midiwall

I have a new problem...

I was driving at highway speeds, kicked it to pass someone, and "something" let loose. The immediate symptom sounded like a "pfffffssffssft" that stopped after a second, kinda' like an air line blowing. The net symptoms are:

• A "pfft" sound pulsing in synch with the engine running, sounds like an exhaust leak. (it's not)
• A reoccurring CEL stating a misfire on cylinder 2
• The slightest load will cause a "much larger than normal" increase in exhaust temp. e.g., "glide" off of a stoplight and watch the EGT run from 600->1000*. 7% grade at 30mph puts me at 1250*. As a coincidence, my EGT sensor is on cylinder 2
• Holding 40mph on a flat road sets me at about 1000*, and the engine will bog after 1-2 miles. Backing off the gas (or applying more) will push through and clear the bogging.
• Idle is "fairly smooth" in neutral, but worse in gear with the brake on (so, under load).

It's not catastrophic (yet?) in that I can't see the engine running as well as it is if this was a valve, cam, piston, cracked block etc.

Things I've done/noticed:

• Pulled the plugs - #2 is wet with fuel. Everything else is fine, all gaps are .040", no cracks in the housings
• No major exhaust leaks (I always have _small_ ones)
• The WOT performance is very good. The overall performance is very good
• Vacuum/Boost are "fine" according to my gauge (-22 -> 8psi)
• A/FR is good across the power band
• No sign of oil (or any fluid) leaking
• Vacuum lines are on and correctly placed
• Plug wires are good
• The "pfft" sound is clearly coming from the driver's side, but seems more towards the rear of the engine (#6) than the front (#2). I can't feel any jet of air that would account for what I'm hearing.

I'm heading out to buy a compression gauge now...

Any ideas? I'd like to think it's a vacuum thing, but dern if I can find a line that's popped off, and that wouldn't really create the "pfft" sound. The wet plug is interesting... The FSM basically says a P0302 (misfire on #2) could be anything "fuel, injector, vacuum, valves, timing...".

dz

partially clogged/grenaded injector (not atomizing fuel properly) comes to mind, would probably result in an excessively lean mixture driving EGT up, although I will admit I'm a bit better used to diagnosing misfires on diesel engines

midiwall

Thanks DZ, I gave that theory a shot and I have more info...

I rotated the injectors on that side of the engine, so 2->6, 6->4, 4->2 and I'm still throwing P0302's (misfire on #2). I think that rules out an injector issue. dunno for sure.


I created a fuel leak though (the fit into the fuel rail on these 370s is such that they eat O-rings) so off comes the S/C and friends again to replace those.

argh

midiwall

update-update...

Fuel leak fixed... pfft'ing still there, but now I'm questioning if the quick run-up in temp is so abnormal for me. I'm pretty sure it is though - I think I'm just setting myself up for psych games to ignore everything and just drive it with a mysterious "pfft" until a rod comes through the side of the block - or somesuch.

sigh.

midiwall

more info...

Fuel leak is back, different injector this time - that's unrealated, but this is my thread and I feel like using it to complain.


Relevant info: I drove the truck to work this morning, and have now found a nasty shudder at 1500rpm when under load. I figure this is from the misfire. It's dead smooth at idle.

I picked up some injectors I had cleaned this morning, so I spent some time chatting up My Injector Guy. He's stumped... He listened to it run for a while, thinks it's an exhaust leak, but that doesn't explain the constant misfire.

I ended up not getting a compression gauge, but I'll be buying a borescope tonight. I think that'll tell me more.


ideas.. I need ideas... I have a big run this weekend that I don't want to miss.

hopper

Ay new news? I have the same proble but on cyl #3

midiwall

Nope... I've been ignoring it and just dealing with the side effects. (yeah, I know that's not good).

My headspace has shifted all over the map, head gasket, cracked cylinder, burned piston, bent valve... all sorts of things. My local guru has been pretty tied up but eventually we'll get our schedules in sync and I'll get a better idea of what's going on.

midiwall

Update...

I got in sync with my local guru last night. The short form is that I burned a valve in #2. The truck will go under the knife for a valve job probably next weekend. The fun part is that we won't know if I also torched a piston or snapped a ring until we get the heads off. if I did, then we're looking at a full rebuild.

The money side of this says that I have too much into the truck to NOT do the work, and I can't get the money I have in it out of it by selling given it's current state. So, I have to do the work.

The upside is that doing it outside of a dealership will save me a TON of cash.

04 Rocko Taco

Well, at least now we know...it was a valve after all...Let us know how the work goes, and if its just valves, or a rebuild. Good Luck Mark!

midiwall

REEEEEEEEEEEEEEEBUILD!

https://www.yotatech.com/forums/f123/3-4-rebuild-100924/