Surging prob.

[conan]

Sorry in advance if this is an obvious one, but I don't have time to do a search. I have a 92 7.3 IDI. The problem is, it surges any time I maintain a constant speed. It is very smooth on accel. and decel., but as soon as the speed/rpm level out, it starts to surge steadily. Not sur where to start.
I appreciate any advise.

Thanks,
Conan

 

[GenLightening]

Need more info. How old is the fuel filter? Next I'd look at the fuel pump, then the IP/injectors. Or, it could be tranny related, maybe the torque converter locking and unlocking or just slipping?

 

[conan]

Sorry, manual tranny so shouldn't be related. Fuel filter replaced about 6000 k ago. Aux. pump recently repaced. Haven't done the injector pump or return line kit. Has about 350,000 km on it, but like I said, runs smooth and pulls good, so I think it's getting enough fuel.

 

[dakotajeep]

What is the RPM shift like? +/- 50rpm +/- 300rpm?

 

[Andylad13]

What is the RPM shift like? +/- 50rpm +/- 300rpm?

in addition to this, how many rpm's does it drop when she starts to surge?

 

[dakotajeep]

in addition to this, how many rpm's does it drop when she starts to surge?

Thats what I meant but failed to get the thought across properly....thanks!

 

[deadeyeb]

Is the truck smoking when it is surging ,sounds close to the problem I'm having. I have a automatic though. when the rpm's level out my truck stutters and will smoke , but hit the gas and clears right up. when you find a solution I would be very interested on what it took to fix it. thanks for your time.

 

[conan]

It doesn't smoke at all. I would say it surges about 75-100rpm on average.

 

[69dieselfreak]

mine sureges at about 65-80 2500-3000 acts like nitrous

 

[typ4]

I would check for a suction leak, sounds like air is getting in the pump, take my word on this one, I have diesel flavored pits to prove it. Bad prefilter, had a pinhole.

 

[Papabear]

is it turboed? if so i would check the vacuum actuator on the wastegate and/or vac pump. the wastegate could be opening prematurely/intermittantly therefore dumping the boost. Or you may have a fuel system leak that is leaking at that weird point where it is letting air in but no fuel out (as weird as it sounds) i have heard of the tire valve like bleeder getting sucked in because the low pressure pump is not keeping up and the high pressure pump is cavitating the system creating vacuum at the valve therefore sucking the valve pin in. Or the pickup screen in your tank may be plugged causing the same issue. Just a few thoughts from thinking outside the box.

 

[conan]

It doesn't have a turbo. I will check for an air leak on the suction. Would excessive slop in the timing chain cause it? Maybe when the rpm's settle out the fuel pump is inconsistent? Just a thought...

 

[GenLightening]

It doesn't have a turbo. I will check for an air leak on the suction. Would excessive slop in the timing chain cause it? Maybe when the rpm's settle out the fuel pump is inconsistent? Just a thought...

We have a timing chain? Maybe check the fuel lines from the pump back to the tank for possible air leak. And it may not leak fuel, but allow air in when the pump is working.

 

[Fozz]

I have a light surging at speed too. Mine is most pronounced with the cruise on, and engine turning 15-1600 rpm. I just found out my injectors are popping too early and puddling, so I'm hoping new injectors will cure it. I won't get around to replacing for a few weeks yet, but I'll post results if it fixes it.

 

[Agnem]

There is no timing chain in these engines. Your surging is a timing variance caused by one of these possible things...

1) - Bad I.P. (advance piston/bore worn)
2) - Air in fuel
3) - Problem with fuel presure fluctuating.

You don't see the problem on acceleration because your supplying more fuel than the engine can burn, but it is doing it then as well. You just don't feel it.