A few weeks ago, and after paying close to $3500, I had to get my injectors replaced (stock reman'd). While it's idling better than before, it's still missing, especially at idle.

The mechanic says that there is a possible electrical short that is causing one or more of the injectors not to dispense at in-consistent times. He was able to re-test all the injectors and all passed, with his computer hooked up.

I know the valve cover gasket (with the internal harness) was replaced with the injectors. He said the gasket was tested fine too.

I would think that if an injector was not getting enough amps, would it not throw a code? According to his computer, no codes are being seen.

I am at a complete loss and kinda out of money. The mechanic talked about getting two new plugs - but I didn't dig deeper to what he was talking about. Maybe the two harness plugs? Do those really go bad?

Also to note - the overhead computer is now completely out-of-whack. It's reporting 30+ MPG where before it was like 20-21. Relating to this??

Thoughts?

 

Also, I *think* I can hear "air" kinda hissing out at the times that I think it's missing ... but I can't confirm if that is a problem. I never really noticed it and it's very light sounding.

 

Try listening to it with a stethescope or with the handle end of a long screwdriver (or similar) on your ear. If you can isolate it to a given cylinder then go from there. Try switching injectors if the miss is in a single cylinder.

If the miss is not just one cylinder then it might be sucking air somehow.

You might try to unplug one injector at a time and see which has the least effect, again trying to isolate the problem to one cylinder.

Is the valve lash in spec?

If none of this helps then a compression check might reveal something.

Does anyone know if there is an electrical test to load test the power side of the injector driver circuit?

Just some more ideas.

 

Could be your fuel control actuator on the injection pump. Does it miss more when pushing down on the throttle and at idle?

 

I believe the mechanic did that type of test with his computer; he shut down each injector to see which one(s) were causing the problem and he wasn't able to determine really. The valve lash *should* within spec as he said that he adjusted them after he put the injectors back in.

 

The miss seems to be prevelant while it's idling. Shifting through the gears, it seems to smooth out at 1500RPM or move.

Heck, you won't notice a problem at all on the interstate but as soon as you came off the offramp and to the light, you'll notice the rough idle.

Thanks for the FCA tidbit - I'll do some more reading on that...

 

what was the problem?? my truck is acting like this

 

this sounds like what my truck was doing when the injectors were failing. I had them replaced under warranty. Any chance one of the new injectors is failing?

 

Same symptoms. I took it to my mechanic and told him I thought injectors were going. He swapped out the FCA for $200...saved me several grand! Might want to try swapping yours with same year...plug and play.

 

Gasser - did you ever get any solution to your rough idle problem?

 

Hi fellas ... sorry, I haven't replied.

Well, it turned out to be several items. I had to go get a second opinion, so I took it to the dealer.

First, two of the replacement injectors were bad ... so those got replaced again. Dealer spent several days (off and on) to narrow down that the items surrounding the fuel delivery wasn't all electrical.

(drum roll please) ... and the main cause of rough idle and between 1700 and 2100 RPM ... was the clutch! Apparently the inner disc failed and the springs inside the flywheel were all missing. I never figured the clutch, as I was able to shift through the gears just fine ...

So ... lots of money spent (I would very close to having the truck paid off if I haven't spent the money)... but the truck is purring and perfect again. I am now at about 125K miles and it's like day one again.

My take away ... I am glad I took it for a second opinion and to someone who was willing to look outside the box and not focus just on the engine.

 

Thanks.

I have some similar idle roughness. Injectors were replaced before I got it, but it was found to need flex plate (auto trans) and torque converter. The flex plate had loosened and was wobbling, and ovaled out the bolts on the torque converter. That improved the rough idle, but I think there is still too much roughness.

At 85k it is still on warranty for the engine, but I have yet to find a dependable dealer with a real diesel mechanic around Seattle. One might exist, but I haven't found it yet.

Maybe the direct route to cure is to go to Cummins NW.

Dave
07/5.9