'96 C220 - Hesitation, CEL - loss in power

[michakaveli]

Our C220 started acting funny this morning. My girl started her up and she stalled. When she re-fired to get her going it was running rather rough until it smoothed out. My girlfriend called me to inform me of these symptoms and that the car is hesitating a lot, the car won't stall but it bucks when you try to increase the throttle substancially.

I went to check out the car myself. I started the car up and it ran fine but with a CEL. I disconnected the battery, re-connected and started her up. No CEL. I took her back to work and within the first minute car ran smooth, no hesitation. Soon after that the hesitation just above 2,000RPM started to occur and the throughout the RPM range after that for the entire ride back to work. The CEL did not come back on but I was only a few miles from where I picked the car form my girlfriend.

* Yesterday I did do a few things with the car. I replaced the headlamp lenses as the OEM's were cracked down the middle. There is a baffle for the air intake which I have removed due to the fact that it was impossible to get to the side screw to remove the assembly. After that I power-washed the vehicle and engine and changed the oil. Obviously from seeing "power-washing" and hesitation in the same thread you can put 2 + 2 together. The car did have a brief hesitation right after the washing but had cleared away and ran just as it had before. Is it safe to assume that the MAF had gotten damaged and it causing the hesitation and loss of power? The plugs, air filter, etc. are good and have been replaced within the last 20K. The air filter within the last year. I checked the airbox and air filter to see if there was any visible moisture in the air box, but to no avail.

[michakaveli]

Went to Advance Auto Parts to have the computer scanned. No codes were brought up. Also no saved codes came up either. Car is still acting the same.

The engine itself starts right up as normal and is as smooth as can be. I know that the pulgs and wires were replaced before we had purchased the vehicle, the plug wires look new as well, last time I looked.

Wouldn't the MAF through another CEL or will it take some miles for it to come up again, if it is the Mass Air Meter (MAF?)

[aqua190]

start with the simple things first. you said you washed the engine. pull the coil leads and chk to make sure they're not damp or wet. also, chk the visible sensor connections to make sure water didn't get in them either. might be a good idea to clean the contacts of all while you have them apart. then at least you can start to rule things out cheaply.

[michakaveli]

Originally Posted by aqua190

start with the simple things first. you said you washed the engine. pull the coil leads and chk to make sure they're not damp or wet. also, chk the visible sensor connections to make sure water didn't get in them either. might be a good idea to clean the contacts of all while you have them apart. then at least you can start to rule things out cheaply.

I will try to check the plugs today after work. Odd thing is after washing the engine, the engine was runnig for at least 30-40 minutes and driving perfectly fine.

Drove the car to work today. Still has the hesitation, although not as bad as it was at times yesterday, but not good.

Last night I sprayed the MAF with some electric component cleaner, bought at Advance Auto Parts. Disconnected the battery for a few. Everything is the same. Car starts right up with no problems.

I started the car this morning and it started up no problem. Most of the hesitation occurs in the mid-RPM range, around 2,000RPM. If you need to pass someone or when it starts hesitating, you bump up the throttle and it revs up to 4,000rpm with no trouble. Still does not feel like it has the same power, a little less than normally.

If it were the plugs or something wouldn't it be consistent throughout the RPM range? The hesitation is intermittent.

[michakaveli]

Last night I pulled the plug wires from the spark plugs only, not from the coils.

When I pulled out them out, the #3 cylinder had some water in the spark plug hole and the spark plug boot was wet. I blew compressed air in each of the plug holes to blow out any moisture, did the same to the plug wire ends that meet with the spark plugs. The after took some sand paper and twisted it in each of the wire ends to make sure there is a good conenction and to clean up any possible corrosion. I also put a small piece of a 3M scuff pad on the inside of the spark plug socket to clean to contact onthe plug itself. I did not dig in any deeper as I was sure that this was my problem. In the meantime I had to battery disconnected to reset the computer. Put it all back together, started her up and the same thing, nothing had changed...

I also pulled a few plugs of various sensors that are visible on the top of the engine and surraounding areas and cleaned off the contacts with the scuff pad to no avail.

I did not pull the plugs as the spark plug socket I have does not have the rubber boot inside the socket to hold the plug in the socket, it's fairly deep in the spark plug socket and I did not want to just drop the plug in there...

Any other ideas guys? The CEL has never appeared while in my presence and I have been driving the car since.

[michakaveli]

Hesistation has gotten a worse. After disconnecting the battery the car seem sto run decent until it hits 2500rpm then starts hesitating and back to the same routine. Yesterday I also noticed the RPM's when in gear and at a complete stop start bouncing a little, about 25-50rpm. Hasn't stalled again or come up with a CEL yet.

Any other ideas guys?

[96C220]

Originally Posted by michakaveli

Hesistation has gotten a worse. After disconnecting the battery the car seem sto run decent until it hits 2500rpm then starts hesitating and back to the same routine. Yesterday I also noticed the RPM's when in gear and at a complete stop start bouncing a little, about 25-50rpm. Hasn't stalled again or come up with a CEL yet.

Any other ideas guys?

Have you checked the ovp? Over voltage protection relay. Notorious for these sorts of driveabilty issues, really an achilles heel for Mercedes as they get older, and easily damaged if you created a temporary short by getting something wet.

Do a search on them, you'll find tons of stuff.

George

[michakaveli]

Had my indy scan for codes. Stated that there were some stored mis-fire codes in the ECM. They stated that they tested the plugs and wires, which are virtually new and they are operating fine. When I was at the indy and test drove it, it was much better, but still a slight hesitation at low RPM. Later on that night I drove it again and it has gone back to the hesitation at lower RPM.

With the vehicle in park, I connected a voltmeter to the cigarette lighter plug to measure the voltage from the car and revved the engine to about 2,500-3,000rpm holding it steady. The voltage held steady at 14.2 volts. At 2,500rpm you can feel a consistent "mis-fire" if you will, the rpm's fluctuate a little and you can feel the hesitation when the rpm fluctuates. I listened to the exhaust as best as I could also and could hear it miss when the rpm's fluctuated...

The plugs and wires appear to be fine, any possibility that it could be one of the coil packs going bad? I don't know what else it could be. Still no CEL's and no problem starting

[michakaveli]

HAd the indy check for any codes and diagnose. They pulled some stored misfire codes, check the plugs and wires and cleaned those things out to ensure there is a good conenction.

Gave it a few days after and the problem is almost gone. It may hesitate very lightly a t low RPM. The problem definately appears to be water related. I know it seems obvious, but it's good to have a concrete answer.

[michakaveli]

The problem had appeared to clear away on it's own. Yea, must have been moisture related.