Question re: '90 300CE & M104 engine - PeachParts Mercedes-Benz Forum

BENZ-LGB · #1 07-14-2008, 07:10 PM

My 1990 300CE has just developed an "issue" (they are always "issues" and never "problems"). Before I take it to Enrique @ Mr. M.B. Motors, I would like to take a stab at fixing it myself.

Here is the "issue":

1. The car starts fine (though not always on the first crank), it runs fine, accelerates fine and it idles as smooth as butter.

2. If I stop and turn the engine off and then start again a few minutes after stopping the engine, the idle will be a little shaky (but never to the point of rough). If I try to drive the car, the throttle does not respond, I can floor the car and I don't get much movement, then the engine "catches" and the car accelarates normally.

3. If I let the car idle for 30 seconds or so, I don't get the problem.

4. Also, if the car has been stopped for more than just a few minutes, then I don't experince this issue. I have informally timed it, and if the car is stopped for more than 10 to 12 minutes, then there is no problem.

5. Only a short, brief stop causes the problem.

6. When the car experiences the "slow accelaration" issue, it feels as if the car is starved for fuel.

7. Fuel economy has remained the same (in fact, fuel economy went up slightly after putting in a new set of Michelins).

I had suspected the fuel pump(s) or the fuel distributor, but the fact that the car only does this after it has been stopped for a brief while (and does not do it after a long stop) makes me question my diagnosis.

I did a search here and did not quite find the same issue (maybe I was using the wrong search terms).

Any suggestions would be greatly appreciated. Thanks.

crashone · #2 07-14-2008, 09:32 PM

When was the last time the fuel filter was changed?

BENZ-LGB · #3 07-14-2008, 10:50 PM

Quote:

Originally Posted by crashone

When was the last time the fuel filter was changed?

Good question...but how would a dirty fuel filter cause the engine issue only after the engine has been off for 10 - 12 minutes and not cause the engine issue if the engine has been off for a longer period of time?

BENZ-LGB · #4 07-15-2008, 02:37 PM

Any other suggestions????

mbdoc · #5 07-15-2008, 04:26 PM

Slight fuel bleed-off from injector OR fuel distributor.

OR a slightly weak coil or crank sensor.

mr300ce · #6 07-18-2008, 09:35 PM

My very same car did this once or twice. Then all was well, and has not returned, since I did a BG Induction System service.

Pressure bleed-off would cause a hard start condition, but once the engine is started, there should be no noticable troubles.

Carbon build up on the valves and combustion chamber is a likely cause. Find a shop that does this service, it really is the best.

http://www.bgfindashop.com/bgservices/fuelair.htm

fpharryc · #7 07-19-2008, 04:51 PM

BENZ-LGB, Harry here. If you recall, same year, same model. Change your plugs. Torque them to specs. 20 lb-ft.

BENZ-LGB · #8 07-19-2008, 08:17 PM

Quote:

Originally Posted by mr300ce

My very same car did this once or twice. Then all was well, and has not returned, since I did a BG Induction System service.

Pressure bleed-off would cause a hard start condition, but once the engine is started, there should be no noticable troubles.

Carbon build up on the valves and combustion chamber is a likely cause. Find a shop that does this service, it really is the best.

http://www.bgfindashop.com/bgservices/fuelair.htm

I will try that. The local Benz dealer offers the service.

I love your 300CE. As you can see from my signture, I love these cars. I miss my red 300CE very, very, very much.

Would love to see a bigger pic of your 300CE.

Again, thanks for the tip.

iwrock · #9 07-22-2008, 03:56 PM

Smell any fuel at all?

Mine would do that, as one of the fiel lines was a little loose....