Rough/Shake at Idle

[ngagnej]

I can't seem to solve this problem.

My 7.3 has a very poor idle problem. This came about after some revving trying to get out of the snow when I was stuck. I'm not seeing any coolant/oil mix or white smoke and it runs like a sewing machine when I step on the throttle, it just shakes alot at idle and I hear a knocking type noise on the left side that is only present at idle. I put new return line on, new fuel filter, and checked for leaks with a clear hose. Starts up just fine. I'm stumped at this point, just want to see if anyone has any ideas. I haven't got any compression numbers yet, don't have a tester.

Thanks, Nick.

 

[DeepRoots]

try cracking an injector line to isolate the noise.

I've had injectors commit suicide for no apparent reason, and yeah, alot of times it'll run fine and idle like crap.

 

[ngagnej]

When I did that they all change the idle. I pulled the injectors the other day and my #8 was loose and had carbon build up on it. That is probably where I'll start.

I thre in a bottle of power service injector cleaner..maybe that'll help for now.

 

[icanfixall]

That injector that was loose and the bore filled with carbon was loose in the cylinder head... No other way for carbon to get past the injector. Did you change the copper gaskets on the ends of the injectors... This does sound like a bad injector to me. When the engine is running and warmed yp feel all 8 injector lines... See if any are hot near the injectors... That tells you an injector is blowing combustion back thru the supposedly closed injector.... Not a good thing....

 

[towcat]

+3
bad injector. believe it or not easy & cheap fix compared to a injection pump.

 

[RLDSL]

If not an injector, the next thing that comes to mind, what transmission do you have, is it a zf5? if so does it still have a dual mass flywheel? Or is it an automatic?
In either case, i notice you said you were revving trying to get unstuck from the snow and didn't see any smoke, which makes me think not injector, but wasted dual mass flywheel or cracked auto trans flexplate. You can put a heck of a shock load on those things when trying to rock out of a snowbank and it's real easy to trash them.

 

[ngagnej]

If not an injector, the next thing that comes to mind, what transmission do you have, is it a zf5? if so does it still have a dual mass flywheel? Or is it an automatic?

I added a signature. It's the ZF-5 with the dual mass flywheel. I don't think that would be the case because it shifts/drives fine.

+3
bad injector. believe it or not easy & cheap fix compared to a injection pump.

Injectors have maybe 30k on them. I've had the injector pump in/out of this thing too many times. I pulled it out this past time because I took the plate off and all the mounting bolts came off so I wanted to make sure it didn't jump a tooth on the timing and realigned everything with a mirror.

That injector that was loose and the bore filled with carbon was loose in the cylinder head... No other way for carbon to get past the injector. Did you change the copper gaskets on the ends of the injectors... This does sound like a bad injector to me. When the engine is running and warmed yp feel all 8 injector lines... See if any are hot near the injectors... That tells you an injector is blowing combustion back thru the supposedly closed injector.... Not a good thing....

The injector was loose for I don't know how long, found it when I went to bleed air out of the system and the whole injector turned when I turned the injector line nut. I pulled it and replaced the washer on it, then just pulled the the ones and cleaned the bores and put new washers on them.

I did take the truck for a drive and felt the lines on the left side, the one that was coated with carbon (#8) was hot all on the injector cap and the line seemed a little warm compared to the others.

I'm I'm thinking I should order a new matched set of BB injectors from typefour and swap them all out along with a performance I/P I have laying around rather than have one new one and 8 old ones. Is this a good idea or a waste of money? Does anyone actually notice a difference between the "E" injectors and the "BB" injectors?

I appreciate the help!

 

[pybyr]

For what it's worth, my engine always had a lopey idle-- then in early December I had a sudden instance of fuel gelling, and to deal with that, put about 5 gallons of kerosene in the tank, along with a bottle of Diesel-911. The idle has been much smoother ever since. Could be pure coincidence, but it sure coincided.

 

[ngagnej]

Try this for manuals:
http://search.ebscohost.com/

ID: Bedford
Pass: library

Click on the link that says Auto Repair Reference center.
You'll have more info than you ever cared to know.
-Nick

 

[whenry912]

I wouldn't put one new injector in with 7 old ones, unless they were all pop tested and known to be close in pressure. My front #2 injector seems to run a bit hot, it is brand new, when I build my pop tester I am going to pull them all, test them, match them, and put in my new U-Haul IP

 

[icanfixall]

Any injector line thats hotter than the others is leaking combustion back thru the injector... This is a very bad thing. Replace all the injectors now before you ruin the pump. I also would install another pump if you have one... changing only one bad injector can cause an ignition imbalance. The injectors are timed by the pop pressure. So if the new injector pops at a higher pressure that cylinder will be retarded some. It can cause a ruff idle. If it pops at a lower pressure it can also cause a ruff idle because it pops open early or way advanced... So you see why its important to know what the injector pop pressure is for all the injectors. Where did you buy these 30,000 mile old injectors and are they new then or rebuilt....

 

[ngagnej]

I got them from a guy on eBay...I think reman. In about the unbalance I just swapped the one for now and it is alittle off but it'll be better than what it was until spring. I plan to get typefour injectors and out on my new pump along with some other stuff. too cold and nexpensive right now to tear everything apart.

Btw that was the problem. #8 injector seized up I had the shop pop test it.