Misfiring Under Load!!!

[ilikepoultry]

i have a '91 MTX with the standard 3.0...
after doing valve covers and plug wells, the car's crank position sensor went
as i worked, i took a look at the camshaft sensor too
that looked good
the car had oil in the number one plug well, but the misfiring is coming at random times, not when the number one cylinderis firing
the firing order is right and has been checked, rechecked, and checked yt again
the coil pack looks good
the plugs look good, other than the fact they aren't brand-new
i need help to get it running right
any ideas?

p.s.
it only misses under load

 

[SASHO91]

I'd say throw in some cheap copper's and fix the problem....


;P

 

[93rev2sev]

Nah...it's a dirty MAF sensor.

 

[ilikepoultry]

the maf looked clean, but i cleaned the pins and i put some dielectric grease on them
it throws codes 14(ignition pickup) and 19(PCM), but only after throwing 11(the OK) twice
the idle isn't erratic, and the pcm should be good...
could these be old codes that need to get "deleted"?


p.s.
it does not misfire when under HEAVY acceleration

 

[ilikepoultry]

it's back, and even fiercer

replaced : PCM
MAF
crank position sensor(gapped correctly then the screws were cranked on)

the plugs and wires have dielectric grease on them


NEED HELP BADLY(car needs to be ready for graduation - this Sunday)

 

[PAracer]

Have you checked your plug gaps? I had a misfire issue that cleared up after closing the gaps from .050 to .042. .o42 is the factory spec.

Which plug diagram did you use? There are a couple floating around that are incorrect.

Since you had the intake off, did you re-attach the ground strap on the back of the intake?

 

[ilikepoultry]

the ground strap is on and tight

i've used a diagram that i've seen repeatedly and also compared to already running SHOs

the plug gaps have not been checked yet, but they didn't look to be off when they were out 10 miles ago

engine:
1 2 3
4 5 6

coil pack:
5 1
6 2
4 3

 

[93rev2sev]

Did you actually clean the MAF sensor or just look at it? Did you replace it with a new one or a used one? Did you clean that?

 

[ilikepoultry]

replaced with the one from my '93
cleaned and put dielectric grease on it(the pins)

 

[SASHO91]

so when are you going to change the plugs?

 

[ilikepoultry]

we just changed them, it has a very rough idle now versus before, and misfires no matter what gear or RPM
it dies with the key on engine running test

it throws codes 72 and 13 while doing the KOER test
and codes 14 and 19 while doing the KOEO test

 

[ilikepoultry]

code 13 is Idle Speed Control motor or Air Bypass not controlling idle properly (generally idle too high)

code 72 is No MAP or MAF change in "goose" test - retest, check for frequency or voltage change - MAP MAF


code 14 is Ignition pickup was erratic - Ignition Systems

code 19 is No Vehicle Power (pins 37 + 57) or bad PCM VPWR Diagnosis

 

[sho'd]

can't you spray brake cleaner or something into the maf to actually clean the insidel of it out, i can't remember but i think it was electronics cleaner or something. someone will chime in.

 

[ilikepoultry]

the MAF is clean, i've cleaned it four times now...

 

[SASHO91]

hmm ok.. have you changed the wires?

 

[ilikepoultry]

the new wires are on their way, as fast as autozone won't get them to me
heh

i hope the wires fix it, or else i'm back to the board, so to speak

 

[ilikepoultry]

All right then, the plugs AND wires are replaced, reducing the missing only slightly

it misses around 1500-2000 and 2500-3000

i'm hesiatant to replace the coil pack, but that's one of VERY few items that hasn't been replaced

could it be a DIS problem?

it doesn't miss at idle anymore, so i think it MIGHT have something to do with the spark advancing

 

[ilikepoultry]

the tac jumps...
crank position sensor... AGAIN?
i replaced it two miles ago!

 

[SASHO91]

Hmmm.. does sound like a bad DIS. do you have a spare to check it? But if the tach is jumping, that would point to the CID.... IIRC.

I don't recall my tach jumping when my DIS went out.. but that was some time ago....

 

[ilikepoultry]

we're soldering the splices
idk if the DIS is bad, i don't have access to another
i'm going to test the CID in a minute or twelve