300E rough idle & hard starting
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From: Zimbabwe
83 123 230E, 89 W124 230E, 88 w124 250TD, 93 Range Rover Vouge TD, 94 W124 300TE
300E rough idle & hard starting
Hi Guy's.
I have a 1994 300TE 167k which I recently purchased & it has an intermitent rough idle and hard staring problem. The rough idle it sort of hovers between 400-600 rpm and disapears after about 1200 & has no noticable misfire thru the rest of the rev range.....at least not thet I can notice. The hard starting is also intermitant and sometimes starts all day first kick and other times 5-6 attemps before it will catch. I've checked spark plugs, HT leads, dizzy for possible faults and found nothing. Have had suggestions to check for dripping Injectors or possible leak on the vacuum system.......I believe the lock mech for the drop down rear seats is vac operated and this is not unlocking! Any Ideas where to start!! If it's a vac system prob don't want to be replacing Inj Nozzles....could get expensive and I don't know where to start tracing a vacuum leak. I need Heeelp.
Thanks in advance. Mark
I have a 1994 300TE 167k which I recently purchased & it has an intermitent rough idle and hard staring problem. The rough idle it sort of hovers between 400-600 rpm and disapears after about 1200 & has no noticable misfire thru the rest of the rev range.....at least not thet I can notice. The hard starting is also intermitant and sometimes starts all day first kick and other times 5-6 attemps before it will catch. I've checked spark plugs, HT leads, dizzy for possible faults and found nothing. Have had suggestions to check for dripping Injectors or possible leak on the vacuum system.......I believe the lock mech for the drop down rear seats is vac operated and this is not unlocking! Any Ideas where to start!! If it's a vac system prob don't want to be replacing Inj Nozzles....could get expensive and I don't know where to start tracing a vacuum leak. I need Heeelp.
Thanks in advance. Mark
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Joined: Aug 2004
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From: Richmond, Va.
1991 300E
There's a laundry list of things that could be causing this. First and probably easiest thing to check is the engine wiring harness. These are notorious for shorting out on the early M104 engines. search the forum and you'll find all about them. I would cut open a section of the wiring harness and check the insulation on the individual wires. If the insulation is cracked, you'll probably need a new wiring harness. That may or may not fix your idle problem but it will prevent many other problems from arising in the future.
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Joined: Sep 2004
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From: Zimbabwe
83 123 230E, 89 W124 230E, 88 w124 250TD, 93 Range Rover Vouge TD, 94 W124 300TE
Thanks mhorn. Ihaven't got that far yet. This car has a 103 engine......south african assembled.......I seem to recall that the rest of the world discontinued this motor in 93'. I have now been thru the ign system ie HT leads, dist, rotor, Vacuum sytem, OVP, etc basically thru the list bamberger_1 listed elswhere in this forum to no avail. Going to have the injectors cleaned next. This car has done a lot of standing in the last few years approx 5-6 T kms a year. I will have a look at the loom tho'.
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Joined: Aug 2004
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From: Richmond, Va.
1991 300E
If you have the M103 engine, I have heard that as these cars age, the fuel pressure on the lower EHA(the thing that sits next to the fuel distributor) needs to be increased from .4 bar to .45 bar to accomodate for wear in the injection system. Stu Ritter discusses this briefly in his book "W124 owner's bible". This supposedly solves many of the hard starting and rough idle problems but I think you need a special gauge to do this so it's pretty much beyond the reach of your average do it yourselfer.
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From: Zimbabwe
83 123 230E, 89 W124 230E, 88 w124 250TD, 93 Range Rover Vouge TD, 94 W124 300TE
Now this is the first time anyone has brought this up...EHA I mean.......all the mates who have the know how here have all decided that this is an Injector prob' either one (or More!!) faulty or dirty.......we have a problem here with low octane(84 or there abouts) fuel and due to shortages alot of dirty fuel. I've replaced the fuel filter which was dirty and incorrect....was fitted with single pump model.....but that didn't help. Have been told to do a chemical fuel system clean but my mate ( that actually does this job) that on the KE inj system this may drag carbon from the fuel dist and clog the inj's so to rather take them off and have them cleaned. will investigate this EHA...got a book today on Bocsh KE fuel systems and attempt to get it checked before cleaning Inj's.
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Joined: Aug 2004
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From: Richmond, Va.
1991 300E
Puffadder, I'm not a professional mechanic, but I play one on the internet. Not being familiar with Foreign gas, or any other differences between U.S. and South African versions of these cars, I really don't want to send you on a wild goose chase. Here is what I do know:
Many of these cars with the M103 engines are hard to start and have idleing problems in their old age. My car will catch instantly when starting the engine hot or cold, but then immediately stalls out after just a second or two of idleing. However if I give the engine a little throttle while starting, all is well. That is why I think my problem is linked with the lower fuel pressure. I would THINK, but can't say for sure, that a clogged injector would cause problems across the RPM range, not just at idle. But that is just my opinion. Matt.
Many of these cars with the M103 engines are hard to start and have idleing problems in their old age. My car will catch instantly when starting the engine hot or cold, but then immediately stalls out after just a second or two of idleing. However if I give the engine a little throttle while starting, all is well. That is why I think my problem is linked with the lower fuel pressure. I would THINK, but can't say for sure, that a clogged injector would cause problems across the RPM range, not just at idle. But that is just my opinion. Matt.
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Joined: Feb 2002
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From: Chicago
90 300e and B5 S4
Just thought I would mention that my 300e was giving me huge headaches with starting and idleing. I couldn't figure it out (no fuel pressure gauge) but my fuel line (fuel filter out to fuel rail) was rusted and started leaking.
At first there were no signs except for a little fuel smell, thought it was the EHA and I replaced it with a spare one I had and had the same problem. Then I noticed a drop of fuel on the garage floor, jacked the car up and sure enough the line was rusted bad. The line is cheap ($20) and the dealer had it in stock which usually means they sell them often.
Not saying you have this problem I just wanted to let everybody that is chasing problems to check the lines at the fuel filter. Don't forget to check your vac. lines and Egr valve with a vacuum tester (takes like 5 secs.). Egr should hold about -20 in.hg. .
At first there were no signs except for a little fuel smell, thought it was the EHA and I replaced it with a spare one I had and had the same problem. Then I noticed a drop of fuel on the garage floor, jacked the car up and sure enough the line was rusted bad. The line is cheap ($20) and the dealer had it in stock which usually means they sell them often.
Not saying you have this problem I just wanted to let everybody that is chasing problems to check the lines at the fuel filter. Don't forget to check your vac. lines and Egr valve with a vacuum tester (takes like 5 secs.). Egr should hold about -20 in.hg. .
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From: Zimbabwe
83 123 230E, 89 W124 230E, 88 w124 250TD, 93 Range Rover Vouge TD, 94 W124 300TE
[QUOTE=
Not saying you have this problem I just wanted to let everybody that is chasing problems to check the lines at the fuel filter. Don't forget to check your vac. lines and Egr valve with a vacuum tester (takes like 5 secs.). Egr should hold about -20 in.hg. .[/QUOTE]
I'm not convinced that this problem is fuel delivery related.....even tho' all my boffin mates here seem to think so.........the misfire is very mild as for example compared to a spark plug or HT lead related one , it's more like the engine is hunting which leads me to believe it's sucking air from somewhere and it's very erratic......sometime's you can stop in the traffic 20-30 times and the prob is not there. What is an EGR valve and where is it located? Maybe it is vacuum related and I've not found it yet. The car is quite drivable it doesn't stall or cut out when the misfire/hunt starts and if you give it a bit of throttle on start up doesn't hassle too much there either. I agree with mhorn I also think an injector prob would be noticable thru the rev range.
Not saying you have this problem I just wanted to let everybody that is chasing problems to check the lines at the fuel filter. Don't forget to check your vac. lines and Egr valve with a vacuum tester (takes like 5 secs.). Egr should hold about -20 in.hg. .[/QUOTE]
I'm not convinced that this problem is fuel delivery related.....even tho' all my boffin mates here seem to think so.........the misfire is very mild as for example compared to a spark plug or HT lead related one , it's more like the engine is hunting which leads me to believe it's sucking air from somewhere and it's very erratic......sometime's you can stop in the traffic 20-30 times and the prob is not there. What is an EGR valve and where is it located? Maybe it is vacuum related and I've not found it yet. The car is quite drivable it doesn't stall or cut out when the misfire/hunt starts and if you give it a bit of throttle on start up doesn't hassle too much there either. I agree with mhorn I also think an injector prob would be noticable thru the rev range.
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Joined: Aug 2004
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From: Richmond, Va.
1991 300E
Just a thought, if you remove the air filter housing and look at the throttle body underneath, you'll see the "trap door" that lowers to let air from the filter housing into the runners. If something is sticking and or blocking that trap door from returning back to its position it could cause the stalling problems you're referring to. That area is very sensitive. If you have the car running and push down on that trap door, even just a fuzz, it causes the car to stall out. If you decide to check this you might as well lubricate the throttle linkage while you're there. Automaitc transmission fluid works well for this.
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Joined: Sep 2004
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From: Zimbabwe
83 123 230E, 89 W124 230E, 88 w124 250TD, 93 Range Rover Vouge TD, 94 W124 300TE
Hi Guys
Finally managed to sort out my hard rough idle problem......took a while and the wife was living with the prob! Went thru Bamberger_1 list...all the easy ones first..... eventually fuel flow & nozzels, fuel flow was half what it should be but was told by a merc mech that, that may not be the fault. Then removed all the inj's and spray tested them, all were spraying funny i.e not a nice mushroom fan but off to one side etc. Bought one inj and checked it on each cyl fuel pipe and was getting a nice fan on each one, got another 5 fitted and problem gone car runs like a dream.....no more rough idle and the intermittent hard starting prob also solved.......I think one or more inj's may have been weeping & causing the hard start, it only happened between 5-30 min after you shut off the motor and tried to restart. To do all these tests.....I was assisted by a Bosch book......you have to bridge the fuel pump relay to bypass the timer, whilst I was in the middle of the job I decided to check and clean the fuel tank gauze filter and forgot to refill the tank. On attempting another Inj test ran the fuel pump dry and it siezed......I believe the pumps are lubricated by the fuel......so beware this was an expensive mistake!! I also attempted to clean the Inj's!!!! Waste of time made the car run alot worse. Anyway the car .....Eng & fuel Sys.......has now had a thorogh going over and is running like new, thanks guy's for all your advice, much appriciated. Cheers
Finally managed to sort out my hard rough idle problem......took a while and the wife was living with the prob! Went thru Bamberger_1 list...all the easy ones first..... eventually fuel flow & nozzels, fuel flow was half what it should be but was told by a merc mech that, that may not be the fault. Then removed all the inj's and spray tested them, all were spraying funny i.e not a nice mushroom fan but off to one side etc. Bought one inj and checked it on each cyl fuel pipe and was getting a nice fan on each one, got another 5 fitted and problem gone car runs like a dream.....no more rough idle and the intermittent hard starting prob also solved.......I think one or more inj's may have been weeping & causing the hard start, it only happened between 5-30 min after you shut off the motor and tried to restart. To do all these tests.....I was assisted by a Bosch book......you have to bridge the fuel pump relay to bypass the timer, whilst I was in the middle of the job I decided to check and clean the fuel tank gauze filter and forgot to refill the tank. On attempting another Inj test ran the fuel pump dry and it siezed......I believe the pumps are lubricated by the fuel......so beware this was an expensive mistake!! I also attempted to clean the Inj's!!!! Waste of time made the car run alot worse. Anyway the car .....Eng & fuel Sys.......has now had a thorogh going over and is running like new, thanks guy's for all your advice, much appriciated. Cheers
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From: Zimbabwe
83 123 230E, 89 W124 230E, 88 w124 250TD, 93 Range Rover Vouge TD, 94 W124 300TE
First removed all the Inj's.....which was a bit of a job 'cos the No 4 Inj, which is just behind the fuel distributor the cap screw rounded off.........I don't believe any off these inj's had ever been removed in 170 T/Kms. Got all the pipes arranged and refitted the nozzels so I could fit little bottles..all the same size.......on the ends. Bypassed the rely/timer of the fuel pump so I could operate the the nozzels by depressing the plate on the throttle body. First checked volume in each one by holding plate depressed in the same position for about 30 sec's. All volumes were identical then observed the spay pattern on each noz and at the same time checked to see if anyone was dripping after I shut the fuel off. Most of the noz's the pattern was not as described in the book but shooting fuel off to one side in a jet rather than a mist. Now I believe that this type of Injection system all inj's spray fuel at the same time....and not like later types that only suppy fuel to the cyl thats firing......so if your not getting a nice mist type spray the fuel doesn't mix with the air going in properly causing problems. Anyway I decided after all the mucking around I'd been doing that if none of these inj's was spaying properly that this was most likely my problem, and as it turned out it was.
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1990 300e mercedes benz
im having a real pain in the butt problem with no start it sometimes starts and when it does it runs like a champ.. untill its in drive or in gear it wants to stall out , untill i drop into neutral and gas it up it stays idleing?? other than that it just plain doesnt start
anny thoughts please im an auto college student and havent been able to get anywhere this car is my life and really need help
anny thoughts please im an auto college student and havent been able to get anywhere this car is my life and really need help
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From: Northeast PA-Poconos
2014 E350, 2006 C350 Sport(made it to 280k, loved it!), 1990 300E
Alot of threads on this problem. It may be ignition wires, may be OVP, Distributor Cap and rotor, Idle air control, valve. Or maybe simple like spark plugs. You have to go thru the whole rigor to find your solution. Or it may be your fuel pumps. Good luck
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w124 300e 1990
1990 w124 300e sa model
hi all I`m new here my car 1990 w124 300e RSA model no power to cold start injector,ovp when fuse remove engine rev up replace fuse engine rev drop.i replace the sensor with the two horns (green one ),new injectors from merced )no power to sensor in air duct small black one .car is heavy on fuel about 6kilo`s to a litre.I need some expert advice thanks
