Surging

[smoking89IDI]

K for those of you that may know my previous threads I have a rusty '89 SCab with the zf-5speed that chirps going down the road, well I have an old problem that is slowly getting worse, when I downshift to slow down like at 45 mph in OD shifting to 3rd which brings the RPM's to around 2900-3000 it surges and bucks about 3-6 times with NO throttle applied, it feels like it is getting MORE fuel when it bucks because it slows down less and the engine sounds different when it happens, it will only do it when the RPM's are above 2800ish. When it bucks it is enough to shake things in the truck a bit. BTW what is the governed speed on these engines, this thing revs to about 3500 before the limiter kicks in but I think the gauge/sender may be going out because it does not work very well cold and when cold when you turn the headlights on the gauge drops to 0 until you rev it.

1989 7.3L F250 SCab
ZF 5-Speed
ATS Non-Wastegated Turbo
217,800 on as far as I know all original parts, IP is the same exact color as block and has a Ford part number tag that starts with E8somthingsomething

 

[FordGuy100]

Man that is weird. My truck is governed to 3500 in neutral and 3300 when driving around.

 

[82F100SWB]

Sounds like your pump may be starting to die, mine does it now, but, I know for sure the advance is sticking in mine, it bucks very badly if you come out of the throttle to slow down, then re-apply just enough to maintain a lower speed.
As for RPM, not sure what mine does under no load, but under load it's 3750(91 7.3 pump)

 

[smoking89IDI]

Is there any sort of test for the IP? The injectors are already on my to replace list but not the IP yet.

 

[dwaymar]

sounds like ya'll need a good cleaning this happened to mine after a bad case of not cleaning my oil good enough [wvo] and after a good cleaning and running a good add every tank full it stopped i use howes meaner power or diesel kleen double the dose for a tank or so see if it helps

 

[Agnem]

Sounds like your metering valve may be sticking, or something in the govenor is loosing tension. Dose it up as mentioned, and start saving for another pump.

 

[smoking89IDI]

Ok I put some Power Service in and will see what happens, how long should this take to work? BTW I also added some Auto RX to clean things up before I tear into it if I have to.