need help with cold start problem
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need help with cold start problem
I have a 98 1500 4x4 auto with a 5.2 that lately if it sits over night when i start it has a really rough idle in park and if you put it in gear or neutral it almost dies and you can hear it missfireing and theres a loud sucking noise coming from the intake. It does that for exactly 10 min then it runs fine. My check engine light hasnt turned on and this is my first fuel injected car so im kind of lost on were to start so any help would be appriciated. thanks
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From: NH
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Sorry it took awhile to get back ive been busy. thanks for the advice I cleaned the iac but that didnt change anything. Also it doesnt smoke and it does it all the time low on gas or full. And also my check engine light finaly turned on with a 0320 and 1391 code so i changed the crankshaft position sensor and it ran fine when i started it up so i thought that fixed it so i shut it off and let it sit for a couple hrs and then went to move it and it started and idled fine but when i put it in drive it started doing the same thing again even in park. so now im completly lost. anybody got any idea? Thanks i appreciate any help
Grand Champion
Joined: Apr 2010
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From: Meeker, CO
Does it idle okay for the first minute or so after a cold start, then start that stumbling/sucking noise thing until it's good and warmed up?
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Grand Champion
Joined: Apr 2010
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From: Meeker, CO
In that case, it's almost certainly the pre-cat oxygen sensor. I say this because it's about a minute after cold start that the PCM switches over to closed loop operation and starts diddling the injectors to maintain what it thinks is the correct fuel ratio -- but a failing oxygen sensor gives incorrect readings until it's warmer, thus the stumbling and sucking intake.
Be sure to get either Denso or NTK brand, as the rest are iffy at best and there's no sense doing the job over and over until you get a good one. You'd probably be best off replacing the post-cat sensor, too. They don't foul so quickly as the pre-cat because they're in the cleaner exhaust stream, but it gets the job done while you're under there anyway and you don't have to think about either of them for another 100,000 miles or so.
Be sure to get either Denso or NTK brand, as the rest are iffy at best and there's no sense doing the job over and over until you get a good one. You'd probably be best off replacing the post-cat sensor, too. They don't foul so quickly as the pre-cat because they're in the cleaner exhaust stream, but it gets the job done while you're under there anyway and you don't have to think about either of them for another 100,000 miles or so.