Engine/Transmission (1998.5 - 2002) 02 HO cuts out, smokes, and backfires under load

[dieselluver]

You said that the boost pressure goes into a vac after this starts. But what is the boost before it starts? You put the pedal to the floor, it starts to pull, smoke increases, boost does what? then it starts to smoke real bad, boost drops off and back fires?

The boost starts out at 14psia (0 boost) and ramps up to 28psia (14# boost) at WOT just before it looses power and backfires and the smoke turns white. Then it goes from 7 to 9 psia (vacuum???). It then returns to 14 psi if you let off the pedal and let it idle.

 

[cerberusiam]

The boost starts out at 14psia (0 boost) and ramps up to 28psia (14# boost) at WOT just before it looses power and backfires and the smoke turns white. Then it goes from 7 to 9 psia (vacuum???). It then returns to 14 psi if you let off the pedal and let it idle.

How are you reading the boost? Manual gauge or electronic? The electronics are a lot less accurate when it comes to reading actual numbers because they rely on a signal that may not be accurate.



Boost can never go below zero as it is a measure of the difference between atmospheric and manifild pressure. If the manifold pressure went into negative the engine would quit.



Have you pulled all the hoses and checked the insides? A degraded hose could have a flap of rubber that is sucking in under high boost and blocking the air flow.



Don't forget the ECU and the possibility it is telling the pump to back off timing for some reason.

 

[Sticks]

Given the recent info, it is possible that your new VP went TU. Some reman shops do not replace the controller if it tests or calibrates OK. Where did you get the replacement VP?

 

[dieselluver]

I am reading the boost electronically through the ECM. Today it was much cooler and it ran just fine up to 34psia from the MAP sensor (which is 20psi of boost). After it warmed up it started giving problems again, the MAP sensor would only readup to 28psia before it would loose power and instantly drop to 7psia.



I am going to install a boost bolt and some line to verify if there is actually a vacuum or not when it does it's thing. I'll also scope the intake passages and intake tubes for any blockages.



The new IP was from a local certified Bosch pump shop.

 

[MChrist]

My '98. 5 ran like that once, with the white smoke and backfiring. Turned out to be a bad load of fuel with nasty water and debris in it. It tripped the "water in fuel" light, but I destroyed the high pressure pump and 6 injectors... ... maybe you should try draining your fuel filter into a clear jar and inspecting it?

 

[dieselluver]

With a mechanical boost gage hooked up to a boost bolt in the intake plenum, I get a vacuum of 12 inches of Hg when it looses power and cuts out. Can this be possible on a diesel?



I inspected the intake, tubes, boots, and intercooler and found no blockages.

 

[JohnBoy5]

ok so i have been watching my map sensor while driving. let me say one more time i do have a boost fooler installed. mine starts out at 28 to 29 and i can not get it to go under this value at all no matter what i try. i am starting to think you still have a map sensor problem...

EDIT

dieselluver

JohnBoy5 - Out of curiousity, does your boost fooler hold a constant 28 psia no matter what? Or does it offset your boost pressure a certain amount higher than whatever your absolute boost pressure is?

As stated above it starts out at 28 to 29 engine on or off, as boost builds it increases the same amount as the boost indicator in my quadzilla. example i start my truck no boost map reads 29 boost gauge 0 i step on it map reads 39 boost reads 10. so i guess it just offsets it.

with just the map sensor installed and with the engine off it reads 29 . so i guess i have no idea how this thing works lol but i know it does

 

[dieselluver]

I just hooked up a gage to the wastegage fitting on turbo compressor housing. It reads boost until it begins to cut out, then I get a vacuum of 12 inches of Hg. The turbo has a little radial play but spins okay. The turbo must somehow be hanging up when it warms up and begins to build at least 14psi of boost. Any turbo experts out there heard of this before???

 

[JohnBoy5]

could be a turbo also, i am not a turbo expert either. i would think its not normal to draw a vacuum but i might be wrong

 

[JohnBoy5]

well i had thought of something but my idea was wrong. i am trying to figure out why yours starts at 14 and mine at 29. so i looked at weather.com for your area and your pressure was 30. 20 in mg witch is 14. 83 psi in my area it is 30. 15 in mg witch is 14. 81 psi.

what are you using to read your map sensor with? maybe mine is using units of "in mg" and yours scanner is psi??? all the testing i did today was around town driving so i never really got to get on it for a long period of time. so maybe my scanner was not responding as fast as my boost gauge... or i was missing something trying not to hit the person in front of me... lol i will be getting on the interstate tomorrow to got to church and its a LONG on ramp i will see if i can tell more by that. my boost gauge has a peak hold that i will use and i will try and keep an eye on the map sensor to see its peak and i will record the 2 and do the same conversions like i did with the barometric pressure to see it they work out.

 

[Sticks]

If you are pulling a vacuum at the turbo then your problem is somewhere between the turbo and the air box/filter, and you are running a new BHAF???



Pull the intake to the turbo and the back plate on the turbine. For a turbo to be pushing boost and suddenly drop to NADA... . yeah, something is not right. If the turbo shaft is hanging up it should be obvious in lateral play and end play. Possible wastegate issue as well.



I have seen turbos where the turbine breaks off and is not noticeable on the compressor side. You might also have a floater in the turbine housing that is binding up the turbo. These are all shots in the dark with a migraine and the coffee has not kicked in.



Another thought... scary thought. What is your oil pressure doing? Have you had that TSB done for the oil pressure sending unit? That brilliant one that makes it read 40psi regardless of actual pressure? No oil getting to the turbo would definitely cause it to come to a stop.



Then this all leads back to fueling as noted a post or two above. Crap fuel means no fire/heat which leads to no turbo operation.

 

[JohnBoy5]

Ok so i had some interesting findings. When i turned up my programer and floored it my boost was 38 psi and that = 77. 36 in mg. The map sensor only reported 37. 3 in mg and that = 18. 3 psi. So some where along the line it does start to change the out put singnal. I will edit this later for typos as i am on my phone now. .

 

[dieselluver]

I figured out what was happening. The owner of the pickup (not mine) had changed the air filter (BHAF) and had not been washing out the sock. It didn't appear to be that dirty but I couldn't see light through it. It was causing enough suction under load to flatten the rubber intake air tube going to the turbo compressor. When the tube flattened it created a vacuum in the intake and caused the engine to cut out, smoke and backfire. I was able to see this happening by mounting a wireless scope under the hood to view the intake tube while driving.



Thank you to everyone who made suggestions in helping me solve this problem.