2006 ml350 idle surging by itself.
09-29-2021, 11:14 AM
#1
Junior Member
Thread Starter
2006 ml350 idle surging by itself.
Hey everyone. I'm having a bit of a problem that I can't wrap my head around. We don't drive this vehicle very much anymore so this issue has probably been around for a bit but I'm just hearing about it now.
I was getting a misfire code randomly when driving on the highway. It didn't always happen but out of the blue it would be misfiring. Restarting the vehicle cleared it up and it would continue working. Then the check engine light came on for bank 1 and 2 running lean. They would come back shortly after the code was cleared. I checked through things and everything seemed ok, but I decided to unplug to maf to rule that out. With it unplugged the vehicle ran a bit rough and had a code for the maf but the lean codes never returned. So I decided to get a new maf (bosch, from fcp euro) when I plugged it in and cleared the codes the vehicle started up fine and it had power and felt good but the idle was a bit shaky... it kind of felt like it was misfiring. I took it for a drive and everything felt good, except at idle it was shaky. Also when the ac was turned on, it would idle around 7-800rpm. But when I turned the ac off, the idle would drop to around 600, then shortly after it would go from 600 to 2000 then drop to 600 and go back up to 2000.
After looking further I noticed on the front of the intake manifold, there are 3 round vacuum diaphragms. The two outter diaphragms were no longer connected to their pivot point. I took some things apart and got those arms snapped back in.. not sure how long they have been off or how they came off, but after starting it, the vehicle idles smoothly again.
Everything seemed ok again, but after letting it idle a bit again, it started to surge again. It will bounce between 600 and 2000 rpm. I really don't know what this issue could be. I was thinking the next thing I would do is pull off the intake elbow and take a look at the throttle body to see if it is dirty and possibly clean it.
I sprayed some maf cleaner around the intake manifold and breather and vacuum hoses but never noticed anything to signal a vacuum leak. The idle might have gone up just a tiny bit when I sprayed near the maf/throttle body but it might have just been pulling some of the fumes through the intake.
Does anyone have any suggestions for what I should do next? I'm not getting any codes that signals anything right now, but that could change. Is it possible it just needs to be driven more to reset after those intake manifold diaphragms were disconnected / the maf was replaced?
Something else to note, not sure if it is in anyway related, but I noticed a month ago when I started the vehicle and started to pull away that it was making a bit of a whine. It sounded like a power steering pump thats dying. So I checked and I was low on fluid and topped it up. It might have got better but I can still hear it for sure. Which has me wondering if its a vacuum leak that I'm hearing, but I'm not able to find any vacuum leaks on the vehicle right now...
thoughts!?!
I was getting a misfire code randomly when driving on the highway. It didn't always happen but out of the blue it would be misfiring. Restarting the vehicle cleared it up and it would continue working. Then the check engine light came on for bank 1 and 2 running lean. They would come back shortly after the code was cleared. I checked through things and everything seemed ok, but I decided to unplug to maf to rule that out. With it unplugged the vehicle ran a bit rough and had a code for the maf but the lean codes never returned. So I decided to get a new maf (bosch, from fcp euro) when I plugged it in and cleared the codes the vehicle started up fine and it had power and felt good but the idle was a bit shaky... it kind of felt like it was misfiring. I took it for a drive and everything felt good, except at idle it was shaky. Also when the ac was turned on, it would idle around 7-800rpm. But when I turned the ac off, the idle would drop to around 600, then shortly after it would go from 600 to 2000 then drop to 600 and go back up to 2000.
After looking further I noticed on the front of the intake manifold, there are 3 round vacuum diaphragms. The two outter diaphragms were no longer connected to their pivot point. I took some things apart and got those arms snapped back in.. not sure how long they have been off or how they came off, but after starting it, the vehicle idles smoothly again.
Everything seemed ok again, but after letting it idle a bit again, it started to surge again. It will bounce between 600 and 2000 rpm. I really don't know what this issue could be. I was thinking the next thing I would do is pull off the intake elbow and take a look at the throttle body to see if it is dirty and possibly clean it.
I sprayed some maf cleaner around the intake manifold and breather and vacuum hoses but never noticed anything to signal a vacuum leak. The idle might have gone up just a tiny bit when I sprayed near the maf/throttle body but it might have just been pulling some of the fumes through the intake.
Does anyone have any suggestions for what I should do next? I'm not getting any codes that signals anything right now, but that could change. Is it possible it just needs to be driven more to reset after those intake manifold diaphragms were disconnected / the maf was replaced?
Something else to note, not sure if it is in anyway related, but I noticed a month ago when I started the vehicle and started to pull away that it was making a bit of a whine. It sounded like a power steering pump thats dying. So I checked and I was low on fluid and topped it up. It might have got better but I can still hear it for sure. Which has me wondering if its a vacuum leak that I'm hearing, but I'm not able to find any vacuum leaks on the vehicle right now...
thoughts!?!
Last edited by Brettriehl101; 09-29-2021 at 11:30 AM.
