Engine Surging, any ideas?

[Extreme1]

Check my signature for the mechanical details.



Lately when I start the truck cold and take off, for the first couple miles the engine will surge under light acceleration. I notice it most in the 1200-1600 RPM range. It is about a 5 second cycle.



The RPMs don't vary much but you can feel it. The boost will cycle up and down 1/2-2 psi when this is happening whick leads me to believe it is fule related. Nothing has changed on the truck since before it started. I did replace the fuel filter but it made no difference.



Once it's warmed up a bit it stops. Any ideas?

 

[TKemper]

Extreme1, the next time you do this watch your voltmeter. If it drops the same time you feel the power loss its your grid heater coming on. The excess draw on the alternator causes the engine to labor slightly. The only reason I say this is because you said it's about a five second cycle. Let me know what you notice. Todd

 

[BCFAST]

Sounds like it's almost GSK time!!! My guess is your governer is acting up... I am hunting a similar problem.

 

[Extreme1]

I'm sure it's not the grid heaters, they turn off at 18 mph and I usually let the truck warm up a for a minute or two before I head out. I usually don't notice it until it is in second or D.



I was wondering about the govorner, and yes, a spring kit is on the list. I'm waiting for Piers to put them on sale!



Any other ideas?

 

[Fireman Dave]

Eric,



Could it be the TPS?



Dave

 

[Cooker]

I'm waiting for the GSK to go on sale too. Even though I don't have any money, I'm sure I can convince myself that I need one sooner than later.



I'd try to eliminate the possibility of a transmission issue first.



JMHO

 

[Extreme1]

No, not the TPS. On our classic machanical engines the TPS is used to control shifting into OD and TC lockup.



Any other thoughts or ideas?



The governor springs seem most likely at this point. Is this something that needs to be adjusted on "high milage" engines? It only does it when cold.

 

[illflem]

Don't count the TPS quite so fast. When mine needed cleaning before I got onto a regular cleaning schedule it would surge as you describe. The cycles of surging where so rapid that you couldn't feel the TC kick out but the rpm varied for just a fraction of a second. Give cleaning the TPS with electronic cleaner a try at least.

 

[Extreme1]

It does it before the TC locks. Engine cold, air cold, low speed (2nd or D), light throttle. Tach barely moves but the boost gauge does move (lower, slows down) with the surge.

 

[Extreme1]

TTT!

 

[Extreme1]

ONE

MORE

TIME!

 

[jmtandem]

surging when cold

Extreme1,



I had a similar problem and it was fuel related. With 200,000+ miles you might look into the fuel pump or the fuel injection pump if you have not replaced them. In my case it was both that were weak and caused a mild surging.



Good luck!