944 running out of ideas

[bombard]

Greetings, I own a 944 1985/2 NA
Love it, but currently it's got me dumbfounded.
The issue is that the engine bogs down when i try to accelerate, but in waves.
It idles beautifully, but refuses to perform under load.
I've replaced:
Vacuum Lines
All air hoses
AFM (got a used one, so it's questionable)
Fuel Pressure Regulator
Fuel Pressure Damper
Injectors
Spark Plugs
Spark Wires/Coils
Speed Sensor
Reference Sensor
https://youtu.be/D-x1K74jlNg

[rick13]

What is your fuel pressure at the rail?

[v2rocket_aka944]

Fuel filter, or the DME temperature sensor is faulty.
Mine would have very low power at heavy throttle inputs, turned out the bad sensor was making the car run really lean aka no power under load.

Swapped the sensor, all was well with the world.

[Jfrahm]

Yeah based on the surging it could be a classic case of a lack of fuel flow. If the filter has never been replaced that's a sensible thing to do as well as the testing of the DME temp sensor, preferably at the DME in case there are wiring concerns. If it's still boggy you could try to install a fuel pressure gauge you can watch while driving to see if the pressure is constant or see if it will pass a fuel flow test. The fuel pumps are pretty robust but they can wear out. It's also possible (but not likely) that the in-tank prefilter is badly plugged, I think it's the 928 part 92820108104.

[mytrplseven]

Have you checked the catalytic converter? If it's plugged it can cause acceleration issues.

[jhowell371]

Underside of J-boot cracked?

[dgcantrell]

Yeah.. If you've not replaced the j-boot, after 30 years, I recommend it.. Mine was split underneath. When I pulled it off, it came apart right where the flex bellows are.

[mytrplseven]

Mine, too, especially where the 1" vacuum hose is connected underneath.

[75ohm]

Originally Posted by mytrplseven

Mine, too, especially where the 1" vacuum hose is connected underneath.

Also check the intake manifold <-> brake booster hose... I forgot to put that back on once and lost my sense of humor over it...

[bombard]

The fuel pump and filter have been replaced, guess ill have to try the J-boot and temp sensor next
the boot seems to be in good condition, i've removed it multiple times in this effort to smooth things, and the weren't any visible discrepancies, but 30 years is long enough, i suppose...

[944matt]

J boot might do the trick, seems like it's a vacume leak or a fuel pressure problem

[bombard]

Good and bad news, the catalytic converter is fine, car still tripping out... i'll post an update once the DME temp sensor arrives.

[Rasta Monsta]

How many volts when running? What kind of spark plugs?

[944tothefloor]

What's your gas mileage / fuel consumption?

[CatsEyes]

Clark's Garage explains how to check the following sensors:

* engine temperature sensor (as advised in previous posts)

* AFM

* Idle control valve/AAC

* throttle position sensor/switch.

You've replaced a lot of stuff, and spent a lot of money. But simply testing resistances with a multimeter can save a lot of cash...

[bombard]

Given that its been 30 years, i figured replacing some of the parts wouldn't hurt. i've checked the DME temp sensor and it works fine, i've ordered another O2 sensor, figured it's about time it needed replacing either way. I can't exactly calculate the fuel consumption right now, i can't get it to rev steady to shift gears, so i haven't taken it out onto any main roads.

[Bukowski]

still hoping to hear the Big Solution to this one...

[djnolan]

I had this situation once. I was like a dog chasing its tail. It turned out to be an arcing spark plug wire. At the time the symbology eluded me.

[callmethewander]

It still eludes me...
???

[bombard]

So I've replaced the O2 sensor and am still where I started, and not sure when I lost it, but oil pressure is now nonexistent, and it seems that the oil inst getting up into the valve cover.