PeachParts Mercedes-Benz Forum - View Single Post

stevebfl · #45 04-30-2003, 08:09 AM

After years of working on this system I find out new things every day.

A while ago I started recieving email from a gent who had a high idle problem. I replied with lots of what has been said here. I basically challenged him to identify his exact problem. He started calling me about this situation and I might have even been a little short with him one time. From the amount of time he was spending on this I thought he was a DIYer from this board. Well he solved his problem and he wrote me with extreme detail all his procedures.

It turns out that he is a tech from another board I participate in and the car was his wifes. I gave him my speel on how to ID where the air was coming from and I told him to start using various fixed substitute signals to find his problem.

He found that there is an exact voltage threshold from the POT that activates the idle control MAP. He found this voltage to be around .7v. Untill the voltage is that low the air valve is held at the ready state. This is a fixed state slightly more open than the average idle state.

I can tell you from many personal experiences that the manufacturers put only what they have to into service manuals. From every vantage they appear mortified by rampant access to info.

I think that this info is basically accurate and can state that from multiple fixes that the airflow meter pot is one of the most common idle problems. I have fixed two cars in the last couple months using his exact data. I too for a long time ignored the POT because of its stated function.