I know this topic has been discussed many times, and I've spent a good amount of time reading through threads on the subject, but I can't seem to find the problem. 98 LC, 255K miles. My issue is only on cold starts and will disappear once the engine temp begins to rise. I have the classic rough idle/shutter that's typically related to ignition coils, but only when idling in gear or moving from a stop when the engine is cold. I don't have a CEL on, I have pulled each individual ignition coil while cold and running to check for a bad coil (I've tried while in park and while in gear), I just replaced all spark plugs less than 10K miles ago, I cleaned my throttle body, IAC valve, MAF sensor, and my air filter is spotless. Is there anything I'm missing? Would a code scanner locate the potential misfire without the CEL on and even though I've checked all my ignition coils and they all are functional? Thanks for any input.
Rough Idle In Gear (topic beaten to death, but I'm still stumped)
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- #2
EDIT - turns out 1998 LC's don't have an IAC, so what I cleaned was the PCV.
Depending on the scanner, yes it will find a bad coil without CEL. CEL are triggered by number of events in a set period, but the code reader should show the events as they are recorded.
My "rough idle" at startup was pretty tame. I checked plugs and rebooted my ignition coils. That made a very minor difference.
Most of the improvement came from running fuel injector cleaner through several tanks in a row.
Others have found motor and transmission mounts did most of it.
Or vacuum leaks.
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- #4
I've got a buddy coming over tomorrow with a higher quality scanner, I'll see what it has to say. Aside from that, would injectors be next up the food chain? I don't think its transmission/motor mounts, I can actually watch the throttle body door moving with in sync with the rough idle.
Check for vacuum leaks, that's what yours sounds like.
The injectors on these rarely clog, and are expensive to replace. Some injector cleaner takes 30 seconds.
I had this exact same thing, changed spark plugs, no difference. I scanned and no pending or stored codes. Eventually just bit the bullet and replaced all coils with OEM ones after 240k miles, and it's fixed the idle issue 90%. I believe the remaining 10% is the PCV valve which I'll get to next. Truck also pulls better with new coils as well, and is giving me about 1mpg more. Coils may not be bad enough to throw a coil, but after 20+ years and 200k miles, you can't expect them to perform as well as a new one.
Mauser
Supporting Vendor
While in gear hold the brake and press the accelerator. If it stutters or wants to die then you most likely have a vacuum leak. When your friend checks it with their scanner check your fuel trim numbers.
When I first bought my 2001 LX with 107,000 miles in 2017, it would randomly get rough and sometimes stall. It always started right back up.
I changed the fuel and air filter first but, no change. Then I replaced the MAF sensor with one from Toyota. The old MAF sensor looked new but, wasn't an OEM. So I think the previous owner had this problem too. The new MAF sensor fixed most of my problems.
The engine still would shudder after a long road trip when the fuel pump was getting hot. So I replaced it with a Denso pump and it solved that problem.
The engine still had a little vibration in it when I put my hand on the automatic gear shift lever. I replaced all 8 coil packs and now my 2001 LX is just as smooth as a new vehicle.
Just remember that all the electronics on these things are now 20 years old. You can either wait for them to go completely out or change them out at your own convenience before you have problems. But, they are going to go out.
I changed the fuel and air filter first but, no change. Then I replaced the MAF sensor with one from Toyota. The old MAF sensor looked new but, wasn't an OEM. So I think the previous owner had this problem too. The new MAF sensor fixed most of my problems.
The engine still would shudder after a long road trip when the fuel pump was getting hot. So I replaced it with a Denso pump and it solved that problem.
The engine still had a little vibration in it when I put my hand on the automatic gear shift lever. I replaced all 8 coil packs and now my 2001 LX is just as smooth as a new vehicle.
Just remember that all the electronics on these things are now 20 years old. You can either wait for them to go completely out or change them out at your own convenience before you have problems. But, they are going to go out.
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- #9
Misfire in cylinder 5! popped in a new ignition coil and she runs like butter. I guess the misfire just wasn't bad enough yet or maybe too intermittent to be found the old fashioned way. Anyways, thanks for the suggestions guys, I think i'll be chasing some vacuum lines in the future as some of them are beginning to look a little worn out. Cheers.
