ClassicBenz500

Hi All,

I'm trying to diagnose a high idle on my 500 and am after some help. I know this topic has been done to death but the threads never seem to lead anywhere. Also, I'm not expecting anyone to tell me what my problem is, just how I can troubleshoot the IACV further.

Since buying the car a year ago, it has idled at about 1200 + rpm. Starts at where it should be when the engine is turned over and then slowly rises. So far I've done the following;

- Found several vacuum leaks and replaced all the offending hoses.
- Replaced the OVP relay (shot in the dark really but it was the original and looked like it had been tampered with before

- Cleaned the IACV and observed the following;
1. Nothing happens to the idle when it's unplugged
2. If I unplug the valve and put power to it, it opens and the engine slowly cuts out. So at least I know it's not just stuck completely.

So my question is, before just blindly throwing money at a new IACV, how can I determine it's actually faulty? Please note, besides doing very basic multimeter checks, I'm a total novice when it comes to electrics.


Thanks in advance!

4funtime2

I took my 560 SEC to an old school mechanic and he indicated that you (we) need to replace the AIC relay and was told to change the
fuel pump relay as well.. The worst part is he said the aftermarket ones don't work with a **** and that factory relays are as rare as
hens teeth wiht an average cost of $1,200 dollars.

I am dissenchanted with the power this vehicle has, so I've purchased a mint e55 with 37,000 miles on it and plan to move the
drivetrain accross to the SEC.. I like the idea of the e-55 driveline, however there have those that follow these cars that tell me
not to change it for fear of de-valuing the car. The drive line swap together with the wide body kit (fenders and quarters being
hand reproduced in steel) will likely result in a **** show between purists and people like me that like the look of the car/whole
package. I'm not intending to run AMG 6.0 badging when done, however I may do some creative E55 badges that folloow the
old AMG font/s.... Here is a rendering of what I'm looking to do with my car that a buddy drew for me...