OK, my car is an automatic 91 RS that is stock except for intake, lowering springs, and camber kit. OK, so ever since I bought the car when I am idle…at red light and stuff on ‘D’…the rpm hovers around 500. The car has always trembled a bit when idle, but now that i have lowered the car I can feel the tremble even more. I can see the passenger seat literally shaking (not very much, but it shakes when no ones sitting there) and my side view mirrors also shake. The rpm is still at the same level when idle…kinda jumps around 500 rpm (not major jumping…probably goes up and down from 400-600). So the car has done this since I bought it a year ago and it didn’t annoy me before, but annoys me now. I just want to know if this is normal or if I need a tune up or something like that.
- motor mounts
- get your timing redone, you’re engine’s timing could be off, i.e. valvetrain is off from the pistons. TDC settings are off i mean.
- Do a tune up and see from there. Could be ignition components being worn. i.e. dist. cap and rotor, wires, plugs…etc.
I just got my new custom exhaust installed today and the trembling has settled down quite a bit since the installation. Could the old muffler have been a factor? Anyone with any insight, please post!!!
i had/have that same problem. i fixed it somewhat , but it still does it a little. i cleaned the I.A.C. (located behind the the throttle body…clean the hell out of it!!!). that calmed down the “trembling”, but my car still does it a little. thats because i still have to replace one of my motor mounts - its broken. try that stuff and you should be ok.
Hey japes… offtopic but how much was your custom exhaust and what kind is it?? Thanx.
Dan Martin
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RED 1992 GS
I actually got a deal from my cousin down in California. He deals with certain companies, usually the lower end ones and sent me an OBX Bomber at 150 CDN…I actually ended up getting it for cheaper because he sold out of the B3 tips and had to send me a B2 tip; so he sent me a $50 CDN back for the mistake, but that cost was swallowed by him and not his company. So 100 bucks CDN for an OBX b2 Bomber is a pretty good deal. I also got Maxspeed lowering springs from him for $175 CDN and a generic intake for $75 CDN.
you can adjust the idle by turing a flat head looking screw that is right above the opening on the throttlebody.
which way would I turn…make it tighter?
If I remember correctly, tightening will make you idle lower, and loosening will make you idle higher. Ideally you want to idle between 750-1000 rpms. You can adjust while your engine is running so there isnt really any guesswork
For what its worth, I just replaced my old ignition wires with new Accel 300+ and I find my ‘91 LS-S’ motor idles and revs much more smoothly. You can get 'em for just $45 at www.summitracing.com.
thanks for the input so far, i’ll have to get i checked out sometime
Idling at 500 rpm is too low. It’s definately your idle that is causing the virbration – turn that screw like the other guy said, and bring the idle up to around 750 +/- 50 RPM, with a FULLY WARMED ENGINE. Let the engine run to a normal operating temp before doing this, otherwise its a waste of time.
Once you are idling at around 750 or so, drive like this for a day or two and check the RPM’s when at stoplights – if they stay around the level you set them, then you’re done, and problem solved.
This is NOT something you want to being to a shop to get checked out, becuse they will probably tell you that 50 other things are wrong, or possibly wrong, with your car, and then charge you an assload of money to fix it, when all they had to do was turn the IAC screw on the throttlebody. 
~Eric
ok, im just a real dumbass when it comes to mechanics…this doesn’t seem too hard to do though if I can find the screw. Where exactly is the throttlebody and where would the screw be in relation to it? thanks for the help so far
well, I got the rpm to idle at 750, but I still feel some trembling from the engine…is this something that only a tune up may fix?
A full tune up couldn’t hurt if it is still trembling while idling at 750.
Shouldn’t cost much anyhow, and is worth it, to keep your car in good condition and running for a long time.
~Eric
trembling
i have the same friggin problem, i think it might be my timing though because when my car is at idle the rev drops and my car feels like its gonna stall, can it be my battery or alternator too ?
i got my battery replaced a few months ago and it was the same before and after
Mine does the same thing every now and then… When I first start it it will idle REAL high like a 1500, then 2 minuts later bounce between 1500 and 2000. Then after its warm it goes down to 500. If its warmed and I shut it off then turn it on 5 minuts later the idle will drop below 500 like its going to stall then go back up. Weird huh. I have a 1990 4dr LS, any ideas whats wrong here?
-Mike
hahah everyone goes through that junk, thats integras lol
remember join the no breathers act…there for american cars…and could only hurt ours.
-lack of coolent
-improperly gapped plugs
-bad iac
-dirty throttle body
-bad thermostat
-sparkplug wires
-ignitor
-coil
-cap
-rotor
-airfilter
-02 sensor
-low set idle
-timing off
if you have a cold air…it might hesitate…and lack some air…on stoping…so it could drop because of that, modifications also somewhat contribute
just an update: I haven’t touched it yet, haven’t gotten it looked at yet and it doesn’t tremble all that much if at all anymore.