04 mach 1 problems

[v6mustang01]

here are some stats on the car

04 mach 5spd with kooks longtube headers and catted xpipe, jlt cold air intake, mach exhaust and 410 gears. Custom dyno tune from dave guy.
Car made 313hp and 332tq.

So heres my question, as i leave work yesterday in the middle of the heat.. over a 100 out..i drive about mile n a half down the road and as i go up thru the gears and get to go into 4th gear at about 3400rpms, the car completely shuts down. the instrument panel every light on it lights up and i coast to a stop along side the road. i turned the ignition off and restarted the car. suprisingly it fired right back up like nothing ever happened. NO codes no service engine light. nothing. so i pulled out easy and proceeded to head towards I-81. As i go to merge on 81 im in 3rd gear and need to speed up to merge...i hit right around the same rpms and the car dies again. Same symptoms and everything. so i pull over...shut off the ignition and restart the car. it starts fine and pulls out like nothing happened. I eased it down 81 all the way up thru the gears but never gettin above 3000rpms clear into 5th gear and the car ran fine. Felt sluggish but maybe it was just me babying it. so i get the car home...and try an obdII reader to pull the codes and it gets nothing. so i disconnect the negative side of the battery for about 15mins and fire the car up and go for a ride. It had its snap back and i thought maybe the problem was a fluke. so i wanted to concrete the idea that it was a fluke and stopped in the middle of the road n launched it at about 2000rpms and it went right up thru the rpms thru the first 3 gears.. run third gear above 3000 rpms n went to shift into 4th...n the car died again. Im lost on what could cause this. Ive checked all the battery cables...the wiring harness by the longtubes, the ecu fuses under the hood in the power dist. box. all were good. What would cause this? is the ecu going bad or is the interface chip loose? i cant get ahold of dave til tomm am but wanted sum ideas asap as to what this could be. one thing i left out was that sittin in neutral the car revs all the way up like normal...it doesnt cut out. Im stumped on what this could be. Theres no misfire...no stutter.
sorry for the lengthy question but i wanted to have all the info out there to get the best answer.

Thanks
Ryan

[John4cam]

A mechanic friend of mine had a crown vic in his shop a few years ago doing the same thing. I don't think they ever found out what was wrong. I believe they even swapped computers.

IMO it sounds like an ecu issue since there is no cel on.

[v6mustang01]

A mechanic friend of mine had a crown vic in his shop a few years ago doing the same thing. I don't think they ever found out what was wrong. I believe they even swapped computers.

IMO it sounds like an ecu issue since there is no cel on.

Thats what i was wondering but idk.. i was wondering if the interface came loose or burnt up or sumthing. Its just weird. I even checked the harness going into the computer for mayb a loose wire or the ground being off but came up empty. Im just baffled now.

[mustang50lx]

I would try EEC and fuel pump relays if it has them.

[v6mustang01]

ok..so i just figd id take the mach for a ride this evening and i beat on it clear up til 5k rpms and nothing..no shut off no nothing..run like a champ... got back here to the house popped the hood...lookin under it for anything that might b off... n nothing...shut the hood..and bam the car shut off...n the instrument cluster did the same thing it did yesterday driving... so i started it back up and popped the hood...opened the hood up and shut it again..n bam it did the same thing...so repeated that 2 more times and both times it did the same thing... so now what could that be? the trip odometer never lost its miles and the radio station stayed where it was..so that leads me to believe that its not to do with the battery but where else are there grounds at that by shutting the hood it disrupts the connection to the computer?

[sutyak]

A buddy of mine had a Vette that would die randomly. It ended up being a bad ground.

[somethingclever]

def an electrical issue/loose wire

[blackfive-o]

I had this issue with my 2010 Fusion. The dealer ended up replacing the throttle body. No problems since. I know different car different engine, but a very similar problem.

[1Badbird]

I don't know if the newer cars have them or not but I had an older Festieva that when I shut the hood it woud die like that. I went to a shop to ask about it and he told me it was a fusable link by the battery. Sure enough I could feel it was broken so I bared the wires and twisted them together and it ran until I was able to replace it.

[Sonic03snake]

is it tuned with a chip or flasher?

[v6mustang01]

sorry everyone...its been crazy busy at work but we did find the problem. Here when the longtubes were installed apparently the relay wire from the starter to solenoid wasnt properly tied up nor placed back in the wire loom. The headers finally melted through the coating on the wire causing a short. everytime the car would hit a bump or shut the hood, it would move the wire enough to cause a short apparently. We just got extremely lucky monday evening and jacked the car up to check the ground on the transmission and my buddy noticed the burnt wire. Ever since we tied it back up and fixed the wire. Car runs like a champ.

Lou the car was programmed with a chip. I had wanted a programmer but the shop made a mistake and gave me a chip and said it'd cost another 100. to get the programmer instead even though my original quote was for a programmer. but the car runs great so i guess it worked out.
Thanks everyone for your input.. it definitely gave me places to start on where to fix the problem because i was definitely in the dark on this!

[PaxtonShelby]

Congrats on the fix. Go treat yourself to some fun miles now!

[2000GT]

Glad to hear you fixed it. Especially that it didn't cost you a dime

[sutyak]

Great to hear!

[v6mustang01]

Yes..i def glad it was a free fix! It was a lucky find and very thankful for friends who helped! It'll get some 1/4 miles on it next friday at mason dixion! Im no where near what the car has potential to do but its fun to rip thru some gears on a friday nite with friends! everyone keeps saying drag radials or slicks and it'll run 12s but i dont think the axels will hold up to that kind of beating unless i upgrade!

[sutyak]

Yes..i def glad it was a free fix! It was a lucky find and very thankful for friends who helped! It'll get some 1/4 miles on it next friday at mason dixion! Im no where near what the car has potential to do but its fun to rip thru some gears on a friday nite with friends! everyone keeps saying drag radials or slicks and it'll run 12s but i dont think the axels will hold up to that kind of beating unless i upgrade!

Just run on stock tires for now and avoid breaking the axles. You should be able to pull off some 13.3-13.6 runs and still have fun. The heat might come into play though and slow you down further.

[PaxtonShelby]

Do you guys really think a stock-ish Mach I will break the stock axles on slicks or drag radials? Is that because the 4v motors typically launch at a pretty high rpm?

[sutyak]

Do you guys really think a stock-ish Mach I will break the stock axles on slicks or drag radials? Is that because the 4v motors typically launch at a pretty high rpm?

Yeah. I had a Mach for a couple years and was highly active in the Mach forums. The axles are the first weak point and the first thing drag racers upgrade. I put well over 100 passes on my Mach, but the majority were on a built rear.
I didn't get below 13.1 on stock tires and weight reduction. ET streets and skinnies it went 12.6 with a 4.56 gear.

[v6mustang01]

Yeah. I had a Mach for a couple years and was highly active in the Mach forums. The axles are the first weak point and the first thing drag racers upgrade. I put well over 100 passes on my Mach, but the majority were on a built rear.
I didn't get below 13.1 on stock tires and weight reduction. ET streets and skinnies it went 12.6 with a 4.56 gear.

Best with the car is a 13.4 on nitto 555( not the drag radial) and that was b4 the longtubes and a retune. Hoping for descent temps next friday but i dont think thats goin to happen. forecast is for in the 90s. but i just wanna go practice and see what i can do at the strip. havent made many passes on with the mach and im new to drag racing so i have a lot to learn.

[v6mustang01]

UPDATE*** it wasnt the relay wire causing the problems...it was actually the chip...it wasnt in tight and every bump would cause a break in the computer connection so $100 later to upgrade to a programmer(what i asked for originially) problem is fixed and car runs great again!