Engine miss (injector?)1995 Chev 4X4 1500 Suburban 6.5 TD

[N9Phil]

Last Friday as I came up to a light I punched the pedal in order to make the light. It was for a few seconds and the tach never got past 3k. As I got thru the intersection I gave it some more fuel and I had a miss like a bad plug in a gas engine. I pulled into a parking spot and let it idle for a few seconds and it stopped missing. After leaving I drove easy for about 5 or 6 miles to my next stop with no problem until I got about a block away. At that point it started the miss again. When I started the engine after the stop it continued to miss. I managed to limp home (about 7 miles) going about 30 mph. The truck would vibrate at start up and would settle down (still missing) at around 30 mph. I wasn't smelling fuel or having any loud knocking so I felt safe limping home.

After getting home I put the Tech 1A on and determined that it was # 7 that wasn't firing. Codes 91, 92, 93 came up (cylinder unbalance)
Therefore I figured that the # 7 Injector was causing the problem. I had just replaced the injectors within the last 6 months so I thought I might have gotten a bad one.

After replacing the #7 Injector the truck started up and still missed for a while until all of the air got out of the line. After running the engine for about 5 minutes it started to knock. There was a loud clanging knock that appeared to come from the left rear of the engine. I shut everything down for a while to think about the situation. I then started the engine again and the miss seemed to be started again and there was still the knock. I then pulled it into the garage and shut it down.

I went into the house and called a mechanic friend to talk it over with him. Having not coming to any conclusion and being that this was my last running vehicle, I needed to do something soon. I got on the internet and started to look for another Diesel Suburban but was UN successful. I did however find a 1999 4X4 Suburban Gas 7.4 that I purchased.

Now on Sunday when I backed the 6.5 out of the garage to make room for the 7.4 the miss was still there but I didn't listen for the knock. On Monday morning I went to move my tools and things from the 6.5 to the 7.4 so I decided to start the 6.5 back up. The miss was gone and so was the knock. I let it warm up and I drove it around the block and it ran fine.

Now for my questions, does anyone have any idea why I had the knock? Did a hydraulic lifter collapse? I am hesitant to start using the 6.5 for fear of breaking down again especially in this cold weather.

I believe that the original problem was the injector however it is the knock that has me concerned.

Any info or suggestions will be appreciated

Phil

[Robyn]

A lifter that has colapsed will make a noise just like a gasser and not a loud clang.

What was the source of the injector you used to replace the #7 unit?

Mechanical things generallly dont heal up. When I was reading your post for the first time I was suspect of a broken rocker guide button. This will allow the rocker to fall off the valve and can result in a dropped valve and or a bent pushrod if allowed to run long.

Now if the engine is a high miler and also a 1500 series truck with EGR there exists the possibility that your "Hard romp" dislodged a chunk of carbon that forms in the intake passages from all the crap that gets dumped in during egr cycles.

There is almost no room in the cylinder when the piston is at TDC and any carbon will get smacked into the head and make one HELLUVA noise.
It can also cause a valve to get stuck partially open and this would explain the miss.

I would do this.
Remove the intake manifold and have a look see at what sort of crap has built up in the passages and clean it all very well. A shop vac can help to suck out any loose junk.

Carefully clean out the intake ports of any and all crap. **Now to avoid more junk falling into the engine do this*** Roll the engine by hand and make sure the intake valve you are going to clean around is CLOSED, then clean things and suck out the port. Do all the valves this way. If you do not, you can drop more junk into other cylinders.

Now I would suggest removing the # 7 injector or glow plug and pouring in a defouling solution such as carb out or even some tranny fluid with a bit of diesel oil to soften any carbon in the cylinder that fell in.

Make sure the cylinder is close to TDC, pour the skunk piss in the injector hole and let it sit for a day or so.

Roll the engine over with the INJECTOR out before you do a restart to blow out any mix left over to prevent hydro lock. **Important**

Clean your intake real good and replace.

I think this is a minor issue if handled right and most likely is not serious.

I had a 454 that would do this after it sat for a week or two during major temp changes.

Another thing you can do once the engine is back running is to use a little mist type spray bottle and have a helper run the engine at about 12-1500 RPM and then mist in WATER through the turbo inlet (keep fingers, shop rags and other loose stuff away)

You can spray a fair amount but dont overdo it. This will "steam Clean" the cobustion chambers and get rid of some of the crap.

I have seen this scenario on a couple other 6.5's with EGR.
Usually its a high mile thing. Time just allows tons of soot and junk to form in the intake.

I really think your little creature can be "healed" easily and run fine again for you.

Give it a go and let us know how it comes out

Best

Robyn

[JohnC]

...determined that it was # 7 that wasn't firing. Codes 91, 92, 93 came up (cylinder unbalance)
Therefore I figured that the # 7 Injector was causing the problem.

I don't follow your logic. (91, 92 and 93 refer to cylinders 1, 2 and 3 respectively, IIRC...

Use the scanner to shut each injector down. The ones that are missing will cause less drop than the good ones.

[N9Phil]

Robyn, Thanks for the ideas. I replaced #7 with a new Bosch injector.
The engine has around 140K miles on it and it does have the emission junk. Since I don't have emission checks on this age of a diesel, I have thought about disconnecting it. I will pull the intake and clean the carbon as you suggest when it gets a little warmer out. I can use the gasser for my service vehicle until then. In the past I have used trans fluid thru the carb on gas vehicles. That would really send out some smoke into the neighborhood.

John C, after limping home last Friday, I shut off the engine and hooked up the Tech 1A and those are the codes I received. Acording to the manual,I should have reset them before checking them but that thought never crossed my mind. I did shut off each cylinder one at a time and listened for a change. When I got to #7 there was no change in the missing, all other cylinders caused the engine to miss more when they were shut off. I never did check for balance between each one. At that point in time I was so happy that it wasn't # 6 or 8 that I ended my testing.

Phil