603 Shakey Lumpy Idle Almost feels like Missing! - PeachParts Mercedes-Benz Forum

777funk · #1 12-30-2007, 09:08 AM

I'm beginning to wonder if my IP is slowly dying. My 603 turbo is so shakey at idle. It seems the worst after the engine has been on for a long period of time, such as a 500 mile trip.

When I first start it it's smooth as a top (when it's not below freezing outside anyways). But man once it warms up it's very shakey. Literally my knee will shake back and forth an inch or so when I'm stopped.

I've cracked all the lines one at a time several weeks ago. But it's hard to track because it's not quite a miss-fire, but it's not a smooth clean fire either. When I do crack the line it shakes much worse. I'm thinking it's on all 6 cyls. Just a weak injection maybe or not enough fuel. The thing I've been wondering is that it's probably somehow at low RPM's fuel is leaking past the plungers in the IP? How could I check for that?

It runs great when it's not up to temp. It's as smooth as a top. That's why I don't think it's injectors (new Bozio nozzles). I do notice they are a little wet on a few of the injectors where they screw together but not a visible leak, just slightly wet.

My thought is still maybe the IP is leaking fuel pressure or quantity somewhere at Lower RPM's. Could this be?

Anyone else ever had problems with IPs. I've heard that many Injection Pumps on MBs get needlessly rebuilt. I don't want to even consider it if maybe there's something there I'm overlooking.

Lastly... for fuel economy I'm getting 27MPG on this '87 300D (winter fuel of course) and driving 75-80mph.

jshadows · #2 12-30-2007, 12:35 PM

could try the delivery valve seals. just need special multipoint crow's foot tool for pulling them off. seals are cheap so worth a try if you can find the tool (which I don't think is outrageously expensive either). I had some weird behavior in my 603 too but while it was warming up. I suspected the seals but sold it before I got around to trying the fix.

777funk · #3 12-30-2007, 04:33 PM

Hi Bob, I had the delivery valve o-rings go on my first MB (190d with a n/a 602 engine). I could tell they were bad because I could smell diesel while just going down the road. When I looked to see what it was, one of the valves was leaking fuel all over the pump. But it ran great. This one is dry as a bone. But idling it just is too shakey to be easy for me to feel ok about. Worrying about a problem drives me nuts. I noticed when I ran out of fuel about a month a go on a trip (my fuel level sender was acting up and I ran out of diesel while driving), in a pinch, I filled the tank with motor oil and trans fluid and the engine ran as smooth as could be at idle. Then when I got to the gas station and filled it up on #2D again, back comes the shakes. That's the other reason I wonder if the IP is the culprit.

Hatterasguy · #4 12-30-2007, 04:37 PM

Yeah mine does it a bit to, the engine has to be really hot like right after a long highway run.

The Bosch shop said it was the IP, I forget the part it was a few years ago. They run about $700 to rebuild.

777funk · #5 12-30-2007, 04:51 PM

Quote:

Originally Posted by Hatterasguy

Yeah mine does it a bit to, the engine has to be really hot like right after a long highway run.

The Bosch shop said it was the IP, I forget the part it was a few years ago. They run about $700 to rebuild.

I took my first MB (190d with the bad IP-ruined by a shop fixing leaky delivery valves) to a Bosch shop and they said it'd be around what you said ($700, I Believe) to rebuild the 602's IP back then.

Is it the Idle control stabilizer that was bad or the whole IP needs to be rebuilt to smooth out the idle?

Hatterasguy · #6 12-30-2007, 04:53 PM

I honestly don't remember, it was four years ago. As you can see its really high on the list.

The last thing I did to my IP was the delivery valve seals, and I had the injectors done around that time as well. Havn't touched them in four years.

777funk · #7 12-30-2007, 05:13 PM

Quote:

Originally Posted by Hatterasguy

I honestly don't remember, it was four years ago. As you can see its really high on the list.

...

Yeah, I'll probably be the same way. As long as it still turns and squirts fuel at the pistons/prechambers, I'm happy with the IP.

Glad to hear yours has been fine for 4 years.

... by the way Hatty, why do you have a planned date to junk one of your cars?
Sorry, just had to ask.

babymog · #8 12-30-2007, 05:30 PM

Sounds like fuel starvation, plugged filter or strainer.

777funk · #9 12-30-2007, 06:37 PM

Quote:

Originally Posted by babymog

Sounds like fuel starvation, plugged filter or strainer.

Yeah, I suspected my strainer was plugged. I cleaned it out to where I could spray through EVERY hole with a garden hose and put a new fuel filters on a month or two ago and it didn't seem to help. However, thicker fuel improved the idle (the motor oil from when we ran out of diesel while driving). That's where I think maybe the barrels in the IP have diesel leaking past.

Hatterasguy · #10 12-30-2007, 06:42 PM

Quote:

Originally Posted by 777funk

... by the way Hatty, why do you have a planned date to junk one of your cars?
Sorry, just had to ask.

I prefer to think of it as removel of life suppurt.

777funk · #11 12-30-2007, 07:01 PM

Quote:

Originally Posted by Hatterasguy

I prefer to think of it as removel of life suppurt.

Ha ha I see. That makes more sense now.

Biodiesel300TD · #12 12-30-2007, 07:39 PM

Rough warm idle sounds a lot like the bad rack damper bolt on the 617's. Do the 603's have a rack damper? If so try adjusting it, or replacing it.

babymog · #13 12-30-2007, 07:51 PM

Try unplugging the fuse or relay (overvoltage protection relay) and see if it changes. If it doesn't, something in the idle control is amiss, could be a thermal intermittant electronic issue.

I think other things than removing the OVP will do the same, but I'm not sure what the easiest un-plug would be to disable the idle control.

Hatterasguy · #14 12-30-2007, 09:34 PM

Oh I just remembered what the Bosch shop told me to do, turn the idle up! I think mines set on like 5 or 6, give that a try.

777funk · #15 12-31-2007, 07:40 PM

What is the Overvoltage Protection Relay? Where is it located?

Also, Hatty mentioned turning the idle up. Mine's on 7 and still pretty lopey. I can even hold the accellerator to 1kRPMs and it's still lopey. But again, only when it's hot. My exhaust smells weird since the dealer adjusted the timing. It used to smell like a small tractor engine's exhaust. Now it smells like sulfer burning.

Quote:

Originally Posted by babymog

Try unplugging the fuse or relay (overvoltage protection relay) and see if it changes. If it doesn't, something in the idle control is amiss, could be a thermal intermittant electronic issue.

I think other things than removing the OVP will do the same, but I'm not sure what the easiest un-plug would be to disable the idle control.