1. Fuel pressure was 52 psig by my gauge and 54 psig. Fuel trims normal so drove 3400 miles. When I returned changed fuel filter after about 9k miles. Fuel pressure 55-57 by my gauge. Changed out fuel pump on warranty and got 60 psig. After wires, plugs, compression test, vacuum leak test and distributor swap without change. Asked here and was told that is ok for MPFI system which I have. Delphi pump was installed last year and warranty swap a couple of weeks ago.

2. When I drove the truck to the mechanic at mile 6 of 7 the P0300 popped up. Showed cylinder as the issue. Mechanic tested spark at plug end of wire and found spark. He found the vacuum harness was as I described easy knock off a hose. He redid this as this was done by him 2 years when trans was rebuilt. Issue moved to cylinder 1. Still would set the P0300 code he noticed the ignition coil was original after 230k miles recommended change out. I agree as it was on my list and after 30k miles he noticed cap and rotor corrosion. Changed out those. ECM would now permit relearn to be done. Still had issue on cylinder 1 so changed out #1 wire and plug with AC Delco. Drove vehicle from KC to Laramie WY. Noticed that #1 would count misfire and set P0300 after quick drive i.e. 500 feet and restart. Did that once.

3. Relearn done with crank sensor tight but loosened up with pounding on US Forrest service roads. Had wrong bolt with stacked washers so change out to correct bolt. When removing wrong bolt the nut insert came out. Pushed back in but would pop out with slight tug on bolt head. Crank sensor moved slightly during this but ran like before after JB Weld used to hold nut insert in place.

4. Timing chain was rotated till cam and crank gear were alinged by the marks. New unit installed same orientation.

Checked distributor orientation yesterday or day before and when the timing mark was aligned with notch on cover first time pointed to #4 post location or very near. Was between back cap mount hole cam position sensor. 2nd time was pointing to where #1 post should between the front cap mount hole and the 6 mark on the dist body. Closer to mount hole.

Reinstalled the rotor that came with distributor and 1,4 and 6 now have counting misfires. Will swap out cap tomorrow or next day and reinstall AC Delco rotor.

 

Since you are chasing ghosts here, the proper way to really verify the distr install is with #1 at TDC with the plug out and physical verification of the piston location. A guy here a while ago was chasing strange problems and then determined that the harmonic balancer had slipped and rotated the alignment marks.


George

 

Thank you George

Here what I think I should do.

If I get a chance I should change the cap back as the #2 wire was kind of difficult to re attach when I took it off to change the rotor. Maybe something is in it or the wire while new has an issue.

I am wondering if I have two bad cam sensors or a wiring issue.

The exhaust leak on the passenger side is getting worse so I may have to address it. Would let me do compression test on #6. Currently seems impossible with the headers.

May havevto replacereplacternator on my son's truck 1st.

 

Check that distr location

Did your crank sensor come with instructions/specs on checking the clearance?

So you don’t have a complete compression test?

AC Delco ignition parts are preferred in these engines

What is the condition of the ignition wires?

Inspect the cam sensor connector and wiring

Sure you could have two failed cam sensors but that not the most likely situation. The p1345 code is a correlation problem between the cam and crank sensors. The most likely cause is an actual timing problem. That’s why I asked about the timing chain install and I am suggesting a more thorough check of the distr position.

Do you have a scope?


George

 

I have done a rough check but will need help to confirm tdc. Hard to turn engine and watch #1. @TDC should it point to the 6 on dist body or #1 post.

Reused crank sensor so no instructions but worked before and worked after timing change.. Mechanic didn't see issue with it.. and I asked to check as part of relearn.

Wires are new ACDelco and routed to avoid headers but will check #2 as it seems different.

Yes have been open about #6 not being tested but get 15+ mpg with mixed driving and fuel trims are still as reported earlier. My son has a leaking intake valve and you can see the affect on the bank 2 fuel trims Also a 4.3 engine in a Blazer

Have looked at Cam Sensor and wiring at distributor without finding issue. Need to know voltage for sensor so I can test.

 

Physically verify #1 cylinder at Tdc with plug out and then rotor to 6 mark

cam sensor is: red=12v ref, pink/balk= signal gnd, Brn/wht= signal output.

At some point you need to do the Les drop cylinder test to proves that the misfire counter is working correctly. Pull a plug wire and ground it to see if that cylinder is misfiring/counted.

the clearance to the crank sensor starts to reduce with engine wear and can get to close and mess up the output.



George

 

I was able to pull the number 1 plug and rotate the engine to top dead center. Found the Distributor wasn't lined up so I moved it. At the end of this I have a miss on 6 and the CMP retard is unable to corrected any better to -3.0 degrees

As Found:



After I moved it


Also didn't like the way the plug wires looked. Installed on right and on that has never been installed

 

You’ll need to modify the distr hold down to be able to get cmp to zero.

once you get your cmp retard and ignition wires straightened out you should do the Les drop cylinder test to be sure that your misfire counter is accurate.


George

 

Agreed. Some of the inexpensive bluetooth scanners get two of the cylinders switched.

 

Sounds like you never had the crank relearn done after using JB Weld. That is a mistake. Obviously you don't have much of a misfire if it took 7 miles to come on - so is it a real misfire you can feel? Or are you just relying on the scanner to tell you there is no problem. At this point I don't know if problem is crank sensor moving around, or if something in your distributor is wrong.

If it was mine, I would be putting in a new distributor, cap, and rotor - and installing a new timing cover. Then have the crank sensor relearn done and see where you are at then. Life's too short to jack around so much with too many unknowns (and that is exactly what you have). Sorry!