Driveability troubleshooting 92MTX

[DPHRAG]

Well, It's a 1992 MTX, 167k. I bought it and have been driving it since the beginning of this year with seemingly good luck so far. My main complaint is having to run the A/C to keep the engine fan on. Some genius decided to try to bypass the stock fan controls with this prize:

I finally traced it today and figured out how it works. There are two relays and a coolant fan switch (I dunno what temp. it switches at though, too high apparently) When I ran into this:

WTF, is that the ECT? In it's place is the "switch" for my rat's nest above. I only found two things that look like temp sensors, the one in the rear near where that is dangling, and one in the front with one wire connected which I think is for the temp gauge.

It always has barely ran when cold, and finally would smooth out as it warms, but I'm thinking if that's the coolant sensor for the ecm then of course i'm going to have drivability and fuel economy issues.

It also will barely even run on 93 octane without spark knock under load.

Here are some codes I have pulled:

KOEO
211 - PIP circuit fault
219 - SPOUT signal defaulted to 10 degrees BTDC / SPOUT circuit open. (the jumper is there)
542 (It stalled, i know)
557 - Low speed primary fuel pump circuit failure.

KOER
116 (I know)
225 - Knock sensor (KS) not sensed during dynamic response test.

OH! I also found THIS:

looks like some kind of map sensor? with no vacuum line connected!! ahh!!


How do you guys think I should proceed with the cooling fan thing? Obviously if they took that much effort to bypass it there is some sort of problem. But #1 objective is making sure the ecm knows what the temp is. I can use some kind of fan controller switch that mounts a probe on the radiator I guess. I dunno!

 

[DPHRAG]

Oh yeah, also, the motor died during the KOER test, right after I got the knock sensor code. Should I run it again and see what happens? Or replace the knock sensor and coolant sensor before I try again?

 

[93superSHO]

Get that thing out of there and put the ECT back where it is supposed to be(top pic, lower left). It runs so bad because the EEC has no idea what temp the engine is at and the other codes are probably do to the fact that the EEC is staying in "loop" mode. I would start with that and it will more than likely take care of the other issues. W/o the correct ECT signal the EEC is running "blind". That's why you fan is not turning on.

 

[AutoSHO]

Buy a new ECT and put it in where it is supposed to be. Reset the computer and try pulling codes again to see where it gets you.

And, if you can, get rid of that horrific mess of wiring!

Also, the MAP sensor is not supposed to be connected to anything- it is actually used as a Barometric pressure sensor (you'll hear it referred to as BARO or BAP sensor).

As far as the knock sensor... Make sure when you do the test that you put your foot to the floor and rev the engine to at least 3000 rpms. This will give the car a chance to knock and give the computer the feedback it is looking for.

 

[DPHRAG]

I'm hoping the stock ECT sensor was messed up and that's why they took it out and why the fans weren't coming on in the first place. Should I just pick one up at advance, or is there a ford part# I should use?

I basically wanted to confirm that that was in fact the ECT, because I can't imagine someone pulling it out ON PURPOSE.

Thanks for your help, I will definately start there and let everyone know how it goes. The knock sensor looked original so I will probably go ahead and replace that while I'm at it.

 

[projectSHO89]

Leave the KS for later. Fix the important stuff first, like your ECT, fan, and PIP/ignition issues.

Knock sensors don't fail very often. Usually, when they set a code, it's due to something else, most often testing procedures.

Steve

 

[DPHRAG]

Replaced the ECT with a new gp sorensen unit from advance today and reset the ecm. I drove it around a little afterwards and it seems I have gained alot of lower end throttle response! I used to have to slip the clutch at around 2000rpm just to get it to go without dieing, but now if I want I can putt off at about 1300rpm. Seems alot smoother and less jerky with the power delivery (I thought it was axles or motor mounts or something)

Idles about 950rpm, whereas before it was a little above 1000. I know it has some other issues but this seems to be a good step in the right direction.

The weather has been too crappy to check the codes, but as soon as it stops raining I will be out there.

Thanks alot guys.

 

[AutoSHO]

Out of curiousity, what kind of fuel economy were you getting prior to that fix? It is very possible your onygen sensors are trashed from the car running rich for a long time.