The truck randomly lopes about 50-100 rpms at idle. It's barely noticeable but the tach needle bouncing around is annoying me. I'm not getting any codes. I was thinking I may have a bad IAT sensor or CPS. The truck has been like this for about 20,000 miles. Am I in line tracking this down or is there something else I should look at.

Matt

 

Are you just going by what the tach says or can you hear the change in speed?

 

I don't know if what your truck is doing is the same as mine but mine has done that since it was new. If you watch the needle it is bumping a little. I think I have already seen a post on here about other people experiencing the same.

 

My 99 does it too. But with the scanner on the rpm is dead steady even though the dash tach is fluxuating a bit.

 

My tach has always moved around some at idel but I started getting a noticable lope at idel after I put in the 90hp sticks.I guess this is normal ?

 

Yep, it's normal. Mine sounds like a big block with a cam in it. I get some weird looks but I think they are just jealous.

 

be warned, i had the same thing start about 3 days before my injection pump threw a p-code. that was before i had a fuel pressure gauge. the lift pump was out. i ran the truck like that with check engine light on and lopeing engine (@under 1500rpm) for 4 weeks, till i replaced and upgraded. i had never heard of lopeing as a sign of failure, but it was in my case.

 

It's not just the tach, my engine is loping very lightly. I replaced the IP in January. The engine was loping long before the IP failed. The strange thing is sometimes it's fine, other times it lopes as soon as the throttle is released.

 

I have developed a lope myself at idle but only when in gear. I've gotta figure it out cause it's been worrying me to death. My vp was replaced at 87K with absolutely NO warning or codes. Just shut down running down the highway, No brakes, No steering and in traffic. Of course the 0216 and 1688 after getting it towed home. Only things I can think of is the valve on the vp for the return(fuel), Air in the fuel system, injector problem. My idle was way smoother after the sticks went in. I just gotta find the time to check everything out.

 

Mine lopes at idle too, but only after a cold start and once it warms up it is gone.

Doug

 

Mine does it too but I think it's the parts I had put in it.

 

Mine did the same.............. sometimes. But I started running fuel additives and the problem went away. Now I run YamaLube 2-stroke oil. Much cheaper since I buy it it bulk for the bikes and truck.