99 5.4l occasional miss????

[jimmi308]

slight miss at idle, and sometimes under load as well. Other day on freeway on ramp was going up hill, felt like no power and cel flashing. Only did that once, and doesnt miss all the time..... Im thinking I have a cop bad or going bad. plugs about 4 mos old. Also no coolant leaking on the passenger side back one anymore. any suggestions would be helpful

Thanks

 

[panda24619]

you ever change the elbow in the back of the throttle body? sounds like you might have a vacuum leak.

 

[walnuts4x4]

if you can get the CEL to stay on get the code read... but a COP going bad can cause a low grade miss that wont trip the CEL until it gets really bad... if your looking for a cheap set of COPs look up global automotive or UNEEK on ebay... they sell an 8 pack for under 100 shipped with a good warranty and great customer service... mine are from global and have been going good for over a year now...

 

[walnuts4x4]

also how old are the plugs? my .02 would be to use motorcraft or autolite double platinum since other plugs can cause issues with the motor... also be careful of the dreaded spark plug blow out....just FYI if ya didn't know...

 

[designit]

You don't have to have a solid CEL to have it read. You should still get a freeze frame reading off the computer to know what hole it is... Take it to a parts store & have a reader put on it.

You'll also likely get a P0300 code along with the misfire hole number... The 300 code should be 'in relation' to the misfire hole (not in addition to).. In other words, you're not likely to pull a 300 without knowing the culprit (plug, cop or injector)

A blinking CEL is indication a misfire is happening right then and there. Then will turn off... You likely got it to flash while accelerating up to speed on a freeway onramp or something (at about 50mph'ish) ?? (just a guess)

My advice to anyone who has a rig out of warranty... Go get a cheap code reader... Best $70.00 I ever spent for a car. (or spend a few hundred more and get a programmer... they can read / clear codes too)

 

[designit]

Another thought too...

You need to run the ODBII misfire test...

Cycle key on (do not start) then back off... Then on & start car... >> This will prep computer for entry.

(misfire test): From stop, accelerate to 65 at 1/2 to 3/4 throttle then off the gas (no brake) and coast down to 40mph +/- before appliing the brakes >> to a stop. Repeat this 3 times

Then take it over to the parts store for a reading.

 

[jimmi308]

its very intermittent just have to replace all the cops I guess. Maybe go with accel coils

 

[99 Expy]

I would try COPs first, but like designit said, the computer will still have codes after the CEL goes off, but you can erase them with a scanner.