Idle issue after tune
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
Idle issue after tune I got my car tuned by Ed Wright earlier this month. I am not blaming him at all, because he did a good job, but I cannot get this thing to idle correctly, and it is driving me crazy.
On a cold start, it will start, idle for maybe 15 minutes, then out of nowhere, die. It will start right back up, idle for maybe 5 minutes, then die, suddenly. Occasionally it will almost die, try and catch itself, then die shortly after, but most of the time it just dies out of nowhere. So apparently it is something getting hot and just killing a signal. I had a code for Crank Pos. Sensor, replaced it, relearned it, and it didn't help.
I think my engine is is getting hotter than my temp gauge shows also. I have a 98 which is supposedly not a dummy guage. Would a bad coolant temp sensor cause these symptoms?
Don't know if this is related at all, but when I am braking after getting off the highway or something, my rpms jump around before finally stabalizing. Also, it seems to have a slight hesitation and stumble when I punch it. After the hesitation, it feels like it pulls hard, but it sputters, then goes.
Any ideas on anything is appreciated. Thanks.
On a cold start, it will start, idle for maybe 15 minutes, then out of nowhere, die. It will start right back up, idle for maybe 5 minutes, then die, suddenly. Occasionally it will almost die, try and catch itself, then die shortly after, but most of the time it just dies out of nowhere. So apparently it is something getting hot and just killing a signal. I had a code for Crank Pos. Sensor, replaced it, relearned it, and it didn't help.
I think my engine is is getting hotter than my temp gauge shows also. I have a 98 which is supposedly not a dummy guage. Would a bad coolant temp sensor cause these symptoms?
Don't know if this is related at all, but when I am braking after getting off the highway or something, my rpms jump around before finally stabalizing. Also, it seems to have a slight hesitation and stumble when I punch it. After the hesitation, it feels like it pulls hard, but it sputters, then goes.
Any ideas on anything is appreciated. Thanks.
On The Tree
Joined: Jun 2006
Posts: 129
Likes: 0
From: Macungie PA
Maybe o2 sensors. its a common problem with them fouling out on f-bodies. have had it happen twice. unplug them and drive around. I see in your sig you have an automatic. Does your torque convertor lock up when your driving?
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
Yea it locks up in OD under normal conditions. When I took it to back to Ed, he was trying to help me figure this out. He had the car ignore any fuel trim adjustements at idle from O2 sensors and it still died, so I dont think it's O2's.
Last edited by transam98989898; Apr 27, 2009 at 07:24 AM.
Just something to check, but the temp sensor/wiring could cause this if it's faulty. You may or may not notice it on the gauge if it occasionally makes a wild swing or two. Ask me how I know.
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
i ordered a new sensor because I here bad ones can cause erratic/spurratic issues, it'll be here later this week. I'll check the wiring too, they looked good for the half inch that is exposed, but I guess I can unwrap it a ways to be sure. any other ideas to check if this fails? I'm not throwing codes at all right now, and I hate just throwing sensors at problems but I am at a point that I will give anything to have this thing running properly.
it was the wiring on mine. it intermittently thought it was cold and ran really bad sometimes stalling but never throwing codes.
also check how rich/lean it idles with a wideband. it is almost impossible to get the maf accurate down low, so get it close then get the VE as close as possible while tuning in sd mode. they both must be close or the afr will not be right.
Why is a good sized cam engine idling for 15 mins? Lsa on the cam? choppy idling cams foul the plugs easy and need to be revved a little
Tuning a heads/cam car without a wideband in the pipes (not the tailpipe) is a waste of time. you'll get close but not kick ***.
also check how rich/lean it idles with a wideband. it is almost impossible to get the maf accurate down low, so get it close then get the VE as close as possible while tuning in sd mode. they both must be close or the afr will not be right.
Why is a good sized cam engine idling for 15 mins? Lsa on the cam? choppy idling cams foul the plugs easy and need to be revved a little
Tuning a heads/cam car without a wideband in the pipes (not the tailpipe) is a waste of time. you'll get close but not kick ***.
Trending Topics
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
I don't really know anything about how to tune or have any software to learn on. When I took it back to Ed, he messed with it for a while, and couldn't get it, but it did have the Crank position sensor code, so I assume he thought if I fix that, it might fix itself. He did say the IAC would open all it could to try and catch it, but it would still die.
I don't really make a habit of letting my car idle for 15 minutes, but on a cold start that's what it takes before it dies, I was just throwin it out there for info purposes. I first noticed it on my way home, stopping at a toll booth, then it died later at a stop light closer to my house. It tries to die after it is warmed up and sitting in the same spot for a minute or more.
I haven't pulled a plug to see, but I installed brand new ones before the tune, and it had this problem on the way home from the tune, so I assume that isn't the issue. I'll pull a couple anyway to see. Is this sensor a shot in the dark, or is this something that is going to have to be fixed with tuning?
I don't really make a habit of letting my car idle for 15 minutes, but on a cold start that's what it takes before it dies, I was just throwin it out there for info purposes. I first noticed it on my way home, stopping at a toll booth, then it died later at a stop light closer to my house. It tries to die after it is warmed up and sitting in the same spot for a minute or more.
I haven't pulled a plug to see, but I installed brand new ones before the tune, and it had this problem on the way home from the tune, so I assume that isn't the issue. I'll pull a couple anyway to see. Is this sensor a shot in the dark, or is this something that is going to have to be fixed with tuning?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo The Temp sensor with mine was not a shot in the dark. I could see the wiring was **** and 2-3 times just happened to catch it dropping from 200* to 80* and the engine suddenly went rich, OL, and died. That may not be the case with yours, just something to check. The wiring gets hot there at the sensor and can get f'ed up while working on it.
I have helped on more than one professionally tuned car that were way off at idle and put down good HP numbers then stalled and idled like ****. Make him get it right.
If the maf and VE aren't right down low(WITH A WIDEBAND!) then everything else you change is trying to band aid the real problem. If he says it is right, make him show you. It should be commanding stoich (14.62AFR) and actual should be close. On a cammed car it may move around 14.00-15.5 fluctuating but shouldn't go off the charts either way.
I'm not slamming him (don't know him from a hole in the ground) I just know that many people have trouble with driveability issues and look for every solution except the simple one.
I have helped on more than one professionally tuned car that were way off at idle and put down good HP numbers then stalled and idled like ****. Make him get it right.
If the maf and VE aren't right down low(WITH A WIDEBAND!) then everything else you change is trying to band aid the real problem. If he says it is right, make him show you. It should be commanding stoich (14.62AFR) and actual should be close. On a cammed car it may move around 14.00-15.5 fluctuating but shouldn't go off the charts either way.
I'm not slamming him (don't know him from a hole in the ground) I just know that many people have trouble with driveability issues and look for every solution except the simple one.
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
Update: I've been back to Ed several times and still no luck on fixing the issue. Could this be fuel pump related? The only thing is that it only does it once it is warmed up. There aren't vacuum leaks anywhere. All the grounds are good. I've replaced several sensors I thought might be the culprit. There are no codes, and it sucks trying to throw money at it to fix it. I don't have enough car knowledge to figure this out. Ed thinks for sure it is not the tune, and again I am definately not smart enough to disprove that and he sounds like a stand up guy. Anyone have any ideas? Any help is appreciated, thanks.
it is not the tune. I am sure Ed has the tune spot on. I had poor cold start idle issues with mine. Surging when warm. Found a few things. 1) Wire for IAC at ecm connector was corroded. Fixed that and it helped, but not perfect. 2) I have a blue maxx 90mm t/b and found the depth of the iac port wasnt correct. Shimmed the iac out with very small washers, put a better o-ring on it and all was good, well good after i got efi-live and got the fueling and timing right. The second tuner i took the car to found the iac stuff. But man his tune was a hack job. The first tune was terrible too. (done by a reputable sponsor here)
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
I got to looking at my iac today, and it had been cleaned not too long ago, but the washer is pretty trashed, and it looks like it has uneven/unsmooth edges. When I unplug the iac, the idle smooths out, but just gets really high. When I plug it back in, the idle lowers to normal, but then starts fluctuating RPMs like crazy. Does this sound like something is definately wrong with the IAC? If so, it would be an easy, yet oddly pricey fix, but I don't want to drop $90 if it won't help.
I also checked the fuel pressure and it held good pressure ~60 psi throughout the surging, so I assume my pump is ok.
I also checked the fuel pressure and it held good pressure ~60 psi throughout the surging, so I assume my pump is ok.
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
Yes, I have done the crankshaft position sensor relearn. That code has not been back since I replaced the sensor and did that relearn. I have no codes being thrown at all now, even during the idle fluxuations and the dieing.
The idle problem is probly caused by the PCM opening/shutting the IAC valve suddenly.I've run into this alot on 98-00 cars.Only about 10% of the cars do it for no apparent reason.
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
So have you been able to fix this through tuning, or what? If it is able to be tuned out, do you have anything I can tell Ed on where to look for something, or should I keep looking for other things wrong with my car mechanically. I replaced the IAC valve, and it did nothing. I know, I shouldn't just replace things randomly, but nobody has an answer for me, and it sucks not being able to drive my car in the nice weather. I'm getting desperate at this point.
Do you have access to a scan tool to log the car when it's having the problem ? Just to throw it out there, maybe airflow tuning problems with RAF in the upper ECT temps ?
How did the car run before it was tuned ?
Rob (Bad30th)
How did the car run before it was tuned ?
Rob (Bad30th)
try setting the tb set screw so that the engine speed is just shy of stall, the the iac should learn up if not, You need to work ur airflow and AF decay. Your tuner should be able to do this. Or log the iac steps.
Thread Starter
Staging Lane
Joined: Jan 2008
Posts: 57
Likes: 0
From: Joplin, MO
Car ran good and idled good with the old cam and ls6 intake. new cam and fast intake were installed about the same time and shortly after is when I got a tune. It wasn't idleing correctly after the swap, but I didn't care since I knew the cam and intake would throw it off with no tune. I got a tune, and it died on the way home at a toll booth. So basically, I have never had the car idling right since the cam/intake swap.
Another thing we've seen is Bad FAST intakes.Some just have serious leaks in them. A stock intake will hold 10 inches of vacuumwhen you plate up all the runners/vacuum lines. Most FAST intakes will hold no vacuum.This can affect idle situations.