85 190E 8vlv Hesitation
I have a problem I have been trying to fix for quite a bit now. I bought the car in April 2002, with a new engine. Car has 250K km on it, and engine about half that.
My problem is that the car hesitates as soon as it warms up. It will even sometimes miss ( think I hear a thump from the engine) when I accelerate hard and it only does this in the 1500-2000rpm, anything above 2000 is solid as steel.
I went through the test procedures outlined in the manual for all the electrical parts and my tests are not very conclusive.
Here is what I gathered so far
EHA current is fine on start up, once the car warms up, it will drop to 0mA when I come to a stop and the car will hesitate until the current to the EHA jumps up for about a second or two. I think this might give a good idea to someone who knows these cars as to what the cluprit is.
When the car is really hot, and in idle, the current in the EHA will jump to 8mA and then the car takes off like it should, no hesitation, I think this is how it's supposed to be.
I pulled the spark plugs and an examination shows that the engine is running rich, lots of carbon deposit on new platinum plugs, I heard these are bad for your car.
As I was going through the test procedures in the manual I came to the MAF (Mass air flor sensor) and Discovered that the Resistance on it is not in the right range, 0.98Kohm to 3Kohm as opposed to 3.2-5.2 Kohm as the manul states. I now have a multimeter hooked up to pin #1 and #3 and I see 18V flowing in idle and current dropping down to 10V around 3000rpm. I don't know if this is it but I think it should be corrected either way.
Having tested all other electical parts, the only other part not working right is the barmoteric sensor which I get no signal from at all, I have yet to re-test it for some kind of results.
Post enrichement of mixture checks out to be correct and the car starts up every time with 0 problems.
Hesitation is sometimes sever sometimes not so sever.
The current in the EHA sometimes jumps up right away, sometimes not at all until I reach 2000rpm and then it slowly goes up.
When engien is cold the current in the EHA jumps up very quickly.
I have a few questions. What should be the current in pin #1 and #3 in the MAF? Should I check this any other way?
And of course, what else besides a fuel pressure test can I do to find out what could be causing this???
I'm a bit stumped right now since I was quite sure it was the MAF, but the readings from it are very nice and never erratic, but I can't cofirm if they are our of range or not, if so I can just put a resistor there to get them to the right value, I dont' want to replace a sensor that works since this one is very expencive.
Any other suggestions are welcomed.
Thanks everyone, this forum is great.