Lumpy Idle and high cold start rpm.

[mike65]

Bit by bit my 190e is running better (and quieter) but its lumpy idle remains, the plugs and leads have been renewed, so what do I need to look for and in what order of cause proberbility?

I should add that the cold start is rather hectic with tickover reaching 1350-1400 rpm for a short while and settling down to 900 after about 90 seconds (the 900 rpm is deliberate to try to smooth out the idle).

Also I usually have to crank the engine twice on a warm start. I dunno if all this is related but all knowledge is greatly welcomed. Also if you mention something like the aux air device please explain what it is and what is does...cheers.

Mike.

 

[mike65]

Quick bump....anyone?

 

[talbir]

I would check the Over-Voltage Protection relay first - it's a silver relay with a red-top, usually located in one of 3 places- in the fuse-box, behind the battery or midway between the two.

Next up check the idle air valve - this controls the amount of air and should shut after car has warmed up. Your idle should be approx 900rpm at cold and approx 650rpm at operating temp. So your idle air valve may not be closing fully.

Or you may have a vacuum leak after the throttle body - could be anywhere in the array of vacuum pipes, but most likely are the injector seals. Spray WD40 around the injector seals with engine running - if engnie revs drop then you have a vacuum leak caused by injector seals.

Your warm start problem maybe casued by an over-rich mixture. I would reccomend getting the CO mixture adjusted first by a tech and then proceed with the fault finding.

If warm hard-starting problems persist, then it's probably the fuel accumulator, which maintains fuel pressure for a while after car is switched off. This fuel accumulator is located at the back under the car, with the fuel pump and fuel filter.

 

[mike65]

Useful clear info - I like it!

Cheers

Mike.