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1999 ES300 - Intermittent CEL / Rough Idle


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Hi all,

I've had an intermittent check engine light illuminate over the last few weeks. When it comes on, the car experiences a very rough idle but seems okay at driving speeds.

I originally suspected it may be due to the fact that my battery terminal connectors have been coming loose and the connection was spotty at times, however, I have rectified that situation and still have had the CEL and rough idle return a couple of times since.

It seems to most often occur after I've already driven (not necessarily a long distance) and have stopped somewhere and gone to head out to somewhere else.

Two occurrences ago, I parked and popped the hood after the light came on to adjust the battery connections and it looked like the (pardon if I use the wrong terminology) pipe coming off the exhaust manifold was glowing red. It only happened that time, no others, but it was after maybe driving 10 min one way, stopping for 5 min, and driving for another 15 min - so not long enough I'd imagine anything would be glowing. I've included a pic of what had been glowing red (note, it is not glowing in the pic).

I tried to pull the code with an OBD2 scanner. The version I had was asking which interface to access and I chose ISOsomething. I can't recall which, however.

At this time there is no CEL and the scanner did not retrieve a code. I thought codes were stored as long as they were not cleared, so I am not quite sure why it's not returning anything.

Anyone have any ideas? Should I be concerned at this point as long as it happens intermittently? It's a VERY rough idle and the CEL is blinking, which to my understanding is worse than a solid CEL.

Not sure if I could've picked the wrong reading option on the OBD2 scanner - it's an Ancel AD410 if that's any help.

I may be driving my car across Colorado and Kansas next month over the holidays and am wondering if this issue needs to be addressed or perhaps is a ghost in the machine.

Appreciate any advice!



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First off, always give the mileage of the car because it often points us in a certain direction for a diagnosis.

For an exhaust to get hot enough to glow means the engine was asked to work very hard (racing), or you have an exhaust restriction (plugged catalytic converter), or similar. You really need to get the car to somewhere and have a proper DTC code reading done. With the runs you are expecting to do shortly, it would be very unwise to neglect the heads up you car is giving you with its symptoms and engine light.

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Update: the CEL came back on Thanksgiving and the car starting running rough again, this time not just at idle.

Was able to pull a code this time - P1354.

After plenty of Googling, I pulled out the OCV closer to the front of the engine, cleaned it with some brake cleaner and reinstalled. Took it for a short test drive, and *fingers crossed* it seems to have remedied my issue. Will circle back if I have any more issues.


For anyone else that may encounter the same issue, these two videos were helpful for me:




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Well, I'm back. After driving fine for a few days, the car started idling rough again today. I pulled the code, assuming it was probably P1354 again. However, that is NOT one of the codes this time - now it's P0300, P0302, P0304 and P0306. I will have to check my paperwork, but I believe I had the corresponding ignition coil replaced less than 3 years ago. 

Anyone have any recos? Seems weird that this happened right after P1354 and was hoping for advance before I go on a wild goose chase.



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