Engine loads up and backfires

[Kirby2]

I have posted before, usually answers say check vacume lines.. they are OK.
When the car backfires(like a hickup, sometimes it goes dead...wait a while and it starts again.
Fuel additives like techroline seem to help, short term. I can't believe I am the only one with this problem. HELP!

[AFJuvat]

Crystal ball is out for polishing this week.

Please state year and model

AFJuvat

[Kirby2]

1986 N/A Manual 944, aftermarket header, k&n drop in.

[AFJuvat]

OK, need some more information.

When does the car backfire? Engine hot?, Cold? after running engine hard, daily driving?

Can you reproduce the problem consistantly?

What kind of gasoline are you putting in it?

How does the car run when it isn't backfiring?

Any other modifications to the car?

When was the last tune up? cap, rotor, plugs, wires, air and fuel filter?

AFJuvat

[Kirby2]

In List order:
Happens hot and cold in daily around town driving.
Happens infrequently, but once started (if no fuel aditive) gets more often.
Using Mobil Prem (91 oct)
Other than backfire runs smoothly(few misses), it does stumble as a prelude to the hickup though.
Ignition is A-1 new plugs,new coil, clean cap and rotor, new wires.
filter K&N (clean), new (1 month)fuel filter.

[Kirby2]

Also: the plugs are clean - no scaling or carbon buildup.

[Scott R]

Maybe a weak or broken AFM causing the load up?

[Kirby2]

What is your experience with rebuilt air flow meters? They are about 1/2 the price of a new unit.

[ae1969]

Take a look at FRwilks site.

If you pop the black cover you will see how this gizmo work..... You can sometimes make a temporary fix. At least it will allow you to test to see if it is the AF.

I am not sure how you could test for a weak AFM spring ... but a bad AFM would explain your intermittent backfires.

I would suggest you look for cracks in the intake side hoses as well. AN intake leak will definitely cause backfires....... ask me how I know!!!!