198firebird

iTrader: (1)

Hi, new to the fourm as you can see my first time posting but ive been reading it for a while. Got a 98 solar gold trans am (a4) (all stock) probably 3-4 months ago and its been great/ lots of fun until recently its been having some idle problems.
Issues: the idle runs is about 900rpm-1100rpm in drive/reverse and 1000rpm-1200rpm in neutral/park, its throwing a p0507 code (idle to high) and thats the only code. When i'm in drive and stop at a stop sign or light the car will take a second or two and starts dropping to around 800rpm and then starts bouncing between 800rpm-900rpm, if i put it in neutral the car reves up to about 1500rpm then comes back down and starts bouncing between 1000rpm-1100rpm. This all happens once the car gets to regular operating temperature.
What I've tried: replaced the IAC, replaced the MAF, replaced pcv valve, took the intake off and replaced the intake gaskets, replaced TB gasket, sealed around the map sensor in the back with a gasket sealer, performed a smoke test, used propane to find any vaccume leaks, looked at PCM connections, cleaned tb.
-From what ive found on this fourm most people say a vaccum leak or MAF and i'm pretty sure its not either of those. The person who had the car behind us had a ported MAF and TB, can tell he did it him self, so we are thinking maybe we need to replace the TB (maybe he tried to tune it or maybe went bad) or replace the PCM (again maybe he tried to tune it or just went bad) Anybody any ideas???

greatskiiiier

iTrader: (10)

im having a simular problem with my m6 i thought it was the iac but dont want to spend $100 on one so i guess ill never find out

youve done everything i was going to say, maybe you need a tune?

THE SHOP

You prolly have a vacumm leak or IAC issue do you have any codes?

RPM WS6

iTrader: (3)

Can you get the issue to clear up with a restart of the engine, or is it always there?

This is similar to a problem I'm having, except that mine doesn't hang quite high enough to set the P0507. Here is my thread on the issue, for your review: https://ls1tech.com/forums/general-m...rt-needed.html

I've been through many of the same tests as you, and replaced many of the same parts. At this point, I am convinced that mine is either due to the EVAP purge solenoid or the EGR valve. I replaced the purge solenoid first because it's a fraction of the cost. If my issue comes back, EGR will be next. There is NO where else that an intermittent vac leak could be occuring that can be cleared with a restart.

But, with yours you have not specified if the condition is always present or if it's intermittent. Also, you have a modified TB, which also means there's a chance that for some reason the idle set screw may have been adjusted resulting in idle weirdness. My first suggestion would be to use a scanner to verify certain data fields, like IAC counts (during the issue), LTFT & STFT, TPS voltage, and throttle position angle. This will help to clear up any possibility of a TPS/idle screw adjustment issue.

EDIT: Another thing to check, since your TB was messed with; make sure that the hole in the throttle blade has not been enlarged. Stock hole diameter is 5/32".

198firebird

iTrader: (1)

Don't think i should need a tune, the car is completely stock, except for the ported throttle body, unless for some weird reason the previous owner had it tuned?

code: p0507, Put in a brand new IAC and still doing it, I guess its always possible to have a vacuum leak but we've checked everything, put new intake gaskets on it, used propane to go over everything, performed a smoke test, not sure what else to check?
The condition is always present as long as the car is warmed up, just seems like the idle does not want to come down that much when it warms up and then it starts surging, checked the hole in the throttle body and it has not been enlarged, and the thing is this problem just occured one day it used to run fine and withough ever touching the tb it started to act up so im starting to lean away from that. My dad works at a (former pontiac) Buick GMC dealer and has taken it in for them to check it out when they have spare time. Originally we were told they performed all the scans and everything seemed to be normal except it was running lean, they then told us to replace the intake gaskets, i don't have any of the numbers except that they told my dad they seemed to be good, I think hes going to take it back tommorrow and see if they can play with it some?
Also it seems after doing everything i meantioned orignaly it seems alittle better yet is not fixed, the surging happens maybe every 2 seconds instead of originaly every 1 second and the idle is alittle lower then when this started, seems weird that some of the stuff we have done, helped the car but did not fix it?

LS1WS6dreamer

iTrader: (1)

Wow! I am having the same issue. Wonder if this guy ever got this fixed and what he had to do. Thing is with mine is I can unplug the IACV and the idle quits "searching"/rising. Got the p0507 code as well. **** is getting freakin annoying.

jim ravencraft

Hi, i had same codes and issues repaced tps/iac/vacuum lines/pvc and then checked most obvious things last. Throttle bump stop and size of hole in throttle blade. Had it tuned and everything works great with no codes. I also added a light spring to help throttle bottom out. Good luck and keep after the problem until you overcome the issue. Have a blessed day........
Jim

mike171562

iTrader: (4)

Back from the dead thread

did you ever get this fixed? My problem is similar to ls1ws6dreamer, but im getting an intermittent code for idle too low. Unplug the IAC when it is partway out and it runs fine

LS1Z28

iTrader: (18)

A P0507 DTC trouble code may be caused by one or more of the following:

A vacuum leak
Leaking air intake after the throttle body
EGR valve leaking vacuum
A faulty positive crankcase ventilation (PCV) valve
Damaged/failed/dirty throttle body
Failed EVAP system
Failed IAC (idle air controller) or faulty IAC circuit

BYBYCOP

I don't believe this thread will EVER DIE, not as long as this VERY ANNOYING and potentially EXPENSIVE problem continues to exist! I need to find a REAL fix, before it does become expensive and I resort to the infamous "throwing money at the problem" solution! I was wondering if ANYONE who has had an issue with a high idle,(1050 RPMs to 1250 RPM's), accompanied with the, ever so lovely, P0507 code, AND HAS ACTUALLY FIXED the issue, could list his/her solution that ended this FRUSTRATING problem! There are plenty of wonderful solutions to diagnose the problem already listed in this post. I would love to know EXACTLY what fixed the problem for each individual. I was also wondering if my SLP mass airflow sensor could be the culprit and Yes, I've already tried the ideas/possible solutions listed on this post. The EXACT solution would be GREATLY appreciated! I'm hoping to find that this problem is being corrected by one particular solution more times than the other ones. This will allow me to focus and give more attention to that solution first! My car has been idling this high for about 2 years and I just can't take it anymore!:judge Thanks!

whiteNrude01

iTrader: (8)

I bought a PP TB froma sponsor on here...my car was doing same crap...unless i u
plugged IAC cable..then it would idle decent enough...to drive it.....I was tols by so called sponsir..it couldnt be his TB hes NEVER had a complaint..lol....so i sent my TB to John Potz from ebay..he sent me a free loaner..and found over 9 serious problems with the throttle body..he sent me one of his PP TB..and took the other as a core..even though it was junk and only good thing about it was the powder coatin job...NEEDLESS TO SAY...i installed the new one and whola all problems fixed...i reset the TPS and all codes gone...idle was normal...and acceleration was awesone...so yea..im thinking your TB hole..plate..IAC slot..anyhing could be messed up by the porter of the TB

MIDNITE Z

iTrader: (1)

I'm having the same issue any solution

wsierra1993

iTrader: (2)

Bump. Any solution?

fountjr

Im having the same issue. Any resolution that can be posted would be helpful! Thanks

LS2 6.0L (stock) swap into 1967 Camaro
T56 - 6 speed

LS1121

iTrader: (17)

I had a similar issue and thought the IAC was bad so I bought one on ebay and still had the issue. I broke down and spent the money for a GM IAC and now the car runs normal. Moral of the story...do not buy cheap ebay electrical parts for my car.

johngrn

did you get a fix on the ls1 high idle problem ??

Airbrush dude

Same problem, 98 formula completely stock except for headers, egr and air pump delete.
New IAC, TPS. Two cans of brake clean later no vacuum leaks. If I unplug the IAC it idle perfect
but crappy throttle response. Is everyone bored to tears talkin about this?

wannafbody

iTrader: (2)

Mine was acting up slightly one night. I pulled the IAC and cleaned the passage and the IAC with CRC electronic cleaner. Seems to be fine now.

Airbrush dude

New details. I fired this up the other day, blocked the wheels, set the brake, put the thing in drive.
It idled perfect for almost fourty minutes. Put it in park, same for another ten minutes.
So now I get in the car put in in gear and start idling down the driveway. About 20 feet later the thing
kicks up to about 1200-1500, I let it keep going to see what would happen. Well we got into 2nd goin about 35mph.
Stopped at the end of the driveway and it kicked down but was surging between about 6 and 900 rpm.
Does anyone know if there is some connection between idle and maybe wheel sensors? I'm about ready
to burn this thing to the ground. HEEEELP!

RPM WS6

iTrader: (3)

Have you looked at IAC counts at all when the issue is occurring? I know you mentioned that unplugging the IAC results in a normal idle, but is the PCM at least directing the IAC to be shut (0) when the idle is well beyond the commanded idle speed? If the count is NOT 0 then the problem relates to a failure of the PCM to issue a proper command to the IAC (for one of several possible reasons). However, if the count IS 0 then the PCM is making the correct command to bring idle back under control, but the IAC is either not responding properly (or at all) or is unable to adequately limit air intake (such as a vacuum leak). I know you mentioned that no vacuum leak was found, but this could be from an internal source - specifically the EVAP purge solenoid. Too much air supplied from that source will behave like a vacuum leak but you will never find it with brake clean or any other external test process. EGR could also cause this, but you mentioned having an EGR delete so that's not going to be the problem here. In any event, if unplugging the IAC works as a solution then I doubt the issue is related to the EVAP system either.

It would be interesting to see IAC counts when it's idling too high.