Rough idle

[Likecars]

Well, prior to shelling out 200.00 for my deduct thought I'd try here first (really second).

Car was running fine two weeks ago, thought it may be rebelling this week for making it sit by giving me a rough idle.

Been hoping it would work itself out, but no luck.

Here's what I have (2000 w/29,000, 6sp) rough idle after about 15-20 seconds of sitting. Not a I want to stall just a steady: smooth smooth rough smooth smooth rough type of idle. It has not quit or acted like it wants to. It accels fine out of first as if there is no problem. I purposely put it in 6th going slow to see if it would bog down, does not like that, begins to buck pretty good. 5th will do the same if in the low 30's (mph). A low 1 to 4th, ~20-25, will yield the same result.

I'm thinking fuel/air mixture, but do not know what to check. Will put some injector cleaner in for the heck of it. I have changed nothing and have pushed and prodded every visible plug and wire to see if that would help.

Oddly, I have also noticed the circulate / recirculate light jumping to the circulate on it's own, related????

Thoughts? I have not pulled up codes, will figure out how and post anything relevant. (only codes: BO - RFAU1016 Loss of Communication with PCM
U1064 Loss of Communication with BCM
U1096 Loss of Communication with IPC )


Tx.

 

[atmmac]

I think that the C5's normally idle rough. My hsifter moves a little bit when im idling never thought much of it.

 

[Mr. Lucky]

I think that the C5's normally idle rough.

:confused
A stock C5 should idle smooth as silk.

Likecars, since you have checked the obvious (codes, connectors) with no luck, I would suspect a bad plug or plug wire. You should also carefully check the clamp connections on both sides of the air bridge, though I would expect a "lean" code if you had an air leak there.

GL!

 

[Likecars]

Gents, appreciate the input.

I guess I have been fortunate because my idle has always been smooth, at least enough that I noticed this problem.

Bob, yesterday I put in a bottle of Valvoline Fuel Inj cleaner and it made a noticeable difference, thought it fixed the problem, however it still would miss if I try to accelerate in 5th or 6th.

While wiping down the engine last night I double checked the plugs and found the plug wire closest to the fire wall, pass. side, was not seated. I pulled it off and found corrosion in the wire! If this wasn't the problem it could not have been helping performance. I cleaned it out, and the portion going into the block. Question: Can you leave WD-40 on the plug wire? I spot checked the other wires to see if they had a similar problem. Look forward to driving it today. I feel like I have been letting by baby walk around with a thorn in her paw.

Thanks for your time, thought I'd get a few more nibbles. Maybe folks are out enjoying summer. On another note I had to leave CA for a few years, have been counting the days until I can get back: 1046 to go.

 

[Mr. Lucky]

Question: Can you leave WD-40 on the plug wire?

Yep, it's primarily a moisture displacer. If you really feel the need to wipe it off, spray some tire dressing on your rag first to give them that "new" look. Enjoy!

 

[99WhiteC5Coupe]

Well, prior to shelling out 200.00 for my deduct thought I'd try here first (really second).

Car was running fine two weeks ago, thought it may be rebelling this week for making it sit by giving me a rough idle.

Been hoping it would work itself out, but no luck.

Here's what I have (2000 w/29,000, 6sp) rough idle after about 15-20 seconds of sitting. Not a I want to stall just a steady: smooth smooth rough smooth smooth rough type of idle. It has not quit or acted like it wants to. It accels fine out of first as if there is no problem. I purposely put it in 6th going slow to see if it would bog down, does not like that, begins to buck pretty good. 5th will do the same if in the low 30's (mph). A low 1 to 4th, ~20-25, will yield the same result.

I'm thinking fuel/air mixture, but do not know what to check. Will put some injector cleaner in for the heck of it. I have changed nothing and have pushed and prodded every visible plug and wire to see if that would help.

Oddly, I have also noticed the circulate / recirculate light jumping to the circulate on it's own, related????

Thoughts? I have not pulled up codes, will figure out how and post anything relevant. (only codes: BO - RFAU1016 Loss of Communication with PCM
U1064 Loss of Communication with BCM
U1096 Loss of Communication with IPC )


Tx.

I changed the original Delco plugs in my 1999 C5 coupe (A4) at 30,000 miles and replaced them with Delco plugs.

Although the plugs are rated at 100,000 miles, the idle was MUCH smoother when I replaced the plugs. The original plugs all looked the same, just slightly discolored.

Try replacing your sparkplugs. Good luck.

 

[DRTH VTR]

(only codes: BO - RFAU1016 Loss of Communication with PCM
U1064 Loss of Communication with BCM
U1096 Loss of Communication with IPC )


Tx.

This looks like it needs some diagnosis to me. Are these history (do they clear)?