low power when hot 92 500sel - PeachParts Mercedes-Benz Forum

Victor300E · #1 09-26-2007, 11:54 PM

Hi guys,

My car 1992 500sel m119 172kml has low power when car warms up. Car starts to hesitate when coolant reaches 90 degrees and as it get hotter it gets worse. At around 100 degrees if i floor it it sounds like it floods the cylinders or maybe not enough gas. I dont know how to test it. Engine is very hot to work around. It seems to pick up rpms with stress even on idle. I suspect timing (which is electronic and it seems to change timing when i use a strobe light to check), tranny overload sensor that alters timing or fuel pump or fuel filter. Problem is so bad that if I have ac on and need to move when light turns green the car would barely move forward. People honk behind for me to move

Intake makes a sound like those Maximas with cold air intakes when floored but my car doesnt move nowhere. Sounds like its about to stall but it doesnt. When its cold it picks up speed pretty well. Any thoughts? Could it be one of the ignition coils?

I have changed coolant temperature sensor, thermostat, water pump, spark plugs, cleaned wires, rotor caps and rotors.

Im stuck here.

Please help.

Thank you

mbdoc · #2 09-27-2007, 08:35 AM

Possibly start with basics.. compression & secondary ignition.

Victor300E · #3 09-27-2007, 08:40 AM

What is the proper procedure to check compression? I checked compression twice. Car was cold, I took out spark plugs, screwed in compression tester and cranked the engine few times. At first crank compression is low and it gets into normal range at second crank. Also If I crank the engine few times before I check compression, first crank reading is way higher. Am I doing it right?

What is the secondary ignition?

Thanks

mbdoc · #4 09-27-2007, 09:14 AM

Secondary ignition is plugs, wires, cap, rotor, coils...ect

I suggested the compression in lieu of checking the basic cam timing in case the timing chain has jumped.

david s poole · #5 09-27-2007, 12:01 PM

based on your description that as car gets hot power gets worse i would suspect the catalyst blocking up.easy check,remove the front 02 sensors and then drive.

dukegrad98 · #6 09-27-2007, 12:29 PM

Mr. Poole has a good suggestion there, strange as it may sound. I had never seen a catalytic converter grind a car to a halt, until a few weeks ago -- when it happened to my parents in their S-class. It required dealer replacement (both of them, just to be on the safe side), and the car is back to running like a champ.

Cheers, John

Victor300E · #7 09-27-2007, 04:06 PM

Thanks a lot for replies,guys.
I have replaced a catalytic converter with another used one with 75kml on it. It made no improvement. But I am sure that my caps and rotors should be replaced because they are old too. I have them cleaned once already. Also I hear a slight clicking from one of the ignition coils. MB Doc suggest checking them too. I just noticed clicking from the coil today. Maybe that is the cause. Is there a way to check coils? It's funny but the car always had that low power than hot problem when I bought it 2 years ago.

Timing was checked twice by removing top covers and inserting pins into camshafts aligning vibration damper to 45 mark. My mechanic says timing is off but all marks line up. It's a strange problem.