E300 w124 engine stutter during warm-up

[mat9000]

W124 300E 1988 Auto

Recent work (at different times) includes: new leads/rotor/HT leads (sprayed with damp sealant); new fuel filter(s?) and tank drain. Problems disappear for a while after this work but eventually reappear!
Hot starting; good; cold starting; ok
250k miles - engine still in great shape except..
The engine misfires and usually stalls about 1-2 miles after I have set off. Normally occurs in damp weather having been left at least overnight. Takes 5mins for problem to sort itself with engine running (usually doesn’t stall on idle only on really bad days). The “misfire” is actually an engine “stutter” which stops the engine revving and usually kills the engine at some stage. It is most pronounced when setting off eg from traffic lights or anywhere embarrassing!!

Any suggestions or diagnostics very welcome.

Thx

Mat Mitchell
Enfield

 

[Bolide]

That's an early car without all the electronics of the later AFM engines so it should be a little easier to diagnose. I assume it has a crank position sensor and I'd suspect that and maybe a temperature sensor

There are plenty of threads about similar problems on the forum so have a search

Ivan at Automerc on Hornsey High Street (behind Wood Green Shopping City) will be able to solve this. 020 8340 2966

Nick Froome
www.w124.co.uk

 

[Number_Cruncher]

It sounds like it's an HT related fault, and you've changed most of the HT components.

One part I might be suspicious of is the plastic disc behind the rotor arm, these can fail and allow the spark to track to earth.

I *think* it's not a cheap part, and so, I would want to see some evidence of sporadic / short burn times on an oscilloscope or engine analyzer before I bought one.

 

[mat9000]

That's an early car without all the electronics of the later AFM engines so it should be a little easier to diagnose. I assume it has a crank position sensor and I'd suspect that and maybe a temperature sensor

There are plenty of threads about similar problems on the forum so have a search

Ivan at Automerc on Hornsey High Street (behind Wood Green Shopping City) will be able to solve this. 020 8340 2966

Nick Froome
www.w124.co.uk

thanks Nick, yes there are good threads as you suggested. I may well contact Ivan if hes a guru on these engines and can pinpoint the problem without the expense of changing every component in sight! M

 

[mat9000]

It sounds like it's an HT related fault, and you've changed most of the HT components.

One part I might be suspicious of is the plastic disc behind the rotor arm, these can fail and allow the spark to track to earth.

I *think* it's not a cheap part, and so, I would want to see some evidence of sporadic / short burn times on an oscilloscope or engine analyzer before I bought one.

thanks for info, do you know if this part known as the suppressor cover?

 

[Number_Cruncher]

I was thinking of part No 14 on here;

http://www.detali.ru/cat/oem_mb2.as...GM=717.430&CT=M&cat=505&SID=15&SGR=060&SGN=04

or its equivalent if yours is a different engine.

 

[mat9000]

Yes thats the one, thx 4 the link. I'll b getting my spanners out next week and shall report back.. M

 

[Number_Cruncher]

>>I'll b getting my spanners out next week

It's not a cheap part, and so, I would want ot be sure before fitting one - hence my sugestion of checking the ignition firing waveforms.

 

[mat9000]

and the problem was... a poor sealing (not o/e) dizzy cap! the inside was green with mould algae/condensation! I sealed with bathroom sealant (as per my budget..), works a treat! but did take on your suggestion of checking HTs, and 2 had started to split (cheap ones!!)

cheers, Mat