tech help needed 1991 300E 2.6 Gas - PeachParts Mercedes-Benz Forum

xmether · #1 08-19-2006, 04:55 AM

Help! Just bought my first benz. 1991 300E 2.6 Gas, 200,000 miles and in excellent condition. It's a very nice car. However, It has a small problem and I don't know much about this type of car. The car has NO power off the line. It starts and idles at around 700 rpm. I put the car in drive and when I step on the gas, the engin responds with little too no power. It pulls away so slow. If I lift the gas pedal a little I feel a brife rush of power, and by fethering the pedle I can sometimes help it slowly speed up. Once the rpm reaches about 1300 rpm and the car is going about 15 miles an hour I can feel the power start to increase quickly and the car then runs as if there's nothing wrong with it. If I come to a stop, the problem repeats. It runs great as long as I don't come to a stop. (note) each morning when I leave for work the car runs just fine for about six blocks untill the temp gage begains to move. However, durring that first six block the trany seems relucktent to shift. As soon as the car starts to warm up the power is gone. (note) I can keep this problem from affecting performace by Power-Braking when I come to a stop. If I take care not to let the rpm drop below 1100 as I stop and keep it at that rpm or higher while stoped, the car has excellent power when I take my foot off the brake and pull away. Again, once I get the car past its first "flowndering", it runs fine. before I bought it, I drove it from Lodi Calif. near Sacremento too Las Angeles Calif. over 400 miles. It was summer and very hot, (105*) and I drove most of the way at 80 miles an hour with the air condistioner on the whole way on one tank of gas and it ran great. Again as long as I didn't let the rpm drop below 1100rpm when I stoped. Here are some of the things I've tryed. The plug wires where replaced but it seemed to run wrose so the old ones where put back on. I changed the spark plugs from the bosh single platums too double platums. (now the car runs rougher) It has a new Cat and I know that the EGR valve does not work. But I'm fairly sure thats not the problem. Any help would be great. A freind told me they thought it might be the "Throtle Possition Senser" but parts are so expencive I feel it would be better to get the advice of people who have expereance working on the Benz. Again, any help would be great, Thank you

dpetryk · #2 08-19-2006, 06:59 AM

It could be the TPS. The TPS senses rate of change of the throttle and when to apply extra fuel during acceleration. Sort of what carburators did when you opened the throttle. They squirted fuel down the throat. The TPS and the ECU accomplish the same thing. The TPS can be checked with a ohm meter. Setting its position is simle but you have to move the pressure regulator to accomplish it. There are a number of threads that talk about how to set them. Have a search.

cjlipps · #3 08-20-2006, 01:29 AM

Remove and toss the platinum plugs and replace them with the factory-recommended copper plugs. Check the owner's manual or any online source. It's probably the easiest, cheapest and least time-consuming thing to try and very likely to be the problem.

dkveuro · #4 08-20-2006, 01:57 AM

Ditto the plugs...Bosch copper only.

A weak coil will procuce this power loss....as will burnt center contact in distributor cap.

It sounds like the ASR is fighting the throttle movement...under the hood, with engine running...throttle the engine up and watch the ASR on the manifold to see if it is shutting off throttle plate.

The delayed upshift is a factory designed programme to allow the cat to light up quickly...on passengers side under car, there is a vacuum line to the delay valve capsule..remove it from the capsule and plug the end.

BTW..Welcome to MBS......How long have you been here on mercedesshop ?

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