93 SHO missing

[t5535]

I have a 1993 sho mtx that is missing. it does not miss all the time but most of the time. I plugged it into a OTC scanner and it came up with the atmospheric pressure sensor. I replaced it and no change. I cant find what is making it miss. When the scanner was doing its test it stopped missing during the test so I think it something electrical but not sure. I have a 1992 SHO mtx parts car so I have spare parts but I don't know what to try. any help would be great. Thanks

 

[NORMAN]

Are the spark plug wells dry of oil?

 

[93rev2sev]

Clean the MAF.

 

[220ksho]

Are the spark plug wells dry of oil?

+1. Primary cause of misfires.

 

[urban88]

ya look at the plug wells

 

[MadMiike]

Thought someone stole your car!! :swing:

 

[freecop]

Thats what I thought! Woulda had everyone hunting for plate numbers

 

[ryandeyoung]

My 93MTX had the same thing and it was the DIS module. Change it with the on from your 92, and make sure it is grounded good and the bolts are tight.

 

[t5535]

Ok I just got time to look at it and the plug wells are full of oil. What causes that? What gaskets/seals do I need to change?

 

[93rev2sev]

Valve cover gaskets.


Again:
Clean your MAF

 

[1998v8sho]

Change up the spark plugs, wires, valve cover gaskets, and the spark plug gaskets. I think you should be able to find everything at Rockauto.com or from shosource.com.
Before you pull out the spark plugs out of the wells get a vacuum attachment that will go down the wells and suck out as much oil as you can.
Use a high temp gasket sealer when doing the gaskets.
Now would also be a good time to do a upper 60K or even clean out your intake.
Hope this helps.

 

[t5535]

I cleaned the plug hole's out and found 1 bad plug. I replaced the bad plug and it quit missing but at low rpm there is a miss that goes away if you feather the pedal. I plan on replacing all the plugs and the gaskets but I am trying to get all the missing out before hand so I know what all I need to replace. any ideas what is making it miss at a low rpm? its not all the time. I still have not cleaned the maf yet gonna get to it and the rest of the work this weekend.

 

[1998v8sho]

I would check the Throttle Position Sensor or the Idle Air Control Valve. Cleaning out the MAF should help too.

 

[frosho]

One of more of the wires was probably damaged by the oil. That will cause a miss like yours.

If you replace the gaskets, change all the plugs and wires, and clean out your MAF, your miss will most likely be gone.

 

[93rev2sev]

Glad you found the bad plug. Guess I was wrong about the MAF, but it's the easiest to correct, most overlooked cause for a "miss" that I can think of. We'll see if what's left of yours is affected with a good cleaning. let us know.

 

[t5535]

should I adjust valves?

 

[t5535]

I bet he MAF is dirty. I haven't touched anything under the hood for over a year and 15000 miles. Its been a good car it has 150k on it.

 

[1998v8sho]

Adjusting the valves would be a good idea. Might as well if you are taking the valve covers off to do the gaskets. You might as well knock everything out in one shot.
Def. do the all the plugs and wires.

 

[NealVA61]

Not my intent to hijack t5535's thread, however my '95 AT began missing, sputtering, occasionally backfiring, and idling roughly all of the sudden shortly after filling my fuel tank but still almost a whole day later.

It's gotten a little better over the course of a week since the fill-up and the severity of the sputtering/bucking and frequency of the backfiring has lessened but the rough idle and hesitation on acceleration are still present.

The plug wells are dry, the plug and wires only have about 40K on them and the CPS and cam sensor were replaced about the same time as the plugs & wires.

I haven't cleaned the MAF but would that cause the sudden start of my problems as well as the intermittent problems?

It starts right up as if nothing is wrong and there is no CE light. It will also cruise at 65 mph on the hwy w/o issue.

All help will be appreciated as this is my daily driver with no viable alternative.

 

[t5535]

well I went ahead and pulled the motor and rebuilt it lol. no more miss runs like a top. had allot of miles on it any way and needed something to do.