Everyones Hero

I have an '86 5.0 & recently it's started breaking up under high load & in higher RPMs at around 50% throttle. Running 92-93 octane fuel on a stock motor w/ bolt-ons. It's fuel injected w/ MAF conversion.

I did an oil change & today I changed the fuel filter. Filter seemed to help a little, but it's still breaking up. I got a new set of plugs but didn't put them in yet.

I pulled one of the plugs & they were a little white, so I'm guessing it was running a little lean.

Aside from the plugs & fuel filter what else could be causing it to break up under load? It's not bogging like it would if it were rich, but seems to be running out of fuel or the ignition is breaking up.

Thanks,
-Nick

mjr46

nope, not an accurate way to diagnose an efi set up.
about a 100 different things cap, rotor, wires, dirty maf, weak pump, restriction in fuel sysytem, fuel management issues........ect ect...run a koer test and look for codes first

joshs89gt

I had the same problem when i put my msd coil in with stock style cap and rotor but after i changed it all it helped. what about your fuel pressure?

Everyones Hero

I don't have a fuel pressure gauge. Nothing has changed on the car & it just started breaking up.

I'm going to do the plugs tomorrow & if that doesn't do it I'll head to Autozone & see if they can pull any codes & I'll pick up a can of carb cleaner & clean off the MAF sensor.

If that isn't it I'll go with a new cap/rotor & plugs. Is it worth going with an MSD ignition on a 5.0 with just bolt-ons?

mjr46

autozone won't help you on an obd 1 koer test for a ford, I doubt anyone there will even know how to run the test or much less even have the tool to do it....google DIY KOER and you can do it at home

Everyones Hero

Thanks. That's just like how it was on my Civic. Jumper was just in a different part of the car.

Bubba 95SN

Please refrain from any comparison of a Mustang and Civic. Some,not I, Mustang owners will have a high-self-esteem-seizure. I made a funny. Bubba

Everyones Hero

lol. They'll just have to get over it. My single cam coupe went 13.7@105 on a homemade turbo setup that was put together for less than $1k. :P

02WhiteGTVert

What's your timing set at? when you say "breaking up" i'm guessing your meaning misfiring under WOT? start with the basics (plugs, wires, rotor, cap)...if you remove your cap and check the points, if they are corroded you can clean then up with sandpaper as a temporary fix...if your issue isn't fixed there move on to fuel system...by the plugs "looking white" this could actually be detonation occuring due to too much timing...

mattdel

my first inspection point, aside from running codes, would be distributor shaft bearings.
a wobbly rotor does no good for spark conduction.

if you check everything else and cant find it, yank the dizzy and see if you have play in the shaft. if your dizzy is stock, its a good bet they're at least "more looser" than they were in 1986. i'll almost guarantee you have spark issues somewhere along the line... if you had fuel issues it wouldn't be misfiring throughout the higher RPM's, it simply wouldn't reach the higher RPMs.