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C124 E220 misfire running out of ideas

GRHunter

New Member
Joined
Dec 10, 2024
Messages
1
Location
nottingham
Car
W124 Coupe 220 1992
Hi
I have been looking after my C124 E220 1992 for 5 years and I have done a lot of work on her. She has a problem with a very lumpy engine at less than 2500rpm.
The following have been checked:
No OBD1 error codes on pin 6, (she has the new silicon harness)
Runs perfectly when cold up to 65deg, throttle body is moving the as it should to maintain nice tick over
After 60deg tick over becomes lumpy and poor power until suddenly at 2500rpm it runs ok, maybe a little down on power
Plugs new and all look good
No sign of a inlet manifold leek
Any thoughts as to my next move?
Thanks
Geoff
 
I have a similar issue that I am just trying to diagnose, mines slightly lumpy when cold then absolutely fine for ages but when hot after a 30min drive, stationary and I. Drive suddenly it sounds like it’s dropped a cylinder no power but will clear if revved or driven for another few 100m.
Advice seems to be either ecu coil packs or ht leads. Trouble is I cannot replicate it on the driveway it even when hot and I have the old code reader system so need a flashing reader.
On yours check the fuel pressure valve when running pull off the vaccine line and see if fuel is dripping if so replace may sort the issue.
 
FAULTY throttle position sensor [at top of accelerator pedal in cabin] if you have a non mechanical throttle linkage??
Symptoms of a faulty throttle position sensor include poor acceleration, rough idling, stalling, erratic throttle response, and a Check Engine light on.
 
FAULTY throttle position sensor [at top of accelerator pedal in cabin] if you have a non mechanical throttle linkage??
Symptoms of a faulty throttle position sensor include poor acceleration, rough idling, stalling, erratic throttle response, and a Check Engine light on.
Thanks sounds like it might be, I guess these can be intermittent when on the way out and HT leads are an easy change. I did wiggle all of the leads but couldn’t replicate.
I did notice a fair bit of oil in the air intake side of the throttle body which seemed odd.
 

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Thats too much oil! There's a breather pipe from the cam cover to this area of the inlet manifold--IF THE ENGINE IS BLOWING A BIT OF OIL WHEN HOT? Then this could be a problem?
 
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Thats too much oil! There's a breather pipe from the cam cover to this area of the inlet manifold--IF THE ENGINE IS BLOWING A BIT OF OIL WHEN HOT? Then this could be a problem?
I did feel there was a bit of blow by, ie pressurisation when oil filler cap is off when running it’s quite strong and spits a bit of oil other reports suggest this is normal but maybe not
 
So i would go for a item by the name of - RED X ..open up the spark plug holes, and put an egg cup full in to each cylinder .Next , let it do its work over night .Next day cover the plug holes with a cloth to catch exiting RED X then spin the engine over .Next step is repace spark plugs.Then start the engine up --important dont do this if people are about, reason is , it will fill the street with smoke as all old ccarbon is burned off. Its worth a try for the price . You can buy this from Halfords
 
Do these have the same ignition insulator problem that the m104 and m119 have?
Wiring harness been replaced recently?
 
So i changed the MAF sensor and air filter and it seemed to run better, took it for a spin thought i had solved the issue. then back at teh garage i topped up the oil ( i think this is a concidence) and then it started running rough ie sounds like its dropped the cylinder.
Anyway i unplugged the MAF sensor to see if that made any difference whilst running, and unfortunately when plugging back in, the MAF sensor cable shorted and burnt out! SO i now have to look for a new loom.

On further inspection the loom was fubar back to the bulkhead so iguess it was only a matter of time.

Now im worried about spending a packet on the loom only to still have an undignosed issue!
 

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