Major Backfire + Anyone seen my muffler?

[st0878]

I just bought a 75 280z. I have been doing alot of major rust repair for a 4-5 weeks so I'm just geting around to trying to make this thing run. I thought that I had it almost there untill today I took it out for a very short spin. When I accellerate slowly it seems to run pretty smooth but if I push the peddal too hard it starts to buck and misfire. I had a car comming right at me so I guess I dug my spurs in a little too hard beacuse I blew seam right out my muffler. I've been trying to get the engine running right for a few weeks and have had problems running really rich and really rough. I changed the plug wires, cleaned the injectors, put in a new PVC, fuel filter, ripped out the cataletic converter and finally I put a new exhast/intake gasket and flange gasket. I guess I had a major vacume leak because the gasket seemed to make a big difference. Well before I tore my muffler a new one. I saw a huge cloud of black smoke and the car sputter-pops on down shift. Well tomorrow is Monday and I still don't have a ride... As my wife and neigbors are starting to give me the harry eye ball, I'm swallowing my pride and asking for a little help. You guys are great and I've gotten alot of good info from the site.

Thanks

EZ

[seerex]

have you checked your timing and your ignition parts , rotor, cap and such?

[st0878]

Yep. New wires and the cap looks pretty good. The coil is probably the original though. I don't have a timing light so I'm not sure that the timing is off or not. The engine seems to only have this problem when under load. I can rev the engine at a stand still and it runs great. I am inclined to believe that the engine is running rich but I don't know how to lean it up.

[TomoHawk]

Can you legally remove a catalytic converter? I know the muffler guy asked me if there was one there, because he could NOT remove it legally.

[st0878]

God bless Florida....good weather and NO emissions!

[st0878]

Actually Florida had an emission program until a few years ago and they shut it down because an entire industry was evolving to circumvent the system. Even if it was still operational I think that cars over 20yrs could be classified as collectors and exempt from the program. When I cut out the catalytic converter I found out that it was a fake anyway...solid pipe strait through.

[mdbrandy]

Check out the FI Manual at:

http://www.72hours.net/~zcar/

For the problems you're having, it tells you to go through the ignition system first (which you've apparently done), and then indicates you might look at the air flow meter.

Good luck.

[TomoHawk]

I think he has carbs on the early 280.

[mdbrandy]

Originally posted by TomoHawk

I think he has carbs on the early 280.

All 280's are injected, and he says in his original post that he cleaned the injectors, so I suspect not :classic: .

[sblake01]

Originally posted by mdbrandy

All 280's are injected, and he says in his original post that he cleaned the injectors, so I suspect not.

Based on what st0878 said, that would have been my guess. But seriously, When I experienced a similar problem, it turned out to be the coil. A bad AFM could cause the richness he speaks of however.

[st0878]

You know I forgot to mention that when I pulled the injectors out I dropped one on the ground and broke the plastic cap and the little atomizing pin. So I ran over to ebay and there was a set of injectors from 81zx with 40 minutes left on the auction. So now I'm wonder if the flow rates on the ZX are higher because they are turbo? Also one of those was bad so I mixed in one of my old 280z injectors in with 5 zx injectors.

[TomoHawk]

While you're at it, maybe you could check all the injectors you have to see if they work, drip, or what? I think you just pull them out, pull off the wire from the coil-distrubutor, and have somebody crank the engine. Spray fuel in a bucket.

Don't spray yourself! It'll get UNDER you skin!