94 Q45t FPCM and Knock sensor Question

[ahardb0dy]

I just replaced the plugs and cleaned the TB, took the car for a ride and it doesn't want to move, if you floor it sometimes I hear a poping noise under the hood, I know from previous posts that the knock sensors being bad retard the timing and that's what I thought was happening here, BUT if I flip the switch I installed to bypass the FPCM the car runs fine, downshifts no problem, RPM's rise nice and steady. So My question is why does bypassing the FPCM make the car run good if it still has the code saying the knock sensors are bad? Thanks

[3Q Jay]

sounds like 2 different issues. car will still run when you floor it with bad ks and should gain rpm smooth, just that the timing is retarded. but if the high mode of the fpcu is fried, the fp will shut down when you floor it (high mode trying to engage). as you already know, the bypass switch will force high flow mode.

[mattd1979]

How do you test a 3 modes of the fuel pump? I may the same problem with the fuel pump because my car doesn't seem to have the power it should and when I put my foot to the floor, it will bog and if I keep my foot to the floor long enough then it will start to catch up and then go. I also notice that when I am on the highway, I start to hear pinging like I have bad gas when I accelerate. Right now I am trying to locate an inline fuel pressure gauge that I can hook up to the fuel line.

[3Q Jay]

easiest way to check high mode is to unplug the fpcu harness, and jumper pin 8 of the HARNESS(i think---goin by memory on the number--look for the one with brown singe marks around it on fpcu side) to ground.

looks from another post that you did indeed try that.

may not be all of your issues, but i'd try the tps voltage. s/b 0.44V at hot idle. adjust your accel cable slack (careful to still leave 0.25 in vertical play at HOT idle). if you can ge to about 3.5V on tps WOT position, you should be able to hit first from about 30 on a kickdown. may solve some other issues, too.

idle smooth you say?