Hi All,
new post to fourms here....
I recently picked up a 2000 Excursion with the 5.4 V8. Engine has 150,000.
I got it cheap because it has a surging problem over 1500 RPM.
This problem is intermittent.
I have 1 DTC. P1000 which is OBDII checks not complete. I cannot clear this even using the factory procedures. FYI..I have a snap on solus scanner.
This problem is NOT a miss.... something isn't opening or shutting off above 1500 RPM.
This truck doesn't have an EGR system, it has the EVAP system. This may be the problem, thats why I'm here.
OK. heres a list of what I've replaced since I started working on it.
Engine oil and filter
air filter
fuel filter
8 COP's
8 plugs gapped properly
cam position sensor
IAC sensor
MASS sensor
Removed throttle body and cleaned.
Vacuum checks. 22" at purge valve,fuel dia, and vacuum canister
Checking with the scanner at 1500 RPM with problem
SFtrim1% bounces between5-15
SFtrim2% bounces between2-0
LFtrim1% bounces between11-13
LFtrim2% bounces between 5-6
O2S11(mv) bounces between 200-781
O2S21(mv) bounces between 200-800
system is in closed loop holding throttle at 1500 RPM... Note enging surges when at the RPM or above
Idle is fine
Problem is intermittent
also noticed that engine will only advance spark to 30 degrees @2000 RPM during this problem
I have seen it advance to 38-40 degrees when I do not have this problem, so I kind of understand the power loss,knock etc due to the timing, my question is whats causing it to do this?

EVAP question....
the purge valve should open according to PCM command a certain value, correct?
I can monitor the duty cycle % but cannot activate and check proper duty cycle through scanner . When I try to I get an error message of module error -unspecified.
Disconnected hoses at purge valve,Full manifold vacumn on one, nothing on other, no flow through purge valve, but scanner shows 30% duty cycle. I would think the should be a little flow at 30% Maybe my problem?
Troubleshoot procedure for the EVAP would help.

Thanks Jeff