I have a 2001 Lincoln Ls 3.9 V8, I just replaced the plugs and coils and it has this rough idle when its n park. I drove it around for a few and nothing. But the time I park it, its back idling rough. I'm hoping its nothing serious being I just had the transmission rebuilt a week ago!! I was told that it could be a vacuum leak, a dirty MAF sensor or the plugs need to be checked for being gapped correctly. As always any help would be greatly appreciated, Thanks All
Mysterious rough idle??
- Thread starter Mercman76
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joegr
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You do need to check all those things, as well as checking that the COPs (Coil-On-Plug, not coil packs) are all plugged in completely.
What brands of COPs did you use?
The spark plugs all need to be carefully set to a 1.0mm gap.
Is the check engine light on?
What brands of COPs did you use?
The spark plugs all need to be carefully set to a 1.0mm gap.
Is the check engine light on?
Ummm.... The coils are individual, not packs. As you just replaced your coils the first step would be to make sure all the connectors are correctly seated. Did you hear a "snap" or "click" when you plugged in the coils?
No engine light and I replaced all 8 coils, I was also told the plug gap should be .44 so no issue there. Someone said I could have a dead cylinder which I hope not.
Ok thanks for the correction I was thinking since theres more than one I said packs.....
A dead cylinder would be obvious; ESPECIALLY under acceleration. Also, did you just fuel-up? Quality fuel or an independent?
NO she accelerates fine that I know of,....Um I got fresh gas a couple of days ago...Premium fuel all the way. This is my first LS and I want to get it right you know? I dont want to further damage anything either by driving it until I figure this out....
No it was the reason I change out everything but it seems that it didn't work, it did however have a mis-fire on cylinder #3, then #7 after just the plugs were changed, so then I replaced the coils.....It drives out fine but when it comes to a idle it misses and no engine light as of yet.....perplexed!!
Ahhhh.... A bad coil will kill a good plug and a bad plug will kill a good coil. They (coils and plugs) should (MUST) be changed as a unit.
RigsLS
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Any change in the rough idling when you unplug the connector to the MAF sensor, while it's running?
EDIT: myself I would first make sure, I was running with a fresh fuel filter and intake breather element, making sure all the clamps on the intake are tight not allowing any unmetered air into the intake after MAF.
EDIT: myself I would first make sure, I was running with a fresh fuel filter and intake breather element, making sure all the clamps on the intake are tight not allowing any unmetered air into the intake after MAF.
Ok, I will try those things tomorrow I have noticed that one of the tubes leading to the intake tube has been siliconed by the previous owner. I will unplug the MAF sensor too and see what happens. I would've just assumed a engine light would've come on.
RigsLS
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Just understand that these LS'es are real fussy with the ignition system, it's always advised to replace ALL coils & plugs at the same time, coils really should be OEM and plugs need to be gapped correctly, connectors have to click in firmly. You are going to be pulling hair out of your head if you only change a plug/coil here and there, specially with them cheaper coils.
Check all your vacuum lines carefully, have a look at the EGR and IAC valve also, check the little connectors. Fuel injectors might also be suspect.
Check all your vacuum lines carefully, have a look at the EGR and IAC valve also, check the little connectors. Fuel injectors might also be suspect.
Ok thanks, I did change them all but I guess this is a different beast than a Mercury Grand Marquis. I will however check all my vacuum lines and MAF in the morning. I just looked again and the second tube on the intake heading towards the air filter box is barely on. the previous owner attempted to glue it together and it has a gap.
Yup... The LS and Grand Marquis have nothing in common; other than they are both automobiles.
ANY un-metered air will cause idling issues. Make sure the intake run is sealed tightly from the airbox to the throttle body.
joegr
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You were told wrong. 0.044" is not equal to 1.0mm, and is outside of spec. 1.0mm = 0.039". The spec allows for the plug gap to wear to up to 0.043" at the end of its 100K life. Using a gap of 0.044" will result in shortened COP life!
RigsLS
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Merc, any update on this rough idle of yours, did you go back over the coils and plugs, like Joe said, ensuring they are gapped correctly, as well did you get a chance to go over everything we listed. Still an issue for you ? I hate rough idles'.
Blueberryyum02
Well-Known LVC Member
Joegr if you are not the holy grail of the ls you should be I just replaced all eight of my spark plugs because the gaps where set to 0.044 was reading on the forum and seen that it was suppose to be 0.039 went bought new plugs regal to correct specs and wow what difference in gas mileage.
no not yet Im gonna dig into it in the morning....Im hoping between the loose tube connect and maybe the wrong plug gap it'll be fixed...