Strange things are happening under my hood

96 Vortec · July 20, 2006

In Feb, at 132xxx miles I had to have a new auto trans. put in my '96 K1500 with the 350. I get the truck back and it drove exactly as it did before. It had a rough idle at around 600 rpm just like it had for several months. For the previous year the SES light would come on for a day and go off for 3 months.

Now, I'm having trouble with occasional rough 1-2 shifts. They most commonly happen under light acceleration. Although at full throttle the 1-2 shift is so hard I had to look in my rearview to see if I left a trans. on the road behind me. Now my SES light is on 70% of the time. I've taken the truck back to the shop that installed the trans. and they gave me a printout of the misfire counter. I have a large misfire in cylinder #3. I did a full tune up and a compression test. I determine with the help of several friends that I need new valve seals. I had a machine shop change the valve seals with the heads still on the truck. They said the seals they pulled off were still rubbery and pliable with no holes. I still have signs of oil in that cylinder. Although now there are small signs in #1 and #5 also.

I've had trouble for the past 2 years with a cold start hesitation. Last Sunday I removed and cleaned the throttle body and IAC. After I put everything back together it started real funny. Instantly starting at 1100rpm diving to 400 back up and down one more time then steady idle at 600. Aside from the rough start, the truck has run great for the last 4 days. Runs smooth and no hard shifts. Tonight I opened the hood to the truck and realized I forgot to plug in the MAF sensor and the IAT sensor. I plug them in and leave to go to class. The SES light is off but the rough shifts have returned.

Finally, my question, is my engine/trans. trouble (not the oil in the cylinders) caused by the MAF or IAT?

And second, can someone give me a diagnoses of my sparkplug? I assume that is oil buildup, but why is it only on one side of the plug? (sorry it's out of focus, but it's the best pic I could manage)

getcrunk88 · July 21, 2006

Mabey ur egr valve is stuck open and forcing too much air into the intake inturn making the map sensor think that there is ALOT of air entering the tb and making it rich i would also make a trip to the local parts store and buy a pcv valve because ur spark plugs seem to be oil fouled this could be several things like rings and cylender walls but if your pcv valve is clogged or stuck closed its building up crankcase pressure and forcing oil in under your rings in turn fouling ur plugs and burning oil i would do this because they are very cheap parts but can cause alot of problems so if i were you thats what i would do hopfully that helps.

Getcrunk

Rammer · July 22, 2006

Was the SES light on during the 4 day period? I'm not sure how the 96 is, but the newer ones will run in speed density mode with the MAF disconected. This basically is the engine is running off a table in the PCM's programming for fueling using the MAP sensor instead of the MAF. I disable the MAF on mine to tune it and mine will run great in speed density mode. But this will put the SES light on after the second start and most of the older models, this will command max line pressure for the transmission but, maybe not yours. Misfires will reak havoc on transmission shifting and torque converter locking also.

Sounds like you do have a bad MAF sensor to me.