Sc400 Idle And Cel/trac Lights

[Oldtreemech]

In the middle of chasing ISC (ICAV) valve repair and interaction with CEL and TRAC lights. I've read several post over the forums and chased down thru the following checkouts: Plugs, Plug wiring, Distributors caps/rotors, coil packs, igniters, temperature sensor, temperature switch, MAF, Throttle plates cleaned, VFV for EGR and Pressure Regulator. I've replaced the ICAV with an Ebay one, same problems just different idle speed. I've taken the ICAV apart and cleaned and oiled it slightly with Mobil 1 oil. Started up at 800 rpm and no CEL or Trac lights! I thought I was finished... wrong! It idles for say 3-5 minutes and then stumbles and misfires a couple of times and dies! Starts up again and then misfires and CEL and TRAC lights back on! Runs a while longer and dies again after more misfires and backfires. Spray some throttle cleaner in the intake and start it back up. It hits immediately and runs great and no CEL or TRAC lights runs for another 2-4 minutes at 800 rpm and revved up with no misfires etc. Dies again and I start it again and this time idle speed goes up to 1500 rpm and CEL and TRAC lights back on. Now I'm thinking its partly related to some bad fuel problems so I've added SeaFoam to tank with a few more gallons of fresh fuel and tried it again about 5-6 hours later. Cranked right up no lights again runs for 3-4 minutes and back to misfires and CEL and TRAC lights. Will change fuel filter tomorrow after PBwrench soaks over night.

Earlier checked oxygen sensor voltages at temperature and showed rich condition ~ .975 V. When I'd rev the engine up to constant 2-3K voltage would lean some to say .900 or so. But if I revved it up and released the throttle the voltage would reflect ~.500v a good operating range at normal conditions. But then it quickly returns to the rich voltage level. Haven't killed the sensors or CATs yet but it won't be long if I don't get this corrected.

I don't get any Check engine codes when shorting E1 and T1. This may be due to ECU moving to BACKUP/LIMP HOME mode. Not sure so I have a Ebay ECU on way to check this out.

Any Other suggestions? :(

[Oldtreemech]

In the middle of chasing ISC (ICAV) valve repair and interaction with CEL and TRAC lights. I've read several post over the forums and chased down thru the following checkouts: Plugs, Plug wiring, Distributors caps/rotors, coil packs, igniters, temperature sensor, temperature switch, MAF, Throttle plates cleaned, VFV for EGR and Pressure Regulator. I've replaced the ICAV with an Ebay one, same problems just different idle speed. I've taken the ICAV apart and cleaned and oiled it slightly with Mobil 1 oil. Started up at 800 rpm and no CEL or Trac lights! I thought I was finished... wrong! It idles for say 3-5 minutes and then stumbles and misfires a couple of times and dies! Starts up again and then misfires and CEL and TRAC lights back on! Runs a while longer and dies again after more misfires and backfires. Spray some throttle cleaner in the intake and start it back up. It hits immediately and runs great and no CEL or TRAC lights runs for another 2-4 minutes at 800 rpm and revved up with no misfires etc. Dies again and I start it again and this time idle speed goes up to 1500 rpm and CEL and TRAC lights back on. Now I'm thinking its partly related to some bad fuel problems so I've added SeaFoam to tank with a few more gallons of fresh fuel and tried it again about 5-6 hours later. Cranked right up no lights again runs for 3-4 minutes and back to misfires and CEL and TRAC lights. Will change fuel filter tomorrow after PBwrench soaks over night.

Earlier checked oxygen sensor voltages at temperature and showed rich condition ~ .975 V. When I'd rev the engine up to constant 2-3K voltage would lean some to say .900 or so. But if I revved it up and released the throttle the voltage would reflect ~.500v a good operating range at normal conditions. But then it quickly returns to the rich voltage level. Haven't killed the sensors or CATs yet but it won't be long if I don't get this corrected.

I don't get any Check engine codes when shorting E1 and T1. This may be due to ECU moving to BACKUP/LIMP HOME mode. Not sure so I have a Ebay ECU on way to check this out.

Any Other suggestions? :(

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup.

[Oldtreemech]

In the middle of chasing ISC (ICAV) valve repair and interaction with CEL and TRAC lights. I've read several post over the forums and chased down thru the following checkouts: Plugs, Plug wiring, Distributors caps/rotors, coil packs, igniters, temperature sensor, temperature switch, MAF, Throttle plates cleaned, VFV for EGR and Pressure Regulator. I've replaced the ICAV with an Ebay one, same problems just different idle speed. I've taken the ICAV apart and cleaned and oiled it slightly with Mobil 1 oil. Started up at 800 rpm and no CEL or Trac lights! I thought I was finished... wrong! It idles for say 3-5 minutes and then stumbles and misfires a couple of times and dies! Starts up again and then misfires and CEL and TRAC lights back on! Runs a while longer and dies again after more misfires and backfires. Spray some throttle cleaner in the intake and start it back up. It hits immediately and runs great and no CEL or TRAC lights runs for another 2-4 minutes at 800 rpm and revved up with no misfires etc. Dies again and I start it again and this time idle speed goes up to 1500 rpm and CEL and TRAC lights back on. Now I'm thinking its partly related to some bad fuel problems so I've added SeaFoam to tank with a few more gallons of fresh fuel and tried it again about 5-6 hours later. Cranked right up no lights again runs for 3-4 minutes and back to misfires and CEL and TRAC lights. Will change fuel filter tomorrow after PBwrench soaks over night.

Earlier checked oxygen sensor voltages at temperature and showed rich condition ~ .975 V. When I'd rev the engine up to constant 2-3K voltage would lean some to say .900 or so. But if I revved it up and released the throttle the voltage would reflect ~.500v a good operating range at normal conditions. But then it quickly returns to the rich voltage level. Haven't killed the sensors or CATs yet but it won't be long if I don't get this corrected.

I don't get any Check engine codes when shorting E1 and T1. This may be due to ECU moving to BACKUP/LIMP HOME mode. Not sure so I have a Ebay ECU on way to check this out.

Any Other suggestions? :(

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup.

UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :)

[Oldtreemech]

In the middle of chasing ISC (ICAV) valve repair and interaction with CEL and TRAC lights. I've read several post over the forums and chased down thru the following checkouts: Plugs, Plug wiring, Distributors caps/rotors, coil packs, igniters, temperature sensor, temperature switch, MAF, Throttle plates cleaned, VFV for EGR and Pressure Regulator. I've replaced the ICAV with an Ebay one, same problems just different idle speed. I've taken the ICAV apart and cleaned and oiled it slightly with Mobil 1 oil. Started up at 800 rpm and no CEL or Trac lights! I thought I was finished... wrong! It idles for say 3-5 minutes and then stumbles and misfires a couple of times and dies! Starts up again and then misfires and CEL and TRAC lights back on! Runs a while longer and dies again after more misfires and backfires. Spray some throttle cleaner in the intake and start it back up. It hits immediately and runs great and no CEL or TRAC lights runs for another 2-4 minutes at 800 rpm and revved up with no misfires etc. Dies again and I start it again and this time idle speed goes up to 1500 rpm and CEL and TRAC lights back on. Now I'm thinking its partly related to some bad fuel problems so I've added SeaFoam to tank with a few more gallons of fresh fuel and tried it again about 5-6 hours later. Cranked right up no lights again runs for 3-4 minutes and back to misfires and CEL and TRAC lights. Will change fuel filter tomorrow after PBwrench soaks over night.

Earlier checked oxygen sensor voltages at temperature and showed rich condition ~ .975 V. When I'd rev the engine up to constant 2-3K voltage would lean some to say .900 or so. But if I revved it up and released the throttle the voltage would reflect ~.500v a good operating range at normal conditions. But then it quickly returns to the rich voltage level. Haven't killed the sensors or CATs yet but it won't be long if I don't get this corrected.

I don't get any Check engine codes when shorting E1 and T1. This may be due to ECU moving to BACKUP/LIMP HOME mode. Not sure so I have a Ebay ECU on way to check this out.

Any Other suggestions? :(

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup.

UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :)

[Oldtreemech]

In the middle of chasing ISC (ICAV) valve repair and interaction with CEL and TRAC lights. I've read several post over the forums and chased down thru the following checkouts: Plugs, Plug wiring, Distributors caps/rotors, coil packs, igniters, temperature sensor, temperature switch, MAF, Throttle plates cleaned, VFV for EGR and Pressure Regulator. I've replaced the ICAV with an Ebay one, same problems just different idle speed. I've taken the ICAV apart and cleaned and oiled it slightly with Mobil 1 oil. Started up at 800 rpm and no CEL or Trac lights! I thought I was finished... wrong! It idles for say 3-5 minutes and then stumbles and misfires a couple of times and dies! Starts up again and then misfires and CEL and TRAC lights back on! Runs a while longer and dies again after more misfires and backfires. Spray some throttle cleaner in the intake and start it back up. It hits immediately and runs great and no CEL or TRAC lights runs for another 2-4 minutes at 800 rpm and revved up with no misfires etc. Dies again and I start it again and this time idle speed goes up to 1500 rpm and CEL and TRAC lights back on. Now I'm thinking its partly related to some bad fuel problems so I've added SeaFoam to tank with a few more gallons of fresh fuel and tried it again about 5-6 hours later. Cranked right up no lights again runs for 3-4 minutes and back to misfires and CEL and TRAC lights. Will change fuel filter tomorrow after PBwrench soaks over night.

Earlier checked oxygen sensor voltages at temperature and showed rich condition ~ .975 V. When I'd rev the engine up to constant 2-3K voltage would lean some to say .900 or so. But if I revved it up and released the throttle the voltage would reflect ~.500v a good operating range at normal conditions. But then it quickly returns to the rich voltage level. Haven't killed the sensors or CATs yet but it won't be long if I don't get this corrected.

I don't get any Check engine codes when shorting E1 and T1. This may be due to ECU moving to BACKUP/LIMP HOME mode. Not sure so I have a Ebay ECU on way to check this out.

Any Other suggestions? :(

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup.

UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :)

UPDATE: Okay it ran well enough to get to the emission test and passed. Then on way home back to high idle then a little later surging and hunting idlle speed and finally back to choking and missfiring but never went to backup mode. So back to more Sea Foam and changing fuel filter and maybe another IACV rebuild. <_<

Quick Note: Before I left to go to emission test check the O2 sensors which read about .250V which normally would be really lean compared to other Manufacturers which normally would say around .5V. I did pass but now it looks like I'm getting close on the Catalytic converters needing replacement because the NO was very near the limit!

[Oldtreemech]

In the middle of chasing ISC (ICAV) valve repair and interaction with CEL and TRAC lights. I've read several post over the forums and chased down thru the following checkouts: Plugs, Plug wiring, Distributors caps/rotors, coil packs, igniters, temperature sensor, temperature switch, MAF, Throttle plates cleaned, VFV for EGR and Pressure Regulator. I've replaced the ICAV with an Ebay one, same problems just different idle speed. I've taken the ICAV apart and cleaned and oiled it slightly with Mobil 1 oil. Started up at 800 rpm and no CEL or Trac lights! I thought I was finished... wrong! It idles for say 3-5 minutes and then stumbles and misfires a couple of times and dies! Starts up again and then misfires and CEL and TRAC lights back on! Runs a while longer and dies again after more misfires and backfires. Spray some throttle cleaner in the intake and start it back up. It hits immediately and runs great and no CEL or TRAC lights runs for another 2-4 minutes at 800 rpm and revved up with no misfires etc. Dies again and I start it again and this time idle speed goes up to 1500 rpm and CEL and TRAC lights back on. Now I'm thinking its partly related to some bad fuel problems so I've added SeaFoam to tank with a few more gallons of fresh fuel and tried it again about 5-6 hours later. Cranked right up no lights again runs for 3-4 minutes and back to misfires and CEL and TRAC lights. Will change fuel filter tomorrow after PBwrench soaks over night.

Earlier checked oxygen sensor voltages at temperature and showed rich condition ~ .975 V. When I'd rev the engine up to constant 2-3K voltage would lean some to say .900 or so. But if I revved it up and released the throttle the voltage would reflect ~.500v a good operating range at normal conditions. But then it quickly returns to the rich voltage level. Haven't killed the sensors or CATs yet but it won't be long if I don't get this corrected.

I don't get any Check engine codes when shorting E1 and T1. This may be due to ECU moving to BACKUP/LIMP HOME mode. Not sure so I have a Ebay ECU on way to check this out.

Any Other suggestions? :(

UPDATE: Cranked it up today and immediately caught and ran smoothly at correct cold rpm setting of around 1600. Ran for 1-2 minutes and rpm began to decline to around 1000 so I was beginning to think that Sea Foam had cleaned everything out and I was finished...........wrong! It stumbled/misfired a couple of times and the Trac and CEL lights came on and the rpm climbed to 1600 rpm. Restarted a couple of times same CEL and Trac lights. let it set a couple of hours and started right again No lights , ran 1-2 minutes and stumbled again but not as bad then the lights came on. Drove around about 5-10 minutes to try and mixup the gas and Sea Foam to clear it out some more. Still trying to get the fuel filter off without damaging the fuel lines etc. Maybe change out temperature sensor next since it seems to show up as it lowers rpm in warmup.

UPDATE: Cross my fingers maybe the adventure if over. Cranked up immediately this morning and no CEL or Trac lights and ran smoothly. Held the rpms up to 2-3K and let it warm up. Had one little period of reducing rpm and one stumble but very minor. After warmup was at correct rpm and ran excellentl. Cranked it up a couple of more times and ran it around the block several times an a couple of full throttle drills to finish mixing and purging bad gas or water in the tank. Added more fuel and will press on for now. Will add more Sea Foam for SURE. :)

UPDATE: Okay it ran well enough to get to the emission test and passed. Then on way home back to high idle then a little later surging and hunting idlle speed and finally back to choking and missfiring but never went to backup mode. So back to more Sea Foam and changing fuel filter and maybe another IACV rebuild. <_<

Quick Note: Before I left to go to emission test check the O2 sensors which read about .250V which normally would be really lean compared to other Manufacturers which normally would say around .5V. I did pass but now it looks like I'm getting close on the Catalytic converters needing replacement because the NO was very near the limit!

Followup: Cold night startup went well but back to idle speed surge hunt betweeen 1500-2000 rpm. Revved it up a little a couple of time s and let it warm up a little above 2500-3000 rpm. Still hunting rpm so shut it down and restarted and then its stable at 1600 and continued to warm up and settled down to 1000 at warm temperature. Oh one follow-up after the codes went away this morning did a double check on test codes before emission test trip. All Clear and quick 11111 all clear code. It didn't store any codes from earlier stumbling and misfires and was out of BACKUP/LIMP home mode. :D

[mikeinmichigan]

Maybe I can add something that will be of use. 1992 SC400 175k miles. I had the surging/bucking @ 40-55 mph at a steady state or trailing throttle. I also had the CEL and Trac off light come on. The engine also didn't seem to be running at the proper temp (too low)and when I pulled the code it was "DTC 25 lean condition".

Ok first I cleared the code, replaced the thermostat and test drove it. So far the bucking and surging are gone and no CEL or Trac off indications. The coolant temp is right in the middle of the gage now.

Going through the troubleshooting in the manual enging temp is possibly tied to the DTC 25 code so hopefully that is all my problem was. I'm going to drive to work tomorrow and see if it gives me any more problems and will post again with the results.

I know on the LS this is tied to the ECU programming causing "off throttle shock" but don't know if it affects our models as well.

In addition, I have never had any idle problems whatsoever.

This site has been a big help and it downloads faster than the other one, Thanks everyone.

Mike

[mikeinmichigan]

Nope, that didn't fix it. It took longer, but she is still throwing the DTC 25 code in combo with the CEL/Trac Off. At least the heater kept me toasty warm this morning. For the minor inconvenience I might just live with it, as long as it doesn't get any worse.

[mikeinmichigan]

Ok I finally fixed the bucking/surging between 40-50 mph a couple nights ago. One foggy day after an extended nighttime rain storm the engine was severely missing, and it didn't get any better when it was warmed up. I figured this was an electrical problem and ordered all the ignition parts.

Saturday night I replaced the sparkplugs, plug wires, rotors, distributor caps, and coils. When I pulled out the plugs, I could see that two of them were not firing well or at all.

It took about 4 hours to do it, but now the engine runs perfectly. I have 177k miles on it and for those of you who have a slight miss that gets worse in damp weather you might want to try this approach. Cost about 400.00 for all the parts.

Mike