Throttle Suring at times when rolling at 45 - 55 mph it seems like the transaction and the engine aren't on the same revolution, I was wondering what to check first. It is a 2000 LT Blazer 4wd, have changed all vac hoses and still might think it's related to my 4wd actuator solinoid. Have read multiple posts on here could be a lot of things just want some thoughts on the subject, and where to start first.

 

Does the truck surge in speed or surge in RPM with no increase in vehicle speed?

George

 

Yes it will surge while driving with out pushing the throttle any more, it seems like it does it when it needs to shift gears but it will shoot the rpms over 2000 then it goes in gear and runs fine till you down shirt again then it will do it again. Some days it won't do it at all I've tried to watch for signs like the 4wd light on , then when it's out the 4 wd light on the dash will be on saying server 4 wd. And it will be sometimes off. If that's any help

 

Does surge mean the speed increases or the rpm increases but the speed stays the same?

George

 

Yes the tach jumps but no speed increase, it's like all of sudden it decides to jump the rpms but it seems like the engine dosent react, could it be a bad tach gage or maybe throttle cable needs adjusting. There are a number of ways in could go.

 

"it seems like the engine dosent react".

So the tach dial shows a higher rpm but the vehicle speed does not increase AND the engine does not actually increase in rpm? This is a tach gauge or rpm sensor problem only, the engine rpm is not actually surging/"reacting"? I just want to make sure that I understand what is happening here before we try to solve your problem

George

 

No the engine dosent react ,the rpm gauge surges then drops back down to normal ,

 

So this is a gauge problem because the engine and vehicle speed are unaffected? If so then there are a number of possibilities:

1. The instrument cluster is defective
2. The power or ground to the IPC are corrupt
3. The VCM or its pwr/gnds is/are damaged
4. The Crank sensor or its power/gnd is damaged (not likely if the truck runs good)
5. There is a wiring fault from the crank sensor to the VCM or the VCM to the IPC

Getting to the bottom of this will likely not be easy. About the easiest trynostic move is swap IPC's to see if its the gauge even though I am not a fan of the parts cannon. I wouldnt swap the crank sensor since thats not likely it and then you will have to do a relearn. The next best move would be to check all the wiring, power and grounds (sensor, VCM, IPC). Then its monitor the tach input on the white A3 wire to the IPC to see if the tach signal goes up with the gauge but that would require a scope to do right. A digital meter on AC might be able to monitor that signal and show if the level moves with the gauge but we would have to do some experimenting.

Let me know what your up for and Ill help.

George