stange problem

i would check the fule system...maybe clogged or dirty injectors...sludge in the bottom of the gas tank...have you recentaly almost run the tank dry?..sounds like fule not electrical to me...

The backfiring suggests ignition problems in my opinion. Might be worth checking the basics like rotor, distributor cap, spark plugs. Check that you have enough spark. Does the problem vary with weather? Hot/cold, dry/wet?

If you have a catalyst, you have electronic injection and ignition, and the two are interlinked. To get more more specific help, you should if possible state what kind of engine, what country/state the car was sold in. Not all '86 were equally equipped. In Europe there were cars with K-jetronic mechanical fuel injection for example.

As far as I know, the fuel pump relay either works or quits (Þad engine). I think it's safe to rule that out. That's about as far as my limited knowledge about the fuel system goes.

Fuel pump relay gives intermittent problems at first and can be very misleading.

Cheers, Peter.

it was the fuel pressure regulator, also right after i fixed that, the ignition coil gave up and had to replace it too. thanks for all the advice and ideas for what to look for.