944ryan

1986 944 NA
Backfires Under load only revs to redline in neutral
Misfires and backfires or both not sure, Bucks, Jerks, hesitates, and violently lunges forward and backward in 3-4 k rpm range when problem occurs
Not effected by unplugging 02 sensor or tps
car starts drives fine under 2900 rpm you could drive my car all the time keeping revs under 2.9k rpm you would never know there was anything wrong
after driving for about 15 min at WOT or any hard or quick acceleration basically me flooring it will result in the issue
When experiencing issue I can ease off gas back below 2900 rpm and all goes back to normal and all power is regained or I can slowly push the car when it hesitates but continues to backfire. seems like im forcing it and it really doesn't wanna go past 4k and I don't wanna push it too hard
Again at WOT or hard throttle it will stop me at 3k rpm
HOWEVER I can get issue to completely go away. when I experience the blockage in throttle response I can turn the car off and back on wile driving it and the problem disappears for about 15 min. like I said completely gone car will go back up to redline like usual and behave great then happens again
CAN ALWAYS get issue to go away but its annoying turning your car on and off haha especially when your driving!
always RUN GOOD min 91 OCTANE FUEL
AGAIN have great power up till 3k rpm ALWAYS
problem always After 3k rpm

Things iv done that could have effected it
NEW
LR coolant hose kit + Vacuum hose kit
ignition Rotor
Cylinder head rebuilt new valves ect
fuel pump- Brand name Carter I have my doubts its too loud to me? maybe blocked?
plugs
clutch

tired
unplugging 02 sensor = nothing
unplugging tps = problem still only smooth's out idle ( not my issue)
no vacuum leaks at all, GOOD THERE

THINGS I THINK IT COULD BE
bad speed sensor -has a crack and I have a new one but would like to save this as a last resort looks like I gotta take the beellhousing out or drop the clutch to replace mine is stuck.
clogged cat - whenever car is restarted stuff is moved around inside allowing partial flow?
clogged fuel filters in tanks and post pump buth never been touched and could be repressurized when car is turned off and on then allow flow
Bad tps - since idle smooth's out dramatically
bad fuel pump - loud
bad injectors
incorrect gapped plugs
bad distributor cap
bad coil under load
bad spark plug wires
incorrectly adjusted idle
knock sensor

Weird things and more info
this issue is not effected by more electrical strain example heater, wipers,defrost ect always the same
not effected by the rain
Hot air always in cabin even when heat and vents are closed
Strong smell of fuel in cabin and smell of another weird smell not sure just smells weird like ozone haha

Please help me!!!!

944ryan

Please help!!!!!

944hal

My S2 started idling rough and just quit on day. Had it towed home. Problem was a cracked reference sensor. So.....looks like you might have to unstuck yours to find out.

Funn944

I had an issue some time ago similar to this. Car had been sitting for awhile as I did a bunch of other work to it. I couldn't figure it out, took it to The Winning Formula in Louisville when I lived there. He took it for a test drive and told me right away......bad plug wires. Pulled the plugs, cleaned inside the wire caps, and the porcelan on the plugs.....fixed.

mro763

Check the mass air flow meter, which controls air intake; back fires can cause a warp and binding flap within the unit causing similar issues. I would change the fuel filter if you haven't already done that. You might also have a bad catalytic converter which may cause similar issues. Start with checking all exhaust, then all the fuel system and then systematically check all electrical sensors, etc. Good luck!

Tiger03447

You might start (cheaply) by putting Isopropyl alcohol in the tank..Commonly referred to as Iso Heet. You may have some water in the gas, especially if this occurs on hills...might help in curing some of it..Also have you run any Lucas Fuel Injector cleaner through it lately...?? Two cheap fixes before you start throwing heavy $$ at it...jus sayin...

944ryan

Ok im unable to try anything to the car now I'm very busy and can just think about what would fix it. I appreciate all of your replies and took all of them into account. Im not really sure what to start trying i think its electrical? My only real clue is that i can get the problem to disappear when i turn the car off and on, did you have this with spark plug wires or speed ref sensor wires? I think putting barrymans into the system would help but since the strainer and filter are original i figure just replace them. Any other help is appreciated. I will keep posting updates of how i fix this issue within a week or so.