280z Engine misfire, backfire & bogs down while driving

[pnkrkz]

Car is a 78' 280z

 

Okay, first off the problem(s):

1. Car starts fine idles around 800-900 rpm.

2. during idle, there is a slight hesitation you can hear from the engine after 4 Mississippi's

3. When revved up and let go of throttle, car would backfire

4. Now, the biggie...when driving in the street, the car runs fine for about 10 minutes (running gears from 1-4 at around 0-45 mph) or so and then it just bogs down (no power)then put the gear in neutral the engine revs but seems to misfire and when you put back it in 1st gear the engine sputters, backfires, car runs in crawl less than 10 mph. really annoying and dangerous. I am trying to get this 2 yr. project out of the garage and hopefully focus on the cosmetic problems rather than mechanical and electrical. Thanks for your help.

 

other things i noticed -

engine gets hot pretty quick (compared to the my other z)engine temp gauge 1/4 away from max temp.

i keep losing coolant in my reservoir after driving (no leaks though)

 

 

2nd off, here is a little history of the engine:

 

Engine block is fully rebuilt L28e from top to bottom new pistons, rings, etc. The head is a p90 with solid lifters, adjusted and 3 angle valve job and new valve boots, seats, etc. The fuel injectors are from the original car not rebuilt (no leaks), starter injector (no leaks), fpr is original(btw already checked fuel pressure it's at 30 psi, when revved it slight goes north of that and then once you let go it goes down to 28 and then goes back to 30.), dizzy i have is from a 280zx the one with 3 wires (ground, red and green), it has a header and a straight 2.5" exhaust from Motorsports auto, intake manifold top and bottom (pipe that goes into factory exhaust manifold) are blocked off. TPS checked okay. AFM is set to where it was factory (haven't done anything to it, only took out the cover to see if it gets stuck. Timing is adjusted 10 deg advance (if i placed the timing to 0 deg, it backfires even more just to let you guys know). One more thing, the tang timing for the distributor shaft is 180 degrees off, I already adjusted the order of the spark plugs per

 

here is a video that i took hopefully this helps:

[CruiZZZin 78]

Sounds like your on the right path to tacking down the problem. I have the same car that used to have the same problem. Have you done a wiring/component diagnostic through the ecu? I don't have the manual any more because my computer was stolen unfortunately. Have you checked for all vacuum leaks? Have you checked to see if the vacuum advance holds vacuum? The intake boots can be cracked like mine were.

Edited July 15, 2010 by CruiZZZin 78

[pnkrkz]

Thanks, I actually got the problem fixed by recoating the gas tank and replacing all the fuel lines in the back end of the car. The fuel pump was being clogged by the rust and varnish from the gas tank, which is why I think it would bog down when the car accelerates, which in turn starves of fuel. The pre-filter from the fuel pump was so clogged that there was no way for me to remove it without ripping it to shreds. I ended up adding another inline filter between the tank and fuel pump. Now it runs great, I would still get an occasional backfire once in awhile, but even w/ that I still passed smog.