E-Class (W124) 1984-1995: E 260, E 300, E 320, E 420, E 500 (Includes CE, T, TD models)

hesitation drives me mad..

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Old 06-11-2006, 01:15 PM
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hesitation drives me mad..

hey all,
recently my car developed a hesitation habit when i accelerate with (or more than) half throttle from standstill.. it would hesitate for a second or so (probably less) and would stutter but after that, the car runs fine..

i've just replaced my spark plugs..

oh and just to top everything off.. after servicing my car (DIY), my parking brake light would come on whenever the car accelerates.. i.e. when the inertia is going backwards.. this seems really strange and at the same time really annoying..

the DIY included... spraying carb cleaner into manifold, replacing the spark plugs, resetting the ECU by disconnecting the battery for 30mins

any ideas?

cheers,
jeff
Old 06-11-2006, 01:45 PM
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1992.5 400E W124
I had this problem (sometimes) until I changed the fuel filter.
Old 06-11-2006, 02:01 PM
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Did you change the plug wires along with the plugs? Bad wires will give you some hesitation. And I agree - check the fuel filter for sure.

Look at the wires for the engine wiring harness. If they are cracked and disintegrating, you'll need to replace that. ($$$$)

I hope it's not that.
Old 06-11-2006, 11:20 PM
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Could the fuel filter really be the culprit? This is really strange as I am only feeling the hesitation when I accelerate from standstill… Although the car has been a bit reluctant in terms of acceleration recently…

Is there anything I should get done while I’m getting the filter replaced? Oh this is not an expensive fix is it?

Lastly, how often do you guys change the fuel filter(s)? I don’t think mine has ever been changed. It’s done 93000km (equivalent to 58000miles)…

Cheers,
Jeff

P.S. No I didn't change the leads. Should I?

Last edited by jeffreyli86; 06-12-2006 at 04:46 AM.
Old 06-12-2006, 10:13 AM
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Originally Posted by jeffreyli86
P.S. No I didn't change the leads. Should I?
The leads are more likely to be the problem. Buy Bosch.
Old 06-12-2006, 10:52 AM
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Was 89' 300E, Now 93' 500SEL
Hey! i have the exact same problem as you. my car studders when i take off fast. So its the fuel filter you say? i ahve new spark plugs but not new wires...
Old 06-12-2006, 02:31 PM
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Originally Posted by hellah fresh
Hey! i have the exact same problem as you. my car studders when i take off fast. So its the fuel filter you say? i ahve new spark plugs but not new wires...
If it were me, I would figure out which of the two (fuel filter or plug wires) I would need to replace soonest and start there.

However, I think I would replace the wires first as they are the most likely culprit IMHO.

It seems to me that although a clogged fuel filter would cause hesitation during acceleration as opposed to idling or other low RPM situations, it would also do the same thing during other high fuel consumption times, like high speed driving.
Old 06-12-2006, 02:49 PM
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Was 89' 300E, Now 93' 500SEL
Originally Posted by mgw_300e
If it were me, I would figure out which of the two (fuel filter or plug wires) I would need to replace soonest and start there.

However, I think I would replace the wires first as they are the most likely culprit IMHO.

It seems to me that although a clogged fuel filter would cause hesitation during acceleration as opposed to idling or other low RPM situations, it would also do the same thing during other high fuel consumption times, like high speed driving.

Well my car kinda hesitates when i start it up. Sometime when i start it, the car will stay on for like 3 seconds and then die. Then i have to restart it and everything will be fine. But my car kinda seems like it wants to die while on idle. So plug wires and fuel filter change you think?
Old 06-13-2006, 12:30 AM
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Originally Posted by hellah fresh
Well my car kinda hesitates when i start it up. Sometime when i start it, the car will stay on for like 3 seconds and then die. Then i have to restart it and everything will be fine. But my car kinda seems like it wants to die while on idle. So plug wires and fuel filter change you think?
If it seems like it's missing on a cylinder or two, it's probably the plug wires.
It'll chug and pop especially when you start up or accelerate from a stop, but it will seem to run ok other times.

If it's a clogged fuel filter, it's going to drive like it's running out of gas - or like you've got a potato in the tail pipe, and it'll probably do it most of the time. When I had a clogged fuel filter on my k-jetronic rabbit, it would start to die, but if I turned it off and started back up again it would run ok for a little while. Mainly it ran awful at any speed until I fixed the problem.
Old 06-13-2006, 05:12 AM
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Have just been on the phone with the mechanic. He reckons that another reason for the hesitation might be due to a bad “electric throttle”?! He describes it as the part right next to the manifold… Worse thing is, it would cost around $800 USD to replace…

I hope it is not that. However, the hesitation that I can feel is only apparent when you accelerate with more than half throttle from a standstill. I tried to hit the kick down switch on the go quite a few times and the car seems to run fine…

My mechanic also recommended me to take the time to change the new spark plugs back to the old ones that I had. I’ll try that in the next few days and let you guys know about the outcome…

However, I really doubt that the spark plugs is the reason for the hesitation. This is because this problem has been developing overtime. It appeared last year and eventually got a bit worse, but the state it is in now is kinda unacceptable… Could this be the slow clogging up of the fuel filter? I’ve left the car standing for around 4months and had to exhaust the fuel in the tank (my fault for not filling it up when the light comes on). Could this cause the fuel pump to suck in all the deposits and then the deposits get caught in the filter? This is the only probable reason why this problem has gotten worse overtime my incompetent brain could think of…

Cheers
Jeff

Last edited by jeffreyli86; 06-13-2006 at 06:34 AM. Reason: spelling
Old 06-13-2006, 07:58 AM
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Have any of you checked or replaced your wiring harness. I had the same symptoms as what you all are describing, did the plugs and wires first and so on. Then changed the wiring harness and BAM, hesitation gone.
Old 06-13-2006, 09:33 AM
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Originally Posted by joef
Have any of you checked or replaced your wiring harness. I had the same symptoms as what you all are describing, did the plugs and wires first and so on. Then changed the wiring harness and BAM, hesitation gone.
Sorry mate what's the BAM?

I truly hope it is not the wiring harness ........
To be honest, if it is the wiring harness, I might just leave the car somewhere and not use it until I finally rebuild it inside out.. Just hate to drive around a car with a developing fault
Old 06-13-2006, 10:27 AM
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Was 89' 300E, Now 93' 500SEL
Dude i think im going to try to change the fuel filter. I got new spark plugs and not the wires. So slowly i will find the problem. Oh my car dies right after i start it up. Then i start it up for the second time it stays. Anyone knows what the cause of this?
Old 06-13-2006, 11:46 PM
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Could it be injectors? (Just a random thought)
Old 06-14-2006, 12:14 AM
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1993 300CE Sportline
don't use carb cleaner

Did you use "carb cleaner"? Carb cleaner is not for engines w/ fuel injection systems. If it was they would call it fuel injection cleaner. Some carb cleaners can harm the various engine sensors in the intake manifold. The correct cleaner is a dielectric cleaner. Purchase the correct cleaner and spray it again...if you are lucky it will fix the problem...probably not. Worth a try. Good luck.
Old 06-14-2006, 12:46 AM
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i think BAM is the sound it makes when it gets fixed.
Old 06-14-2006, 02:52 AM
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oh god i did use carb cleaner however, I didn't spray it through the intake hose. I had it off and sprayed it directly into the manifold. Would this eliminate the problem?

Cheers,
Jeff
Old 06-14-2006, 03:18 AM
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90 300e and B5 S4
Injectors are very problematic on older bosch fuel systems. I wouldn't be surprised if this was your problem.
Old 06-14-2006, 03:47 AM
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Originally Posted by overboostTSI
Injectors are very problematic on older bosch fuel systems. I wouldn't be surprised if this was your problem.
Oh god. This reminds me of something. I've poured some Gunk Injector Cleaner into the tank before I last filled up. Could this have damaged the injectors?

Cheers,
Jeff
Old 06-14-2006, 10:05 AM
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Was 89' 300E, Now 93' 500SEL
Originally Posted by mgw_300e
If it seems like it's missing on a cylinder or two, it's probably the plug wires.
It'll chug and pop especially when you start up or accelerate from a stop, but it will seem to run ok other times.

If it's a clogged fuel filter, it's going to drive like it's running out of gas - or like you've got a potato in the tail pipe, and it'll probably do it most of the time. When I had a clogged fuel filter on my k-jetronic rabbit, it would start to die, but if I turned it off and started back up again it would run ok for a little while. Mainly it ran awful at any speed until I fixed the problem.

DuDE! Those are the exact symptoms of my car. Whenever i go to start my car it will start up then 2 seconds later it will die. Then when i goto start it up its fine... kinda like its not getting enough fuel or something? And sometimes it likes to act like its going to shut of when idling but it doesnt. As for the stalling it only happends when i take off fast from a complete stop. But when i take off normally with out gunning my car it doesnt even stall. So Plus wires and a new fuel filter should atleast solve me problem aye?
Old 06-14-2006, 03:46 PM
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I have had similar symptoms, I took the car into the shop and they could not produce the same symptoms. The car would sometimes have a hesitation and then accelerate very quickly thus producing a jerking motion. Also at time it would do it while breaking when pulling into a parking stall or a stop light. The car seems to have a mind of its own. Im ready to take the car in and have them check the engine wiring harness, I believe that the harness is the culprit.
Old 06-14-2006, 06:06 PM
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Originally Posted by hellah fresh
Dude i think im going to try to change the fuel filter. I got new spark plugs and not the wires. So slowly i will find the problem. Oh my car dies right after i start it up. Then i start it up for the second time it stays. Anyone knows what the cause of this?
if you change the fuel filter, do a DIY so we can use it for future refrence
Old 06-15-2006, 02:31 AM
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fuel filter change is good but that did not solve my problem.
Old 06-15-2006, 04:01 AM
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is fuel filter change a DIY job though?
do i have to drain the tank?
Old 06-16-2006, 01:40 AM
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Seeing as there was no reply to my previous question, I've taken the car to the mech.. He was instructed to do a tune up, fix the window regulator and change the fuel filter..

Funnily enough though, the car's hesitation was gone since last night. This got me thinking. I've changed the spark plugs in my last DIY service and disconnected the negative end of the battery.. Could the launching hesitation be due to the ECU trying to *learn* the new spark plugs? The car is running great and this is the only probable answer to my problem that I could think of..

Any ideas?

Jeff


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