idle surge issue
Thread Starter
Launching!
Joined: Mar 2008
Posts: 214
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From: West Chester PA
idle surge issue Can someone help me mods as below. Idle surges sometimes not all the time 2 or 300 rpms. And sometimes it will do it in drive but not neutral or park or vise versa. Also, it has been doing it since before I got my ls6 intake put on, and has continued to do it after. Mods are below in the sig. Ive cleaned everything Mass air, changed fliter, fuel filter.Also, I sprayed carb cleaner around intake and hoses to see if it changed the idle it did not. It's really starting to bother me Id appreciate some help from someone? thanks guys I thought it might be a intake leak but the chances it is on both intakes is slim I think.. any other ideas appreciated
Did you check and clean your IAC valve. It is a pintle and seat, if there is a build up it could cause the pintle not to seal which would allow additional air in the inlet , which would cause the rpms to go up. Jyst a suggestion of a possible cause. Hope this helps.
Thread Starter
Launching!
Joined: Mar 2008
Posts: 214
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From: West Chester PA
yes, i cleaned it last night after i posted on here it was pretty covered with carbon. It is still doing it the surging after the cleaning . Im wondering if the mass air is bad being it is the slp, or if there is more carbon in the holes of the IAC.. Any other suggestions
does your iac have a o-ring on it? also being your car is a 1998 the pcv system is probably dryrotted. i would pull all that **** out and inspect it very thoroughly. a hole in on eof those hoses would cause a idle surge.
Thread Starter
Launching!
Joined: Mar 2008
Posts: 214
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From: West Chester PA
I was thinking the SLP mass air since it was descreened, how can i tell if the mass air sensor is bad? . As far as the pcv system I went through the whole system about 3 months ago when I realized the hose on the valve cover was unhooked and replaced some of the piping. Maybe i should look through it again to make sure its all sealed up properly
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Thread Starter
Launching!
Joined: Mar 2008
Posts: 214
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From: West Chester PA
I am thinking more could it be the MAF is descreened and the car now has the ls6 intake but no tune? Would the tune cause this because i've now went over the whole intake area and could not find an issue. the iac is working properly took it out and tested it.
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Verdad Gallardo Thread Starter
Launching!
Joined: Mar 2008
Posts: 214
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From: West Chester PA
Ok got an update the car starts surging while its heating up. So i pulled the IAC plug and the idle smoothed right out and didnt surge anymore. I switched with a old one I had sitting that one did the same thing??? are they both bad or why would it do that. I always that once it was unpluged it should start surging not when its plugged in??
No you shouldnt "need" a tune to correct the problem.
I would just try capping the Pcv valve connection to the throttle body.
Not sure why it would get better with unplugging the sensor unless the sensor itself was at fault.
The slp maf is a truck maf with a resistor on it. I had one on a 98 Trans am and it ran fine.
I would just try capping the Pcv valve connection to the throttle body.
Not sure why it would get better with unplugging the sensor unless the sensor itself was at fault.
The slp maf is a truck maf with a resistor on it. I had one on a 98 Trans am and it ran fine.
hmmm any engine codes? i had the same thing with my Ls6 intake but turned out to be my O2 sensors..id suggest you place the IAC sensor and replace both your O2s and see if it still does it...i dont think its a vacuum leak tho..
TECH Fanatic
Joined: Jun 2007
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From: Westminster, MD
It's something in the PCV system, most likely.
I had a very similar (near identical) problem with my 2002 Taurus. Basically while in D at idle the rpm's would surge and drop repeatedly and almost stall the car. Battery light would come on occasionally. I noticed that it did this when the A/C or max A/C was on, the defroster was on, or floor vents were on the vent controls set to them. It wouldn't do it if the vent control was sent to off and I don't think it did it for the dash vents. I drove it for a year while trying to figure it out. Cleaned the IAC valve, TB, new battery, checked out the alternator, etc.
I took it to my mechanic and he eventually found it. When those vent settings were on there was a problem in the PVC system that was hard to spot. (At least in my Taurus) there was a extended rubber elbow and under vacuum (thats the easiest way to describe it) the elbow would contract and basically close because it was old and had lost its structural strength.
New rubber PVC elbow = no more surging problems. Not a guarantee for you but its definitely worth a shot.
I had a very similar (near identical) problem with my 2002 Taurus. Basically while in D at idle the rpm's would surge and drop repeatedly and almost stall the car. Battery light would come on occasionally. I noticed that it did this when the A/C or max A/C was on, the defroster was on, or floor vents were on the vent controls set to them. It wouldn't do it if the vent control was sent to off and I don't think it did it for the dash vents. I drove it for a year while trying to figure it out. Cleaned the IAC valve, TB, new battery, checked out the alternator, etc.
I took it to my mechanic and he eventually found it. When those vent settings were on there was a problem in the PVC system that was hard to spot. (At least in my Taurus) there was a extended rubber elbow and under vacuum (thats the easiest way to describe it) the elbow would contract and basically close because it was old and had lost its structural strength.
New rubber PVC elbow = no more surging problems. Not a guarantee for you but its definitely worth a shot.
Thread Starter
Launching!
Joined: Mar 2008
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From: West Chester PA
Im gonna try capping the pcv system. See if that helps then and change the O2 sensors and give it a tune up. I have them sitting here just havent gotten around to doing it. Btw i did switch to a stock MAF and that didnt help at all. Im not sure why the IAC being unpluged makes a difference and teh idle stays calm. There is the rubber o-ring maybe thats not seating right as well?
Thread Starter
Launching!
Joined: Mar 2008
Posts: 214
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From: West Chester PA
Update: I capped the pcv system and no difference so its definitely not that. I am going to do the O2 sensors today. The IAC valve I had 2 sitting here as well and swapped them in no luck either, but it does all stop when I unplug them.
Joined: Nov 2001
Posts: 34,651
Likes: 2,577
From: Schiller Park, ILL Member: #317
I had a similar issue once, except that I could clear the condition by turning the engine off and then right back on. Not sure if that works for your problem as well.
I tried all the same stuff that you have, all to no avail. Through the process of elemination, I eventually worked my way to the EVAP system and replaced the purge solenoid. Never once did it trip an EVAP DTC of any kind, but replacing that solenoid fixed the problem anyway.
Here is a link to a thread I wrote about it a few years ago, as I was narrowing the issue down:
https://ls1tech.com/forums/general-m...rt-needed.html
I tried all the same stuff that you have, all to no avail. Through the process of elemination, I eventually worked my way to the EVAP system and replaced the purge solenoid. Never once did it trip an EVAP DTC of any kind, but replacing that solenoid fixed the problem anyway.
Here is a link to a thread I wrote about it a few years ago, as I was narrowing the issue down:
https://ls1tech.com/forums/general-m...rt-needed.html
Can someone help me mods as below. Idle surges sometimes not all the time 2 or 300 rpms. And sometimes it will do it in drive but not neutral or park or vise versa. Also, it has been doing it since before I got my ls6 intake put on, and has continued to do it after. Mods are below in the sig. Ive cleaned everything Mass air, changed fliter, fuel filter.Also, I sprayed carb cleaner around intake and hoses to see if it changed the idle it did not. It's really starting to bother me Id appreciate some help from someone? thanks guys I thought it might be a intake leak but the chances it is on both intakes is slim I think.. any other ideas appreciated
TECH Enthusiast
Joined: Sep 2005
Posts: 503
Likes: 54
From: TX
Run the engine till its at operating temp, if the idle is too low, turn the screw on the throttle body on which the blade mechanism rests. Adjust untill you are happy with the idle speed. Now turn the key off, unplug the throttle pos sensor, turn the key on engine off for a few seconds. Turn it back off, plug the tps back in. Restart the engine, thats how i fixed my surging issue on my cammed TA.
Joined: Nov 2001
Posts: 34,651
Likes: 2,577
From: Schiller Park, ILL Member: #317
Run the engine till its at operating temp, if the idle is too low, turn the screw on the throttle body on which the blade mechanism rests. Adjust untill you are happy with the idle speed. Now turn the key off, unplug the throttle pos sensor, turn the key on engine off for a few seconds. Turn it back off, plug the tps back in. Restart the engine, thats how i fixed my surging issue on my cammed TA.
Opening the TB blade further would only be a cover up, reducing the effectiveness of the IAC (and thus PCM controlled idle conditions), and would likely introduce other issues on a stock engine (such as idle hang and cruise control effect).
I am having the same problem, except along with the RPM drop, which is about 100-200 rpms, my voltage will drop around 2-3 volts, and it seems like the car is about to stall. Along with the drop, there is this motor sounding noise, and it "whizzes"/"whines"/"buzzes", its weird. However, this has only been happening the past month, as far as the rpm drop, but i have heard the noise before this problem. On a side note, I've replaced alot of external engine parts: fuel pump and filter, got the escalade alternator and optima battery, changed all the pcv hoses and valve, changed the spark plug and wires (NGK laser iridium), cleaned MAF sensor, new air filter, seafoamed fuel lines... since the noise sounds motorized, im thinking its the EGR valve... i need to figure this out too.