'93 300D 2.5T, 0-62 in 20 sec??? - PeachParts Mercedes-Benz Forum

flybywire1 · #1 04-30-2006, 08:18 AM

I'm am having a hard time believing this is normal for these cars, but if I listen to my dealer he says it is! I bought this car from them only two weeks ago and ever since I have got the run around. Took the car to an independent Bosch dealer that the dealer recommended and they said it was probably a worn out I.P....at 100K?? That seemed odd, so I've been doing my research on this site and think I my be closing in on the problem. When I disconnect and block off the pressure line from the intake to the ALDA there is NO change in performance at all. I adjusted the ALDA CCW about 1 turn to check for any change and none again. No matter what I adjust or change on this device it makes no difference. Could it be stuck at one position and unaffected by presuure or adjustment? Can it be replaced and adjusted properly on the car?

The car runs good and starts well, but it also has a noticable roughness and puffs of bluish white smoke if I hold the RPM at 2300 and slightly "tip in" the throttle in neutral.

By the way the economy is quite good. About 29 city and 35 or so Hwy.
Thanks in advance for any help!

pmckechnie · #2 04-30-2006, 01:07 PM

Sounds like a turbo problem to me. I have a 91 300D and it runs very good with lots of power. Check all the vacuum hoses around the turbo and the vacuum valve in front of the air cleaner. On this car, it takes vacuum to close the waste gate on the turbo so it can make boost. This vacuum is controled by the EDS computer. You could also have a problem with the OVP relay. The EGR system has to work or the EDS system will kill the boost. The above rambling is just food for thought.

pmckechnie · #3 04-30-2006, 01:12 PM

Just another thought. Remove the air intake hose from the turbo with the engine OFF. Turn the turbo shaft and make sure it turns free. Poor maintaince (oil changes) can make the turbo gum up and not produce the boost needed. I changed to Mobil 1 syn 15-40 and I could really feel the difference in power. I think this was because the Mobil 1 cleaned things up and as I could tell the turbo turned easer.

2.5Turbo · #4 04-30-2006, 01:13 PM

Clean out your ALDA line off the intake manifold. It most likely will be all gummed up with oil and EGR crud. Once those lines and fittings are cleared out, the ALDA will see the correct turbo pressure and increase the fuel as needed. Mine had the exact same problem when my grandmother handed it down. She never (and I mean never) drove it hard so nobody even knew something was wrong with it! That is until I got it at about 85,000 miles, looked up the specs, and found out that a 17 second 0-60 is not normal, and something needed to be done. It's a whole new car now, getting a 0-60 in 12-13 seconds. I can squeak tires accelerating through a turn now.

If you're not familiar on how the turbo should feel, floor it from a stop and note how it reacts. If it gives you a little kick in the pants at around 2000 RPM, your turbo and ALDA are working properly. If it's just slow all the way up past 3000 (like mine was), you need to do this fix

sixto · #5 04-30-2006, 01:56 PM

If the line from the intake manifold to the ALDA goes through a switcover valve, bypass the switchover valve TEMPORARILY to see if it's clogged or stuck closed when the engine's running.

Plumb a boost gauge into the line leading to the ALDA. The turbo is good if you see 5 psi by 2500 rpm under load.

Does that model bleed boost if it detects a problem with the EGR system?

Sixto

pmari · #6 04-30-2006, 02:04 PM

What 2.5Turbo said.... http://www.mindspring.com/~houlihan/merc/banjo.htm

flybywire1 · #7 04-30-2006, 06:38 PM

I should have mentioned that the boost is a solid 9 psi and the manifold pressure line and fitting have already been cleaned. The fact that I'm getting boost pressure at the ALDA is what is puzzling. With the hose on or off the ALDA seems to make no difference. It runs entirely the same way. I've checked the ALDA and it holds pressure, doesn't leak at all.

It's as if the ALDA is not moving when boost is applied and therefore no enrichment of fuel. If I were to replace the ALDA could it be adusted on the car or would the new one have to be calibrated on a bench?

Tom

pmari · #8 04-30-2006, 07:01 PM

So you got boost, but no fuel. Can we assume you checked the fuel lines and filters? You may want to get some codes ...93 300D 2.5L Turbodiesel Power Loss
Check this thread too...2.5 Turbo Boost problem.

flybywire1 · #9 04-30-2006, 11:25 PM

Yeah, I had the dealer replace the filter and checked for fuel line leaks or bubbles. There were none. The dealer ran codes and says there were none.
I am a little concerned however about the level of boost at 9 psi. I read on a post that the 2.5L should be no less than .95 bar or about 13.5psi. Is this correct? Obviously, with a lower boost comes lower power.
Thanks, Tom

t walgamuth · #10 04-30-2006, 11:49 PM

20 secs is too long for sure. my mb buyer guide says it should do it in 10 sec to 60.

i would take the crossover off and look to see if it is tarred up.

tom w

sixto · #11 05-01-2006, 01:16 AM

If you're getting 9 psi my guess would be a defective ARV circuit. Either a problem with the actuator, an improperly seated or deformed valve, or a broken or weak spring. If you have a Garrett turbo you can dig into the ARV without removing the turbo.

Could be a simpler problem like a misadjusted wastegate flapper but I'm not sure 2.5s have wastegates.

Not to mention a tired turbo :/

Sixto

pmckechnie · #12 05-01-2006, 07:41 AM

Yes, the boost should be higher than 9 psi. My 91 runs 14 psi. I would also recommend you check the cross over and make sure it is not almost plugged up. Also make sure the air valve (or what ever it is called) on the other side of the cross over from the EGR valve is not closing under boost. If it is, that will also make the boost drop. You can temporarly unhood the vacuum line from it and then test drive and check boost. This may cause an error in the EDS system which will then turn off the boost, but it should work at least 1 time. If this happens, simply turn off the engine, reconnect the vacuum line, and you will be back where you were.
Good luck.

flybywire1 · #13 05-01-2006, 06:39 PM

Thanks for the suggestions so far, but I have tried most of those things with no luck. I've removed the crossover and checked it for sludge, there was a little but it had not plugged the port for the ALDA. I think I will check the codes myself and see if any are present. If not, I really don't no where to go next. I do think now that the boost is where my problem lies, however it may go beyond my limited knowledge of these cars as to what to check for. BTW, what is an ARV anyway??

sixto · #14 05-01-2006, 07:41 PM

ARV = air recirculation valve. A stupidity MB started using in the mid 80s. It bleeds boost from the pressure side of the compressor to the intake side to soften the onset of boost. Like these cars produce so much thrust that more acceleration would be objectionable.

I don't know if a 2.5 has ARV but I found the ARV flap wasn't sealing properly in the SDL.

Sixto

speedy · #15 05-01-2006, 10:38 PM

Quote:

Originally Posted by sixto

ARV = air recirculation valve. A stupidity MB started using in the mid 80s. It bleeds boost from the pressure side of the compressor to the intake side to soften the onset of boost.

Holy crap! Does anyone know if the 2.5 Turbo has this device? I can NOT get decent throttle response from my car... maybe this is why.

As for the original subject - 20 seconds is waaay too slow. My car does about 15 seconds to 60mph, which is probably not quite up to par, but not bad. I can't squeal the tires around corners though!

The difference between 15 and 20 seconds is huge - I would tend to agree with pmari that it is a fuel problem, but I'm no expert. I would lean on the dealer to fix the problem - you should be able to find the published 0-60 figures from Mercedes, I think it's 12.8 seconds. If you show them that, they will not have a leg to stand on IMO.

-David