North American Turbocoupe Organization



CEL comes on at idle (pulled codes)
turbospoolin23 Offline
Senior Member
#1
For some reason my CEL keeps coming on at idle. This just started happening not too long ago, around the same time my wastegate actuator let go. I didn't replace the wastegate yet, but the line is capped. I only put on a few easy off boost miles because i don't have a wastegate. I did notice that my narrowband af gauge doesn't go into closed loop at idle, it pretty much sticks at 2 green bars. Under very light acceleration and at cruise i hardly see closed loop, again it mostly sticks at 2 green bars. Almost like it's cold, but this is happening at operating temp.

I also checked for any vacuum/boost leaks with a homemade tester. The only leaks i had were the throttle plate needle, and the egr was leaking. Is the egr supose to leak some? I wouldn't think so. The car still idles beautifully at ~1000RPM, idle doesn't hang, and vacuum is soild 19".

I used the 3120 CanOBD 2&1 Tool Kit to pull codes.

EEC-IV KOEO
DTC:11
System pass, no KOEO fault codes present

EEC-IV CM
DTC:11
System pass, no Continous Memory fault codes present

EEC-IV KOER
DTC:77
Operator error during dynamic response test/wide open throttle not sensed

I did the tests twice and got the same results both times. I did hit the gas for both tests, maybe the pedal didn't hit the floor though. Any ideas why my CEL keeps coming on at idle? And thoughts on the A/F.
87 TC 5 spd... 17X9 Cobra R's, .60/.63 SVO T3 Turbo, Large NPR, Manual Boost Controller, AEM Wideband, BPV, K&N Cone, Walbro 255, Kirban AFPR, 3G Alternator Conversion, Short Throw Shifter, Stinger 3" Exhaust, Magnaflow Catalytic Converter & Muffler.
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BJL Offline
Moderator
#2
check you tps voltage and sweep.
clear the codes and let it idle till light comes on, shut off car and redo koeo test...
you may have a weak o2 since is not moving much...
Brian Larkin
88TC 330,000 miles
Slightly Modified
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Jeff K Offline
Administrator
#3
During the goose test, go to full WOT and be sure the engine gets up to 4000 RPM or so briefly. This test looks at both the TPS and VAM.

If the CEL comes on at idle for more than a few seconds, there will for sure be a CM code stored. Any chance you erased the CM codes while running KOEO test.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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turbospoolin23 Offline
Senior Member
#4
BJL, I already checked the tps 0.91 with the throttle closed, and 4.XX WOT(can't remember now). Sweeps nice and smooth, no dead spots, and returns back to 0.91 if i blip the throttle. It's fairly new and has maybe ten thousand kilometers on it. The o2 is also almost brand new, less then one thousand kilometers on it and was working fine until recently.

Jeff K, I might have just stabbed the gas and let off too quick so the engine didn't reach 4000rpm. I'll have to keep that in mind next time. I am alomost positive i didn't erase the CM codes before doing the test, but it is possible. I was surprized that i didn't get any codes when the CEL had come on around a dozen times at idle. I'll have to wait for the CEL to come on again (shouldn't be long) and try to pull some codes again.
87 TC 5 spd... 17X9 Cobra R's, .60/.63 SVO T3 Turbo, Large NPR, Manual Boost Controller, AEM Wideband, BPV, K&N Cone, Walbro 255, Kirban AFPR, 3G Alternator Conversion, Short Throw Shifter, Stinger 3" Exhaust, Magnaflow Catalytic Converter & Muffler.
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Jeff K Offline
Administrator
#5
If you still dont get any codes with your scanner (not familiar with the one you are using), try to "old fashioned" way of getting codes using a jumper wire and watching the CEL flash.

Check your VAM voltage at hot 1000 RPM idle (BK/W to W/BK wires). Should be under 1 V, especially if you are running any higher than stock fuel press. If VAM voltage is high, it will trigger a CM 42 at idle. There is a way to adjust VAM idle voltage that doesnt involve removing the black cover or messing with the spring tension. Let me know if you want / need to do this and I will tell you how.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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TurboCoupe50 Offline
Posting Freak
#6
I had the same problem on the daughter's TC a dozen years or so ago, no codes, continuous CEL at idle... Problem was originally a leaking "O" ring on the base of an injector, but continued after that was repaired... Never did find any other problem, disconnecting the battery cable for 15 minutes fixed it...
1988 Turbo Coupe331 AOD

1972 Comet GT

1969 Fairlane Cobra 428CJ 4-Speed
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Pete D Offline
Administrator
#7
I was wondering about an air (not vacuum) leak, like the VAM or IC hoses
Pete Dunham


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vegas_ss Offline
Senior Member
#8
Quote:Originally posted by Jeff K:
Check your VAM voltage at hot 1000 RPM idle (BK/W to W/BK wires). Should be under 1 V, especially if you are running any higher than stock fuel press. If VAM voltage is high, it will trigger a CM 42 at idle. There is a way to adjust VAM idle voltage that doesnt involve removing the black cover or messing with the spring tension. Let me know if you want / need to do this and I will tell you how.
I would be interested in this method... Wink
1987 TC, 5sp, Boport Stage 3 Head/2.1 Cam
1996 Impala SS, DCM, Borla Cat Back, too much other stuff!!!
2009 Pontiac G8 GXP 6M, 6.2l LS3, Kooks Long Tube, Hi Flo Cats, Mild Cam
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BJL Offline
Moderator
#9
i would be interested in the VAM adjustment without opening the VAM
Brian Larkin
88TC 330,000 miles
Slightly Modified
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turbospoolin23 Offline
Senior Member
#10
Thanks for the responses guys. I didn't have time to look at it today, hopefully I get off work early tomorrow so I can have a look. Jeff, I would also be interested in vam adjustment info.
87 TC 5 spd... 17X9 Cobra R's, .60/.63 SVO T3 Turbo, Large NPR, Manual Boost Controller, AEM Wideband, BPV, K&N Cone, Walbro 255, Kirban AFPR, 3G Alternator Conversion, Short Throw Shifter, Stinger 3" Exhaust, Magnaflow Catalytic Converter & Muffler.
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