Those fuel trims are very good for an old truck. You add the STFT and LTFT together for a given bank, mindful of sign. You do go from slightly positive to slightly negative as your rpms go up so it’s possible that there is a small vacuum leak but these numbers are not dramatic.


George

 

I hope to get the truck back this evening and can give you updated fuel trims. Those were before I changed the spider which was leaking. Also that was when I only had 9 of the 10 upper manifold hold downs installed. The previous owner crushed the EVAP soleniod and one of the bolt holes. I have put an undamaged upper manifold on it and torqued it to 88 in/lbs.

Here's my plan:
1. Pull the number 1 spark wire and connect my OTC spark tester.
2. Address and issues from that.
3. If still getting misfire then pull number 1 plug. Check compression against previous recorded value of 162.
4. I am thinking about replacing plug to eliminate it as a source of the misfire.
5. I may go to the pick and pull to pick up a throttle body. It seems the issues started when I cleaned it. Misfire is more pronounced when cold so maybe IAC or TPS? I am guessing here.
6. Because of the misfire we are blocked from doing the case relearn.

The shop I use is swamped and Wednesday night someone broke into a customers work truck and damaged the steering column. The truck is parked in front of the shop door. It's a one man operation so lost yesterday to insurance, police reports and working on the disabled van.

I have less than a week before I head out on my.vacation. Time is the one thing I don't have so decisions maybe made on that basis.

 

Running better when warm can mean a couple of things:

Its literally because the engine is warmer: expansion, electronics, etc.

Its because the system transitions to closed loop and fuel delivery is managed by the O2 sensors and not the other sensors and the table values. Does it run better at the moment of closed loop transition?


George

 

The old adage of what did you break when you fixed something else applies here. I removed the spark plugs and wires for removal and reinstall of the headers. I now believe the spider was an issue at higher rpm and loads i.e. climbing hills.

The spark plug wire for cylinder 1 was loose at the plug. Never made a click but got much tighter after I reinstalled it several times. Finally had to squeeze the ring to get it tight.

The constant miss is now only showing up when I slow and sometimes at idle but the more I drove it the better it was. I put in a used plug and will get a new one and replace the spark plug wire.

I am going to check vacuum, compression and test the new wire with my spark tester before I call the install good. I also will get out the fuel pressure gauge and verify those numbers.

I am thinking it's carbon in the cylinder so will add some fuel system cleaner when I fill it up with pure gas today. This will attack possible old gas and a cylinder that may have issues from having fuel leak into it