several parts of the story don't agree, but it could be a plugged cat. you say there is no catylst or trap, is it straight piped? it really sounds like something is plugging up the exhaust.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Or the intake.

Timing doesn't change, so it can't be that if it's intermittant.

Fuel is apparently being delivered. I'd say it's a fuel filter/strainer/vent restriction, but fuel starvation does not deliver black smoke.

Air? Could be a sticky flap in the air-flow meter, unusual but possible. Any other air restriction that I can think of wouldn't be intermittant.

Turbo wastegate won't blow black if it's sticking open, plus it'd have to have full boost to open, and it doesn't sound like you have to drive hard to make it happen.

Turbo seizing? Wouldn't happen over and over, it would likely happen once and finished. Could be binding/hitting the housing if the bearings are that shot I guess, but this would show as low boost to no boost when the power drops off, and it should drop the fuel when the boost drops.

Plugged exhaust would never allow full power and then reduced, so as John mentioned it doesn't fit the symptom as posted.

Stumped based on what you've posted so far.

__________________

Gone to the dark side

- Jeff

Yup, there is a straight pipe

I'm going to guess the IP is damaged, and allowing fuel sometimes and not others, lift pump? air? WEIRD!

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Just for the fun of it close off the return line from the injection pump. Any change post it.

Also a good internal soak of the injection pump might not hurt. Is this car or has this car been on vegatable oil?

As I type this one other thought occured. Set the timing on the damper pully. Pull the bolt covering the timing blade. See if it is centered with a mirror. If not rotate the engine one more time to the timing mark. The blade should now be present.

Look in the oil filler hole on the valve cover if possible without removing the valve cover. I do not know if there is a shield or not on this model. The cam lobes should generally be pointing upward on the number one cylinder. If pointing down you have the injection pump on the wrong stroke.

The possibility of this is indicated by the fact of you finding the timing originally so far off. If the prior individual could not set the timing right he may have screwed up even worse. This is par for the course during a head change on these.

This ten second delay in power of any type coming on is also perhaps another clue for an injection pump possibly on the wrong cycle. Seriously bad fuel milage might also indicate this problem. The non responsiveness to fuel as it is being injected is another indication. The engine has to wait to see fuel injected at the totally wrong point in time in a very inneficient fashion.

The 603 is a more efficient engine than the 617 and 616 so it might not smoke as bad as they do in that situation. It almost takes longer to read this than to check and make sure that injection pump is on the right cycle. In my humble opinion this has to be checked out.

It may not be the problem still but you have to know it is okay. I also freely admit that I do not know how exactly a 603 engine type does react to the injection pump being on the wrong stroke of the cycle. Other than it's going to run piss poor in my opinion. It will of course will still run.

I pulled the valve cover to check cam timing, its spot on. I have the locking tool for the injection pump, pulled it and reset it to 15* ADTD. It is on the correct stroke. I loosened the fuel tank cap to test for a tank vent problem, no change. I just drove the car home. On the highway doing about 50 it drives nice and easy. Give it a little throttle and you see a few psi of boost quickly and it moves. Come to a stop and it runs like crap and almost dies. Floor it from a stop (or any time its running bad) and tons of smoke and no power until the turbo has been on for a few secs (10 or so) then it clears up and runs good.

Oh I clamped the return line also. Seemed like there was more smoke especially at idle but other than that no change.

I'll go through a bunch more of the things Lee posted, only got to about half of them so far.

Oh yeah and I checked the turbo, spins freely and no axial play. New air filter, I checked the EGR, operates normally and closes all the way. I guess I could disconnect it and see if there is a change. I did check the air flow meter too, flap moves normally.

One thing I didn't check is the throttle linkage but I'm not sure how that would cause this issue.

So I finally figured it out!!! It was the EGR. The valve works properly but something in a hose or switch must be hanging up. I haven't had a chance to check on what yet. I disconnected the line from the EGR and plugged it, no more problem. The car runs great. What was happening is that the EGR would be closed when it first started and idled. Once you drive it at speed the EGR opens, which it should, but then as you decelerate it should close, but it was staying open. Something was not allowing it to release the vacuum to the valve fast enough. If you waited long enough the valve would eventually close and it would run good again until it was time to open it up.

This was an odd issue and difficult to trace, especially since there were multiple things originally wrong with the car. Thanks everyone for the help!!

The important thing is you found it. Plus the fix was cheap. In hindsight it makes sense.

Also a good indication that those still having the egrs should disable them. Gotta be a lot of crap entering the engine with them still functional. May help get a little better fuel milage as well come to think of it.

Theres a great thread on here for blocking off the EGR...we have emissions testing in Tennessee and Ive had mine blocked off for years...always passed my test. Theres no computer, no "Check Engine" light, and no cat converter...nothing for them to scrutinize except the actual exhaust. It'll keep the intake manifold cleaner and lower the risk of blocking the turbo overboost orifice.

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"Cool Blue"

If emission testing is done at idle the egr is closed anyways. So this modification should not upset the test.

That egr circuit must introduce a lot of the exhaust component to upset his engine as bad as it did. That has to kill some fuel milage and perhaps general performance even when operating normally I would suspect.

This is true. Im just adding a little reassurance in the event that there was an emissions requirement in his area as it is in mine.

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"Cool Blue"

I'm a little confused as to how a properly functioning EGR could have any effect on performance/MPGs/etc.(?) Why disable it? All it does is open during decelleration in order to re-burn any unburned fuel in the exhaust. It is always closed during acceleration or steady-speed driving. If it's sticking, that's a problem but it's easily solved.

I'm also surprised to hear about gunk plugging-up the over-boost switch, on 617 turbo motors the only thing I've ever seen gunked-up w/ sludge is the banjo fitting @ manifold. IOW, the sludge problem never seems to make it further downstream.

This is a factually incorrect statement.

The EGR is open during all accels and cruise, with the exception of WOT.

Really? Wow...HTF does the turbo create boost w/ a big open passage between the intake and exhaust manifolds? Or are you saying that there is only turbo boost on the OM603 under WOT? This is amazing.