Momentary surge in idle in Park to 2K after Denso Spark Plug change- PLEASE HELP
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Momentary surge in idle in Park to 2K after Denso Spark Plug change- PLEASE HELP
Hi All,
The other night I changed my spark plugs out, and used Denso iridium pre-gapped plugs. I did not check the gap since the box said they were pre-gapped, plus it is my understanding that it is near impossible to change the gap in a iridium plug since the metal is so hard.
The install went fine, but the next day the idle felt strange. While driving without foot on the pedal, the car seemed to want to "go". Most importantly, when I would park the idle would surge up to 2K RPMs for about 3 seconds. It was very upsetting.
Reading through various forum posts, a likely suspect was a vacuum leak. So last night I closely inspected where the engine cover meets the throttle body and made it as snug as possible.
The situation greatly improved, and now the idle only momentarily surges to 2K in park and then stabilizes back down. Before I made the adjustment, the engine would stay at 2K in park for seemingly a long time.
The only course of action I can see is to put in the old plugs (but clean them with wire brush first). I'll also clean the MAF and throttle body for good housekeeping.
Has anyone had a similar experience or can offer suggestions???
The other night I changed my spark plugs out, and used Denso iridium pre-gapped plugs. I did not check the gap since the box said they were pre-gapped, plus it is my understanding that it is near impossible to change the gap in a iridium plug since the metal is so hard.
The install went fine, but the next day the idle felt strange. While driving without foot on the pedal, the car seemed to want to "go". Most importantly, when I would park the idle would surge up to 2K RPMs for about 3 seconds. It was very upsetting.
Reading through various forum posts, a likely suspect was a vacuum leak. So last night I closely inspected where the engine cover meets the throttle body and made it as snug as possible.
The situation greatly improved, and now the idle only momentarily surges to 2K in park and then stabilizes back down. Before I made the adjustment, the engine would stay at 2K in park for seemingly a long time.
The only course of action I can see is to put in the old plugs (but clean them with wire brush first). I'll also clean the MAF and throttle body for good housekeeping.
Has anyone had a similar experience or can offer suggestions???
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Yeah, good point. It occurred to me as I was rereading my post that the ONLY thing that has changed in my car were the spark plugs, so getting back to the baseline with the original plugs seems like the obvious thing to do first, instead of doing new stuff. That way, I can try to isolate the problem. Not sure yet though...
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Actually denso iridium plugs are one of the Mercedes specified plugs. I think that the issue is that the gap varies from plug to plug. Why would you say iridium is not as good for Mercedes? Thank you.
Thread Starter
MBWorld Fanatic!
Joined: Aug 2015
Posts: 1,059
Likes: 73
From: DC Metro Area
2007 Mercedes E550
Well after looking at a couple videos I realized that I am a dummy and did not re-connect the big vacuum line on the bottom side of the engine cover on the passenger side!!
