View Full Version : Dies on a warm start and tries to die when coming to a quick stop

04-30-2009, 07:54 PM
Ok this issue is on my 2003 F-150. I know it's not a SC but I know there's a lot of smart ppl here. Engine 4.6. Mods, K&N intake and flowmaster catback. It's starting to do this more and more. If the engine is at temp and I turn it off... if I restart it within 10 minutes or so, it'll die. It'll start right up to about 1100rpm then come down to 500...400 stumble... dead. 2nd crank it won't start at all unless I hold the key down for a few moments, then it'll start but I have to assist it with the gas pedal by goosing it a little after it starts. It'll have trouble around 500rpm then it seems like the ECM says "hey I gotta problem here" then it revs it up on its own to 1000rpm then back to 700 which is correct.
I think my 2nd problem ties into my 1st. If I'm hard braking and getting close to stopping (15-20mph) the tach will dip down to 500 then it'll recover. One time while making a pretty hard stop, I threw the tranny into neutral to ease the the braking. The engine died the split second I threw it into N. What the hell??!?!
I took the filter off and sprayed throttle body cleaner in the engine while running. Didn't seem to help. When I cut the engine off with the filter off, I hear a exhaust sounding hiss come from the intake tube and it lasts a few seconds. The best I can describe the sound if if you know what the wastegate sounds like on an SC when you shut the engine off.
HELP!! The problem is progressing. THANKS!!