TRD_Power

Hey everyone,

So the other day I noticed that my dad's 2000 GS400 idles a little rough every now and then, usually when warm, but it doesn't do it all the time. Often it will be when the car is warmed up and has come to a stop at a red light or something. I doubt it's anything very serious, but it's kinda weird how it does it every now and then. Any ideas on what this could be? Thanks a bunch.

GS4_Fiend

iTrader: (22)

Clean throttle body and maf sensor. Search.

TRD_Power

Thanks, but I did search before posting and already did both of those since my SC was doing the same thing except it was all of the time, not just every once in a while. None of the posts I skimmed through said anything about the car doing it every once in a while either. Any other ideas? Thanks again.

BLAZE

iTrader: (2)

When was the last tune-up ( esp.. spark plugs), Was the air filter replaced? Did you disconnect the battery before you cleaned the throttle body and the maf? If so, for how long? If all was done, You could adjust the idle control by tightening up the slack, in the cable on the throttle body.

TRD_Power

the car has 73K on it right now and the last tune-up was the 60K. Not sure on the plugs and wires so I should check into that. I did in fact disconnect the battery for about 2 hours (forgot about it once I finished) and the air filter is brand new. Good call on the idle control, I'll go look it over tomorrow. Thanks a bunch for the reply

BLAZE

iTrader: (2)

No problem, the gs4 doesn't have wires though, it has coil packs.

sam430

iTrader: (10)

Your motor mount might be out. You can't really see it until you remove it. Take one side out and inspect it.

TRD_Power

Good idea. Better catch it before it's too late. Thanks, guys

ChampGS3

iTrader: (6)

I don't know about yours but my 98 GS4 idles very close to 400rpm, this has been covered before, and this low idle, especially once warmed up exacerbates the vibration. I have new plugs and it runs perfect and I don't suspect on your fathers car even with slightly older plugs or a dirty TB would contribute to this kind of issue.

Worn or older motor mounts, however will contribute to excessive vibration, felt almost always when at a stop. I have replaced both motor mounts and the tranny mount and I still get this slightly annoying vibrationn when sitting at a red light.

If someone knows a way to raise the base idle to ~600 rpm, please chime in. One thing that really shows that the idle is set too low from the factory is that if you are running MAX AC/(65deg Auto AC setting), and you know the compressor is engaged, the idle is usually closer to 800 rpm and the vibration at least for me is all but gone. So it would seem that at 600 rpm would be a good compromise.

BLAZE

iTrader: (2)

A dirty tb Will cause rough idle, spark plugs as well,when I swapped out my plugs, and sprayed out my tb, my idle raised about 100 rpm or so. I left the old plugs in when I cleaned out the tb, then replaced them once I was done. This way I wouldn't foul out the new plugs. I also cleaned my mass air flow sensor right before the plug change. As far as motor mounts that is a great idea, worn out mounts will cause vibration. To raise the idle I simply took out the slack in the cable on the left side of the tb. just loosen the nut and take in the slack. Good luck.
,

GS4_Fiend

iTrader: (22)

Try this. If it happens when the car is already warmed up. When the car is fully warmed, at "P", turn on your headlights see if the vibration goes away. Or turn on the a/c on. If it does, your engine mounts are wearing out and getting weaker. That's why you can feel at parked, when the car is warmed. I mean engine mounts get weak over time easily because of bad road, speed bumps, from bouncing up and down and etc. Hope that helps.

Also if your PCV is bad, it would cause rough idle too.