Lumpy idle / poor cold starting. Cured

Sat Feb 16, 2008 9:28 pm

So,

I had a problem with the M20B25 idling poorly when warm and not starting ideally from cold. I knew that the plugs, rotor arm, distributor cap and blue temp sensor were all good as I'd just replaced them. After having a look via the search function on here, I tried the following:

Removed air flow meter, idle control valve and all associated hoses. Opened up the airbox and gave the filter a good clean. Cleaned throttle body, air flow meter and idle control valve with the carb cleaner. Could not believe the black crud that came out of the idle control valve !!! Oh yes, I found a split hose from the ICV to TB, which I have temporarly repaired with electrical tape. Refitted everything and started the beast up.

The first thing that I noticed at start up was the increased idle speed which was now approx 1200rpm. Adjusted the screw on the airflow meter, which was screwed fully down to compensate for my the poor idle, by about three full turns. I believe this to be about right.

Took the car for a good run and really felt a difference in driveability, and the poor starting and lumpy idle have completly gone thankfully.

Just thought I'd share this with you guys, as I think that these are some nice and easy things to try if you car's not running 100%.

Sat Feb 16, 2008 10:07 pm

Well done on the job, the smallest crack in some of them hoses can really mess the idle.

Sun Feb 17, 2008 12:22 am

Doesnt the 325 do this when the battery has been disconnected for a while?

I have noticed that if you let the batt go flat the car idles and runs like a dog for a while but after about ten miles sorts itself out while the ECU relearns how to idle properly, could this have been what caused your problem?

Sun Feb 17, 2008 10:32 am

pilt wrote:Doesnt the 325 do this when the battery has been disconnected for a while?

I have noticed that if you let the batt go flat the car idles and runs like a dog for a while but after about ten miles sorts itself out while the ECU relearns how to idle properly, could this have been what caused your problem?

Doubt it very much. The car has never idled correctly since I've had it, and I've fitted a new battery already which made no difference. The ECU has been out to have the zone chip fitted and this also made no difference to the idling.

I believe the clogged up ICV and split hose were the culprits in this case.