Rewired TPS, new and worse problem now.

[Kontakt]

Initial problem: Car would occasionally sputter while driving. Fiddling with TPS plug or wires coming from plug would relieve problem, if it didn't go away on its own in a few hundred feet.

Put 100 miles on car this morning, mostly driving well. 1 trip to 7k in 3rd, pulled like an NA should. Was running fine when parked to do this:

I re-wired my TPS. To be specific, I ran all new 22ga wiring from the TPS all the way to the ECU where I cut and butted the two signal wires from the ECU into the new wires, and I cut the ground on the ECU side of the existing split to make sure all wires stayed grounded in case there was a split in another part of the harness I didn't know about. I aslo added an additional ground to this point.

When I started the vehicle, it sounded a little rough but ran up to 3k and when idle fell it died. It was flooded.

I re-set my TPS with the ohm-meter-test-connector method to no improvement (although, it was off).

I can get it around the block with effort, and i can rev to 7k in neutral with light even throttle input. If I gas it hard at all it is like all spark goes out immediately and when I let off the throttle it bangs out the exhaust (first fireballs were supposed to be at speed, not parked :(... 1k on my rebuild).

Hard throttle and it falls on its face at any RPM.

[FRED]

This a series WHAT car?

[Kontakt]

This a series WHAT car?

I apologise. S4 NA.

If I rev it to 7k in neutral and then go WOT, it will fall to 0 rpm without so much as a single firing trying to save itself. If, while it is falling, I let off the throttle, it will bang a fireball out the exhaust and recover.

[Kontakt]

The problem is identical with TPS plugged in or unplugged.

I am almost certain it is not the TPS, although that hasn't stopped me from keeping on checking it over and over again.

I feel I bent a wire going to something and it died of old age, but I have no idea what it could be.

I used a DVM on the ECU plugs checking against the FSM at idle and with ignition on but engine off. Everything there seems ok.

It runs the same on just the leading coil.

It has to be ignition cut IMO. If it was too much fuel it would be less like an on/off switch.

I have no idea what would cut ignition based on throttle in put though.

[Kontakt]

Ok, this problem has been resolved, but the reason I re-wired the TPS is still there.

Turns out the TPS ref voltage (brown wire) also feeds the AFM ref voltage, so I had eliminated my AFM... Added that to the splice and the car is now exactly as it used to be (driveable).

The problem now, is that it still occasionally stumbles for no apparent reason, and then suddenly brings itself back.

It always gets down the road, but sometimes it really is limping. Idles fine. TPS works fine (I have 3 of them, they all work fine).

I believe that the problem is still electrical (otherwise, how would poking the wiring harness with a stick fix it when it stumbles), but I don't know at this point.

I will leave my DVM hooked up to the primary injector (one at a time of course) pin on the ECU as I drive around to see if it goes nutty when the car goes nutty. Hopefully that gives me a clue before I go ahead and pull the UIM to re-wire my primaries.

Edit: FWIW it did this before I rebuilt my engine as well. My injectors have been cleaned and flow tested.

[NoDOHC]

It appears that you are quite good at troubleshooting, you also don't seem to have any fear of tackling a wiring gremlin.

My theory is that the wiring to your MAP sensor is corroded - specifically the ground. My S4 NA did exactly the same thing and re-grounding the MAP sensor made the problems go away.

I also would clean the engine grounds and the ground on the drivers shock tower.

Hope this helps!

Bear in mind that the S4 only uses the TPS for light throttle cruising.

[Kontakt]

It appears that you are quite good at troubleshooting, you also don't seem to have any fear of tackling a wiring gremlin.

My theory is that the wiring to your MAP sensor is corroded - specifically the ground. My S4 NA did exactly the same thing and re-grounding the MAP sensor made the problems go away.

I also would clean the engine grounds and the ground on the drivers shock tower.

Hope this helps!

Bear in mind that the S4 only uses the TPS for light throttle cruising.

I had some good people on the phone (thanks Brian(s)), and strong motivation. Today is my girl's 30th and I was gonna be damned if I wasn't gonna drive over early and surprise her. :)

Thanks for the tip. I'll have to give that a shot tomorrow when the sun is back.

[Kontakt]

So uh... while you're here...

Where is the MAP sensor on these lol?

When I search MAP sensor it seems to ignore the MAP part of it entirely. You seem to have experience. :)

Thank You!

[Pete_89T2]

Where is the MAP sensor on these lol?

Is this a turbo or NA? I think the general location is the same for both, but on the turbos, it's located on the passenger side strut tower. Look for a small black rectangular box, about 1"X1-3/4", with a wiring plug & vacuum hose attached to it.

[NoDOHC]

This is NA (He mentioned earlier). I think that Mazda calls it the pressure sensor or the boost sensor. Pete_89T2 is right, the MAP sensor (pressure sensor) is mounted between the passenger's shock tower and the airbox. You can find it by following the vacuum line from the LIM (or maybe it is the bottom of the UIM). Please bear with me, I gave the stock ECU up over 5 years ago

[TitaniumTT]

Hmmmm, and I thought I was the only Brian in the world..... who's the other one? Sorry bout not getting back to you via txt.... fighting the FD from hell today and wouldn't ya know, it was a haltech issue :banghead:

Map sensor is on the pass shock tower. I think it would behoove you to go through all the connectors and back probe them lookilng for voltage problems or resistance back to the ecu. This is why standalones, even the rtek are so powerful, even as diagnostic tools.

[Kontakt]

Hmmmm, and I thought I was the only Brian in the world..... who's the other one? Sorry bout not getting back to you via txt.... fighting the FD from hell today and wouldn't ya know, it was a haltech issue :banghead:

Map sensor is on the pass shock tower. I think it would behoove you to go through all the connectors and back probe them lookilng for voltage problems or resistance back to the ecu. This is why standalones, even the rtek are so powerful, even as diagnostic tools.

I did check voltages at all the pins on the ECU at ign on and idle. That's how I found the AFM signal wasn't coming back.

I haven't been able to check them all while it is running poorly though. It's hard to get it to stay in that state.

I'll check the resistance of all of the wires in the harness back to the ECU next time I have a free 3 weekends. ;)

I thought I had it today, but I don't. There is a ground splice right by where I have to poke the harness to make the car run right, and it was for shit. I took care of that, but it did it again when I gave a friend a ride home.

The way the harness is right now though I can poke individual wires while it is running, so maybe that will help.

I could always just set up a little arm on a cable going into the passenger compartment, and when it acts up just pull on the cable to poke the wire. ;)