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My car has a rough idle


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Guest
Anonymous Poster
snoe2006@yahoo.com

Jun 23, 2008, 5:36 AM

Post #1 of 15 (2974 views)
post icon My car has a rough idle Sign In

I have a 97 GrandMarquis, and it is idling very rough. It does not set a code, and I don't understand what it could be, but I do know I'm not getting very good gas mileage anymore. Could it be a vaccum leak, or bad compression? Any ideas on this would be appreciated. Thanks


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 23, 2008, 11:33 AM

Post #2 of 15 (2970 views)
Re: My car has a rough idle Sign In

If the 4.6 the plug wires have a long insulated boot to reach spark plugs and are very common - expensive also. You may be able to hear which one if so. Also might be able to buy just one. Code will be set soon if not on yet and probably won't say which but will suggest trouble of some sort,

T



Guest
Anonymous Poster
snoe2006@yahoo.com

Jun 23, 2008, 3:22 PM

Post #3 of 15 (2966 views)
Re: My car has a rough idle Sign In

The thing is , I purchased a set of Motorcraft plug wires Feb. 08. You say that maybe one or more wires are bad? My code scanner does now say po302, but not setting the check engine light, so changing this wire should work? Thanks


way2old
Veteran / Moderator
way2old profile image

Jun 23, 2008, 5:19 PM

Post #4 of 15 (2965 views)
Re: My car has a rough idle Sign In

If the plug has been misfiring, I recommend replacing the plug also. Once the plug is fuel fouled, it is really hard to clean them off.



Being way2old is why I need help from younger minds


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Jun 23, 2008, 5:41 PM

Post #5 of 15 (2964 views)
Re: My car has a rough idle Sign In

Ok - "back" ...... it may not be plug or wire problem at all. I just thought of that as it was happening a lot once around here.

I don't know what this code means but no matter for a moment. A code will be set when an engine isn't running properly and if something new, still running but has been fine, a vacuum leak is a real possibility or a fouled plug from before if when wires were needed the plug was fouled. As way2old said they really don't clean up well and when in doubt new OE plugs is the way to go.

If you can, try to find out if this is randomly rough or like one cylinder misfiring. If you can feel a rythmic putt at the tail pipe it probably is one cylinder and random suggests another problem. For vacuum leaks you might not see try some carb cleaner (carefully near hot items) at suspect areas, hoses, hose connections etc., and if spray changes the idle for better or worse that's the suspect problem spot....

This still could be a host of things but fairly easy to rule some things out now,

T



way2old
Veteran / Moderator
way2old profile image

Jun 23, 2008, 5:57 PM

Post #6 of 15 (2962 views)
Re: My car has a rough idle Sign In

It is also possible an injector is the cause of your engine misfire. At least we know it is isolated to cylinder number 2. Narrows it down a lot. Also the coil could be failing. Lots of tests need to be done before throwing parts.



Being way2old is why I need help from younger minds


Guest
Anonymous Poster
snoe2006@yahoo.com

Jun 24, 2008, 4:03 AM

Post #7 of 15 (2958 views)
post icon Re: My car has a rough idle Sign In

Thanks guys for your help. Would you recommend taking it to a shop to further diagnose the problem with cylinder No.2 or just replace parts? Either way , it will probably be expensive Thanks


way2old
Veteran / Moderator
way2old profile image

Jun 24, 2008, 5:10 AM

Post #8 of 15 (2957 views)
Re: My car has a rough idle Sign In

Pull number 2 spark plug and look at it. It is the second one back on the passenger side. If it is wet, more than likely the plug, wire or coil is at fault. if it is dry, the injector is probably not opening properly. I have also seen a few of these engines roll the cam follower out of the holder and cause a miss. Just a few possibilities. A spark plug is fairly cheap and I would try installing it first to see if miss goes away. If it does, it might have just been a weak plug. Good luck.



Being way2old is why I need help from younger minds


Guest
Anonymous Poster
snoe2006@yahoo.com

Jun 24, 2008, 9:06 AM

Post #9 of 15 (2953 views)
post icon Re: My car has a rough idle Sign In

The check engine light came on, and showed PO133 oxygen sensor circuit slow response Bank1 Sensor1 .This car has 4 of them which I replaced last year, but I don't know which is which. Would you happen to know? Thanks


way2old
Veteran / Moderator
way2old profile image

Jun 24, 2008, 4:02 PM

Post #10 of 15 (2946 views)
Re: My car has a rough idle Sign In

There is a good possibility the misfire on number 2 cylinder may have caused the code for the O2 sensor. Cure the P0302 first. Erase the codes and see if the O2 sensor code returns.



Being way2old is why I need help from younger minds


Guest
Anonymous Poster
snoe2006@yahoo.com

Jun 25, 2008, 3:57 AM

Post #11 of 15 (2944 views)
post icon Re: My car has a rough idle Sign In

Thanks guys for all the help, I will let you know what happens with it.


Guest
Anonymous Poster
snoe2006@yahoo.com

Jul 4, 2008, 4:43 AM

Post #12 of 15 (2927 views)
Re: My car has a rough idle Sign In

I changed spark plugs(by the way, I changed them back in March 08) seems to help some, however idle is still rough. Is it possible that I have a bad fuel injector? and if so how do you check it? thanks again for the help


way2old
Veteran / Moderator
way2old profile image

Jul 4, 2008, 6:30 AM

Post #13 of 15 (2925 views)
Re: My car has a rough idle Sign In

There is not much of a way the average DIY'er can test the injectors. It takes too much test equipment. About all you can do is che3ck to see if there is current going to the injector and be sure the computer is pulsing the voltage. This can be accomplished with a "noid" light. Or you can move the injector to another cylinder to see if the miiss follows. Was number 2 spark plug fuel fouled? If it was, I might spring for an injector anyway. It could be leaking allowing thew cylinder to run be rich.



Being way2old is why I need help from younger minds


Guest
Anonymous Poster
snoe2006@yahoo.com

Jul 4, 2008, 7:00 AM

Post #14 of 15 (2924 views)
Re: My car has a rough idle Sign In

Thanks for the info. Also I have heard that it may have low compression. Would a compression check be in my best interest?


way2old
Veteran / Moderator
way2old profile image

Jul 4, 2008, 6:17 PM

Post #15 of 15 (2909 views)
Re: My car has a rough idle Sign In

Wouldn't hurt. That should have been the first step.



Being way2old is why I need help from younger minds






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