at what temp does computer go into open loop?

[speadfreak]

The motor in question is bone stock speed density motor. It runs fine until it gets to about 120 degrees or so. Then it leans out to the point to which it eventually dies. Let it sit for awhile and it will be fine until it heats up again. It never did this until I put the OR x pipe on it. I think I might have damaged the O2 sensors in the process and this is the problem, but O2 sensors aren't really all that cheap and I don't want to change them if it's not the problem.

 

[HISSIN50]

It's not so much a black and white coolant temperature with regard to OL vs CL. The O2s are heated, so it takes the heater element ~ 30-120 seconds to light them off. THen their input is utilized, regardless of most-all cooalant temps.

You mentioned that it leans out till it dies - what AF are you reading? The SD motors often default rich when an O2 issue arises, hence my asking.

I would pull codes and check things like the ECT's calibration.

Good luck.

 

[dragnazz5.0]

i wasnt aware that the o2 sensors on our cars are heated...but i could be wrong (wouldnt be the first time)


edit: nevermind...im retarded....i guess my brain isnt working right now

 

[speadfreak]

ok.........update........even when the car had sat for awhile today, it still did the same thing. Definately starving for fuel. The FP test port has some big screw in it and has been JB welded , so I can't really test fuel pressure right now. I have no idea what the AF reading is. This motor is completely stock, so I have had no reason for a wideband or even a stoich guage. The only thing I did was put the OR pipe on it. It ran fine before. I unplugged the O2s and it didn't make a difference. I can tell you that when the car stumbles then dies, I can hear fuel gurgling through the rails or lines for about 3 seconds. I had my wife cycle the pump with the key..........when the fuel pump loads up then shuts off, if you put your ear by the tank filler you can hear fuel dump back into the tank. I thought this was probably normal on a return type system, but when I tried the same thing on my blazer and the wifes GTP, I cant hear the fuel run back into the tank. Just a stab, but kinda makes me think it could be a regulator problem. I'm gonna try to "unrigg" the FP schrader valve tomorrow.....that would definately tell me if I'm correct. Kinda sucks cuz I got this car on Ebay ending tomorrow and I gotta figure it out before new owner takes delivery.

 

[795.0pacecar]

If its starving for fuel try changing the fuel filter. Unplugging the O2s isn't a good way to make sure they are working, the computer will use stored values in their place to keep the engine running.

 

[HISSIN50]

Have you had a FP gauge on when it stumbles and dies? That can help rule out a bad regulator (if pressure holds, chances are it aint the pump or reg). I'm just trying to keep you from having to un-rig something since time is of the essence.

Gotcha about not having an AF gauge - you mentioned it leaning out and I wasnt sure how this was known.

Good luck.

 

[speadfreak]

last night it was running so rough, even after sitting for a couple hours, I could hardly get it into the garage. I just came home from work and it started up fine and runs fine. Like I said, none of this started until I put the OR x pipe on it. Might just be a coincidence, but I'm half tempted to go get some new O2 sensors and through the cats back on it. This is just my luck, the auction ends in like 4 hours.

 

[795.0pacecar]

Not having cats isn't the problem.

Pull the codes to see if the computer can tell you whats up.

Check the O2 sensor wiring, it could have gotten burnt on the new pipes.

 

[speadfreak]

Not having cats isn't the problem.

Pull the codes to see if the computer can tell you whats up.

Check the O2 sensor wiring, it could have gotten burnt on the new pipes.

Like I said, the car started fine after work today. I sat in it and let it idle. It idled and would rev up perfectly until the point when the temp gauge hit the "M" which is approximately 180 degrees, then it instantly went to having the same fuel starvation problem. I shut it off, disconnected the battery for a half an hour, started it back up and it did the same thing........idled fine until the temp got to 180. I pulled the 02 sensors out and found that a white wire on one had been crimped off and was only hanging on by the silicone insulation. The other side has one of the three little slits dented (closed off). So obviously the computer is not pulling information from these sensors until approx. 180 degrees. I'm gonna pick up some new ones tomorrow and hopefully this will solve the problem. Everything points to these sensors being the problem. If someone disagrees, I'd like to hear an alternate solution before I possibly waste $60 on new 02s.

 

[speadfreak]

I changed the O2 sensors and the problem still exists. The car sold for $5100 last night, but now because of this problem the guy has been scared off. That's ok, I hoped it would bring more money anyway. I watched very closely today when i started the car. Ran fine until it hit 180 degrees, then it started to stumble.....then the thermostat opened, the temp dropped, engine smoothed out until the temp got back up to 180, then it slowly stumbled to a stop and would not start back up. Could this be the TFI module?........I don't think the TFI actually controls anything in closed loop, does it?...........could a bad TFI cut fuel like this? What about the PIP? ECT?.......could any of these cause this problem?

 

[HISSIN50]

The TFI is a critical part of the ignition system.

I saw you mention disco'ing the battery (to clear the KAM, I presume). If you dont do this, will the car start right back up after it stalls? If not, you can check for spark.
What's your FP guage showing right as it dies?

You can have your TFI tested at the parts store if you desire. Have them do it repeatedly (to heat it up). When functioning properly, a TFI's critical temp is ~257*F. If there's an issue, that figure can be significantly less.

Good luck.

 

[speadfreak]

Ok, I completed the mass air conversion today. Started up fine, surged a little, it smoothed out, had to turn the idle down for some reason. Seem more responsive when reving it........then it got warmed up and shut off again. I guess I can rule out the ECU being the problem.

 

[speadfreak]

problem solved..........TFI module was bad. I replaced it and it totally fixed the problem. Hope this helps somebody in future searches.