High rpm cutout

[That50]

I posted this awhile back...


At higher RPM's, (4k on up), the car cuts out, and sounds like I'm choking it. I thought it was plugs, so I changed them. Thought it was plug wires. Changed those. Bought 2 new o2 sensors. Still, nothing. Car is an 87, meaning it's SD, not MA. It's an AOD, if that helps any. Maybe Map sensors?If anyone has any idea, please shoot for it. Thanks in advance,

Jordan

 

[N8Miller]

what cam, valve springs?

does it make a sputtering style issue in that rpm zone?

 

[85_SS_302_Coupe]

You don't have any mods listed....is it starving for fuel? Are you running cheap gas? Need more specifics...

 

[That50]

Mods are as follows:


CAI
4:10 gears
Rebuilt AOD(not really a mod, lol)
Trans cooler
Bassani X-pipe, no cats
Hooker mufflers
Shorty headers
14* timing


No, no cheap gas. Only 93.Other than that, all stock.

 

[85_SS_302_Coupe]

I'd have to guess either not enough spark or valve float, like i think N8Miller is getting at.

 

[That50]

It sputters sounding like threw the exhaust...

 

[N8Miller]

I'd have to guess either not enough spark or valve float, like i think N8Miller is getting at.

yep.
i was insinuating that the old valve springs are shot/warn down and cant take the high RPMs anymore.

 

[That50]

It's weird...

It will sometime do it, other times not....


Hoping it's a computer problem?

 

[mackey]

Only does it sometimes? Does the car engine almost shutoff and there is no power? I would check the timing and make sure it is advancing and set right. I had a problem like this but it was always doing it. Turns out I was running too little timing.

 

[That50]

It's at 14*.

It SOMETIMES cuts out at 4k on up. It's weird. Can't seem to think what else it can be. I've got a 302 block bored 30 over in the garage. Can't wait until it's built... I just want this problem to go away, quick.

 

[HISSIN50]

what plugs are you running?

good luck.

 

[Daggar]

Possible causes in addition to what the others have suggested:

Vaccum Leak
Bad MAP sensor
Bad Fuel Pressure Regulator
Sticking/Dirty Injector(s)

A Vac/Boost guage with the vac line running to it that is wide open (no restrictor orifice) can cause what you describe as well.

 

[That50]

How much is a map sensor?

 

[HISSIN50]

it will be cheaper to do some diagnostics than to toss money at parts. did you pull codes yet?

if you are running platinum plugs, that can cause a high speed misfire.

good luck.

 

[Stang8URMPRT]

Don't go buying parts and swapping them. Anything electrical is not returnable. Once you leave with it, it's yours. I had the exact same problem.. Cutting out at high rpm. it turned out to be a very weak coil. Check it by taking the coil wire off the cap, put a spark plug in it... ground the plug to the body or similar and crank the motor. The spark should be VERY bright blue. If it's yellow, the coil isn't putting crap out. Try this out first, before you go spending money on parts you have no idea are bad or not.

Nick

 

[TheTacoWarrior]

Also try looking at your TFI module. I hear they can cause similar issues.

 

[HISSIN50]

It's been awhile - I Hope he got it figured out already.

That said, it's always nice to see Nick in his former glory.