Engine revs at idle

R LTD · Post by **R LTD** » Tue Sep 18, 2007 8:21 pm

I'd like some assistance to diagnose an issue. Once the engine is warm and sitting at the lights the engine revs will suddenly increase by 250-300 revs for about 45-60 sec and then drop back to normal idle speed. I've let the car sit for an extended period and the situation will repeat itself.
What is the likely cause and remedy.
Thanks

R LTD javascript:emoticon(':)')
Smile

poison · Post by **poison** » Tue Sep 18, 2007 8:52 pm

What year is your car??? Some of the early NA 1600's have a front crank/pulley issue that others may explain more clearly. Are you an auto or a manual?

Maybe this is stating the obvious but it's the obvious that's often missed. Is your aircon stuck on??? This turns on and off during idle resulting in verying revs.

R LTD · Post by **R LTD** » Tue Sep 18, 2007 9:03 pm

1995 NA 1800cc. I will need to check the a/c but don’t think stuck on as recently serviced.

Post by **zorruno** » Tue Sep 18, 2007 10:07 pm

R LTD said on 09/18/2007 08:21 PM:

I'd like some assistance to diagnose an issue. Once the engine is warm
and sitting at the lights the engine revs will suddenly increase by
250-300 revs for about 45-60 sec and then drop back to normal idle
speed. I've let the car sit for an extended period and the situation
will repeat itself.
What is the likely cause and remedy.
Thanks

R LTD

I've heard of this a few times, but not sure what the cause/remedy is
sorry. It hasn't happened to my '94.

Firstly is the idle speed adjusted correctly? (800-900rpm - Done with a
timing light & jumpered diagnostic connector?)

This google search may help you find more info:
http://www.google.co.nz/search?q=miata+idle+droop

cheers