Rough Idle at startup and stall..
Thread Starter
Super Member
Joined: Apr 2003
Posts: 690
Likes: 33
From: Bay area - California
2000 ML320 2006 SLK 350
Rough Idle at startup and stall..
ML320 : 132k Miles
I just got my CPS & Fuel pump replaced last month.
Spark plugs were replaced at 100K miles...
I had the classic CPS symptom of engine cranking but not starting when hot, before the CPS was replaced. The fuel gauge had been acting funny for a while and I was starting to hear funny sounds from the fuel tank.
Me & my mechanic agreed that replacing both made the most sense. So, my classic CPS symptom is gone now..
Since last week, I am now noticing a new symptom...crank the engine and it starts off by idling rough...and then stalls..crank again and same thing...do it a couple of times and then fires up...once fired, runs fine...no stalling midway on a red light or anything...so it doesn't seem like the CPS anymore...
I had done the plugs at 100K miles, but not the wires/ignition coils. I am thinking it is probably one of the two and I have even heard of failing oxygen sensors causing this symptom.
Question: Should I do all 3 or start with the plug wires first, then go the coils and then the oxygen sensors?
Would there be a definitive way of pin pointing the real cause?
There is no CEL on my dashboard...
I just got my CPS & Fuel pump replaced last month.
Spark plugs were replaced at 100K miles...
I had the classic CPS symptom of engine cranking but not starting when hot, before the CPS was replaced. The fuel gauge had been acting funny for a while and I was starting to hear funny sounds from the fuel tank.
Me & my mechanic agreed that replacing both made the most sense. So, my classic CPS symptom is gone now..
Since last week, I am now noticing a new symptom...crank the engine and it starts off by idling rough...and then stalls..crank again and same thing...do it a couple of times and then fires up...once fired, runs fine...no stalling midway on a red light or anything...so it doesn't seem like the CPS anymore...
I had done the plugs at 100K miles, but not the wires/ignition coils. I am thinking it is probably one of the two and I have even heard of failing oxygen sensors causing this symptom.
Question: Should I do all 3 or start with the plug wires first, then go the coils and then the oxygen sensors?
Would there be a definitive way of pin pointing the real cause?
There is no CEL on my dashboard...
Newbie
Joined: Apr 2007
Posts: 10
Likes: 0
I would say plugs. Also run a couple of tanks with the big bottle of Chevron Techron.
ML320 : 132k Miles
I just got my CPS & Fuel pump replaced last month.
Spark plugs were replaced at 100K miles...
I had the classic CPS symptom of engine cranking but not starting when hot, before the CPS was replaced. The fuel gauge had been acting funny for a while and I was starting to hear funny sounds from the fuel tank.
Me & my mechanic agreed that replacing both made the most sense. So, my classic CPS symptom is gone now..
Since last week, I am now noticing a new symptom...crank the engine and it starts off by idling rough...and then stalls..crank again and same thing...do it a couple of times and then fires up...once fired, runs fine...no stalling midway on a red light or anything...so it doesn't seem like the CPS anymore...
I had done the plugs at 100K miles, but not the wires/ignition coils. I am thinking it is probably one of the two and I have even heard of failing oxygen sensors causing this symptom.
Question: Should I do all 3 or start with the plug wires first, then go the coils and then the oxygen sensors?
Would there be a definitive way of pin pointing the real cause?
There is no CEL on my dashboard...
I just got my CPS & Fuel pump replaced last month.
Spark plugs were replaced at 100K miles...
I had the classic CPS symptom of engine cranking but not starting when hot, before the CPS was replaced. The fuel gauge had been acting funny for a while and I was starting to hear funny sounds from the fuel tank.
Me & my mechanic agreed that replacing both made the most sense. So, my classic CPS symptom is gone now..
Since last week, I am now noticing a new symptom...crank the engine and it starts off by idling rough...and then stalls..crank again and same thing...do it a couple of times and then fires up...once fired, runs fine...no stalling midway on a red light or anything...so it doesn't seem like the CPS anymore...
I had done the plugs at 100K miles, but not the wires/ignition coils. I am thinking it is probably one of the two and I have even heard of failing oxygen sensors causing this symptom.
Question: Should I do all 3 or start with the plug wires first, then go the coils and then the oxygen sensors?
Would there be a definitive way of pin pointing the real cause?
There is no CEL on my dashboard...
Thread Starter
Super Member
Joined: Apr 2003
Posts: 690
Likes: 33
From: Bay area - California
2000 ML320 2006 SLK 350
My mechanic tells me to start by switching to another ignition key....
I will try the Chevron Techron today...
Plugs are only 30K miles old...they should be okay...
He thinks, the plug wires could be next, then the ignition coils and finally the oxygen sensor..
Last edited by mihir_d; Jul 24, 2009 at 07:37 PM.
Newbie
Joined: Nov 2013
Posts: 3
Likes: 0
ML320
Rough Idle New MAF
Hi, I have just replaced my MAF sensor on my ML320 2002 w163 having tried some cheaper versions had to go for a Bosch. Now I have a rough idle on start up until I give it some gas.... please help.... I love the car but its becoming a bit annoying now...
Super Member
Joined: May 2013
Posts: 504
Likes: 7
From: Harare, Zimbabwe
2003 ML55,2007 ML63
Mihir don't throw money away for nothing. Have the car scanned with a pro level scanner & post the codes. You cant fix an ML by guessing or buying parts that may or not be the cause of the problem. That will be a very expensive & frustrating venture.
