Rough Idle, what to check for
Rough Idle, what to check for I changed my plugs a couple of weekends ago. The car, even with cam installed, idle smooth. Now after the weather has warmed up here (from 50's to 80's) the car is idling really rough. Almost like I have a huge cam. It is running great, does not seem to be missing while under load, etc.
It is not surging as it holds the 850 rpm at idle in D. I A-tap'd it for idle rpm, current and historical misfires for all cylinders, IAC counts and desired IAC counts. All look great. This weekend I will double check the plugs and wires.
Is there anything else I should check, (i.e. EGR in A-tap and what values should I be looking for).
TIA for the help.
- Tom
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
It is not surging as it holds the 850 rpm at idle in D. I A-tap'd it for idle rpm, current and historical misfires for all cylinders, IAC counts and desired IAC counts. All look great. This weekend I will double check the plugs and wires.
Is there anything else I should check, (i.e. EGR in A-tap and what values should I be looking for).
TIA for the help.
- Tom
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />
Re: Rough Idle, what to check for WILWAXU,
What it the best method for checking this? I ensured by intakes bolts are torqued to specs and the EGR is also. Any info would be appreciated.
Thanks,
Tom
What it the best method for checking this? I ensured by intakes bolts are torqued to specs and the EGR is also. Any info would be appreciated.
Thanks,
Tom
Teching In
Joined: Nov 2001
Posts: 37
Likes: 0
Re: Rough Idle, what to check for Actually, mine did exactly the same thing.
My guess is the ECM had adapted to the old plugs by richening the mixture. Now that the new ones have been in there a while, it "readapted" and leaned the mixture back out.
I'm just guessing, though. My idle is currently about the same as it was with the bad plugs, but my gas mileage is still up about 20%.
<small>[ April 18, 2002, 11:10 AM: Message edited by: 84ZZ4 ]</small>
My guess is the ECM had adapted to the old plugs by richening the mixture. Now that the new ones have been in there a while, it "readapted" and leaned the mixture back out.
I'm just guessing, though. My idle is currently about the same as it was with the bad plugs, but my gas mileage is still up about 20%.
<small>[ April 18, 2002, 11:10 AM: Message edited by: 84ZZ4 ]</small>
Re: Rough Idle, what to check for WILWAXU,
I had dyno tuning done 2 days afdter plug swap (Dyno Graph here )
I don't think I am running rich. It idled great for the first 2 days after the dyno tune. Then the third day it started to act up (weather also got alot warmer).
What should I check to see if I am running "Pig Rich"
Thanks for the help
- Tom
I had dyno tuning done 2 days afdter plug swap (Dyno Graph here )
I don't think I am running rich. It idled great for the first 2 days after the dyno tune. Then the third day it started to act up (weather also got alot warmer).
What should I check to see if I am running "Pig Rich"
Thanks for the help
- Tom
Re: Rough Idle, what to check for Tom, one problem I see with "dyno" tuning is that the car is optimized for WOT, but most of our cars spend a larger portion of they're life a part throttle.
If you had custom tuning done.. I'd suggest going back to them. See what they think is the problem.
If you had custom tuning done.. I'd suggest going back to them. See what they think is the problem.
Re: Rough Idle, what to check for Thing is, it idle great for two days after the dyno tuning and the part throttle is fantastic. This only started happening once the weather got warmer (from 55 - 85). My TB is drilled to 13/64 but my IAC are around 80 when in drive (car warm after 1 hr of driving). Could it be that the warmer air needs the TB drilled more? Just a thought.
Again thanks for all the help,
Tom
PS. I am going to ohm test the plus wires, what range should they be in?
<small>[ April 18, 2002, 06:43 PM: Message edited by: Tom99SS ]</small>
Again thanks for all the help,
Tom
PS. I am going to ohm test the plus wires, what range should they be in?
<small>[ April 18, 2002, 06:43 PM: Message edited by: Tom99SS ]</small>
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Re: Rough Idle, what to check for You can use WD40.. spray it around the intake.. if the idle rises.. you've found the problem.
That was another thought.. have you atap'd the car? If it's running pig rich. Might be the plugs.
That was another thought.. have you atap'd the car? If it's running pig rich. Might be the plugs.
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Re: Rough Idle, what to check for </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Tom99SS:
<strong>
...my IAC are around 80 when in drive (car warm after 1 hr of driving). Could it be that the warmer air needs the TB drilled more? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Your desired IAC in gear at a stop when the car is hot would be in the 30 - 40 range. If it is between 20 - 50, I wouldn't worry too much. If it is at 80, that's a bit too high. I'd try opening the TB blade about a 1/2 turn via the idle set screw and see if that helps. It is easier to remove than a hole in the TB blade.
<strong>
...my IAC are around 80 when in drive (car warm after 1 hr of driving). Could it be that the warmer air needs the TB drilled more? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Your desired IAC in gear at a stop when the car is hot would be in the 30 - 40 range. If it is between 20 - 50, I wouldn't worry too much. If it is at 80, that's a bit too high. I'd try opening the TB blade about a 1/2 turn via the idle set screw and see if that helps. It is easier to remove than a hole in the TB blade.
Re: Rough Idle, what to check for Thanks to all for the advice. I just got done pulling all plugs and wires. Stock wires ohm'd between 305 - 317. All the plugs looked good. Found that one of the plug wires was not on all the way at the coil (was very easy to take off compared to the others <img border="0" title="" alt="[Embarrassed]" src="gr_emb.gif" /> ). Put plugs back in and ensure the wires clicked once on the plugs and twice on the coil packs. Started car up and did idle re-learn. Idle is back to where it was with a litle shack/lope to it. I also played with the idle set screw and my IAC counts have gone down but I think I will have to play with it a little more to get them done into the 30's.
Thanks to all for the help.
- Tom
<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Thanks to all for the help.
- Tom
<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
On The Tree
Joined: Dec 2001
Posts: 100
Likes: 0
From: San Jose CA
Re: Rough Idle, what to check for </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Tom99SS:
<strong>Thing is, it idle great for two days after the dyno tuning and the part throttle is fantastic. This only started happening once the weather got warmer (from 55 - 85). ... </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I don't suppose it rained during those two days did it?
I had to have my ECM replaced (under warranty) because of water intrusion damage during a big rain storm. The ECM is located very close to a water downspout. (Duh!) It should be sealed against water, but I guess mine leaked.
However... my symptoms were different. The idle surged between 500 and 800 rpms, and only when the engine was cold. BTW, the service department said the car was not safe to drive with the bad ECM in it.
Dave
<strong>Thing is, it idle great for two days after the dyno tuning and the part throttle is fantastic. This only started happening once the weather got warmer (from 55 - 85). ... </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I don't suppose it rained during those two days did it?
I had to have my ECM replaced (under warranty) because of water intrusion damage during a big rain storm. The ECM is located very close to a water downspout. (Duh!) It should be sealed against water, but I guess mine leaked.
However... my symptoms were different. The idle surged between 500 and 800 rpms, and only when the engine was cold. BTW, the service department said the car was not safe to drive with the bad ECM in it.
Dave
TECH Apprentice
Joined: Nov 2001
Posts: 356
Likes: 0
From: Tucson, AZ
Re: Rough Idle, what to check for Hmmmm don't mean to direct attention away from the guy with the real problem, but I have an idle surge. Is this bad? Should it surge at all?
The motor hasn't really been touched - could it be an intake leak? Is this hurting performance? Help, I'm an idiot!
FYI It only seemed to do it after the converter was installed, since the converter made it looser I can almost sit at stop lights with my foot off the brake and not move but when it surges the car inches forward slowly, is this normal?
The motor hasn't really been touched - could it be an intake leak? Is this hurting performance? Help, I'm an idiot!
FYI It only seemed to do it after the converter was installed, since the converter made it looser I can almost sit at stop lights with my foot off the brake and not move but when it surges the car inches forward slowly, is this normal?
