98 contour 2.5l dohc misfire/rough idle

im new to this thread, however, i've pretty much read almost all of the contour threads on the problems these cars have. timing chain, vacuum leak, etc. Here's my problem/s.

I bought this car 2 1/2 weeks ago. ran good, no check engine light, nothing. then I started it up one day, and it ran the rpm's up to 2500 and back down to 300. If it doesn't die, then it goes back up and down several times until its warmed up. It still does it every day. Once it's warmed up it idles where it's supposed to, around 900 -1100 rpm somewhere in there, however it's still rough. I just replaced the plugs and wires, being that's the cheapest test. No change. Does the same thing. The only other problem, that I know of is that there's a small oil leak on the back valve cover. I check the oil everyday, and it isn't even 1/2 qt low in 2 1/2 weeks. Don't think that it's related to this problem. My guess is a coil pack??? or a maf sensor??? just looking for the best direction to go, without spending big $$$$ fixing this annoyance. Thanks in advance. O, I got the check engine light flashing, and the codes when read were, misfire on 1, and 3. car running to lean/rich, and o2 sensor upstream.

Check the PCV valve and vacuum line going into the intake plenum. Sometimes the elbow develops a crack in it. Replace the PCV valve since it's only a couple bucks.

im new to this thread, however, i've pretty much read almost all of the contour threads on the problems these cars have. timing chain, vacuum leak, etc. Here's my problem/s.

I bought this car 2 1/2 weeks ago. ran good, no check engine light, nothing. then I started it up one day, and it ran the rpm's up to 2500 and back down to 300. If it doesn't die, then it goes back up and down several times until its warmed up. It still does it every day. Once it's warmed up it idles where it's supposed to, around 900 -1100 rpm somewhere in there, however it's still rough. I just replaced the plugs and wires, being that's the cheapest test. No change. Does the same thing. The only other problem, that I know of is that there's a small oil leak on the back valve cover. I check the oil everyday, and it isn't even 1/2 qt low in 2 1/2 weeks. Don't think that it's related to this problem. My guess is a coil pack??? or a maf sensor??? just looking for the best direction to go, without spending big $$$$ fixing this annoyance. Thanks in advance. O, I got the check engine light flashing, and the codes when read were, misfire on 1, and 3. car running to lean/rich, and o2 sensor upstream.

V6's do not have problems with timing chains, so that eliminates that possibility. Youre probably thinking of the timing belt on the I4.

This problem however, is probably covered in the contour.org FAQs.

Engine idles high.
http://contour.org/FAQ/FAQ.php?s=probs&displayid=7

Thanks guys, I will go ahead and try all that stuff tonight. I'll let you know how it works out. O and appriciate letting me know the whole timing chain thing. I am mechanically savvy, however, not good enough to do a complete rebuild. Thanks.

Yeah bud, O2 sensor should do ti. If that fails then your MAF sensor. Allthough you didin't post a bad PCV in the codes.

Yeah bud, O2 sensor should do ti. If that fails then your MAF sensor. Allthough you didin't post a bad PCV in the codes.

No way an 02 sensor would cause irratic idle.

I think most people think that if it throws a lean or rich code, that they think there O2 sensor is faulty, when in reality, its working perfectly and telling you exactly whats going on. If your O2 sensor is faulty, it will give a code like P0140: "Downstream Heated Oxygen Sensor circuit Faulty - Bank No. 1."

I would say, with an irratic idle, your more than likely running lean. Unmetered air is bypassing the MAF and causing your RPM's to shoot up. Could be IAC like I said. If your intake manifold gaskets are original, I would check those next. Those deteriorate pretty bad due to high engine temps and old age.

Btw, was it running lean or rich? It can't be both at the same time. Do you have the codes handy?

Ditto, codes would really help. You're right, I was thinking about the downstream one. Does the IAC throw a code?


Basically, you are having a problem with air, thats all these units do.

sounds like the throddle positioning sensor to me. I had that problem on my ford explorer.

Sounds like what my car had about a year ago. I had a thread posted and it was the Idle Air Control valve (IAC) Try this before anything else. Does it make a humm noise at all?

im new to this thread, however, i've pretty much read almost all of the contour threads on the problems these cars have. timing chain, vacuum leak, etc. Here's my problem/s.

I bought this car 2 1/2 weeks ago. ran good, no check engine light, nothing. then I started it up one day, and it ran the rpm's up to 2500 and back down to 300. If it doesn't die, then it goes back up and down several times until its warmed up. It still does it every day. Once it's warmed up it idles where it's supposed to, around 900 -1100 rpm somewhere in there, however it's still rough. I just replaced the plugs and wires, being that's the cheapest test. No change. Does the same thing. The only other problem, that I know of is that there's a small oil leak on the back valve cover. I check the oil everyday, and it isn't even 1/2 qt low in 2 1/2 weeks. Don't think that it's related to this problem. My guess is a coil pack??? or a maf sensor??? just looking for the best direction to go, without spending big $$$$ fixing this annoyance. Thanks in advance. O, I got the check engine light flashing, and the codes when read were, misfire on 1, and 3. car running to lean/rich, and o2 sensor upstream.


Had a similar issue a month ago. Turned out to be intake manifold gasket(s). Upper was leaking, but did the lower one while i was in there.

Had a similar issue a month ago. Turned out to be intake manifold gasket(s). Upper was leaking, but did the lower one while i was in there.

Like I said in my earlier post. ;) Intake manifold gaskets.

Had the same issue. First i replaced the upper intake manifold. This did not fix the problem.

The problem was the gaskets around the spark plugs on the valve covers. Got oil on the spark plugs and caused a misfire.