pressure diagnose a cat?
Question 5: Could it be a fuel pump? Why can I ease the throttle to redline but not WOT?
Question 6: Does anyone else have any guesses as to what it could be? I'm running out...

 

I had a buddy with a 90 iroc TPI 350 that had the same exact problem. We chased it for months. We were on a college budget, so we had to do one thing at a time every paycheck. I remember we changed the Cap, rotor, plugs, cat, 02 sensors, MAP, and TPS... still the same. We found a used computer from a pick and pull and did that. That worked great for about 6 months, then the problem returned. I still believe it was computer and ignition related. It was his daily driver and it was just too unreliable so he ended up selling it, ten years later he still regrets not doing more to figure it out.

 

It could be the fuel pump. And here's what I'm thinking...
A few years back I bought a 91 that had been sitting for two years, and it ran before it was parked. I could get the engine to start with a prime in the TBI, but it wouldn't stay running. I disconnected the fuel line at the TBI, turned on the key to prime the pump, and gas barely dribbled out. Down at the filter, pressure wasn't much better, so I figured it must be the pump. After dropping the tank and getting the pump/sending unit out, I could see the problem. The short fat rubber hose that connects the pump to the sending unit was deteriorated and split wide open. The gas was just running right back into the tank. At one point, my "wide open" split would have started out as a small opening. If that's what you have, then giving it full throttle all at once is going to expand the split and you'll lose pressure. Whereas slowly nursing the rpm's up could allow the connector to hold out more. I would check your fuel pressure at the TBI and see what you get.
As far as the cat/oxy sensor, yes that could be another thing to check into. If you get a cyclone coming out of the bung hole and the engine stops cutting out, you'll know what's up. Also, enough back-pressure with a restricted cat can force the EGR valve open when it's not supposed to, which will make the engine run crappy.
But to me, it sounds more like a fuel cut off issue. Keep us posted.

 

I had a very similar problem a couple of weeks ago, I was on the highway when i noticed a sudden loss in acceleration and pulled into the next gas station. I checked the engine bay while the engine was idling and started to check around the tbi for any air blowing from where it shouldnt be. When i put my hand around the driver side of the engine, I felt a lot of air blowing from the "Air Check Valve". When i looked closely, I saw that the connection to the air check valve had broken on the valve side of it. I picked up a new check valve for $10 and it solved my problem. Hope this helps.