Random Misfire

[tubjub]

Hello

I just recently purchased a 91 MTX ...

Having an issue that just started today...

Under light part throttle acceleration through the gears (below 3k) I keep dropping a cylinder.


above 3k rpm or when the secondaries are open it doesn't happen. but its becoming very annoying, because I don't want to drive around with my foot glued to the floor.


i am going to pull codes later tonight and post them, it did have new plugs within the last year.

only mod I have done is the airbox silencer delete

it has fresh 10w30 synthetic oil
V-Power in the tank (94 octane)
and a fresh paper air filter.

I noticed it is going to need the plug tube gaskets replaced, they are leaking oil into the cylinders, the rear bank seems fine it was just the front bank i noticed leaking. I did clean the front 3 and i'm going to keep an eye on them (I thought maybe the oil was causing the electricity from the coil going to the plug from making a proper spark below 3k rpm)


any help would be greatly apprecieated.

this car is my Daily driver

thanks in advance

Jacob

 

[SHOmethewayhome]

its the plug tubes.

my 91+ is leaking through them as well and the shop i took it to for the CPS mentioned it could cause a misfire like you are describing.

hopefully i can get to it soon when i find the space.

my apt complex manager caught me sucking the oil out of the tubes today and said if i get caught working on my car in the lot one more time i'll get fined.
(i looked through the lease agreement contract and apparently i should have read it better. i am subject to fines for working on my vehicle in the complex as well as some other oddball stuff)
i got busted back in may for changing a flat tire and argued with that saying it would have been an abandoned vehicle with a flat which they would have towed if i didn't change the tire.

so anyone in the phx area doesnt mind me working on my car in their driveway on a saturday morning i could use the space.

 

[shoshirtsandhat]

I believe SHOsource.com has what you need, valve cover gasket set & plugs + wires..

:Joe

 

[shomtx95]

make sure you replace the wires

 

[tubjub]

cool, i'll scrape up the $150 for the wires.... I did the arc test, and nothing...

Here's the other weird thing... codes are as follows

11
49
67

67 shouldn't be affecting much of anything.

but the 49 has me bothered.
SPOUT signal defaulted to 10* BTDC; SPOUT circuit open

if the SPOUT was messed up, dontcha think the car would run horrible ? cause ... it doesn't, aside from that cylinder dropping out
those were run with the Key On Engine Off


however ... the test with the engine running came back with a single flash and that was it.


but here's the other part of it ...

i parked it after that initial post I made, let it sit overnight, drove it to work... it was fine... then started acting up on the way home.

parked it overnight, was good again the next morning.

seems like when the engine is cold, the miss is non-existant.

but as soon as it warms up, or after the car sits for a short period of time after being run, its kinda hard to start (occasionally) and misses really bad in 1st gear till about 3k or so... and it has also begun to have a dead miss till the secondaries open up... not all the time, just sometimes.

seems if you breathe on the gas, its halfway okay, but if you roll into it, its fine too... stab the gas, its a dead miss till it decides to stop, then it clears out and its fine....

im stumped ... DIS module maybe ? (since the issue is heat related?)


need help ... anything ...something ....

or do i really need to get the plug tubes sealed up asap and replace the wires...



TIA

Jacob

 

[TimboSHO]

Sounds like wires to me. They can be pretty finicky sometimes, and you can wiggle them around to make it better, but the only way to fix it is replacing them. The AC Delco wires are almost identical to Motorcraft and are much cheaper

 

[tubjub]

plug wire #6 ... the insulation on the tube part had a 2inch crack... that was my misfire.

thanks for your help

Jacob

 

[shoshirtsandhat]

Be sure and fix your car properly if you want respect from the SHO