94 C280 cold start problems...

[hancheng]

Hi, all:

Recently I am experiencing some cold start problems. At first (about 2 weeks ago), occasionally when I started the car cold, it died right away. I have to step on the pedal to give it some gas to keep it alive. Once on the road and the car is warm, it worked just fine. This happened about two to three times two weeks ago.

Since last week, occasionally when I started the car cold, I heard a weird sound from the engine compartment. The sound is just like the windshield water pump is running (of course it is not). The engine may die or the RPM is very low. I can give it some gas but it seems like the reaction is delayed for about 0.5 second. I can drive the car at this time with gas pedal lightly pressed. The weird sound goes away about 100 or 200 yards from the parking lot and the car is back to normal. It happened about 3 out of 5 nights last few days when I went back home from the office, about 50 F here in Southern California. I was lucky it seldom happens in the morning maybe because I kept the car in the garage.

About two days ago the check engine was ON in the above situation and stayed on ever since. I haven't taken the car to check for the code yet.

I gave one of my co-worker a jump start about 3 weeks ago. Also, my over voltage relay is 000-540-52-45, not the modified one (000-540-67-45). Could these be the problems?

I found more symptoms this morning (about 47 F). After I started the car, I put the car to drive with the weird sound buzzing. Gas pedal had to be lightly pressed. Too much gas would also stall the car. Gradually built up the speed and the car shifted to 2nd and then to 3rd gears. Usually the car would stay in 2nd until the engine (or O2 sensor) is warmed up a little bit but it's NOT this morning. Drove the car to the distance where the transmission usually shifts to the 3rd gear (in the normal condition, based on my experience before), the weird sound was gone and the car was back to normal. My guess was that the O2 sensor may draw some current to warm itself up during the first few minutes after cold start but something is wrong there. Once it has been properly warmed up then the car is back to normal. Any idea?

[Edited by hancheng on 02-15-2001 at 02:21 PM]

[Benzmac]

I would replace the overvoltage relay first. Then it may need other parts. You should have the check engine light checked for codes to see what caused it, they may be related.

[hancheng]

I found where the buzzing sound is coming from. It's actually the overvoltage relay. I didn't know that a relay can be buzzing and vibrating. Just ordered the relay and one year maintenance supply from the FastLane. I will keep you guys informed as soon as I replace it.

BTW, my order number is 016. Are there just 15 people ordered parts before me? Anyway, I think the price is very good, and the OE parts should be first grade based on my past experience with PartShop.

[hancheng]

Hi, all:

Received the overload relay last Friday (Feb. 23) from FastLane and replaced it. Car ran fine during a short test drive. Reset the check engine light (unplug #31 fuse for 10 seconds). Drove the car on Saturday and Sunday for about 100 miles in total. The car runs fine and the check engine light never comes up again. Thanks.

BTW, my cruise control didn't work during the period when I had the cold start problem. It works fine now with the new overload relay installed. Apparently they are related.

[David C Klasse]

Good to hear you car is running well. I am for sure going to get that new OV Relay and hopefully have a number of my related problems solved.