Been chasing this for weeks now... 1992 LT1 6 speed idles at 850 when warm, 1200 when cold or before coming to a complete stop. Has both cats gutted Borla exhaust, K&N air filter with the housing opened up on each side. Could these mods be causing the high idle? Been through the throttle body and it looks great. No vacuum leaks and the vacuum checks at 21 in Hg and rock steady at idle. Is it possibly a bad oxygen sensor? Any help would be appreciated.:ugh Oh yea it also has a brand new IAC.
High idle
- Thread starter tmkassin
- Start date
What temps are you running when its warm? 170? The coolant temp senser(for the ecm) helps determine idle speed & enrichment. Try wiggling the connection to the senser, make sure the coolant is full. You may have to get it scanned to read the live data of the iac, tps, & ect sensers.
boomdriver
Well-known member
did the new IAC get "set" or adjusted or just installed?
GM describes a proceedure that measures the travel of the Pintle and how it shoud be adjusted so that known distances from tip to seat will allow it to seat properly. The tip screws in/outto get to the right measurement. If the Pintle is not able to close off the air passage, then it will Idle high.
GM describes a proceedure that measures the travel of the Pintle and how it shoud be adjusted so that known distances from tip to seat will allow it to seat properly. The tip screws in/outto get to the right measurement. If the Pintle is not able to close off the air passage, then it will Idle high.
S
surfer93
Guest
Did you set the IAC when you installed?
i.e. Start the car w/gas pedal slightly depressed, let run 5 seconds, shut down, wait 10 seconds and start car again without depressing pedal.
Have you done anything w/the TPS?
Did you check codes?
i.e. Start the car w/gas pedal slightly depressed, let run 5 seconds, shut down, wait 10 seconds and start car again without depressing pedal.
Have you done anything w/the TPS?
Did you check codes?
- Thread starter
- #5
Yes I set the IAC according to the FSM procedure. There are no codes. I am buying an OBD 1 scanner that will give me real time info on the oxygen sensors. TPS is original equiptment and checks good. It is not adjustable.
S
surfer93
Guest
Have you verified you do not have a vacuum leak at the cruise control, when mine idled high, that is where mine was leaking.
But to make sure, block off all the vacuum ports(except FPR) and see if the idle drops.
Also, take off the IAC and turn the pintle down till it is under 1 1/8 inches and reinstall and then have the car relearn it.
But to make sure, block off all the vacuum ports(except FPR) and see if the idle drops.
Also, take off the IAC and turn the pintle down till it is under 1 1/8 inches and reinstall and then have the car relearn it.
- Thread starter
- #7
Yesterday I got the EZ scan 3000 and hooked it up. It says my idle is 685... It still takes about 5-10m seconds after stopping to settle down to that #. The on board Tach is not as accurate as I thought. Did notice a couple of issues: Left oxygen sensor reads 765 and the right is 413. Time to go back to the FSM. I am old school so all these #'s will take some time to figure out. Also the scan tool said it was open loop at 198 degrees, that doesn't seem right.
- Thread starter
- #8
Today I did an Ohm check of the injectors. 6 check 12.3-12.5 ohms. #3 and #6 check 9- 9.3 ohms. From reading other posts this aint right. Cannot find this in the FSM, only an injector balance test. 1992 LT1. Anybody know where this is in the FSM? Thinking about Bosch for replacements. Any recommendations?
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I just installed these over the winter. Jon at FIC provides excellent support. Corvette, Camaro, Firebird, GTO Only - L98 CORVETTE, CAMARO, F'BIRD - 1986-1992 Corvette, Camaro Pontiac T/A Bosch Design III 22lb Fuel Injector - Fuel Injector Connection
Have you tried disconnecting the #3 or #6 injector to see if can settle down the high idle? Left side is showing rich, so try #6 first on the passenger side.
Yes, #3 and #6 are showing internal shorts. All injectors should post similar readings when they are both cold and hot.
Have you tried disconnecting the #3 or #6 injector to see if can settle down the high idle? Left side is showing rich, so try #6 first on the passenger side.
Yes, #3 and #6 are showing internal shorts. All injectors should post similar readings when they are both cold and hot.
92BlackVette
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I just started a thread about this same issue only the opposite problem is occuring. Go with the Bosch III from FIC, just installed them a few weeks ago in my 92. GRRREAT!
- Thread starter
- #11
92BlackVette
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Mine 92 is back to normal idle again today. If you have book 2 there is a section that describes how to check for issues related to "unstable idle," Check it out.
G Winter
Well-known member
It took some digging but the ohm value is in my 90 FSM .
It says 10 or more ohms but I think anything under 12 is questionable and they should be somewhere close to even.
You will find the BoshIII a good choice.
Someplace I had a post on my conversation with John about the source of these injectors.
Glenn
It says 10 or more ohms but I think anything under 12 is questionable and they should be somewhere close to even.
You will find the BoshIII a good choice.
Someplace I had a post on my conversation with John about the source of these injectors.
Glenn
- Thread starter
- #14
Gonna read through this section this weekend, thanks
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- #15
Replaced the injectors with Bosch. What a difference. About half of the o rings on the old ones were shot. Still had idle issues. FSM said check the A.I.R system. Blown fuse at the air pump. Had to pull the pump and fix the impeller as it was stuck. Minor corrosion but enough to stop the motor from turning. Not blowing fuses any more. Still idles aroun 900 when cold. Could be the A.I.R. valves are not operating properly. They are next to get cleaned and inspected. Everything I have done has shown an improvement. I love a good challenge. Feels like a 300 hp motor now.
Schrade
Well-known member
It ain't.
Check FSM for parameters that need to be met for Closed Loop operation.
Coolant temp is one, exhaust temps (on L98 anyway) is another. I bet there's more...
- Thread starter
- #17
Replaced the throttle body today. Still idles high. Found the throttle is not closing all the way when the motor is running. Readjusted the throttle cable to ensure it was not too tight. Turn the motor off and it closes completely. Start the motor back up and it hangs up just enough to cause a high idle. If I push the throttle closed by hand it idles down. Is it possible that too much vacuum is holding the butterflies open? It is holding 21 hg and steady at idle. There is not an appropriate emoticon to express my frustration.
Schrade
Well-known member
As long as you're showin' Open loop at 198, there's gonna' be SOME sort of problem... I think THAT has to be solved first.
- Thread starter
- #20
The open loop issue is no longer happening. I had a prom from a camaro in the ecm and I switched back to the original.
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