[Andy Macfarlane]

Hello folks! I have this weird problem with my 1992 2L 190E. It can be running great the suddenly the power drops. It seems to happen on low gears like when coming out of a roundabout or junction, but it once happened on the motorway. The fuel filter is new, I've changed the OVP and Pump relays, and even the fuel-pressure regulator albeit with a used part. But it still happens. Obviously it never happens when I take it to the mechanic. The weird thing is, that if I turn the ignition key off one click then back on again, it seems to reset and works fine for a time.
(The time on the motorway it happened at 70mph while overtaking-not nice. I somehow drove the 100 miles home turning the key off and on again all the way every so often)
Any ideas?

 

[alain Gillot]

Hello folks! I have this weird problem with my 1992 2L 190E. It can be running great the suddenly the power drops. It seems to happen on low gears like when coming out of a roundabout or junction, but it once happened on the motorway. The fuel filter is new, I've changed the OVP and Pump relays, and even the fuel-pressure regulator albeit with a used part. But it still happens. Obviously it never happens when I take it to the mechanic. The weird thing is, that if I turn the ignition key off one click then back on again, it seems to reset and works fine for a time.
(The time on the motorway it happened at 70mph while overtaking-not nice. I somehow drove the 100 miles home turning the key off and on again all the way every so often)
Any ideas?

this is a problem that occur when you have a half tank of gas or less ., coming around a turn , If that is the case , the gas tank has a issue , the test is to fill up , and if problem is not there , but come back at 1/2 or less , then you know .a weak ignition switch with a ton of keys on , may want to turn off .

 

[John Jones Jr.]

Many moons ago I had a very similar issue on a 190E also. It was failing coil that was the culprit.

 

[dolucasi]

This does sound more like an electrical issue, the way you describe it. Seems the car is bi-modal, a good state and a bad state. And to reset it, you have to turn off car and turn it back on again. Perhaps a relay gets reset when powered off.

This is what I would do if I were you. Firstly, to test out this theory, measure your duty cycle. Make sure it is centered properly. If it is quite a bit off, then and only then I may have a theory, but measure it first.

 

[GaryStofer]

We had a vexing problem with momentary power loss on an 1987 190e, It turned out to be the connector on the temp sensor that feeds the engine computer.. when it didn't make contact the controller enriched the fuel mixture because it read a -60F engine temp. On an other 1992 a similar power drop / stalling occurred beasue of bad contacting of the OVP or the fuel pump relay. Taking the relay connector apart, cleaning and re-springing of the contact barrel solved that.

 

[Dave Kost]

Does ALL the power drop off? Lights? tach? Everything? or just the engine stalls?

 

[dolucasi]

The way OP Andy described the failure in his original post, the engine keeps running but he looses power to/from the engine and the engine does not stall. To get back to the normal running condition he has to turn off ignition and back on again.

I could be mistaken about this but OP has not responded in 3 days, so not likely watching the responses here.

 

[GaryStofer]

Does ALL the power drop off? Lights? tach? Everything? or just the engine stalls?

In our cases the motor was maybe making 5 to 10% power when it happened on the FWY, if it happened standing at the intersection the engine would die. At least with the first case of the temp sensor connector being the culprit the RPM gauge was still running. I belive it was also the case for the loose contacts under the OVP relay, but memory is a bit fuzzy on that one. -- We found the bad connection on the temp sensor finally becasue it happened in our neighborhood and we where able to keep the motor just barely alive to investige under the hood. We also noticed that all the spark plugs where sooty black when we let it finally die. We could positively identify the connector as the culprit by wiggling on it and make the motor spring back to normal operation, however an internally broken temp sensor could do the same thing and would be harder to diagnose if intermittent.

 

[dolucasi]

This is all good info Garry and once again welcome to the forum after a long break.

The condition you are describing suggests that the ECU does not exactly know what to do when the temp sensor input becomes open (infinite resistance) and assumes the worst which is subzero temps and rails the fuel enrichment (EHA current) to maximum and flooding the engine. I am surprised at that and that I would have thought engineers at Bosch would have put in a window comparator at this input so that if the resistance is outside a range (infinite and zero would certainly be outside this range) the emissions system would revert to "zero" EHA current. There must be a good reason for the logic/design decision.

It is good to know the expected behavior in case of an open at the temp sensor.

We still do not know what exactly happens to the OP's car and I'm not sure if he is following the thread any longer.

 

[Andy Macfarlane]

Thanks for all the replies. Sorry but my computer was off-line for a week or so.
I'm intrigued by the temperature theory. I live in italy and the summer temperature is pretty damn hot, and the guy that sold me it had for some reason got his mechanic to weld or bolt the fan so that it's constantly turning. I think he'd had overheating problems or something. I'll write to him, he's a mate. But could a constantly turning fan send the temperature haywire?

 

[Andy Macfarlane]

Does ALL the power drop off? Lights? tach? Everything? or just the engine stalls?

Just the engine.

 

[Andy Macfarlane]

In our cases the motor was maybe making 5 to 10% power when it happened on the FWY, if it happened standing at the intersection the engine would die. At least with the first case of the temp sensor connector being the culprit the RPM gauge was still running. I belive it was also the case for the loose contacts under the OVP relay, but memory is a bit fuzzy on that one. -- We found the bad connection on the temp sensor finally becasue it happened in our neighborhood and we where able to keep the motor just barely alive to investige under the hood. We also noticed that all the spark plugs where sooty black when we let it finally die. We could positively identify the connector as the culprit by wiggling on it and make the motor spring back to normal operation, however an internally broken temp sensor could do the same thing and would be harder to diagnose if intermittent.

This sounds very interesting. I had to change the spark plugs last week after less than 6 months-with Covid restricted travel. One was completely gone and I was running on 3 cylinders. And the car stinks of petrol-my girlfriend won't ride with me. What's the point of a flash car if your girl won't jump in???
Joking apart, the guy that sold me it says the fan has been welded or bolted so it turns continuously (don't ask me why)- could that cause the temp sensor to act up?

 

[Andy Macfarlane]

Many moons ago I had a very similar issue on a 190E also. It was failing coil that was the culprit.

Can you give me a bit more detail please? What coil is this? I have to translate the name of this coil into italian for my mechanic!

 

[John Jones Jr.]

Can you give me a bit more detail please? What coil is this? I have to translate the name of this coil into italian for my mechanic!

Ignition coil
Bobina di accensione

 

[Andy Macfarlane]

Ignition coil
Bobina di accensione

Grazie mille mate!

 

[John Jones Jr.]

Grazie mille mate!

Prego

 

[dolucasi]

Even I understand this level of Italian!

 

[John Jones Jr.]

Even I understand this level of Italian!

You're a better man than me, I had to use Google...

 

[alain Gillot]

This sounds very interesting. I had to change the spark plugs last week after less than 6 months-with Covid restricted travel. One was completely gone and I was running on 3 cylinders. And the car stinks of petrol-my girlfriend won't ride with me. What's the point of a flash car if your girl won't jump in???
Joking apart, the guy that sold me it says the fan has been welded or bolted so it turns continuously (don't ask me why)- could that cause the temp sensor to act up?

welding the fan on is silly , a toggle switch would have been smarter , the fan been on at all time cause engine at time to run too cool .i had a 85 , for a couple of decades , did install a toggle switch to use in town , on freeway if you forget to turn it off , the temp gauge would be bellow the normal cool temp .

 

[GaryStofer]

You mentioned your spark plug being completely gone. What was wrong with it ? All black and fouled up or electrode melted off. If you have problems with the ignition side all bets are off as to why the vehicle looses power at times. One 190E I worked on had a bad ignition cable where the center wire burned back a couple of centimeters. The car would still run in idle and under no load, but as soon as you started driving it would fail to fired that cylinder and instead arc in and around the distributor cap where a nice black trace was found under the black plastic dust cap on the distributor. From the evidence of the "Spare" parts that came along in the trunk one could see that the previous owner had the ignition coil replaced twice before. Needless to say that it didn't solve the problem. Ignition cables do go bad, often times from pulling on the wire instead of on the housing, but are easily tested and replaced, spark plugs on the other hand very seldomly fail these days.

As to "welding" the fan to the motor... That's just plain wrong! We have a 1985 a 1992 and a 1993 of these an none overheat in hot California, although the '85 gets a little on the hot side at 39C outside temps while sitting in traffic and I have threatened to install a bypass switch for the electric fan..