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

 

Reviving my old thread to update the group on what I finally found. I had a very bad assumption...you change the timing set out at TDC on the number cylinder !.

This is not correct the instruction say to pull the timing chain cover and rotate the engine till the marks on the cam and crank gear line.

I can't remember why but the drive gear for the balance shaft come out back August 2020 when this began. I tried to line it back up with the balance shaft using the marks not together but across the drive gear.

I will reassemble but I found my oil leak at the front snout as the seal had cut a groove on the harmonic balancer.

 

Sure, I suppose that could throw things out of balance and potentially cause a P0300. But honestly never heard of it as a problem before. Be interested if this cures your P0300. Please be sure to get back to us on that! Sounds like the P0300 came with the timing chain replacement, but crank sensor was definitely disturbed as well - so ????. Will CASE relearn initiate easily now?

 

I should admit that the photo of the dots aligned was second attempt. But I had verified everything else with most being done twice.

In case this is too long to read I been fighting this since August 16th,2020. The first P0300 code was set driving to the nechanics to get a CASE relearn done.

JB Weld held the insert in place and a 2nd CASE relearn was done. That is until I wanted to check the clearance to see if it was less than 0.030". Then it started spinning again. So I decided to go back to the timing chain install. In addition to the insert not holding I wanted to eliminate a bad chain or bad install.

I didn't report on the MAF changes, thottle body changes and the struggle to get the exhaust leaks eliminated. Always with 900-2700 misfires on my 27 miles to work.

Just to recap:

• 2 distributors OEM and Summit billet
• 2 sets of spark plugs
• 2 sets of wires
• 3 MAF sensors - one I had in my garage and from 1/2 price day at pick n pull
• 2 spiders 2nd for sure AC Delco cured #6 misfires
• exhaustive multiple searches for vacuum leaks even the the vacuum at idle is 18-19 inches or more
• changed the fuel filter due mileage but no change
• Multiple doses of fuel injector no affect on the misfires but the mileage would go up
• Seafoamed the engine twice actually made things worse for several hundred miles
• added Seafoam to crankcase with no change to the oil pressure.
• used 15w-40 diesel oil at an oil change no change in misfires so not likely to be worn bearings
• pulled both valve covers and turn the engine by hand with no issues noted..
• Started the engine and let idle w/o valve covers no issues noted but I relearned the roller lifters don't rotate.
• broke MAP sensor and replace with AC Delco need to learn how to remove for inspection.
• I admit the Pacesetter header have burned several plug wires until I perfected the routing.
• also replaced the headers with a new set and had power coated for thermal barrier. This is decision I would change now..would get OEM exhaust manifolds
• Changed EGR gasket and verified that it work as it should with multimeter
• Replaced squeaking alternator with new to me used on voltage is 13.3-13.5

 

‘67 Camaro, nice!


George