project car pain

[Jerryl]

cool, thanks, ill give it a try and post back

Slow down, and go back and read post #6.

 

[nickd2689]

I really cant afford a scan tool right now, but the ECM isnt throwing any codes, I have air, fuel, and spark, so what would the scanner do for me? the car will run if i give it gas while cranking, but it runs like junk. I would really like to get a scanner, i just cant afford it yet, is there any way around it for now?

 

[Jerryl]

I really cant afford a scan tool right now, but the ECM isnt throwing any codes, I have air, fuel, and spark, so what would the scanner do for me? the car will run if i give it gas while cranking, but it runs like junk. I would really like to get a scanner, i just cant afford it yet, is there any way around it for now?

Nick,
Allow me to clarify: Verify the TPS wires, and/or change the TPS.

 

[nickd2689]

Ok, so I found 4.8xx volts at the TPS when it was closed, and .810 volts when it was at WOT. This is what happened last time when I swapped the TPS out with one from Jays GN. I also unplugged the MAF sensor, and the car still wouldn't start. I forgot to plug it back in before I checked for codes, and all I got was code 12. shouldnt the MAF throw a code if its unplugged? What about the TPS? i know code 12 is supposed to be there when the car is off. Where should I go from here?

 

[BRAD_PADGETT]

Ok, so I found 4.8xx volts at the TPS when it was closed, and .810 volts when it was at WOT. This is what happened last time when I swapped the TPS out with one from Jays GN. I also unplugged the MAF sensor, and the car still wouldn't start. I forgot to plug it back in before I checked for codes, and all I got was code 12. shouldnt the MAF throw a code if its unplugged? What about the TPS? i know code 12 is supposed to be there when the car is off. Where should I go from here?

I smell an 86/87 TPS sensor on your hot air. The readings on your TPS are reversed from normal. Below is a PIC of the 84/85 TPS sensor. The 86/87 TPS sensor has the lever on the right side as opposed to the 84/85 sensor which is on the left. Code 21-TPS too high,code, 22-TPS too low, code 33-MAF signal too high, Code 34-MAF signal too low.
Reverify which TPS sensor is on your car and repost. Thanks- Brad

 

[nickd2689]

this is looking at it from the drivers side fender, the lever is to the left, so this is the 84/85, why would my voltages be reversed? i couldnt get the pic to paste because i took it from my cell and emailed it so it is attached. thank you.

 

[BRAD_PADGETT]

this is looking at it from the drivers side fender, the lever is to the left, so this is the 84/85, why would my voltages be reversed? i couldnt get the pic to paste because i took it from my cell and emailed it so it is attached. thank you.

From where this picture is taken from, the lever should be closest to the fender with the gas pedal not pushed down at all. Still sounds like an 86/87 TPS. Recheck. Thanks- Brad

 

[nickd2689]

ok, if youre sitting in the driver seat, with the throttle completely closed the lever is all the way to the left, (or the driver side fender). so what do you think? could there be a problem in the circuit? maybe the computer? shouldnt it throw a code since its obviously messed up? thanks for the help!

 

[turbonut85]

this is looking at it from the drivers side fender, the lever is to the left, so this is the 84/85, why would my voltages be reversed? i couldnt get the pic to paste because i took it from my cell and emailed it so it is attached. thank you.

What's up with the two wire nuts?? Could you...(or someone)...have reversed the 12v and the ground to the sensor?? This would reverse the polarity in the circuit to the sensor....

 

[BRAD_PADGETT]

What's up with the two wire nuts?? Could you...(or someone)...have reversed the 12v and the ground to the sensor?? This would reverse the polarity in the circuit to the sensor....

I agree with Keith. I failed to notice the wire nuts. The next step is to verify the wires. I can look up the correct TPS wiring in the morning if nobody posts by then. Brad

 

[nickd2689]

the wire nuts are from when I had the last tps sensor, when I noticed the voltages were reversed, i thought to try reversing the wires, I dont recall what it read that way, but I do remember it was incorrect, so I switched them back. Ill verify them again tomorrow morning, but shouldnt it still throw some kind of TPS code?

 

[Jerryl]

Ok, so I found 4.8xx volts at the TPS when it was closed, and .810 volts when it was at WOT. This is what happened last time when I swapped the TPS out with one from Jays GN. I also unplugged the MAF sensor, and the car still wouldn't start. I forgot to plug it back in before I checked for codes, and all I got was code 12. shouldnt the MAF throw a code if its unplugged? What about the TPS? i know code 12 is supposed to be there when the car is off. Where should I go from here?

The MAF and TPS code won't set untill the car starts and runs.
Car will start with MAF unplugged.

FWIW: The TPS get a VERY stable 5V signal from the ECM, not 12V.
What is happening is the ECM places the car in "clear flood mode".

Fix the TPS and I bet the car will start.

 

[nickd2689]

right, just about all sensors get the 5V reference voltage, but what is flood mode? I dont understand why/how A TPS sensor is preventing the car from running, I believe you, but could you explain how that works?

 

[nickd2689]

Also, I replaced the TPS sensor already this last summer, so is it possible that there is another problem thats causing them to go bad like that? The one i bought was used but it still seemed to work well for a while. I just dont want to blow 138.98 for it to go bad again. thank you.

 

[kulungi]

I just bought a 1984 GN with 89000k it in dam good shape. I idles aroung just under a thousand RPS ans is a little rought but no bid deal. From what I gather they all do that. When I bought the car is did idle worse so I cleaned out all he ducting full of all kinds of nasty guwp oils and very dirty carb. I cleaned it all out and began driveing the car. I thing they do;t like to sit for long periods of time. I try to drive it when ever possible. I though mine running a little rough was bad I quess I am lucky. I also run high test. Everything is factory. I think once you tsrat changing parts the motors have a tendance to run worse. Mike

 

[Jerryl]

right, just about all sensors get the 5V reference voltage, but what is flood mode? I dont understand why/how A TPS sensor is preventing the car from running, I believe you, but could you explain how that works?

Here you go.

Cranking Fuel: The first thing the ECM does [$3977] in preparation for the fuel calculation is read a table ($555) that has throttle position (TPS) ($36) as the index. The output from this table is used as a multiplier in the injector pulse-width (on time) calculation.
Although you don’t normally push down the gas pedal during cranking, if it is depressed 38 – 50%, then 8 percent more fuel is injected. At 63% throttle, 17% more fuel is added. At the 75% and 88% entries in the table, the multiplier is zero. This is done to facilitate clearing a ‘flooded’ engine of excess fuel.

Clear Flood Mode: If the engine floods, it can be cleared by pushing the accelerator pedal almost all the way down (75% to 88%), holding it there for a few seconds then releasing. When the ECM sees that the Crank Fuel Multiplier vs. TPS = 0, it goes into the clear flood mode. A multiplier of zero produces a calculated injector pulse-width of zero. A small amount is added because of the Battery Voltage Offset table (as is always), but not enough to start the engine.

There is some ROM code left over from an earlier version that during clear flood mode, wants to produce an air/fuel ratio of 20:1. This code forces the Reference Pulse counter to zero [$E229] and the coolant temperature to a value representing 111 ºF ($28A) [$F377]. These two parameters affect the output of two tables used in the fuel calculation. These tables are described below however, the program for the 86/87 turbo V6 makes the TPS multiplier ($555) zero which in turn, makes the fuel calculation equal zero.

Source; http://www.turbotweak.com/Starting_the_Engine.pdf

 

[O SO LO]

On a HA car the TPS numbers should go from .42-.44 (at idle) to 4.8 (at WOT) so if that is opposite, your sending a WOT signal to the ECM at idle, and a idle signal to the ECM when the car should be at WOT...

 

[kulungi]

Mine is all original stock nothing has been changed. It runs really good at idle is has a little shake of rumble what ever you call it. It just has had a bran new aluminum exhaust installed priot to me purchaseing it. It would be glad to take photos of the ngine and send to you. Thier are allot of vacuum line and they crack and get old as time goes on. I don't think it would take much to effect how an engine runs wit a turbo and all that. It has the typical turbo whine and the gage moves incremtally as it boosts the engine. I personally thing some new vacuum line and getting it back to stock more or less is really what it needs. All of the other folks on this web site have thier cars tricked out to the max. I prefer stock with some slight changes one at a time not allot of changes. How many miles and are they hard miles? I undersatnd that the lower ends of these engines can't take all the torque and the bears on the crack usually start to go. But thats not your issue. Let me know if I can help.

 

[nickd2689]

Thanks for all the info guys. so how can i get it out of clear/flood mode? should it start when its out of c/f mode? do you still think the TPS is preventing it from starting?