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Intermittent miss when cold outside
 
 
Radioman 66 Radioman 66 is offline
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09-12-2006, 12:04 AM
 
I'm new to jeeps so bare with me.
When the temp. is near freezing my YJ 4 cyl starts fine and runs OK for about 15 minutes. After that It backfires through the intake and will not run under load unless I downshift and really bring the RPMs up. It idles and revs fine until I let the clutch out. After about 5 minutes and a few good back fires it clears.
No codes coming from the eng. light.
It also smells of gas all the time. Any suggestions on were to start?
 
 
 
 
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09-12-2006, 12:35 AM
 
it's fuel injected.
 
 
 
 
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09-12-2006, 12:55 AM
 
Could be many things- are you throwing any codes? Sounds like a possible throttle positioning sensor or oxygen sensor- at least that's where I'd start... sounds like something is causing it to run rich.
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09-12-2006, 01:37 PM
 
I am not getting any codes using the check eng. light way. I don't have a reader.
It's backfiring through the air cleaner not the exhaust. This makes me think it is a timing issue.
 
 
 
 
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09-12-2006, 02:37 PM
 
That's possible too. Have you hooked up a timing light to it? It could be many things- fuel delivery and spark timing are pretty open categories. The first thing I'd do now is hook it up to a timing light and re-time it. If it doesn't go away, or is right from the beginning, its definentely a fuel/throttle issue. If it does- than you've isolated it to timing- so it could be your dist. cap/rotor or possibly that your timing chain is slipping. I wish it were easier than trial and error- but without any codes showing up its tough...
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09-12-2006, 04:09 PM
 
Quote:
Originally posted by Radioman 66:
It also smells of gas all the time. Any suggestions on were to start?
Flooded.

Quote:
Originally posted by Radioman 66:
it's fuel injected.
Never mind.
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09-12-2006, 10:01 PM
 
i agree with the timing issue although that distributor cannot be timed by turning it while it's still mounted in the block. fault plugs, wires, cap and or rotor would be my guess. faulty plugs which do not fire properly can give you a rich mixture as well. have you done a tune lately? what year is the jeep? if it's a 91-95 yj, you could have leaking injectors as well dumping too much fuel into your cylinders. i doubt it's the timing chain. also look really good at your vacuum lines for wear and tear.
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09-12-2006, 10:51 PM
 
I'm trying to resolve this before it gets cold again. Its a 93 that was in poor shape when I got it. I only drive it in the fall and winter for hunting. A major tune-up was the first thing I did when this first started last winter. It acts up like clockwork and goes away in about the same time frame.
Would the crank pos. sensor cause this?

The fuel smell is when you walk by the back of it, even when it is sitting. The tank is pressurized when i take the cap off.
 
 
 
 
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09-13-2006, 12:40 AM
 
could very well be, but i had to eliminate the obvious first. you can sort of test the CPS by pulling it out of the bel housing and wave a piece of metal near it slowly. if there is no draw to the CPS, then i'd replace it. if there is some draw, then check to see how it connects to the harness. on my 90 yj, it was hard wired in (no quick connect fitting) and when i had to replace it a while back because of no start, i had to cut and splice the wires together. after a while, the wires became loose and it started doing something very similar to yours but it was consistent. eventually the wires disconnected and i had to tow it home. check that connection and make sure you're getting a voltage reading.
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09-14-2006, 01:17 PM
 
I'll take a look at it. This weekend I am going to take a can of freeze mist to all the sensors one at a time to see if i can get it to act up.
This sure is a pain when I can't make it act up or stay broken.
 
 
 
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