Bought this needing a sunshell.. 300 miles later it spun a main bearing at 110k... cursed... used engine 152k... ran good except for a slight feeling of miss at highway speed, occasional sometimes worse than others.. then it began actinh erratically at higher rpms throwing p0335.. crank sensor erratic, tried another.. multiple crank relearns after each adjustment.. same result.. shimmed, fixed the p0335, but created random misfire, p0300... worst on cyl 4 and 1 trailing it... misfire is worse when warm and most misfires occur the most when high rpm with complete let off of throttle... new plugs wires, complete distributor with cam sensor... cam retard was 7 i set to 0... wires from crank to pcm ohmed out good... please help!!! any ideas..

 

Misfires can be a bit of work to solve but you came to the right place. Let’s get you fixed up.


First make sure that your fuel pressure is solid with no leakdown by doing the fuel pressure test in the sticky

If you swap plugs and wires between the misfiring cylinders and good cylinders does the misfire follow?

Do you have any carbon traces under the distr cap?

mist the engine in the dark and look for arching.

do you have a recent compression test?

what is the history on the injectors?

what are your fuel trims?


George

 

i appreciate the help!
ive done so much ill try to remember all ive done and do any suggestions asap and report back

fuel pressure was 55 but didnt check for leakdown

all cylinders misfire randomly but 4 is the most and i will switch that plug and wire when i can if u think i need to.. did the same with old plugs and wires

it has a new distributor and contents a few days ago... the old cap had alot of build up but it was from the original motor

i did look for arcing in the dsrk but ill have to look into what you mean by misting

i feel i did a compression test on this engine a month ago when i first got it in and wasnt concerned but can do another and report

the intake and injectors are from the original engine that ran perfect until that bearing thought it was a brake drum

STs <5 LTs close to 0

 

One very odd thing i found while check over my work was the 2 black grounds, i think its g117, on the back of the drivers head have 12 volts when unhooked from block! cant be right... lol

 

If you remove a main ground like that it will have voltage on it because something wants it to complete the circuit.

 

Thank you... dealer just called, plenum gasket, injectors, cap, rotor, and 5 psi op at idle.. its about to get full coverage, lol

 

Thank you... dealer just called, plenum gasket, injectors, cap, rotor, and 5 psi op at idle.. its about to get full coverage, lol

 

fuel pressure 54psi.. hits 0 after 6 secs of turning off... ding ding

 

Now you have to determine if it’s in the tank or at the intake plenum.


George

 

So the fuel pressure tester was faulty. Using a new one the, pressure is at 55 while running and when shut off. 1 pulse of each injector with the snap on put the pressure at 45. Dealer said compression test was okay but need to confirm myself... truck is at work, most tools are at home... time is at a premium, but will update as i know more.. thanks again guys