A little cough during Idle

[gammer_ghn]

The car runs great and it has no misses. It started coughing 2 days ago during idle in gear "D" while im stopped it coughs once every 40 seconds and the car runs fine other than that. When the car is not in gear you see the RPM moving very little like someone is revving it by 50rpm and letting go. No codes appear and i have no idea what it is. Does any one know of this? Im thinking electrical but i can use some new knowledge!

Thanks!

[oldmako]

My car will complain about lousy gas in a similar manner. Just a slight bump every few minutes. I only notice it at idle. One tank of good gas later and it usually goes away. Have you recently fueled with questionable gas?

Might as well eliminate the easy one first. Try some ISOheet while you're at it.

[maxnix]

Without a maintenance history, Iso heet and BG44K are recommended.

Scan with OBD II scanner for a cylinder misfire code.

[gammer_ghn]

The thing is i use Bg44k and all the electronic connections have been cleaned and protected but as far as iso heet i have no access to it and my car has not seen any lower octane than 91. The scanner didn't find a miss. I just don't want to go to my garage guy because he will put a few extra things on top of whats wrong and try to charge me for it. This only happens during idle...

is this it?http://cgi.ebay.com/Iso-Heet-F...l1247

[maxnix]

Yes, Should be at any O'Reilly's.

Try 2 intially, then at least one every other tank full if you have ethanol in your gas.

Without codes, it is impossible to diagnose a bad coilpack, let alone which one. Also, a not perfect intake path had an effect with mine identical to your symptoms, but less frequently, after I replaced the defective coilpack. Cleaning the plenum, loser runners, IAC adn EGR valves, TB and the EGR tube in the plenum scrupulously elimanted all hints for the next 4K miles.
Modified by maxnix at 11:04 AM 12/12/2008

[gammer_ghn]

Thanks Brian! But nothing i mean nothing showed on on the Scanner that's why i came running like a sissy to Nico haha! thanks alot!

[Q45tech]

Every year the refiners learn to make a gallon of gasoline from less and less oil................our current thin watery weak product really should not be called gasoline........................but cheap fuel that kinda works in most situations..............except outboards and weed whackers and some Q.

[Mopar]

Whats happening Gammer? Hope you doing good.

My car did the same thing, because I let my mom borrow it for once and she put 87 in it. I got misfires and shakes like crazy. Had to change all the coil packs and spark plugs and the car went to like new condition. Might want to check the coil packs if you have spare time on your hands.

[infinitinut2]

Brought the Q Ship across country, last week (She Who Must Be Obeyed) was following me in it. I noticed a wee bit of stumble at idle, but wife said car performed wonderfully on the road (2000+ miles of it!). Anyway, I bought a couple of bottles of Techron, and was able to get 93 octane Chevron and Shell after getting east of San Antonio (we deal with 91 ????octane in the Rockies). Anyway, the combination of these two things eliminated any problem and, upon getting back to east coast (ughhhhh!), I took Q for a spin and, the love affair continues!

[gammer_ghn]

Whats happening Gammer? Hope you doing good.

My car did the same thing, because I let my mom borrow it for once and she put 87 in it. I got misfires and shakes like crazy. Had to change all the coil packs and spark plugs and the car went to like new condition. Might want to check the coil packs if you have spare time on your hands.

I have been great ma man hope things are well with you too! I saw you speeding couple days ago and a couple of my friends complain about you going too fast by GCC haha!

As for the car the iso heet didn't help... Yet i drove 340 miles today and the car still has the cough. Im going to change the fuel filter tomorrow and see what happens. If that doesn't work sounds like i need to check my coil packs and dish out couple hundred after driving 70k miles in 2 years which means that this is the only car in my history of owning and killing 6 cars that has actually withstood my driving without needing major repairs all the time. I love this car but i will be upgrading soon because of its crash rating but this time ill get the 06 F50 or just wait for the new one to come out. Meanwhile the new camaro looks hot to me as a toy! DD will always be a Q or a flagship Infiniti!