Best way to troubleshoot a miss ??

[Diesel Max]

I have a slight miss in one of my cylinders.... It's not bad and maybe like a quarter cylinder miss but it bugs me because I know it's there. I have replaced all injectors (injectors from Russ), the complete return line kit and glow plugs within the last 7K. Truck gets a new fuel filter about every 10K and I always run Diesel Kleen in every tank of fuel. I cannot tell if the IP has ever been replaced. You can't really hear the miss until about 1,200 - 1,300 RPM. What we be the best way to diagonse and figure out which cylinder has the miss ??? Or diagnose if the IP is causing the problem ???


Thanks in advance

 

[OLDBULL8]

The way I'd do it would be to screw in the idle setting screw to get the 1200-1300 RPM, then crack each individual injector line at the injector, the one that don't make a difference (in sound or RPM) would be the one that is causing the miss. Gotta do that to my 92 today, got a knock in one cylinder, prolly a bad injector, got some smoke and knock at idle, but disappears at higher RPM.
If there is a better way to do it I'm open for suggestions also.

 

[Diesel Max]

The way I'd do it would be to screw in the idle setting screw to get the 1200-1300 RPM, then crack each individual injector line at the injector, the one that don't make a difference (in sound or RPM) would be the one that is causing the miss. Gotta do that to my 92 today, got a knock in one cylinder, prolly a bad injector, got some smoke and knock at idle, but disappears at higher RPM.
If there is a better way to do it I'm open for suggestions also.

Sounds logical, guess I'll try that............... Thanks.....


Any other members have a different way of troubleshooting a missfire that they have had success with ?????

 

[icanfixall]

I'm with the above statement. If that doesn't prove anything then a compression test is in order....

 

[93iditurbo]

also if u have a hand held temp gun, run the idle screw in until u get the miss, then check the temp of each port on the exhaust manifolds and see which one is the coldest.

 

[Diesel Max]

also if u have a hand held temp gun, run the idle screw in until u get the miss, then check the temp of each port on the exhaust manifolds and see which one is the coldest.

I'm guessing you would do this when the engine is at operating temp ???

 

[93iditurbo]

yea

 

[7.3n/anut]

Possibly pump timing. I had a miss above 1200 and a bunch of white smoke. Adjusted the pump and slick as a ribbon

 

[Diesel Max]

Well...... Checked it with the IR gun and cylinder 1 & 3 are about 3 to 5 degree's cooler then the rest although I'm not sure that is anything conclusive since the heater bypass hose runs into the block right between those two cylinders and that may be why they are a little lower in temp. I was hoping to gain something a little more substantial before I just start throwing parts at it.

 

[Diesel Max]

Possibly pump timing. I had a miss above 1200 and a bunch of white smoke. Adjusted the pump and slick as a ribbon

Truck doesn't smoke at all, unless I stand on it and then I get some black smoke. No smoke at idle or when I can feel the miss. Seems I can feel the miss most at about 1200 to 1300 RPM just idleing the truck with my foot on the go pedal holding steady at that RPM. Get a slight engine shake around that RPM as well.

 

[7.3n/anut]

3-5 degrees is negligable. Do you get any smoke at miss rpms?

 

[7.3n/anut]

Sorry a lil late there. No smoke and a shake. Consistant temps. I rekon you could test injector NOP. But a compression test is in order before that.

 

[Diesel Max]

3-5 degrees is negligable. Do you get any smoke at miss rpms?

See post above.................

 

[7.3n/anut]

Ok like the other guys said. Bring up to miss rpms. Crack lines at injectors one at a time. No results compression test. The injector NOP

 

[Diesel Max]

Sorry a lil late there. No smoke and a shake. Consistant temps. I rekon you could test injector NOP. But a compression test is in order before that.

I was hoping to narrow it down to a injector/cylinder to at least have a starting point but I don't feel I have enough good info to know which injector or cylinder to start with. For all I know it could be the IP acting up.