Revs....

[cjgreaves41]

Another Day, another minor issue.

My 1.8 eunos has started to hold revs at about 1500rpm after driving. So pull up at some lights and the revs drop to 750 then climb to 1250-1500rpm for about 7 seconds then drop back down to 750rpm-ish. It's not every time but 9/10.

Not a massive issue more of an annoyance. But I'd prefer it not to do it!

Oddly I didn't notice it until I'd had the cambelt changed last week.

Cheers

[BenF]

sounds like an ICV/ISV to me... ask MM.

sorry- Idle Control Valve / Idle Stabilisation Valve.

could also be an air leak?

[Mazda Mender]

air con switch on? or it's a Air leak or clutch switch? more towards a air leak.
M-m

[paggers]

If the timing belt was changed then they had the intake piping off. In line with MM's comments first place I would look is to check that everything between the air filter and the intake is properly mounted, sealed and undamaged.

Good luck with getting it sorted.

[cjgreaves41]

Hmmm Id assumed air leak. Had a bike engined car that had an air box leak, just used to rev its nuts off.

However why would the revs drop back off to normal idle after afew seconds? Wouldnt it just stay reving??? I will check pipe work and see whats what.

The car has air con, which appears not to work! Sort of havent bothered with it. When you press the button (ON) the revs drop slightly then stablize.

[BenF]

Because the idle stabilisation systems and emission control/ECU will be trying to correct the idle mate, afaik, most bikes don't have that system

[cjgreaves41]

I'll have a look. deffinately only started after the cambelt was done.... There arent any gaskets in between are there?

The bike engined thing we built.... Formula student at uni. Throttle (butterfly) fed directly into the plenum. The carbon plenum we'd built had a slighty crack in it so the engine could suck as much air in as it liked!

Im still fairly convinced carbs are the future!! Will let you now how I get on! Thanks for the help

[cjgreaves41]

So buggered about for an hour checking intake pipe etc for leaks. Couldn't find any problems. Don't have any time to sort this before I need to head off in it next week.

After only a month I'm getting a tad annoyed with it. Dropping it off at Roddisons tomorrow. They can keep it until its right! Fairly sure its not their fault just coincidental, but i'm sure they'll fix it!

Also more water (approx' 100ml) has vanished from the expansion tank again!

[binarypunk]

Definitely sounds like a dodgy connection on the ISC valve to me, as Ben says.

[cjgreaves41]

Bugger.....

They cant pin it down. I'm going to pull one off the spare car and see whats happens!.... Thought these things were reliable!

[BenF]

Bugger.....

They cant pin it down. I'm going to pull one off the spare car and see whats happens!.... Thought these things were reliable!

they are... but not as reliable as a vintage Royce

[paggers]

Everything is reliable until it stops working. Hope you get to the bottom of it soon.

[cjgreaves41]

Ive found an airleak! 4 small holes in the main air feed pipe from MAF to Throttle body, cuase by the theromstat by pass hole clip rubbing on the pipe. Replaced pipe with spare, and moved the clip round, and it now idles great (at 800rpm).

Took it for a drive and warmed it up and still wont return to idle properly! So sitting at junctions for 5 - 10 seconds at 1500rpm.

I Have a spare throttle body with attached idle vavle but am reluctant to change it over as Ive tested the resistance of each and its 12.0 on the spare and 12.5 ohm on the one fitted to the car (both within acceptable rnage accoring to the manual).

If I disconnect the green plug to the idle vavle when the car is idling the revs dont change (800rpm) however there is a slight chnage in engine noise. With the plug connected there is a slight plusing noise (sounds almost like bubbling water) with the plug disconnected this stops.

Obviously if i blip the throttle with the vavle off the engine revs but then drops to almost 0 before returning to idle.

HELP!

[binarypunk]

Just because the solenoid's resistance tests ok, the valve could still be coked up. Worth taking it off and cleaning it up as it's a common problem.

[cjgreaves41]

What's best way to clean it? I've heard carb cleaner can do more harm than good. Any thoughts?