300SL misses after warm up

[jmar12345]

My 1992 300 SL has a problem similar to some described prevously. Starts fine and runs great until warmed up. After reaching operating temp it misses badly and I can smell strong emissions. After driving at highway speed it runs fine and continues to run fine until it sits for 12 hours or more.

 

[NDavies4]

Join the club!

From other posts (both at this forum and others) you'll see this seems to be a common problem on the 103 and 104 engine with a whole range of proposed solutions that, for some, seem to work.

For me I've done the following: distributor cap; ignition leads; plugs; OVP relay; coolant temp sensor; fuel filter; clean butterfly flap in throttle body - but all without success. Latest thing is a new crankshaft position sensor which does seem to have helped, but with the fault being so intermittent I'm not celebrating just yet.......

Keep us informed if you find the problem - like to try to keep track of the various remedies.

 

[43622]

Hi

I had very similar mis-behaviour on my 1991 420s it turned out to be a couple of 'dodgy' connection on the ignition, and the fuel pump relays.

since then it has been first class !....its worth looking into!

good luck

 

[jmar12345]

Thank you for your suggestions.
Since some are costly, I tried the cheap solution to start. I put a can of Gumout injector cleaner in a tank of Shell V formula. After the first tank, the problem seems much better. Doing a second one now and have not had the problem yet.

A friend of mine told me he usually changes out his injectors when he has this problem.

 

[Michaut]

Reply, 300SL24 misses after warm up.

I met exactly the same problem with my 1993 300SL24, engine type 104.
After reaching operating temp, ie driving about 10 mn at low speed in the morning, engine hesitates and stops. I then have to wait at least 15 mn to be able to start the engine again. (Just imagine the mess at the traffic light in town).
MB changed the crankshaft position sensor which did not helped.
I returned the car to MB. They kept it again for one week, tuned the lambda probe, tested all what they could including the electrical system as per what they told me by phone pretending that everything was all right.
When I showed up they said that they had just found out that a sensor electrical plug was not properly connected.
Everything was allright tor a couple of week, then today I just had the same problem again.
I'm fed up with this story. Who could help me, Please.

 

[mjtray]

Michaut,

I sound like you have a classic OVP Relay problem (Over Voltage Protection Relay)

If your car still has the original OVP its likely to be failing....this will typically show itself when you are slowing down in the car and just as the car is about to stop the engine will stall and the rev counter will just go straight down, ie it will not gradually go down.

You will then have to leave the car for 10-15 minutes before it will start again, after which it will be fine for maybe an hour at which point it may well do it again.

I also noticed that its worst when you have started the car from cold and then switch off 5-10 minutes later.....its then very hard to start.

If this discription is close to what is happening with your car, I would say its your OVP.

Very easy to change and cost about £50.

Good luck

 

[Michaut]

Re 300SL misses after warm up

mjtray,
Thanks a lot for your interest in my problem.
I'll check the OVP as per your recommendation but I think I have to be more precise in my description.
- The problem does'nt appear above warm up temperature or twice a day. If everything has been ok for 15 to 20 mn, then it's fine for all day.
- If engine stalls, it's after a first drive at low speed or stopped at traffic light (500 to 1500 rpm) but in all cases it would splutter for about 60 seconds before stalling.
In case I'm allready on highway and speed high enough, engine would splutter but may pass this critical phase because of momentum.
Would you think the 60 seconds splutting is more typical of fuel feed problem (fuel pump relay that i'll change anyway if MB did't allready,...) rather than ignition pb?
Thanks again for your help and comments.

 

[mjtray]

Michaut,

I still think it could be the OVP....my e280 with an M104 engine first started stalling during the warm up stage and would be fine for the rest of the day. It then started getting gradually worse and would cut out at speed.

Try the OVP first and then see how things go.

Good luck and let me know if this cures the problem.

 

[Michaut]

300SL misses at warm up temperature

Thank you mjtray, I'll come back to you.

 

[Michaut]

300sl misses after warm up. Engine 104. year 1993.

Some news as promised, Hello mjtray,
I still keep my fingers crossed after I changed the ignition head (A 104 158 01 02) and ignition finger (A104 158 02 31) the day before yesterday since the head was showing tiny crackles. Total price of parts: 254 Euros including VAT.
As per MB such crackles have probably been the reason of unperfect ignition cycle and stalling after warm up.
The engine turned really fine during a first test yesterday but I still remain prudent since the problem was so intermittent.
I'll keep you aware.
Thanks for your interest.

 

[mjtray]

Hope your problems are now solved!

 

[Arnie]

As I've mentioned before, the OVP relay usually powers the ABS system as well as the Ignition and Injection system. Try to remove the relay and with the key in position 2, see if the ABS light remains lit.

If this is the case and you don't see this ABS light during the intermittent faults, then it isn't a problem with this relay.

Check fuel-filter and ignition leads and then have the KE jetronic (103 Engine) unit checked by a specialist to see if the cold-start valves and other bits are working properly.

 

[NDavies4]

Some news as promised, Hello mjtray,
I still keep my fingers crossed after I changed the ignition head (A 104 158 01 02) and ignition finger (A104 158 02 31) the day before yesterday since the head was showing tiny crackles. Total price of parts: 254 Euros including VAT.
As per MB such crackles have probably been the reason of unperfect ignition cycle and stalling after warm up.
The engine turned really fine during a first test yesterday but I still remain prudent since the problem was so intermittent.
I'll keep you aware.
Thanks for your interest.

9 months on: did this fix it or did you find any other cause? I was having the same problem on mine for some time but appeared fixed for several months after a new cap and rotor arm, but problem has just come back. Took the distribitor cap off last night and there was a fair amount of yellowie oil coating the inside of the cap plus some deposits on the six copper contact points. Tried to clear in up and guess what? - car will fire up then die after 5-10 secs now! What's the technique for cleaning this thing?!!

 

[NDavies4]

Resolved!

Actually read up a bit on the net which pointed me towards some solvent spray to use. Went to Halfords and got a tin of Electrical Contact Cleaner spray for £3.99. Sprayed some inside the distributor cap and wiped round with a cloth which seemed to get all the cr@p out and off the contact points (six round the outside plus the central pin). Also then sprayed a little on the cloth and wiped the metallic end of the rotor arm.

Put it all back together and 'bingo', car idle and ran from a cold engine right through to fully warmed up (80deg) and not once did I get a rough idle, poor acceleration or stall. Cannot believe something so simple could have fixed 3+ years of pain.

I did replace the cap and rotor arm about 5 months (2,000 miles) ago during the last main period of stalling and that fixed things for about a month, but then slowly the poor idle returned, firstly very intermittently and only when warm, then also from cold and finally (last week) the occasional stall came back too.

What's slightly surprising is that the cap has managed to attract sufficient muck to bring the problem back so quickly. Currently I'm thinking that I simply need to clean out the cap again once the first rough idle is felt (could be a monthly exercise!), but is this all an indication of a larger problem maybe lurking behind the rotor arm?

 

[dandpl]

300 sl 1986 misfire when hot

Hi to you all

Similar symtoms to others in this case always starts well from cold and then after reaching normal temp misses at low speed and wants to stall and on occasion if stopped will not start until cold!

Same solutions as before do you think?

many thanks

dandpl

goodtrip

 

[NDavies4]

Definitely start there. From my experience, don't get side-tracked into looking at more 'exotic' solutions until you are sure the: distributor cap; rotor arm; plugs; leads are in good working order (and based on your symptoms I'd suggest to go in that order).

It’s now 3.5 months since I cleaned out my cap and the car's still running like a dream - i.e. not even a single miss at warm idle yet alone any sign of a stall.

I was expecting my problems to gradually come back with me needing to re-clean the cap/rotor arm, but as yet nothing

Good luck,
Neil

p.s. Did get a small leak from the coolant level sensor fixed some months back (a washer had perished). I'm thinking now that these two things could well be connected, and it was leaked coolant liquid vaporising and getting into my cap that was fouling things up.... If my poor idle doesn’t return then I’m pretty sure that was the root cause.