1992 230TE poor idle **SOLVED** + HOWTO

[The Crooner]

Eventually, the car is now idling properly.

The main offender was the throttle position sensor - this is the old one, and you can see quite clearly where the metal contact has worn the resistive coating on the pcb:

this is the new one, sourced from ebay:

you can see the full extent of the coating on the pcb.

My advice to anyone with ongoing idle issues is:

mark very carefully around your throttle position sensor, remove the 2 caps covering the four fixing screws, and examine it.

ensure that the mechanics of your throttle linkage are working as designed, parts are available from the dealer quite cheaply.

change all of the sensors - vacuum and ignition/FI temperature sensor, air inlet temperature sensor, Lambda sensor

change the idle control switch at the end of the throttle linkage.

These parts will cost you around £120, and the sensors will all make your engine run better anyway.

If the throttle position sensor is flaky and you have changed everything else, you will know the problem is that or the ECU.

I have a spare ECU for a 230 should anyone wish to borrow it for testing purposes.

Tony

 

[roofless]

take the wee bug%$£ & put it under the back wheel & run over it several times

 

[television]

This is the third great post of the day

 

[The Crooner]

Quick follow up.

Worked today at an event so left stupidly early and drove to Birmingham, parked in Jury's Inn car park off Broad Street where the event was. Horrendous traffic all the way from the M1/M69 junction - arrived 9.30am.

Left at 4.00pm, so pretty much the same coming back.

262 miles, 8.4857 gallons brim to brim, 30.87 mpg and never stalled once.

Think I'll keep it for ever.

Thanks again everyone for your help.

Tony

 

[The Crooner]

Final update

I received a new idle control switch in the post on Saturday from the ever helpful parts people at Boston Mercedes.

Not a revelation, but another improvement over my original, and the second hand one I had.

I have a theory that as the switch wears, and if you think how many contacts it makes per mile, it must wear, it does not switch the full voltage, or give the correct ohms figure when on and off.

This means that at times the engine will be using the idle circuit when not required, leading to unresponsive performance, and not use it when its required, leading to poor/bad idle.

All I know is the car is now chalk and cheese from when I bought it. Another trip to Birmingham on Thursday, another nightmare journey, but no issues, and just about to click over to 195000 miles.

Now if I could get it to 250000 miles with little more outlay, that would be really cheap motoring...

 

[Mercedes 190E]

Glad you sorted it Tony. Mine has done 235,000 so not far off your target!
I am near Birmingham-if you have time when you are over, we could compare tailgate wiring problems.....

 

[The Crooner]

Next over Tuesday 24 February, where are you?

 

[Mercedes 190E]

Walsall Tony (Just off J7 9 or 10 M6) Can be free on 24th if you want to drop in for a coffee !