300TD question - PeachParts Mercedes-Benz Forum

rjm100 · #1 04-20-2008, 09:53 AM

Hi everyone, I'm new to this forum as well as to my 1985 300TD, something happened yesterday as I was driving along a relatively flat highway. Everything seemed fine for the first half hour of my drive, I was going about 100kph(60mph)but then after accelerating up a small incline (very small) and leveling out again it seemed like the car all of a sudden lost some power, I found with the pedal pushed all the way to the floor I could go no faster than 80kph (50mph) and then the for the next few minutes the car would slowly decelerate and eventually I could not get going any faster than 60km (35mph) as all this was going on I was listing to the engine and I could hear the turbo boosting and the rpm increasing at times but it was not pushing the car. It felt like the transmission was not working. I pulled off the highway and let it cool down for a bit and took the backroads home. It drove fine going on the slower city roads, still lots of power and turbo was working, the only other abnormal thing was the few second delay from when you step on the gas from stand still seemed to be a longer delay than normal. Transmission fluid level was ok. Is my transmission going? Is this a common problem? Thanks -Robby

Chad300tdt · #2 04-20-2008, 10:01 AM

Sounds like it could be fuel starved. Check your filters first.

kerry · #3 04-20-2008, 10:01 AM

What were the rpm's when the car was going 50mph and what gear was it in?
From your description it is hard to diagnose what is going one because it's possible that the rpm's were increasing because the car was downshifting.
Loss of power in these vehicles is often attributable to dirty fuel filters. I would change the filters, making sure to fill the large secondary filter with a burnable fluid like diesel, Purge, or ATF before reinstalling.
Sometimes the accelerator linkage can fail on these cars causing lack of power also. Failure of the transmission in the manner you describe is less common.
How many miles on the car? How long have you owned it? How does it shift? Hard or soft?

MTUpower · #4 04-20-2008, 10:08 AM

The vacuum valve on the tranny may be suspect, or the tranny may not be getting all the vaccum it needs.

tobybul · #5 04-20-2008, 10:22 AM

IMHO, I doubt its tranny related. What was said about fuel starved is a possibility. I would also check the changeover valve that is connected to the turbo and the ALDA. It might be plugged up. Its located on the firewall behind the brake booster. You said the turbo was working. How do you know this?

BTW, DO NOT MESS WITH THE ALDA!!

How many miles?

MTUpower · #6 04-20-2008, 10:50 AM

This is why I dont believe it's a fuel related issue:

I was listing to the engine and I could hear the turbo boosting and the rpm increasing at times but it was not pushing the car.

kerry · #7 04-20-2008, 11:24 AM

Quote:

Originally Posted by MTUpower

This is why I dont believe it's a fuel related issue:

I was listing to the engine and I could hear the turbo boosting and the rpm increasing at times but it was not pushing the car.

That description could be explained by a downshift from the kickdown switch allowing the rpm's to increase but not the speed.

JimFreeh · #8 04-20-2008, 11:54 AM

If this a CA car with a trap, could be the trap is plugged.

Jim

minimike1 · #9 04-20-2008, 10:14 PM

start with the simple stuff first. I was just diagnosed with a bad kickdown switch. You can unplug it under the accelorator pedal and see if that cures your ills. Fuel filter of course is the first thing to check, but if engine revs freely in neutral or park, it's not fuel related. After those two, it's back to this board.

asnowsquall · #10 04-20-2008, 10:22 PM

key thing seems like this statement "and the rpm increasing at times but it was not pushing the car". Check your tranny fluid level. If your RPM's are going up and the car doesn't move then its from the torque converter, the tranny or something that controls the tranny. I'm not sure how the bowden cable or vacuum stuff could effect the tranny so I can't really input on that.
I'm not sure how far up your RPM's are going, but if they rev up, and the car doesn't move then I suspect the above.

TchTchr · #11 04-20-2008, 11:36 PM

My wagon does the same thing when the fuel gauge gets below a quarter tank (need to clean fuel sending unit). The wagons' tank is lower than the sedans', so starvation happens more easily (someone correct me if I'm wrong). The intake screen could be clogged also. If you've run any biodiesel that screen could very well be clogged due to the cleaning abilities of the bio.

rjm100 · #12 04-21-2008, 10:08 AM

Hey everyone thanks for all the input, cleaning the fuel filters sounds like a place to start, .......Kerry I don't know what the rpms were there is no tackometer but it did sound like it was downshifting, I remember as I was on the highway only being able to go 45 mph I had the pedal all the way to the floor and then pushing a lot harder just to see if that would make a difference, and the pedal didn't really move much more but the rpms did jump up significantly at that time, the car has 150000 miles I just bought it and it normally seems to shift alright except going from 1st to second its seems a bit hard and a few second delay before the turbo kicks in and it takes off. ....tobybul The turbo definitely was working going at slower speeds and driving around the city streets, I'll start with the fuel filters that seems like the most logical thing to start with, Thanks for all the help guys I'll check it and see how it goes!

ImBroke · #13 04-21-2008, 12:01 PM

Location would help too. Couple it be a slipping trans. It would still downshift, but if the 4th band is out of adjustment, or the clutches are getting tired.... Hard to believe with only 150k, but you cannot be sure.
I don't think it would rev with a fuel starvation issue either.

kerry · #14 04-21-2008, 12:25 PM

You should have a tach on this car. If there is not one in the instrument panel, the instrument panel is not OE, leaving the mileage highly suspect.
I'm going for plugged fuel filters and not a transmission problem.

vstech · #15 04-21-2008, 01:49 PM

no tach? is your TD a EURO? do you have two heat zone wheels and an a/c switch on the dash, or do you have the colored wheel and the buttons on the dash?
what color are the needle hubs on your instruments? silver? old cluster... mileage unknown. black? possibly ok, but a euro cluster... mileage still unknown...