1992 Camaro Hesitates Off Idle
The car came towed in after it starting running rough over a year ago. Car would barely run found that the egr valve was stuck open. Replace with a new one and car would run but very poorly. I found four shorted injectors so I replace all six for good measure. Car would run but would load up and smelled extremely rich. Found numerous exhaust leaks and the o2 stuck at 70 mv. Customer decided to take the car as is. Now a couple months later its back and most of the exhaust is fixed except a small leak on the drivers manifold. Found the o2 stick stuck at 70mv so I replaced it and now it was reading rich. As soon as it would go into closed loop block learn went strait to 100. Found the oil was full of fuel and the gas was nasty and tarnished. Drained oil and fuel filled back up with fresh. Now the block learn and integrator are at 125. Still had hesitation off idle and found the timing was off 10 degrees. I retimed it to 10 degrees and noticed the cap and rotor had tons of corrosion in them and replaced those as well. It now runs way better but still has a hesitation off idle. Map sensor is reading 13.2 and baro is 29.2 which is pretty normal for my area. The o2 is oscillating and the tps is .6 at idle and goes up to over 4 when i rev it. I've smoked it for leaks and nothing. If you rev it up it will stumble the first time but after that its seems to be better until it idles for a little bit. What am I missing?
Hi Michael, Attach a hand vacuum pump and pull it to 18-20Hg to see if it clears up and acts right. Also replace the MAP vacuum line, these usually crack. I never trust a scanner reading on a MAP, always use a vacuum gauge if possible. Next: Replace inline filter and do a fuel volume and pressure test on the fuel pump. Don't forget to check the fuel pressure regulator for leaking fuel. At…
I forgot to mention i checked fuel pressure with a gauge and it was at 40 psi and with the regulator unplugged it went to 47 or so. I cant remember exactly as i did it last friday. I already tried to use a hand pump on the map and no change. Engine vacuum Is a little low at 14 inHg. I have no leaks to speak of and the iac counts at 37.
14 inches of vacuum is quite low. Compression and exhaust back pressure would be the next items to test. Also, these ECM's had an issue with the injector drivers getting “lazy” on initial throttle up.
Back pressure practically 0 and compression is around 125-130
I'm surprised there is no mention of the fuel pump not being replaced. Those older GMs were not very forgiving when they sat for a while, especially to the point where the fuel goes bad. Usually, the hose connecting the pump to the sending unit deteriorates, first causing the pressure to drop (leaking), then finally splitting completely open, causing the vehicle to go into the walk home mode. If…
Good God what a mess. Does that have a maf in 92? We used to have lots of trouble when the first started computerization from mass air flow sensors loading up the engine and running rich. Kudos to you. I would have never spent that much on that car.
I was just going to repeat what you stated above
… Test the exhaust BP… should be less that 2 psi razzed out. … Dan H. … Hobbs … South Texas …
Hi Michael, Did you disconnect the set timing wire (tan/black, near distributor)? That has to be disconnected to set the base timing at warm idle in neutral. Set the timing then cut the engine off and reconnect the wire.
sure did i saw someone else had been playing around. On this sweet piece the wire is actually by the rf strut tower. I've been through this thing with a fine tooth comb and without blindly just throwing parts at it I'm at somewhat of a loss. But I for some reason can't give up on it
Hi Michael, Did you verify it does not have a very worn timing chain? If not pull the cap and then rock the crank to watch for excess play and the distributor being slow to react. This thing could have jumped a tooth? When they were stock they had a nylon toothed cam gear to reduce engine noise (they were junk). You had to correct the timing, that is a clue right there. One tooth can easily…
I forgot about those junk nylon gears. A certain fiero comes to mind. Thank you so much I'll check that out tomorrow when i get back to the shop. I'm the only guy that does what i do at my work so its nice to have someone to bounce these things off of. I rarely cant figure something out so its been driving me crazy. Its low on power til you get up in rpms
Hi Michael, I use to run into this issue quite often back in the late 90's and early 2000's. Has engine designs have evolved, like most, a lot of this stuff is often forgotten. I still see some of these older vehicles from time to time. Down here in South TX, it's no telling what comes into the independent shops. Sadly many of them are neglected and ragged out.
My mentor in the automotive repair business was a Rolls Royce master. He owned a small shop which was adjacent to his home. (I had hair back then…. Ah! The memories!) He frequently lamented on poor quality and intricacy incorporated into the building of cars ( Not RR) of the day (Early ‘70’s)….. His frequent comment was “The car of the future will be the simple, high quality car”…. Boy, was he…
Check wiring to the ign,cont module, crank to cam correlation, esay fix call lkq pick a part they might give $20.
Going to rip the front cover off and check the timing. Might be a few days as I'm swamped with many other ridiculous problems due to everyone fixing their problem chldren since they can't get a new car.
Michael, Cam Timing and Chain Stretch can be seen on a in-cylinder pressure wave form… do you have that capability?