View Full Version : Lots of smoke - no power
Symptoms
- Runs OK when cold. After it starts warming up I get a major power loss with missing and huge amounts of black smoke out the exhaust. The engine stops making its tell tale diesel rattle. The only way I can get out of it is to keep the pedal down and drop it a gear or 2 to get the revs up. After 5 secs or so she will pull out of it and get up to speed but as soon as I let up on the accelerator its back to the same old same old. It is getting worse.
Codes
- PO236 - Turbo Boost System. No other codes.
Attempted fixes so far
- Replace turbo boost control solenoid - no improvement
- Vac pump is 6mo old and working
- wired waste gate shut - no improvement
- new fuel filter - no improvement
- checked turbo for play - OK
Questions
- would a bad lift pump or plugged cat contribute to this?
Any thoughts / input would be greatly appreciated. It is now getting embarassing and dangerous to drive.
Take a look at the business end of the EGR valve. Sounds like it is choking the engine.
I pulled EGR valve earlier today and it looks like it's fully closed. I also took the vacuum line off the turbo boost control and stuck it on EGR valve as there is vacuum present at an idle. The engine changed pitch immediately and soon started to miss. The EGR solenoid has also been replaced. This could be the problem but I don't get an EGR related code. How do I troubleshoot this?
Sounds like it's working OK. I forgot that it was a '98 which has pretty sophisticated EGR monitoring.
So, when was the last time the air filter was changed?
Make sure the new turbo solenoid is plumbed correctly. The line to the pump goes on the connector with the restricter.
Air filter change unknown - haven't drove it much since I bought it. I will pull it and drive it to see if it makes a diff. Should be OK as we have lots of snow and no dust right now. MAF sensor would catch any chunks. Will let you know how it went. Solenoid should be good as it shares the same common vacuum manifold with EGR slenoid. I don't think it can go on backwards but I will check.
Joy at last. I took the vac line off the EGR valve, plugged it and the truck runs better. It is now driveable. I have about 80% of it's power back. Still have heavy black smoke under full throttle. I'm still not sure why this is like this because it is just not right. When I first bought the truck it ran great. Problems started after the dealer took the intake manifold back off to tighten injector lines they forgot to do the first time.
I will check vac plumbing as you suggested John.
Vac plumbing is good. Is it possible that the spring that holds EGR valve closed is weak or broken?
Problems started after the dealer took the intake manifold back off to tighten injector lines they forgot to do the first time.
You have been withholding information!
Take off the upper manifold and see if there is a gasket (a ring) on the EGR chimney in the center of the lower manifold.
Yes the ring gasket is there. When they replaced the injector pump there is no way they cleaned the upper or lower half of the intake manifold. It is caked with crud. I am still baffled as to why the truck runs better with the EGR vac line plugged. Would it help if I took off the lower intake to clean it out?
Can't hurt, but I doubt if it will have an effect on the problem.
Check the air filter. Do you have a boost gauge?
It runs the same with or without the air filter in it. No boost gauge. With the EGR vac line plugged it runs better. So is the EGR valve opening when it shouldn't? When I took the turbo control vac line and put it on the EGR valve at an idle the engine stopped making its diesel rattle and shortly after it started missing. These are the same symptoms I described in my first post. Could a plugged cat cause excessive back pressure which would cause this condition? This is definately a Serlock Holmes mystery so far.
tanman_2006
02-11-2010, 22:39
You don't need no stinkin cat anyways! :D Good reason to get rid of it IMHO.
IMHO
The EGR system valve could be leaking by or the manifold has an internal leak through to the Exhaust crossover.
The Cat could be plugged too.
With the improvement while messing with the EGR I think you are getting closer to the cause.
EGR bleed at the wrong time will totally destroy power and mileage along with contributing to loads of smoke.
I would yank the Intake off completely and clean that beast out real good.
Be sure to check all the passages and make sure there is not a place that has erroded through into the intake (bad gasket or ???)
If the EGR is not new I would do one of two things, either scrap it or replace it with new.
If you have to pass inspection then you need to keep it in top order.
The turbo boost code is telling us that the manifold pressure is likely LOW.
Get a boost gauge hooked up (even if temporary) and see whats happening.
If there is no boost then the issue could be a plugged cat.
If the exhasut can't get out, air can't get in and then there can be no boost.
Check these things and keep us posted.
Robyn
Good point on the converter. If it's plugged then you'll get a lot more EGR flow than expected, and the PCM may even reduce boost to compensate. Also, with a plugged converter the backpressure may force the EGR valve open when it should be shut.
If you have any sort of inspection at all, be advised it will code if you bypass the EGR.
Thanks Robyn & John
It will take a day or three to get this stuff done. Will keep you posted.
Unbolted the flange from the turbo down pipe to the Cat and spread it about an inch. Hooked up the EGR and took it for a spin. End of all issues! I didn't know an L-56 could have that much power. The stock system sure gags the engine. I'm forseeing a straight pipe in my near future.
I will pull intake for cleaning as soon as I order a PMD harness for relocation as the PMD and IP are new. I have a heat sinc so I can do all at the same time.
Thanks for the help.
Dave
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