Help runs good cold misses bad hot 90 5.0efi

[tonyvt]

my 1990 Chevy 5.0L 5spd. runs good cold misses bad hot. For the first 3 or so miles it goes great...but then It pings and looses power and is worse at higher rpms. If I back off and dont make it work too hard its not bad. Its been doing this for a while but I havent been driving it much. In the past it would miss for a while then once it was full hot it would be ok. I havent had a chance to drive it too far yet to see if it will stop once completely warmed up. I just drove it home about 10 miles and once it started missing it didnt stop unless I backed off and drove like 45-50 in 4th gear. I think its related to mid temps?? Something with the fuel/ or timing at mid temp>>??? has over 160k miles...

I need this fixed.???

Thanks!!

[03chevy]

when's the last time you did a full tune up? (air and fuel filter,plugs,wires, cap, rotor) or could be a number of things like knock sencer, cam shaft sencer, map sencer, mass air flow sencer.

[Case 7230]

Do you have a check engine light on? If so you could pull any error codes stored. How long since you changed spark plugs? How long since you changed plug wires? Could be something to check.

[tonyvt]

Ok so I found the coil was bad on Fri. it was arching like crazy. So I figured I found my problem.. NOPE> But it was really bad.

So now it runs just fine cold. As soon as the temp starts to come up it starts to ping/knock looses power. BAD So could it be a timing issue? What could cause this? It had new cap/rotor fuel filter. last fall.. It idles fine hot or cold .

No lights on.

Please help?? Thanks

[mudseeker]

i would look at the temp sensor. i believe when they fail, they peg out all the way cold or all the way hot. so your truck thinks it is still cold when you have reached operating temps, causeing your misfire.

[tonyvt]

Thanks!

I will today!

[tonyvt]

IF my gage works could the sensor still be causing the problem ???

[mudseeker]

it could be possible, here's a little reading for you.
http://www.autozone.com/az/cds/en_us...rInfoPages.htm

i would also look at the MAF sensor, it measures the density of the air. the colder the air, the denser it will be. if the MAf sensor is bad, your air/fuel ratio will be off, possibly causing your problem.

[keithr0005005]

wait your saying its pinging...a lot of the time pinging can come from a poor grade of fuel. sooooooooooo we know these trucks from factory are designed to run off of 87 octane and if your pinging and running like **** when the truck warms up then my guess is your timing is slightly advanced. advanced timing requires a higher octane fuel for better combustion which can potentially explain your pinging and poor performance.

[tonyvt]

FIXED!!

I cant belive it... It was a plug wire fell off cyl.2...

holy ****....

but I learned alot about testing my efi electronics...