Rough idle

[walela1]

I had a rough idle this morning when I started the car, ( '04 300A black MM, ). It smoothed out a bit while moving, but still felt a little ragged , especially on the freeway.

Yesterday I pulled the passenger side coil cover and pulled each coil off to inspect the spark plugs for tightness, as last year I had a loose plug in the second cylinder back from the front. Not finding any loose, I replaced the coil cover and buttoned every thing back up. I thought I had snapped every coil connector back on every plug, I am running the Granitelli stainless ones, but now I have doubts.

Any thoughts? I had a little ragged type running from the engine lately, when commuting, especially on the return trip,which led me to check if any loose plugs, but not this rough idle. car has 44k miles so plugs are original. using a Dennis Reinhart tune.

[CBT]

I've had a rough idle for months, replaced and cleaned lots of stuff, never could track it down and nothing turned up on the diagnostical machine. No one seems to be able to notice but me :mad:

[Blackened300a]

Try checking vacuum lines off the intake lid. I had a rough idle when one loosened up.

[walela1]

No rough idle when I left work, nor this morning. I did'nt remove the negative battery cable sunday when I before pulling the coils , so maybe there was a computer related issue that resolved itself between the drive in yesterday A.M. and P.M. drive home

There still is something at freeway speeds, such as a surge or some type of a glitch, not sure if it may be a trans mission sensor or other. I will check the vaccum lines though.

[LeoVampire]

No rough idle when I left work, nor this morning. I did'nt remove the negative battery cable sunday when I before pulling the coils , so maybe there was a computer related issue that resolved itself between the drive in yesterday A.M. and P.M. drive home

There still is something at freeway speeds, such as a surge or some type of a glitch, not sure if it may be a trans mission sensor or other. I will check the vaccum lines though.

I don't know about anyone else but I never reconect anything to a spark plug without Di-Electric Grease especialy with the super high voltage of cars coils now a day's. Electricity love's to find week spot's to jump through on it's way to a spark plug and the grease seriously helps to make a great connection to the plug and helps with conductivity as well as making it a lot easier to take wire's and coil's off of them and back on as well.

In that small area it is easy for the spark to jump to the wall's of the spark plug chamber so it is a posability that some of the spark is arching to the wall and not all of it going to the plug if the boot's are original on the coil's.

[eric jones]

Get rid of the Granatelli's! If they aren't the problem, I would bet they will be a problem sooner than later! I bought those and was not happy at all and I tell anyone here don't waste your money. Two COP's failed at approx. 15,000 mi. Went back to OEM's, which are said to be the best offering even for supercharged applications. Ofcourse, this is my opinion

[offroadkarter]

Change your plugs

If problem still persists, try returning your stock tune

[rescuerandy2]

Might be a bit early at 44K, but take a look at the throttle body for build up. Dealt with my dealer for several months till one of the techs pulled the TB and found a mess. This started at 55K and they found the problem at a 65K. Idles great now. Randy.

[Marauderjack]

I've had the "Granatelli's" for over 3 years and never had a problem!!:beer::bows: 116,000 miles on them with the blower!!:bows:

OEM's caused me mis-fires and I'd never go back to them!!:shake:

[darkvader1]

What the difference in performance from stock to granatelli? Be cause iam thinking of getting msd's dual coil packs. Answers any one?

[jdenning002]

Any follow up?????

[B.C. Bake]

:bigcry: That's what happened to me, and then the fuel pump went out. Anyway, changed it out , problem solved. But I'm not saying that's your problem but consider it "maybe"?:coolman:

[RF Overlord]

eric jones, he said he has the Granatelli coil CONNECTORS, not the COPs. There is nothing wrong with their coil connectors.

[Krytin]

I don't know about anyone else but I never reconect anything to a spark plug without Di-Electric Grease especialy with the super high voltage of cars coils now a day's. Electricity love's to find week spot's to jump through on it's way to a spark plug and the grease seriously helps to make a great connection to the plug and helps with conductivity as well as making it a lot easier to take wire's and coil's off of them and back on as well.

In that small area it is easy for the spark to jump to the wall's of the spark plug chamber so it is a posability that some of the spark is arching to the wall and not all of it going to the plug if the boot's are original on the coil's.


As stated this VERY important!

The grease is a Dielectric conductor/insulator. At very close range/point of contact it actually increases conductivity. As distance increases so does the resistance to the flow of electricity. It also seals out any moisture which could also contribute to a short.
I've been using this stuff for over thirty years now and it really does work AND is VERY important to use on the spark plug terminals.

[Marauderjack]

eric jones, he said he has the Granatelli coil CONNECTORS, not the COPs. There is nothing wrong with their coil connectors.

^^^+10^^^:bows::D