Lope from idle to about 1300rpm

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w250_93

FNG
Joined
Jul 7, 2010
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21
What would make the motor smooth out when you crack the injector line? Air? Bad injection pump?
 
I've had 2 different pumps on the truck it still does it. I've tried different gov springs an delivery valves too, I've done compression test an leak down test an I can't figure this thing out. The only thing I haven't changed it the air dog but I have replaced the fuel line on the suction side, it made no difference.
 
w250_93 said:
I've had 2 different pumps on the truck it still does it. I've tried different gov springs an delivery valves too, I've done compression test an leak down test an I can't figure this thing out. The only thing I haven't changed it the air dog but I have replaced the fuel line on the suction side, it made no difference.
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I don't think the air dog would could cause it because its only on the 1 cylinder. If u wanna try my rear set of lines or somethin off my truck, let me know n ill bring it over when I get it back
 
im sure you checked is the valve train operateing properly on that cylinder?
 
Run a compression check on that cylinder. It could be down on compression in that cylinder
 
^this! Check the valves first in any type of misfire situation. If you've run dirty oil, high rpm's, or any high mileage situation the cams sometimes deteriorate and cause a misfire. They make a thumping sound out of the intake when it happens too.
 
my truck had a lope only when the idle was set to around 550. my truck has a studder up till 1000 rpm. new mech lift pump, new sticks, new hg, checked all valves when the head was off, all is good. prolly the inj pump since thats the only thing i havnt had gone over. so id guess the same for ur truck.
 
Do you have the injection lines on it right? Dont have 2 switched on the pump?
 
I just finished a new cam install (188-208) I bought new 24v tappets an new push rods. I noticed the intake push rod on #2 wasn't spinning so I started taking it apart to pull the cam an found that the gear had came off the cam about half an inch but after I put it everything back together it still has the lope. Before I did the cam it was cyl#2 that you could Crack an it would smooth out but now its on #4. I've been chasing this lope for over a year now, I did a compression test an every cylinder was 370psi +- 10psi, I had just installed a new head gasket an studs about a month before the lope started. I can hear a hiss when I shut it down so it could be a compression issue but you would think it would've showed up on the compression test. Ive had 2 different injection pumps on it with the same issue so I'm pretty sure it's not the pump. I guess I could go back through the valve lash again an make sure I didn't miss something.

Yeah justin we can try your lines but we tried the lines when it was on #2 an it didn't fix it.
 
I guess I have the injector lines on right, i didnt know you could switch them around but I'll check an make sure there right.
 
w250_93 said:
I just finished a new cam install (188-208) I bought new 24v tappets an new push rods. I noticed the intake push rod on #2 wasn't spinning so I started taking it apart to pull the cam an found that the gear had came off the cam about half an inch but after I put it everything back together it still has the lope. Before I did the cam it was cyl#2 that you could Crack an it would smooth out but now its on #4. I've been chasing this lope for over a year now, I did a compression test an every cylinder was 370psi +- 10psi, I had just installed a new head gasket an studs about a month before the lope started. I can hear a hiss when I shut it down so it could be a compression issue but you would think it would've showed up on the compression test. Ive had 2 different injection pumps on it with the same issue so I'm pretty sure it's not the pump. I guess I could go back through the valve lash again an make sure I didn't miss something.

Yeah justin we can try your lines but we tried the lines when it was on #2 an it didn't fix it.
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I had a cam retainer bolt that holds the gear on the cam in my pull er break and it let the cam walk. When it did that it let the fuel pump lobe hit the lifter for the number 5 cylinder. its possible that the cam moving that much forward and backwards could be hitting other things in there especially with the wider tappet
 
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No everything was stock when the gear came off, that why I put a new cam an everything in it lol.

I didn't know 370 was low, What's it supposed to be?
 
Most of the ones i have checked have been in the mid 400's
 
Did you have all the injectors out when checked the compression on those other motor or did you just pull one at a time an check it cause that would've raise the rpm the starter turn the motor over since it wasn't fighting the compression an would've given you a higher reading than me cause I pulled one at a time
 
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