Erratic Idle - Changing Throttle Body / ICV

[rossyl]

Hi All.

I have the following issue with a MX5 mk1 1.8.

Occasionally the idle surges to above 1000 RPM, then drops and stalls. Or, very occasionally, drops pretty low for a shirt while before recovering.

It tends to happen when the car is hot, after a hard run, and is then sat idling and stationery.

Dipping the clutch makes no difference.

I tried a different MAF, initially this led to a higher idle speed, but now the same problem has returned.

I have been advised to change the throttle body and ICV. I've found this video:
https://www.youtube.com/watch?v=G7keMMthYrQ
https://www.youtube.com/watch?v=a0P2p8QMOIA

It looks manageable. However, will i not need to re-set the ICV screw?

Also - the gasket for the throttle body, what is this? In the first video they just use a paste, in the second an actual gasket.

Thanks

[David-cuykx]

I had something similar on Sunday with my 1.6 Eunos, thought I would try and clean the idle control valve or replace it, but I filled her up with some fresh petrol first as the old stuff had been in there from last summer. Problem went and the idle was back to normal!

Hope yours is an easy fix too!

[Pete Franklin]

Use injector cleaner to clean through the butterfly valve. This should sort the issue.

[rossyl]

The issue was actually the Clutch Switch. Which lets the ECU know that the car is in gear.

[finishing touch]

And there was me thinking, it's the MAF sensor.

[WonkeyDonkey]

I know your problem has now been solved, and this is for a different car but may be relevant to most cars.

I had an almost exact same issue in my k series Elise. Battery change ended up solving my issue.

Just thought this may be helpful for anyone googling this problem in the future.

[anonymous-user]

I had a similar issue on my 1996 1.8; a slight blip of the throttle saw the idle go to 2000 rpm, and just hang there for 10-20 seconds, making travel in slow traffic a pain.

Used some intake cleaner first to check there were no leaks around the injectors, then clean the intake. Engine off, I decided to give the butterfly on the throttle body a clean. Big mistake, because the little straw on the cleaner aerosol shot off deep inside the inlet manifold. Confirmed on the 1.8., the gasket is a reusable plastic gasket (on the 1.6 I had, it was a paper gasket). Trying a vacumm cleaner to move the straw was a fail, but it really cleaned that intake manifold. I just fired it up with the straw in place. Besides a few seconds of what seemed like a burning plastic smell, no apparent ill effects. Reset the idle, and the car idles better than it has in years,