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Discussion Starter #1
Alright I have had this problem for a while and still trying to figure it out. Hopefully someone here can give me a hand.

I have a rough idle when the car is cold. It only happens in Drive and when the car is completely stopped (so while I am waiting at a light). I can only really describe it as a constant vibration. It tends to be worse the colder it is outside but goes away after a while. On a warm day it may not happen at all. So right now in the winter it will idle rough when I start it but by the time I get to work it is gone. Kind of annoying. Oh it's at about 700 RPM and doesn't seem to change when I turn the AC on. Is that right? I thought the RPM should go up.

I took it to my mechanic who is usually pretty good and fair and they tried a few things. Changed my spark plugs and wires and cleaned the intake manifold. They said they checked all the vacuum and fuel pressures and they looked good. I am almost at the point of giving up but I don't want to just start changing things randomly. I guess I am leaning towards the IAC but not sure if that makes sense. Any ideas or tests I should do? Thanks. This forum has been very helpful so far.

Oh by the way I don't have a CEL.
 

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master486 said:
Clean the MAF and reset the computer. Then see if it still happens.
dittop on the MAF cleaning. Use windex, electrical parts cleaner, or CRC now has a MAF cleaning arosal can. Anything else will corode the wire.

Also, how many miles are on the car? And have the o2 sensors ever been changed? They generally need replacing every 80-90,000 miles. And usually they dont throw a code if they're just plane old and worn out.

-Thomas
 

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Discussion Starter #4 (Edited)
Hmm I guess I will get a can of electrical contact cleaner tonight. The O2 sensors have never been replaced and the car has 75k miles. This problem has been around for a while though, maybe 10k miles.

Oh how do I reset the computer? It wasn't in the Tech article for MAF cleaning.

Fuse 15, found it by using the search. Should have done that in the first place.
 

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try changing your pcv valve.. its on the passenger side valve cover, near teh back.. the part is like 2 bucks at autozone.. also, check all your vaccuum lines for leaks, or if the hose is rotted. and.. does your oil pressure drop at idle by chance? i had teh same problem for a while, but i fixed teh vaccum line, and changed plugs, wires, distributor cap, rotor, and pcv valve.. also teh air filter... then clean your maf, throttle body and check the o2 sensors. then to top it off (and see if it might be clogged injectors) go get a can of seafoam engine treatment. (ask for it at autozone, its like 6 bucks) add one can to your fuel tank, then another can to your crankcase when you change the oil... you should have eliminated all the small possibilities by then.. (and given your car a full tune-up)
 

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Discussion Starter #7
So I guess it took me a little longer to actually get around to this. I replaced the PCV value and cleaned the MAF and no change. I remembed to reset the computer too. Air filter is still good, and hoses look good. About the oil pressure, I don't have a gauge to check it but the light never comes on. The fact that it stops when the car warms up really confuses me.
 

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Lets look at the facts:

There is a rough idle ONLY when the car is cold.

If the O2 sensors were bad you be getting bad gas mileage all the time. Do you get good gas mileage? It is possible that only one is bad. If you have the money I would replace them both and see what happens, depending on when they were last replaced.

It could STILL be your MAF. There is a cold temperature resistor or something (I can't pinpoint what its called) in the MAF sensor, if this is bad then it will send bad air readings to the ECM when the engine is cold. Which will cause it to adjust the air ratios when there really is nothing wrong. But once again, these aren't cheap so If you have the money go ahead and replace it.

A vacuum leak would NOT seal when the car gets warm. I highly doubt this is the problem.

When my IAC went bad the car was idling at around 1500 rpms. I don't know if yours may just be contaminated, but its possible.

I would also check your EGR valve.

Hope this helps!
 

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Discussion Starter #10
I just got 21-22 mpg with a mix of city/highway driving. I guess I can try the o2 sensors next since they have almost 80k on them. not sure if jeleighlover and i have the same problem. Someone told me it sounded like a misfire but I have no idea.
 

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I have the exact same problem with my 97. I just changed the plugs, and the problem is still there.

Mine actually does the rough idle all the time (cold or hot). The only time it stops is when I start moving forward.

I am subscribing to this thread! I sure hope someone can help us!

-Kornhaus
 

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Mine does it too, but I have a head gasket leak and that may be a big reason. I had done all the things mentioned above and I still had the problem. Although, running SeaFoam through the system gave great results and showed that it has to do with the intake system and the injectors as well as the head gasket leak.

1) Run the SeaFoam through the system as suggested and see if that helps. If it does, have the injectors cleaned or replaced. If they are cracked, they will cause these same problems.

2) Check the motor mounts. If they are worn (and they will over time) the engine will seem like its idling poorly when its cold, but then again, the engine will do it when it’s hot as well but not all the time.

Try the SeaFoam.

On the other hand, you could have a head gasket leak and not know it. It may be small enough that when the engine is cold, the area in question is opened more causing a leak and rough idle. When the engine gets hot, the engine and heads swell enough to close off the gap and idles fine. Even though my car idles fine when its hot, I smell coolant and have less power than years ago. So ya, I'm doing the heads in a couple weeks. Any suggestions are welcome on how to change out the heads.
 

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might not be anyones problem, but i once had a rough idle when cold...i found oil leaking and looked for the source. well my filter was leaking and so after i tightend it up the rough idle went away...i also had a set of catless downtubes intstalled, so it might have been a clogged cat or somthing? because my cats also fell apart.


i also had a rough idle when hot, i used redline fuel system cleaner to clean my injectors, because it was brought to my attention that it might be my car starving for fuel, it helped. also changed my plugs and wires, that helped alot.
 

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Okay, stupid question.... where do I add the SeaFoam (gas tank, oil, etc.)? I am going to buy some tonight, and want to try and fix my low idle.

-Kornhaus
 

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I ran mine in the tank. One can per full tank (I think - read the lable). Then do it again on the next fill up and see if that helps.
 

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same

:mad: 97 -3.8, 104 k, been doing this for about 10k miles now. Only when idling @ alight or stop sign...mine doesn't care if hot or cold, very sporadic. Just a miss, can feel it at the exhaust when you are outside, a blip ever so quick. Doesn't affect the tach reading when it does it. Pisses me off....I have relaced plugs, wires, car is driven by my wife. Run techron about twice a year, changed fuel filter, air filter, cleaned the MAF with CRC, and the TB when I had to remove intake to replace O Ring off water pump. Motor mounts were changed about 10K ago....what is IAC? I guess I could replace the O2 sensors. Mine idles fine ...just this annoying little blip that happens sometimes...sometimes not. Happening more now so it seems to me. I rarely drive the car except when something needs fixing. Also changed PCV valve out.
 

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Could be a head gasket going or the head is getting warped.

The IAC is the Idle Air Control. If you have rough idle at a stop, it could be the IAC, but they are over a $100 to replace.
 

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Discussion Starter #18
elvis you sound just like me..getting tired of trying stuff. Did the problem start before or after you changed the motor mounts? Just noticing they both happened 10k ago. The reason I ask is I know my dad got mine changed, and wonder if they could be the problem.
 

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I think it was there slight b4 the motor mounts. They were bad!!! Whole side of motor went up 2-3" when I gave it gas with brake on. I am starting to think it is the cat convertor also. I know after 10years that thing has to be used up. I still get great mpgs...28-30 on hwy, but historically the cats need changing after 50k. Just another thing that I take for granted that it will work 4ever. Will put it in line after my daughter's Accord oil leak at the auto trans connecting point...bad casting "honda Bulletin"sux. Hate those things, not a recall, they just screwed up.
 

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i would say the 02's could be a likely culprit. could be clogged up, tellign your system it is runnign lean, so it overcompensates with more air.... change em.. see what happens
 
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