First off, it was good to see everyone! We always hate leaving all of our friends after seeing them! Also, Eric, it was great to meet you and Nancy and talking with you.
Now onto the fun trip home...
I knew something was not right with the Yukon after being on 494 a couple miles this morning. the Yukon's RPMs were running a tad bit high but I really wasn't too worried after it finally settled down and cruised at its normal engine speed. After about a half hour on US 169 heading towards Mankato (beautiful drive by the way) we ran into some steep grades that caused the Yukon to down shift to above 3000 rpm. well on the second assent I felt what I thought was a vibration of a tire, thought maybe the trailer and nothing seemed amiss. after we crested the top of the hill I noticed the check engine light had come on. On the next grade climb the truck down shifted as it should and the vibration showed up again, but this time the check engine light started flashing. I tapped the brakes and babied the Yukon through the rest of the steep hill. We stopped for fuel at st. peter and took off again.
So down the road we go and I am constantly watching the rpms not run where they are supposed to for the next 2 hours and babying possibly a wounded engine struggling to keep the pace on the hills and sometimes on the flats but still manages to maintain the speed limit until we got to Windom, MN. Then all of a sudden, the Yukon starts behaving normally, except I am controlling the throttle on the hills and setting the cruise on the flats. We get to Worthington, MN get fuel, and add Lucas injector cleaner to the fuel and take off again. getting up to speed after Worthington I push the truck above 3000 rpm and the whole truck just starts to shake. I let out of the throttle and peddle it a few times and the engine starts running good again.
We picked up some lunch at La Mars, IA and I drove the truck up to speed as I normally would and reached 3500 rpm with no problem, no misfires from the engine, not flashing check engine light. So I set the cruise and watch the tach needle fall to the normal operating rpms at 65 mph and then comes the hill. The Yukon Down shifts and the tach jumps to 2700 rpm we crest the hill the Yukon shifts into overdrive and the rps fall to normal operation range.
So down the road we go and stop at the little town of Pilger, NE for a break. Get back on the highway and the check engine light is now off. So I stomp on the throttle and push the Yukon over 4500 rpm on the tach, and no misfire or check engine light. The rest of the trip home was very uneventful. I pulled out my scanner for the truck and found multiple misfire code and cylinder #4 to be the culprit.
So now it could be one of two things either the #4 plug is fouling out and not handling the engine load some of the time or the plastic GM intake manifold gasket is leaking coolant into the #4 cylinder. Btw, the intake gaskets were last changed at 90,000 miles and the Yukon now has 209,000 miles on it the plugs and wires have just over 10,000 miles on them. I am leaning towards the intake but will look at the simpler solution first.
Again it was great to see everyone, and we hope to see everyone in August if not sooner.
