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  #1  
Old 11-25-2003, 08:35 AM
mattsuzie
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Trouble when idle / taking off (420 SEL)

On my 420 SEL, 230K miles, the car bumbles and shakes a little more than desired when the car is in drive and when I am stopped (like at a traffic light) and when I first hit the gas pedal. The trembling completely goes away after 10 mph.

Usually something like this has happened when I had a bad spark plug. I had all the wires and plugs replaced about 4 months ago for routine maintenance. About 2 weeks ago this trembling started and the mechanic could not figure it out. He replaced all of the spark plugs just to be sure yesterday for $105 and nothing has changed.

The tech's only other idea is the fuel injectors. He "leaned" out the fuel mixture a little bit, according to him, to try a cheap remedy, but it did not work, maybe a tiny bit, but nothing significant.

Does anyone have any ideas? Despite the mileage, the car runs pretty strong. This trembling is annoying and may cause engine damage if I do not address it. My only other option is to take it to a dealer and replace one of the fuel injectors? How to determine what the cause is?

Thanks.


Last edited by mattsuzie; 12-01-2003 at 12:02 PM.
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  #2  
Old 11-25-2003, 09:09 AM
mattsuzie
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The tech thinks that it could be the "fuel distributor head", something like that. There is a filter in that head which could clog up and the only way to fix it is to replace it which cost $500 just for the part. He said it most likely cannot be anything else.

Any thoughts would be appreciated.
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  #3  
Old 11-25-2003, 09:18 AM
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That is a very expensive "could be".
Did you check/clean the idle control valve?
Clean the throtle body?
I would keep searching before I spend $500.00
$105.00 is too much to change sparkplugs.
I would be suspicious of the mechanic.
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  #4  
Old 11-25-2003, 09:33 AM
mattsuzie
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Thanks. Not sure. My guess is if that is a quick thing I would guess so, but I need to ask. I've been going to him for 5 years, but yeah $105 bucks is steep for changing the plugs. Maybe he added the labor for tweeking the fuel mixture or something.

Normally he has been pretty good, but this time, it has been difficult.

Another suggestion was putting fuel injection cleaner in my gas tank.
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  #5  
Old 11-25-2003, 09:47 AM
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That is something I would try, but use Techron.
I was experiencing sort of the same problem, cleaned the Idle control Valve (thoroughly) ran Techron (big bottle) went to Asheville, and problem disappeared. Try to run the Techron right before an oil change.
I see you are at the RTP. I am in Clayton, NC.
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  #6  
Old 11-25-2003, 10:02 AM
mattsuzie
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I can get to Clayton. Are you a tech or a MB owner? Thanks.
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  #7  
Old 11-25-2003, 10:16 AM
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I am an owner, who loves to tinker with cars under a "shade tree"
I can't wait for my job to give me a final placement such that I can buy a house with a 2 car garage. The apartment complex where I reside recently sent me a letter of "encouragent to stop my mechanical practices in the parking lot". HAHA
This was after I decided to change the discs rotors, brake pads, and faulty starter in my trusty Geo Tracker. I had an audience of guys around me trying to learn. It was so funny, they thought that I actually was a mechanic.
There is a member of this forum who works (owns?) in a shop in Raleigh. His name is Joe P - Acme Automotive.
Still, just let me know, and one of these days we can meet to discuss car problems and try to fix them over a few beers.
Are there any other members in the Raleigh area?
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  #8  
Old 11-25-2003, 10:50 AM
mattsuzie
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The tech really thinks that it is the fuel head (said it had nothing to do with the idle thing). He said that the fuel head replacement can run as high as $1500.

Another option is to try running fuel injector cleaner in the gas tank. Any ideas of what brands work the best?

Any thoughts? Is stevefl still out there?

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  #9  
Old 11-25-2003, 10:51 AM
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I'm not sure from your description if your problem is a varying idle speed and the engine stumbling off idle..... or if you simply feel too much vibration or bouncing around of the engine. If the latter, I would first suspect engine mounts having collapsed.

Steve
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  #10  
Old 11-25-2003, 12:02 PM
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The tech REALLY THINKS it is the fuel head?, the one that runs between 500 and now 1500?
And the car only stumbles at IDLE, and after 10 mph drives well?
Buddy, time for a second opinion. If the problem is ONLY at low RPM's (idle) I do not think now 1500, on top of 105 to change the sparkplugs is a solution.
We have not even looked at wires, distributor cap and rotor yet.
Fuel filter, air filter when were they changed?
Good point about the motor mounts.
I always go for the cheap fixes first. Clean the ICV, see what happens, clean throttle body, see what happens, change sparkplugs, see what happens, remove dist. cap and rotor-inspect and clean-replace if necessary, see what happens,... and so on.
I get scared when a mechanic tells me:

"I THINK the problem is this..., it is going to cost $$$$$$ to replace it" ....(and let's see what happens)
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  #11  
Old 11-25-2003, 12:47 PM
mattsuzie
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The motor mounts were checked first thing and it ain't the problem.

Fuel filter, air filter, Wires, distributor, rotor, plugs, etc., was replaced around 3,000 miles ago (~ 3 months ago). The plugs were also replaced yesterday. The throttle thing ain't it.

The problem is how I described earlier. While the car is in drive and at a stop the car trembles and shakes a little due to the engine. It also continues to do that as you lift your foot off the brake and give it gas. The engine runs smooth after 10 mph on up. The idle speed does not taper off nor does it vary significantly. The RPM does bump up and down (when < 10 mph)a little bit during this because the engine is not running right. The tech said that the "fuel head" has a mechanisim in there that is dirty and the only way to fix it is to replace it. "You cannot clean it. "

I have been going to this guy for 5 years and had done great. He said he tried everything, and according to him, he is sure that it is the "fuel head". Let's stop beating him up. I don't think he is trying to pull a fast one, I am just wanting to see if anyone else had similar issues and found something else. Yeah, I might take it to the dealer if the additives don't work.

What I am looking for is input on does anyone know what this $1500 fuel head does? Is it that expensive? Does anyone have any fuel injector brand recommendations other than Techron?

They told me that BG products has a good product and to try that first. I was also thinking, although a long shot, it could be the tank of gas that we last bought could be bad?
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  #12  
Old 11-25-2003, 12:51 PM
mattsuzie
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Just to clarify. It is not the motor mounts. I can feel that the engine is not running right when < 10 mph. Can the engine get proper fuel when > 10 mph, but not < 10 mph? I don't understand how the fuel head works.
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  #13  
Old 11-25-2003, 01:09 PM
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Ok, the only thing that has that price is the fuel distributor @1800.
The second thing I can think of is the air flow meter @600.
Again, let's do the methodical step by step troubleshooting method.
This happens only at slow speed, low RPM.
If it was fuel delivery problem (fuel head=fuel distributor?) I would expect it to be at all times.
Now, partially clogged injector(s) could do this at idle. Faulty ICV, OVP, EHA could also cause the problems you describe.
What I do not understand is what is the fuel head (fuel distributor?)
ICV,OVP and EHA haven't been checked/cleaned? those are relatively cheap, and possible causes for the problems you describe.
I was experiencing similar problems, and cleaning ICV, running Techron and cleaning Throttle Body FIXED my problems (about 8 months ago).
I have found that Techron is the best Injector cleaner.
I hope your problem gets fixed, I have one right now, with the water pump (I think)
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  #14  
Old 11-25-2003, 01:24 PM
Q Q is offline
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BG 44K is the product you were talking about. I picked some up today.
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  #15  
Old 11-25-2003, 01:28 PM
mattsuzie
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Thanks. Yeah, I am talking about the fuel distributor. Could the fuel distributor be slightly clogged? Good point about happening at all times. The bumbling goes away after 10 mph. I guess I need to try some cleaner and fresh tank of good gas.

Is the fuel distributor something that can clog or does it just fail completely when it is shot?

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