Irratic idle 1991 Acura Integra .

[trobbins]

Hi all .
Hoping someone has had this problem and can help diagnose .
1991 Integra LS . Street car with header and cold air intake .
Irregular idle , idles up and down between I think +or- 750 and 1000 RPM just after start up when engine starts to warm up . This will continue even when the engine is up to full operating temp for longer than 15 minutes . More in particular the ambient temp today was about 25 deg's
I was thinking temp sensor . But I'm not sure where to look for it .
The thing that leads me to believe it is a temp sensor is that the cooling fan runs continuosly untill the battery is dead .
Thanks .

[Xian]

Not sure about the fan running but here are the two things that I'd check out:

The FITV can cause idle fluctuation: http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=1167

I had a swapped Civic that had idle problems and the cause was the "white plunger" looking part had unscrewed itself over time... tightened it up and it ran like a champ.

Other option may be the IACV could need to be cleaned: http://www.honda-tech.com/showthread.php?t=1575913

Christian

[iambhooper]

it could also be a vacuum leak.

hoop

[jermjerm2]

Not sure about the fan running but here are the two things that I'd check out:


Other option may be the IACV could need to be cleaned:

Christian

+1 on the IACV. I had the same problem on a 91'. Removed IACV, cleaned, put back on and problem solved

[trobbins]

Thanks for the info guys . I'll try these when it gets a little warmer . It's about 17 deg today . Good thing this isn't a daily driver .

[Streetwise guy]

Clean throttle body and Idle air control valve.

Make sure throttle stop screw hasn't been moved from factory spec.

Make sure there is good coolant flow to the fast idle valve.

If it has the fast idle valve with a sheet metal cover held on with three screws, pull the cover and make sure the white plastic seat has not loosened and screwed its way up the bore.

Check the minimum airflow rate, which usually involves some combination of fully warmed up, unplugged idle motor and air bypass screw adjustment. Check reputable source (online or book)for the process for your specific model.

Make sure the throttle position sensor output voltage is between .4 and .5 volts.

Coolant temp sensor should read somewhere around 200-400 ohms at 190 degrees. Check a book or online for the spec for your specific application.

If that doesn't work, go to school, get a job in the trade, put in 5 years of apprenticeship and another ten as a diagnostic tech, and then you'll be able to figure it out for yourself, all while being paid less than a framing carpenter.:blink: Hmmm-Maybe that sounds bitter....

[R2 Racing]

Todd, I replied to your PM before seeing this thread. I also thought IACV problem, but look at the PM for more description.

[spnkzss]

+ whatever for IACV. Also possible temp sensor.

[Chip42]

the IACV is the usual suspect. if the idle shoots HIGHER than ~1200 then drops, then repeats ad nauseum, check the air bypass (idle adjustment) screw - tightining (restricting) that will often bring a surging idle under control when the IACV / FITV / temp sensor, coolant paths etc.. are verified to be good. leave it alone until those are verified, though.

[trobbins]

Thanks again to all who responded .