Higher rpm backfiring, searched

[281pony]

this is not for my car. i have a friend who is having alot of trouble with his car, so i figured i would try and get him some additional help.

car runs fine driving normal, but higher rpm's 4k +. it just falls on its face, and backfires. not sure if its through the intake or how its backfiring. i havent heard it/seen it in person recently. this is a brief list of stuff im quoting/know hes checked.

Compression test
Replace all vacuum lines
Go to new Intake
Different Throttle Body
New IAC
New TPS
Used.....known to be good Distributor
Check all fuel lines

also replaced a fuel pump i know.

i believe this all started for him after he tried to swap out a distributor. no, its not off a tooth. timing is set to 10.

any input here? i ran everything i could think of by him the other day on the phone. thanks guys.

 

[jadedinpa]

mines doing something similar right now, but it seems more like it's missing at high RPMs than backfiring. i haven't touched it yet, short of a long-overdue tuneup.

I would recommend your friend run codes, i'm going to do the same.

-subscribing-

 

[281pony]

i mentioned the same thing to him. dont know if he ran codes or not though, im thinking not.

 

[joeyd0730]

i had similar problem back in the day, my problem was a crack in the plug, me or someone must have dropped it, you couldnt even see the crack, i would go with plug change first. joe

 

[criticman]

I had a similar issue - after installing my AFM PMS, all issues were resolved. I am positive mine had to do with the air/fuel ratio.

 

[J90GT]

Pull codes, could various sensors, if its more of miss then backfire could be valves floating

 

[HISSIN50]

He did not happen to use Platinum plugs, did he?

 

[black93gthatch]

I heard that those plugs are nothing but crap.. i used those on my old 5.0 and it ran like crap.. then i talked to some mechanic b4 i went out and got new ones and he told me to go with motocraft.. i never had a problem after that.. but that's if the plugs are the problem.

 

[HISSIN50]

I heard that those plugs are nothing but crap.. i used those on my old 5.0 and it ran like crap.. then i talked to some mechanic b4 i went out and got new ones and he told me to go with motocraft.. i never had a problem after that.. but that's if the plugs are the problem.

True dat. Some folks see a crappy idle and some see a high speed (around 4000 RPM) misfire. Autolites are also very good plugs.

 

[281pony]

True dat. Some folks see a crappy idle and some see a high speed (around 4000 RPM) misfire. Autolites are also very good plugs.

i dont believe he did JT.

they did something today and it got better while i was passed out after work. so i think he has fixed it. ill talk to him and see whats going on now.

thanks for all the input. im not sure what exactly fixed it, but ill post it up for you jadedinpa once i find out.

 

[BlooDReigN]

In my experience, problems like this are usually casued by the ignition system. One of my buddies had this problem a little while ago. His car would start back firing like crazy at about 4500 rpm and wouldn't really rev past there. We went and got a new distributor from the JY and all was good