190 2L Misfire

[JeffP]

Hi, I have a 1990 190e 2.0litre Auto with a misfire.

It's only done just over 92,000 miles from new.

I've recently put it back on the road having had it on a SORN for 18 months.

First time out it ran beautifully for about 20 miles but then started misfiring at low revs. The misfire then started to work its way up the rev range.

I changed the HT leads and plugs, because I thought maybe standing still for so long may not have agreed with them.

All seemed well as I went for a good long test drive, but just as I arrived back home it started missing and shuddering on the drive.

It's really annoying because I want to use the car but this makes me have no confidence in it.

Any ideas please?

Many thanks,

Jeff

 

[stwat]

Did you replace the dissy cap and rotor?

 

[grober]

WOT HE SAID^^^ other problem might be dodgy fuel if it been sitting around a long time. Condensation in the base of the distributor body can also be a problem. Car starts OK then as the engine warms up water vapour migrates into top half of the distributor causing shorting.

 

[JeffP]

Thanks for the replies, much appreciated.

I changed the distributor cap and rotor arm about 3k ago. I've been turning it over now and then and it ran out of fuel. So when I got it going again it had fresh fuel and I had to bleed the system so I think the fuel is OK. Is it a simple job to get rid of condensation from the distributor body?

 

[grober]

Just remove the cap+ rotor arm +plastic shield and apply a hairdrier for a few minutes. its wise to use a good quality distributor cap Bosch or Beru or best of all MERCEDES own. Cheap replacements can fail in a remarkably short time.

 

[JeffP]

Thanks again, I'll try that.

If it doesn't work I'll try the cap.

Can't remember the brand but I'm a regular at my local parts store and he doesn't usually sell rubbish. I paid £27 for it, a genuine one was £97 so seemed a bit too steep.

Jeff

 

[JeffP]

I've done the hair dryer thing and given the rotor arm and cap a good clean.

Drove OK at first then as soon as it got hot it started missing again.

Before I spend money on a rotor and cap is there anything else it could be?

Fuel filter was changed about 5k ago.

What's really confusing me is that it runs beautifully when cold.

Jeff

 

[herby thr cls]

check the inlet manifold gasket, had a similar fault on my 190 some years back, let the engine tick over and spray some WD40 around the manifold and listen for any change in the engine sound, hope this helps

 

[grober]

Have a look at the plugs - any of them wet or carboned up?

 

[JeffP]

Thanks Herby I'll give that a go.

Plugs were replaced yesterday grober but thanks anyway.

Jeff

 

[Bellow]

What's really confusing me is that it runs beautifully when cold.

Jeff

1) Cold fuel enrichment not clearing - check for black exhaust smoke.

2) Fuel starvation due to some fuel venting issue.

3) Electronic component failure with temp - ignition unit most probably.


That's where I start. And monitor coolant level.

 

[JeffP]

There is some black exhaust smoke.

Also from what Herby said, yesterday when I removed the old spark plugs they were very tight. So I sprayed WD40 done the recesses. The WD40 leaked out directly under the spark plug for cyl 1 where the head overhangs.

Does this mean I've got a cracked head? (Hope not)

Jeff

 

[Bellow]

Black smoke is rich - and to misfire it has to be pretty rich. I'd suspect cold start enrichment - faulty temp sensor etc, etc...

I wouldn't dismiss the dizzy cap condensation theory yet. More condensation could occur even though it has been previously dried. Next time it is misfiring, try removing the cap, drying it, and replacing immediately (while engine is still warm) to see if that effects a cure.

Whatever the problem is is, you will have to drill down on all the possible causes and eliminate them one by one until the true cause is identified.

 

[JeffP]

OK thanks Bellow, looks like I'm going to have a busy few days.

Jeff