190E 2.5 16v

[slartybardfast]

Hi All

My 190E has an interesting problem every now and then whilst sitting in traffic the idle will rev up to 1500-2000 rpm then settle back to 1000rpm. It can be fine for days on end then mysteriously it will happen once ore twice. I have also noticed that when slowing down in traffic that the idle drops below the 1000rpm then levels out or on a couple occasions stalled. I think maybe the idle control valve is suspect????? Origianally I thought it might of been my right foot doing it whilst braking or the floor mats. This has now sinced been ruled out. Any ideas??
T.I.A

 

[tom7035]

Hi All

My 190E has an interesting problem every now and then whilst sitting in traffic the idle will rev up to 1500-2000 rpm then settle back to 1000rpm. It can be fine for days on end then mysteriously it will happen once ore twice. I have also noticed that when slowing down in traffic that the idle drops below the 1000rpm then levels out or on a couple occasions stalled. I think maybe the idle control valve is suspect????? Origianally I thought it might of been my right foot doing it whilst braking or the floor mats. This has now sinced been ruled out. Any ideas??
T.I.A

Reminds me of a similar problem I had on my 200E 16v. I found the cure, so if your 190E is the same, worth a try, at no cost! On mine there's a black plastic-like cover about 5" x 3" on the side of the throttle body which uses 4 'security' torx screws to prevent 'unauthorised' access. These screws have a pin in the centre so you will need the torx bits with the hole in the nose to undo them. Inside is a very lightly sprung (or weighted) electronically controlled lever 'gizmo' which on mine was sticking. A squirt in the innards with magic WD40 did the trick! This was around 6 months ago and no problem since.
Good luck.
(Edit; If you can replicate the problem while at home you can try the 'tap with a small hammer' test, and it may determine whether the fault is in there).

 

[flyingtech55]

Hi Slarty...

Here is part of a post I posted previously. I don't know if your car has exactly the same setup as mine ('92 190E 2.0L). Hope this helps though. Various people told me it was the idle air valve. Happily it wasn't.

When I bought the car it would start and idle fine at 800 rpm. However, very occasionally it would idle at about 1200 rpm after starting. It would sometimes recover by itself or stopping the engine and restarting it would cure the problem. I checked for air leaks etc. and checked the electrical connectors on the engine for tarnished/corroded connections. The occurances gradually became more frequent and then the fault began to appear after the engine had been running normally. It would also sometimes idle so slowly that the engine would stall or it would stall if you switched on the blower motor. The idle speed eventually would vary between 2200 and less than 500 rpm but sometimes would be spot on. The fact that it would idle slow ruled out air leaks at least. The fault became at last solid enough to do sensible diagnosis on it.

The upshot was that I found the fault condition was caused by the microswitch fitted to the throttle linkage mechanism. It is clearly visible on the near-side of the engine beneath the air filter box and is held in position by one small hex head machine screw and is fitted with one electrical connector. The part number could be 002 545 68 14 or might be 3056-0611-0. There's several numbers on the poly bag. I'm not sure which one is the part number. Anyway it cost £15 and had to be specially ordered by the dealer. Only took a couple of days to arrive and ten minutes to fit. No dismantling involved. Incidentally, that's the only part I've bought from the dealer that had to be ordered. They've always had any other parts in stock. I fitted it six weeks ago and the car's been fine ever since (touch wood). I was told it was probably the idle air valve but it costs £160. I'm glad I went for the switch first.