Truck cranks and runs, When Idling, engine surges. Gets worse when you drive it down the road. Will surge & buck after 40mph. Replaced throttle position switch, coolant sensor, distributor, cap, rotor, plugs & wires. Removed upper intake, cleaned it out. New gaskets, cleaned throttle body including EGR ports, replaced MAP sensor, and replaced fuel filter. Seemed to help for about 15 minutes, then began surging & bucking again. Any suggestions as what to try next?
Have you checked for codes? Fuel pressure correct? Same colde as warmed?
January, 6, 2012 AT 8:50 PM
Fuel pressure was 49 psi. Only code that shows is MAP sensor, which I replaced, but code still comes up. & Yes, runs same cold or warm
January, 6, 2012 AT 9:04 PM
See diagram Dist look like it? If yes remove TFI have tested VERY prone to cause problems.
January, 6, 2012 AT 9:14 PM
What diagram? & What is a TFI?
January, 6, 2012 AT 9:17 PM
That fuel pressure is whyll the problem is happening?
January, 6, 2012 AT 9:22 PM
Fuel pressure good 45 psi
January, 6, 2012 AT 9:29 PM
As far as I can tell, fuel pressure to engine is ok, it seems to get plenty of fuel. Shows 39 PSI at the post on the fuel rail. (Miss typed the last one, not 49) As long as you give it gas, it runs great. Has a little miss, but once you let it idle or hold at a steady speed, it surges, & bucks like a mule.
January, 6, 2012 AT 9:30 PM
No TFI Module on this distributor
January, 6, 2012 AT 9:38 PM
Truck is late 94 so Dist has shutter vane and ICM see diagrams locate and have ICM tested
January, 14, 2012 AT 6:28 PM
Had Ignition module tested, passed ( cycled 25 times )
Would the IAC cause this problem? I know it might at idle, but would it cause the problem while driving as well?