My Car Idles Rough Somtimes

Reader Question: My car runs a bit rough. If I put it in neutral or park it will rev up and then stop, rev up and stop. The RPM needle will go from 1 – 1.5 then back to 1 and continue doing this. I have given a tune up to my car and had my mechanic clean out my fuel injectors. I have also put in premium gas and fuel cleaners but nothing seems to help.

I have a 1989 Honda Accord SEI and I end up getting about 20 – 23 mpg. I bought this car and someone put in a used engine that has 60,000 miles on it. On my next oil change, I plan on putting something in the oil to help clean up the engine. What do you think the problem is?

Thank you for your time,

Hi Moe,

Sounds like you engine is idling too fast.

The first thing I would look at is the base idle speed, and if it can be manually lowered to help smooth out the idle. If things are ok there, and the idle speed is set correctly (not set too high) I would then inspect and clean the throttle body and idle speed control motor of any dirt or built up carbon deposits.

If there is still a problem I would inspect the engine for a vacuum leak in a rubber hose or in a intake manifold gasket etc. Listen for a hissing noise in the engine area, and look for any rubber hoses that are not properly attached to “something” or a vacuum hose that might have a split in it or a broken plastic connector.

If you still have a problem, I would then have your mechanic read the onboard computer codes and test the idle speed control motor and see what the readings are.

Keep me posted,
Austin C. Davis

Posted in: Running Problems

2 Comments on "My Car Idles Rough Somtimes"

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  1. dale says:

    Never thought of looking for a vacuum leak, sweet. Thanks man

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