1990 Honda accord runs rough at start - always


Old 06-29-10, 09:22 AM
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Join Date: Jun 2010
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1990 Honda accord runs rough at start - always

My 1990 Honda Accord runs rough every time I start it. It doesn't matter if the engine is hot or cold, or if the engine has been off for 5 minutes or 5 hours. It acts like it is missing or not getting fuel. It does that for 10 to 15 seconds. Then it smooths out and runs good. I changed the fuel filter - no change.
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Old 06-29-10, 06:39 PM
hopkinsr2's Avatar
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Time for Plugs & wires maybe??? Check the bottom of the wires & the plugs as you remove them for oil as the Rocker cover gasket may leak & fill the plug hole with oil & cause a rough running engine.... Just a couple thoughts,,, Roger
Old 06-29-10, 07:30 PM
Join Date: Oct 2008
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Try pressing on the accelerator just a tad and see if that makes the problem go away.

If yes, then there could be a problem with the IAC valve (Idle Air Control Valve), the wiring to that, or the switch or whatever tells the engine computer to activate that valve.

This valve normally lets in enough air at idle so the engine idles ok. When you press on the accelerator a tad, you are letting in air the same as that valve should do.

Note: Different manufacturers call that valve different names...
Old 06-30-10, 05:38 AM
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Join Date: Jun 2010
Location: united states
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I tried holding down the accelerator slightly while it is running rough. It continues to run rough until is smooths out. Not sure if it gets better sooner. I'll check the IAC. You also made me think that I may have a vacuum leak, but I'm not sure which leak would only affect me after starting and not during driving.

I changed the plugs and wires a few months ago. No problems after I did that. I'll pull the wires out and see if they are coated with oil.

Thanks for the suggestions.
Old 06-30-10, 06:39 AM
mickblock's Avatar
Join Date: Feb 2009
Location: Calumet Township, Indiana
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Is you engine light on?
Seems like this is something that the PCM is noticing and then compensating for. Usually the only thing that isn't detected by the PCM as a faulty condition is a vacuum leak. It just starts thinking of it as an outside condition and adapts. This is speculation though.

I bet you've at least got pending codes stored that could be read with a scanner and narrow it down. Cause this is a good one!
Cold or hot, five minutes or five hours, and it smooths out at 10-15 seconds. Repeatable. It's the fact that it's repeatable that's nagging me!
Old 07-05-10, 04:55 PM
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Join Date: Mar 2010
Location: USA/ Pacific NW
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well, you can locate your ECU and read codes light flashes or turn dashboard lights to on, and see if check engine light flashes twice and goes away, or keeps flashing. if it keeps flashing, turn it of and back to position 2, and count flashes. that's your error codes.
my 91 civic rough idled on cold no matter what i did, but cleaning air control valve helped a lot. it's a box with odd plumbing system, has coolant running - or should - through it, and at that age, there's a lot of deposit built up inside both from coolant and from gasoline. mine was covered with tar on little metal meshes and half way clogged from coolant deposits.
btw, replacing engine and trannie mounts helps.
run few cans of seafoam through tankfuls. or stp gas treatment through the next about 10 fill ups. it's inexpensive and works well.
if it's four cyl, you will never get rid of some shake, it's a four cyl sickness.
Old 07-07-10, 03:01 PM
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Location: united states
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Thanks for the advice.
I noticed a broken vacuum line from the intake side of the air filter over to the intake system. This tube connected to a small chamber with an electrical connection. Not sure what that is for, but I fixed it last night.
When I crank it now, it runs rough until I really press the accelerator down. It smooths out pretty quickly.
I'll start using additive, clean the IAC valve and see how it goes over the next few weeks.

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