stalls when i step on it
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Joined: Sep 2001
Posts: 9
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From: Gatlinburg, TN, U.S.A
stalls when i step on it
i have a 91 rs camaro with a 305 tbi and latly when i step on it when i hit second gear it stalls and kills in order to get it cranked back up i have to set ther holding the key while foot on the gas to the floor then after a coulpe secs it will crank and it blows tons of black smoke out . the only time it blows any smoke is when this happens and the only time it is hard to crank is when i get on the gas . has anyone had this happen to them or know what could be causing this any help would be greatly appreciated
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Joined: Jan 2000
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NF6,
Your mix definitely sounds like it is on the rich side. Oddly, low fuel pressure can cause a rich mixture. TBIs are pretty sensitive to that. With lower pressure, the ECM widens the injector pulses to compensate, but since it can only compensate in steps, it tends to over-compensate just to keep the engine running. High pressure has a similar but opposite effect, up to a point where the pressure is so high that it overpowers the injectors and floods through. Your stock pump probably can't do that, so it isn't likely an issue.
If you haven't changed the fuel filter in a while, it might be a good idea if for nothing else than to eliminate the possibility. You should change it every three years / 30,000 miles anyway. If that's enough to solve the problem you'll be lucky.
You may also have a problem with the MAP sensor or the vaccum source to it.
Another thing that will cause a rich mixture is a plugged or stuck PCV valve. Clean or replace it as well, but do yourself a favor and get only an AC replacement. I had a real problem with aftermarkets, but that's another long story.
If you have a fuel pressure gauge, check the pump output. You should be getting between 11-13 PSIG at the TBI unit.
You should also scan the ECM for error codes. They can be a great hint to finding the problem.
------------------
Later,
Vader
------------------
Justice and Freedom will Prevail
Your mix definitely sounds like it is on the rich side. Oddly, low fuel pressure can cause a rich mixture. TBIs are pretty sensitive to that. With lower pressure, the ECM widens the injector pulses to compensate, but since it can only compensate in steps, it tends to over-compensate just to keep the engine running. High pressure has a similar but opposite effect, up to a point where the pressure is so high that it overpowers the injectors and floods through. Your stock pump probably can't do that, so it isn't likely an issue.
If you haven't changed the fuel filter in a while, it might be a good idea if for nothing else than to eliminate the possibility. You should change it every three years / 30,000 miles anyway. If that's enough to solve the problem you'll be lucky.
You may also have a problem with the MAP sensor or the vaccum source to it.
Another thing that will cause a rich mixture is a plugged or stuck PCV valve. Clean or replace it as well, but do yourself a favor and get only an AC replacement. I had a real problem with aftermarkets, but that's another long story.
If you have a fuel pressure gauge, check the pump output. You should be getting between 11-13 PSIG at the TBI unit.
You should also scan the ECM for error codes. They can be a great hint to finding the problem.
------------------
Later,
Vader
------------------
Justice and Freedom will Prevail
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