I know this has been discussed, so forgive me for bringing it up again, I'm just hoping for some more specific answers than I've found by searching the forums.
I was recently given a 2001 ML 320 for free, so I figure I can't go too far wrong, but I don't want to get too deep into it and find it needs too much work. The car has 157,000 miles on it, it's a little rough, but in generally good shape.
Previous owner says they weren't able to fix the throttle delay, but I don't know what they tried.
Symptoms:
Car starts and idles fine (around 600-750 rpm), when I press the throttle nothing happens for several seconds, then the engine revs normally (same symptoms whether hot or cold). This happens with transmission in park or neutral and when driving. Acceleration seems normal after the delay (although I don't have anything to compare it to). While driving at any speed, the delay is still there. For instance, while driving at 45mph I can press the throttle and nothing happens for several seconds, then the car will accelerate.

I tried the throttle position reset procedure: Key on, pedal down for 5 seconds, key off, wait 2 minutes, start car. Does the key need to come out at the end of this procedure?
With a basic scanner I got the following codes:
P0120
P0220
P0401

I cleaned the EGR, it was about 30-50% clogged. Cleaned MAF, it didn't look bad. Replaced throttle position sensor. Cleared codes and still had same symptoms. Did the throttle position reset with the key again and it worked great. I drove the car, highway and city for about 20 minutes with no problems. Car was not driven for about 2 weeks and now the problem came back as soon as I started the car.

Code P0220 is back. I drove the car for a little while, and now the 0120 code is also back as a pending code.

Any ideas on what to pursue next would be greatly appreciated!

 

anduril3019,

Based on what rudeney supposed to you (in the other forum), have you followed thru on it yet?
Also, it wouldnt hurt, but try throwing 2/3 can of seafoam via the brake booster vacuum line (be careful when removing the vacuum line) to clean out the top end.
You'll need help with someone at the pedal to keep the revs up above 2500-3500rpm when doing this. And you're going to get alot of white smoke at the tail when you do this. The balance of the seafoam into the gas tank.
And run this until the white smoke is gone.
You may get a code or check engine light pop up during this process, but thats ok.
Did you check of any vacuum leaks?

 

Thanks khomer2.
I haven't followed thru on other suggestions yet, hoping to get to it this coming weekend.
Yesterday I tried disconnecting the battery and letting it sit a while. When I reconnected, the throttle is back working normally. I drove for about 20 minutes and it ran great. Fired it up again this morning and it seems all good. I'll still follow thru on throttle body cleaning and try the seafoam.
Keeping fingers crossed!