My Headache ...

[Furyian]

I have an interesting situation. Upon start up, the car is a little hard to start [from what I read all 7M's are a little rough to start at times] but none the less pumping the throttle while cranking gets the job done. However, I must keep it revved for a short period of time to make it idle properly at which point it is fine to drive. With that being said, I have 3 trouble codes detected.

Code 22 - Coolant Temperature Sesnor
[My educated/uneducated guess is that it is caused by the simple fact that the previous owner disable the OEM temperature gauge in the cluster. He [for whatever reason] deemed it okay to just run an aftermarket gauge so the computer looks at the coolant temperature sensor as missing from my guess.

Code 34 - Abnormal Boost Pressure
[This one is probably pretty easy. The most common problem is a boost leak via intercooler piping. However I'm pretty sure it's the fact that the previous owner forgot something in the swap. Originally, the car had a 7MGE in it and he performed the swap over to a 7MGTE. He swaped computer and all but he forgot the thing under the hood that would relay the boost to the ECU. From what I understand, the ECU is setup to read the boost made by the turbo but there is nothing underneath the hood to send the message to the ECU. However, I could be wrong ... it happens from time to time unfortunately.]

last but not least everyone's favorite ...
Code 51 - Open IDL/AC switch aka just a big pain
[Here is the one I'm not sure about. I just changed out the TPS however I still get the code. My next step is to check the wiring going to the TPS. Here is where my headache sets in. I read that the car will perform horrible and real sluggish with a code 51. Unfornately, I have nothing to compare it against as I have never driven a stock or properly running 7MGTE. This is the first Supra I have ever owned and bought the car in the condition it is in. I can get the car to idle fine and I can achieve boost. It pulls alright it's not 100% but I don't find it sluggish. Another note is that the car has no AC what so ever.]

My overall opinion ...
[The car runs pretty well but I find that it is running way to rich which would definitely explain why the car doesn't perform at 100%. Now, do I install the HKS FCon & GCC that came with the car and hope that rights the ship so to speak? Would the FCon help the ECU read the boost properly and the GCC help lean out the engine?]

Any comments, ideas, or suggestions would be highly appreciated.

PS I understand that my unfamiliar nature with Supra's or 7M's may open up all sorts of flaming in my direction but I am trying to make and effort to learn whatever I can ... everyone has to start somewhere

 

[Tire Shredder]

1) the ECU's coolant temperature sensor is a completley seperate sensor from the one that is displayed on your dash cluster. Inspect the wiring and test the temperature sensor as per the tsrm's instructions. most likely it's the sensor.

2)probably boost leak somewhere. inspect all hoses. find it, fix it.

3) Did you calibrate your TPS properly? a brand new tps installed incorrect can throw this code.

 

[Furyian]

I was not aware that buying a new TPS that it would still have to be calibrated. Also, does anyone have a picture of their coolant temperature sensor because I did buy a brand new one but what I have doesn't seem to match up at all and I know what I bought is right. So any pictures pointing it out on their engine I would appreciate. I will also go back over all the intercooler piping and remove and reinstall every clamp. But with the boost sensor missing underneath the hood would that make a difference?

 

[suprarx7nut]

Code 51 will be triggered if the A/C switch sensor piece near the bvsv on the thermostat housing is not connected. I had that problem with my turbo.

You also need to calibrate the TPS though...

 

[Furyian]

Update: Found the Coolant Temperature Sensor ... that is where the good news stops.

The reason I did not notice/see the sensor is because the wires that are supposed to run to it have been ripped out. And to make matters worse, I don't see any trace of of wiring for the sensor and the plug that goes into the sensor is useless ...

 

[Furyian]

Code 51 will be triggered if the A/C switch sensor piece near the bvsv on the thermostat housing is not connected. I had that problem with my turbo.

You also need to calibrate the TPS though...

My BVSV is just bare with no hoses running to it if that makes a difference for anything. The A/C Coolant Sensor Switch? Yeah that is hooked up so I guess I just need to take the throttle body off and calibrate the TPS then

 

[dumbo]

the boost pres. sensor is strictly for the gauge, the AFM tells the ecu air intake. is the waste gate set to 7-8llbs?

 

[suprarx7nut]

the boost pres. sensor is strictly for the gauge, the AFM tells the ecu air intake. is the waste gate set to 7-8llbs?

And if there is a boost leak, he would end up rich, correct? AFM would read more air coming in than was actually making it to combustion?

 

[Furyian]

I will calibrate the TPS when I get home from work but does anyone have any thoughts or suggestions on what to do about the coolant sensor? The plug coming from the harness is destroyed. How vital is it that, that sensor be hooked up?

 

[supraguy@aol]

I will calibrate the TPS when I get home from work but does anyone have any thoughts or suggestions on what to do about the coolant sensor? The plug coming from the harness is destroyed. How vital is it that, that sensor be hooked up?

Someone please correct me if I'm wrong, but If you have no temp sensor connected, the ecu will always consider the engine to be cold, thus you might continue to run the cold start injector, and your engine will be in open loop- AKA- the ecu won't be reading the O2 sensor, thus always rich. Not sure of this, though, I admit. The wiring for it should be in the plastic-covered harness that runs over the front top part of your valve covers, along with the Oil pressure wiring, cam position sensor, etc. Look for it. You have to find where it's been cut, and splice into that to make a connection.

 

[Furyian]

Someone please correct me if I'm wrong, but If you have no temp sensor connected, the ecu will always consider the engine to be cold, thus you might continue to run the cold start injector, and your engine will be in open loop- AKA- the ecu won't be reading the O2 sensor, thus always rich. Not sure of this, though, I admit. The wiring for it should be in the plastic-covered harness that runs over the front top part of your valve covers, along with the Oil pressure wiring, cam position sensor, etc. Look for it. You have to find where it's been cut, and splice into that to make a connection.

That's what I'm afraid of ... So I will try to find the wires regardless but I will have to find another plug to splice on to the harness. I guess anyone would happen to have one handy they could sell me? Are there any other engine harnesses I could get one off of [i.e. going to a junk yard]?

 

[jdub]

Someone please correct me if I'm wrong, but If you have no temp sensor connected, the ecu will always consider the engine to be cold, thus you might continue to run the cold start injector, and your engine will be in open loop- AKA- the ecu won't be reading the O2 sensor, thus always rich. Not sure of this, though, I admit.

No, this is not correct.

If the ECU temp sensor is disconnected the TCCS uses an 80 deg C (176 F) std temp...this is the threshold where the ECU goes from warm-up enrichment to normal ops, so there is no warm-up enrichment. If the engine is cranked when cold, it actually causes a lean condition...the motor will run poorly until it warms up. Start-up and after-start enrichment will be less as well since the ECU thinks the motor is warm...both help stablize the engine.

The CSI only operates during engine crank when coolant temp is low (based on the CSI time switch)...once the motor is started, CSI operation is terminated. If anything, the engine will be difficult to crank when cold.

Concerning open vs cold loop: The ECU is in open loop when coolant temps are below a certain value. With the ECU temp sensor disconnected, this is not the case...the std 80 deg C value is in the normal range. Based on this, the ECU should be in closed loop. However, a disconnected ECU temp sensor puts the ECU in fail safe mode...I am not 100% sure if this directly affects AFR feedback. In any case, open loop will not result in running rich 100% of the time across the engine operating range.

 

[Furyian]

JDUB ... you are awesome dude because it does take a while to get the engine to idle and is hard to start but once it is warm, cranks no problem and idles nicely. That definitely diagnosed my rough start problem. Thanks for the advice/info

 

[Furyian]

Okay I have set the TPS as stated. I turned it until my ohm meter went from "OL" to a small reading ... Now what? I check the codes and I still get a Code 51

Also ... I wasn't able to find a .700MM feeler gauge so I used a .711MM feeler gauge. Will that hurt the calibration?

 

[Furyian]

Ahhhh finally some progress ... I finally cleared the Code 51 and next is swapping out the coolant sensor since I have found where the wires were cut. *prays* Hopefully this will fix my problems and I don't have to track down any possible vacuum leaks.

As always thank everyone for any advice/input

 

[jetjock]

Since you asked I'll be happy to correct you:

1) A disconnected (or shorted for that matter) EFI coolant sensor will result in the ECU interperting the coolant as being hot.

2) Cold start injector operation cannot occur unless the engine is being cranked. Besides, the coolant sensor isn't really involved in it's operation.

3) This thread has a mess of other misinformation in it. Too much to pick apart at this point.

edit: Seems I'm a little slow tonight...

 

[jdub]

However, a disconnected ECU temp sensor puts the ECU in fail safe mode...I am not 100% sure if this directly affects AFR feedback.

JJ - any insight on this part?

 

[jetjock]

No effect. Closed loop will be the same as if the sensor was working and reading hot. Even with a working sensor closed loop occurs long before the coolant reaches normal temp...

 

[jdub]

Thanks! I thought so, but wasn't sure if there was some other subtle effect.