89mustangfive0

i took the stang out for a drive and reallly opend it up in 4th gear i hit like around 5000 rpms i noticed it kind broke up ( almost like a rev limiter) but when i switched into 5th gear it stoped

67mustang302

Is it in 4th only at 5,000rpm or any gear at 5,000rpm?

89mustangfive0

well i noticed it in 4th i never really bring the car up past 3500 rpms...i noticed i have to bump my fuel pressure up ( it was at wide open throttle) and my dad mentioned the breaking up could be from the car having too much timing

mjr46

could be timing.. I had a issue with my 92 recently and thought it was timing but ruled out plug wires cause they were realatively new in terms of miles = 6000 miles use in 5 years but turned out the accel wires were bad..swapped for a set of ford racing ones and fixed the break up prob in higher rpm's

89mustangfive0

yea i just thru on new ford racing wires..i had my scorpions rockers put on today and i actually took the car wide open throttle and my dad said were gonna mess with the timing..i have one of those stupid suechips chips on my ecu and were gonna rip it out and re-time the car

smythge

Could be your valves floating at 5200 RPM, what springs are you running?

mjr46

butnow this is a stretch Isn't there a fuel cut off on the factory ecu of 6250??? if tac is off maybe it's cutting fuel??? but I doubt it...fuel quality is an issue nowadays with all the methanol/ethonal added..suppose to be a max of 10 to 15 percent but some places have it diluted more[&:]

PJC Racing

My vote is for valve float.

89mustangfive0

well i noticed my number 1 spark plug was very lean, so im going to bump up fuel pressure...and im going to mess with the timing also...my damn balancer rusted up so i gotta clean it off and re-time the car..i did a bunch of work to it since last timing it.

mjr46

as long as he used the reccommended springs for cam and are set up correctly.. you'd think that may not be the prob...but anything is possible if coil bind occured and broke a spring