Engine Skip

[TAZZ9963]

Well I got my fouled injectors fixed, as per a previous thread, but the engine still has a miss and it sounds like a knock that shouldn't be there. Now there is also a intermittent pop, pop sound from the intake and from the exhaust. These sounds usually happen when I first start the truck mainly throught the intake, but when I shut the truck off I hear it through the exhaust. The miss is more pronounced after the truck is at operating temp. But tke truck still runs well on the highway. I just installed the exhaust and intake a couple of weeks ago along withe the pmd and #9 resistor. The truck was running well before I swapped injectors, no miss, knock or popping. Now I have this problem, I removed the marine injectors for now and have a set of stock ones installed so I don't think it's an injector problem.

Does anybody have any ideas? I think it could be a broken valve spring or maybe a worn rocker shaft but I'm not real famillar with 6.5's.

I just recently purchased the truck so I don't know it's history. The current milleage is 165,000.

[TedReminder]

I have had broken valve springs. Intake will make a huffing noise back through the intake manifold when the cylinder loses fire. Exhaust will produce a pretty good cloud of smoke. Both will really shake the engine with the missing. With my intake spring, the lost fire in the cylinder would come and go. Most of the time it ran ok. Exhaust just happened one day and kept missing. Both were pretty easy to fix without removing the heads. :D
When the exhaust spring broke, I pulled the upper intake and ran the engine. With a small hose in my ear, I heard a pretty good racket from the cylinder with the broke spring. Must have had some extra lash clearance.:eek:
Ted

[Bennie]

did you check the harmonic balancer. it can make a knocking sound if its going out and also you could break a crankshaft if run long enough!

[TAZZ9963]

Well a month or so later I finally got a chance to do some work on the truck, as usual in my driveway on a very cold day. I had a friend put it on a Tech II and found that the #7 cylinder has the miss. I pulled the injector and brought it to my local diesel shop and had them test the injector and it tested fine, not good for me. I then decided to replace both valve springs and found that they were both good, even worse for me. Both valves moved freely in the head so I don't think it's that. My next step I think is to pull the head and most likley the piston well at least the head and see what's going on in there. I have a funny feeling that I have a bad set of rings in that cylinder.

I should most likley do a compression check but I think I know what I'll find, either way I have to pull the head to fix it. I might even try to run some engine flush through it to see if it's just a stuck ring.

I made a air fitting tool to keep the valves up when I did the valve springs. I used an old glow plug. I drilled out the center and welded a air fitting to it, worked great, just thought I would let you guys know and not that hard to make.

Dan

[sixnickel]

Dan, if your losing compression through the piston, or the rings, you will DEFINATELY know it. When I listened to your truck a couple weeks ago, that is not the problem. A few years back, my eldest son's 6.2 burnt a hole in a piston, it still ran pretty good but the blowby was unbelievable. It tried to blow the oil fill cap off, it bent the ears on it. I don't know how common it is to have a pump cause a skip, but I would look into that before yanking the head. Walt might have an idea on that. Good Luck.

Doug

[sixnickel]

Dan, I was thinking some more (thats dangerous) If you pressurised the cyl. to change the springs you would have heard the compression leak. I am assuming you did not fear a leak. Like a cyl. leak test on a P&W R985! Just a thought. Doug

[Chevylover]

Dan, what about a piston slap ?

Cu,
Sven

[TAZZ9963]

when I did the springs I didn't really listen for where the air was going, I was in a rush as I was watching both kids that day. I did notice that I am getting some good flow out of my breather that goes into the air cleaner and the turbo is wet with oil so !!!!!!

[TAZZ9963]

Would an injection pump do that for just one cylinder?

[TAZZ9963]

Well I decided to buy a compression tester before I do any more work to the engine, that should tell me where to look now as I have already eliminated a few of the easy things. I'll let you guys know what I come up with.

[TAZZ9963]

Ok the results are in. I got a new-used compression tester and checked driver side compressions.
1) 225-275-350-400-410
3) 200-300-350-400-410
5) 200-300-350-400-410
7) 50-200-300-400-405

All these readings were done through five revolutions and all readings are in psi. I'm confused about these readings and I think the #7 cyl. might need a set of rings. I hope I'm wrong.

Dan

[Chevylover]

Could be possible with the #7 cylinder rings.

The 6.5l TD should have between 380 - 400 PSI (warmed up).

Cu,
Sven

[jgorden]

i had this problem in a pickup that i woorked on about 6 mounths ago check the rocker arms and make sure that they are not worn the truck that i worked on had wore throughthe rocker armand stuck the push rod througth it when it did this it blew the head gasket between two cylinders. What you are decribing may have been the first sign something wrong but this person didnt think anything of it. I had heard the truck running and a gas station several weeks beforew he brought it to me and didnt think it was right but owner wasn't worried about it. Look at rocker arms real close

[sixnickel]

Dan , If you pull the v/cover off again check for lift flat cam lobe?

[brokenparts1]

Hey TedReminder,
My truck huffs like you mention but only right after I start it when its really cold, like in the single digets or colder, once it runs for a minute its good, any thaughts? thanks ryan

[TAZZ9963]

Well I did a leakdown test and found that there is blow-by at the rings. Here's the question: peace-meal it and just do what needs to be done or spring for a long block?

[THE SUPERTECH]

Identify which cylinder it is then check the movement of the rocker arms. If the rockers move full travel like the rest I suspect something has gone down the intake or in through an injector hole in the past and bent a valve. The slight bend will cause a rough idle but may not be noticeable on the highway and your fuel mileage would drop. This would also cause a pop in the intake.

[TAZZ9963]

Just an update, haven't work on the truck because it's been too f-ing cold out but it looks like the weather might break this week where I'm at. So I might get a chance to rip the heads off this thing and get to the bottom of this problem. HaHa the bottom is right!!!!!! right to the oil pan and pull that #7 piston. At least I'll be able to feel my fingers as it looks like we might hit some 60 degree days.

[TAZZ9963]

Ok so it's mid May and the truck has been back up for about a month now and runs great. So let me tell you what I ended up doing. First thing I did was replace th IP with brand new, a friend of mine owed me a favor and sent me a new pump, that didn't fix the problem. Next I pulled both heads and the #7 piston. I honed the cyl. and installed new rings and yes everything measured up ok. There was some scoring in the cyl. Next I brought the heads to my local shop, they magnafluxed them and found that they both had cracks in the usual places so I sprung for a new set. Put it all back together in a few late nights and all is well. Oh yea, while I had the engine jacked and the heads off I relaced the oil cooler lines and fitttings as they were leaking. Now I'm thinking of my next job and that's going to be a new post, clutch and flywheel.