93 300D 2.5 surging or hesitating?? - PeachParts Mercedes-Benz Forum

benmack1 · #1 03-13-2009, 08:19 PM

My 93 300D 2.5 tonight seemed to have a hesitation at constant throttle. This was a fairly harmonic event (1 sec on 1 sec off.....). It cruised OK but the hesitation would appear intermittantly. maybe more when going up an incline at throttle. Also happened at 30 mph leaving work. A little background. I just replace the GP's last weekend and it ran fine tues-today. Just fueled up today and the first 30 miles seemed OK. I had the IM off and swung the crossover pipe to do the GP's. I cleaned alot of crap out of the IM. Idles and sounds fine at idle. I was worried I stirred up some crap in the IM when I cleaned it. But have driven 300 miles since with no problems. It feels like the turbo kicking out and in. Seems better under hard accel and sometimes runs OK for several miles. I don't think it is filters or fuel. It is too syncopated for that, seems like air or fuel control issue. It usually blows a cloud of smoke when I first accelerate up the on ramp from work. this seemed larger and blacker smoke than normal today. Maybe I'm just freaked out and my mind is playing tricks about that but it was a big cloud of black smoke going ~45-60 MPH under hard accel when it was surging/hesistating on the first take off tonight. I'm way out of my league here just trying to explain as best I can. Any suggestions of cause?

2.5Turbo · #2 03-13-2009, 11:43 PM

Check and make sure you didn't dislodge some gunk from the manifold and get it in the line to the ALDA. If something is in there intermittently blocking the boost pressure signal, it will feel like surging. You have a 93 so there isn't a switchover valve for overboost protection, so there should be a line straight from the manifold to the ALDA; there also might be a Y in there to get the boost pressure to the pressure sensor. Make sure all those lines are clean and clear. If it's all good, it's time to start digging into the boost control/wastegate electronics and transducers.

Easiest way to diagnose a boost control problem is to bypass the transducer and temporarily give the wastegate actuator constant vacuum. It's easy to overboost with this test configuration, so be very careful and drive with a light foot. If your surging is gone, it's probably the transducer. Swap the two transducers (I think there's one on the intake flapper valve on the 93) and test drive, this time with the wastegate actuator connected.

compress ignite · #3 03-14-2009, 04:05 AM

2.5Turbo has given you the first most likely source of your problem!

This would be an Improvement/Simplification of your system:

Long Post...Very Much Worth considering the modification!

Wastegate actuator swap for OM602.962?

benmack1 · #4 03-14-2009, 01:34 PM

OK, I understand what to clean. Now how to clean it. I have a black oily residue on the IM to ALDA outlet port, and on the ALDO nipple. I'm worried when I 'cleaned' the IM last week I have just liquified alot of the stuff and definitely didn't get it out. 3 questions.

1) How to best clean the hoses? Can I use something like WD-40 on these. I have a Y-connector. One end to the IM, one end to the ALDA and one end to a small hard plastic line that runs into the firewall then I can't see it. With the 2 nipple connections off (I can't get the plastic line free) I can blow through the hose so it isn't totally constricted there.

2) Can I spray WD-40 into the ALDA nipple to clean it or is there a better way. I assume since this oily goop has gotten all the way to the nipple it is also inside the ALDA housing.

3) Can the ALDA be replaced if this all doesn't clean it up?

compress ignite · #5 03-14-2009, 05:20 PM

I'd not use WD-40 ANYWHERE , It leaves a gummy residue (which hardens)
when the Volatiles evaporate.
[The only application I have for WD-40 is removal of adhesive materials,say
Duct Tape "Goo"(works great),followed by a wipe down of C3H7OH.]

If you've got "Goo" in your ALDA ,It will come clean!(Spray your cleaner of
choice into the portal until it runs clean.)

For hard plastic tubing and rubber connectors:

Legal Disclaimer:

[Initially,my suggestion would be Brake Parts Cleaner(leaves no residue)
(AND in a Pressurized container it's Sooo easy to use)BUT
there are different formulations (Chlorinated/Non-Chlorinated,Etc.)
and some may or may not be harmful to rubber /plastic components.
YOU, WILL HAVE TO CHECK WITH THE DIFFERENT MANUFACTURERS]

(I've used BPC on almost all these parts with no problem)

Electrical Parts cleaner?(Instead of Brake Parts cleaner)

For the I.M.:

One member swears by filling your IM (Upside down of course) for a couple
of days with BioDiesel...Breaks up all that "Goo",rinse well with Kerosene
and blow dry with compressed air.

benmack1 · #6 03-14-2009, 05:58 PM

One additional point/question. The hose on the IM nipple. When I removed last week for the GP job, it just slipped off with the metal crimp ring still in place. I then just slipped it back on. Clearly that isn't all that tight. Any chance this hose not being real tight could cause my 'jerking' symptoms. I think jerking is a better description than surge/hesitate like I used orignally to characterize. Where can I get this hose if I want to replace the 3-way alltogether in case anyone thinks this may be my cause.

benmack1 · #7 03-15-2009, 05:21 PM

Well, I have cleaned the ALDA line and still have the pulsing problem.

When I rev the engine by hand up to 1500-2000 RPM(estimate) there is a vacuum solenoid on the front above the turbo that seems to be pulsing similar to what I am feeling on the road. It seems to my untrained mind that this is the problem. This solenoid is open/closing once or twice a second. It doesn't seem right. Anyone got thoughts on this? Is this normal? I don't see any reason for it to be cycling. I would have thought open or closed but not cycling...... grrrrr