Low RPM jerking

[Justinkins]

Hey everybody, I recently purchased a 1990 Mustang 5.0 LX coupe. It has been Board over headers straight piped ex BBK 70 mm throttlebody Plenum spacer cobra intake . I have redone the vacuum lines. The car has been sitting for a while at wide open throttle. It seems to be OK but you can still feel like it’s holding back a tad. But higher gears trying to cruise jumps back-and-forth like it’s missing spark I got my timing set up about 14 cannot figure this out also has a E303 Cam someone please help!!!!

 

[FastDriver]

E303 bucks at 1,400 and below. This may be somewhat tuneable, as I've had it where I could lope along lower when I played around with things, but after more adjustments, it's bucking there and lower again. If you're at 1,500 RPM and above, then I'd say you're probably right about your concerns.

 

[keel]

Have you pulled codes?

 

[General karthief]

Also check the sweep on the TPS make sure it's smooth and does not jump around.
Do you know how to do that?
Yeah, the E cam is a pain in the driveline below 1500 rpms.

 

[Willybill32]

E303 bucks at 1,400 and below. This may be somewhat tuneable, as I've had it where I could lope along lower when I played around with things, but after more adjustments, it's bucking there and lower again. If you're at 1,500 RPM and above, then I'd say you're probably right about your concerns.

@FastDriver, thank you for this comment! My ‘86 has an E303 installed and has a tendency to buck at 1500 and below. My assumption has always been the cam causes this. Thanks for your confirmation.

Bill

 

[fasterthangas]

You mention cruising in higher gears results in jerking. Have you tried shifting down a gear? Also, is the engine tuned? What is the rear gear ratio? Tire size?
I have a much larger cam and my car never bucks, but it's properly tuned.