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FFCobra Fanatic
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Discussion Starter #1
Still trying to get this thing to start when it's hot, I will be doing the chip but money is kinda tight right now.
When measuring tps voltage I get 120 mv and when you move the plastic paddles it goes to 75 mv. I am sure it is installed correctly( printed wade chamberlains instructions from last week..thanx) I tried readings on all three wires.
I have never had it read close to the majical.98 v. I even removed it completely from the throttle body while the engine was running and it didn't make a bit of difference. I feel that this may have something to do with the running rich and not hot starting.
All my sensors and wiring worked fine with the old 302, never a stutter or hesitation.

Thanx for any ideas,

chris.
 

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Chris,

You are checking this voltage with the ign. switch ON? If so and you're getting a mv reading, you don't have any voltage going to the TPS. One wire should have aproximately 12v (dc) on it. Check all three to ground. (Be sure your volt meter is on DC and if possible select 000 volt. On the mv (or auto) setting you can read your body voltage. ;)

Check'em and post a reply.

Whoops... Now I see your "Engine On" comment. What year donor did you use. I have a '89 Helm's electrical manual. I think we (you) need to run the voltage back cause you have to be loosing it somewhere and Yes Sir Ree, this will cause your computer to do really bad stuff. (This is how the computer knows the position of the throttle or gas pedal.)

Mike
FFR 2335

[ August 28, 2002, 06:17 PM: Message edited by: Mcathcart ]
 

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FFCobra Fanatic
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Discussion Starter #3
I remember a while back cking tps and found a constant 12v, not today. I grounded on the batt(on footbox) and all three wires are around 5v, moved the throttle and little response. ign. was on.
Could this be the reason it doesn't want to hot start?
and that would be a reason why the comp. didn't know it was floored to avoid the flooding. But how come it idled just fine, of course with that lumpy cam maybe I couldn't tell.
I don't remember what year, 92 or 93 I think.

thanx for the help.

chris.

[ August 28, 2002, 06:36 PM: Message edited by: thunderball ]
 

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if you unplug the TPS and measure the voltage at each of the three pins at the harness, you should have only one that's 5V (reference). The grey/white wire is TPS voltage to the computer. The brown/white wire is 5V power to engine sensors (reference voltage). The grey/red wire is "sensor signal return" (essentially a ground made by the EEC internally).

If you have 5V on the grey/red wire, then you've probably got a bad ground somewhere and none of your engine sensors are reading properly. Been there, done that. ;)
 

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Thunderball...If you are not getting about .98 volts with the engine off and key on you probably have a ground problem. In this case the TPS is not sending the correct throttle postion setting to the computer and you are lost. It sounds like you have the procedure down ok but make sure you have continuity on all three wires and make sure you have a good ground. In my case one of the wires was not makeing a ground back at the computer. After I grounded the TPS setting was easy and the idle was smooth and steady.

San Rafael Mike
 

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Discussion Starter #6
is there a way I could check the ohms/resistence of the tps to make sure it is working correctly?
I have three wires going in- orange, brown and black.
As far as the car electrical systems the car has been on the road for 6 months with no electrical bugs so I can be relatively sure wiring grounds are ok.
As far as engine grounds I have the little orange wire in the injector harness that grounds to the back of the drivers head. This wire sandwiched with a stainless braid strap that goes to the body. I then have a ground from the pass. front on the block to frame and starter mount bolts to frame.

ah ha! Does the tps ground thru the intake? I remember my stocker had a bar connecting the upper intake to the block( maybe a ground bar), I have nothing grounding the uppere intake.

[ August 28, 2002, 07:39 PM: Message edited by: thunderball ]
 

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OK Batman...

Helm's is only showing DG/LG (dark green/light green) #47 out of the computer, this should have Voltage on it.

The other two wires leaving the TPS, O/W (on '89) connect to the EGR Valve, #26 Computer and Barometric Pressure Sensor, the other wire out goes to Air Charge Temp. Sensor and to #25 at the computer & also through the Engine Coolant Temp then to #7 at the computer. By looking at the drawing, if the Air Charge sensor or the Coolant temp. is NG then the computer won't receive the voltage from the TPS.

Wade said 5v, going to the TPS (I didn't check and I've trashed a lot of brain cells lately) so I could be wrong on the 12v but you should see voltage on one wire to ground. If you don't have voltage check #47 at the computer plug for voltage. (Even though the colors are different,I'd guess #47 still might be correct at the 'puter.)

No, the TPS does not ground through the intake, the TPS is a pot that directs voltage to the computer.
Let us know what you find. It's like 0-5 one direction and 5-0 the other (0 could =.98).

Mike
FFR 2335

[ August 28, 2002, 10:51 PM: Message edited by: Mcathcart ]
 

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Discussion Starter #8
thanx mike, I won't be able to get to the car today but I will tomorrow.
hhmmmm....egr valve. That is another difference between the two motors. I unplugged the egr and the plug is just hanging there. Would that need to be plugged in or a resisitor of some kind to complete a circuit? I was hoping not to use the egr.

thanx again, chris.

[ August 29, 2002, 07:30 AM: Message edited by: thunderball ]
 

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Chris,

EGR...? After "Creamsicle Rick" built his engine this year he couldn't get the sucker to idle. I make time on a Saturday to ride up and see him. He'd tried and done A to Z, set the .98 volt, re-set computer, adjust throttle plate and so on. Looking at Rick's engine...Humm..yep..yep...Hey Rick, where's the old EGR? "Don't need it, it's still on the old intake". OK, we need to remove the electrical part on the old EGR (3 small screws) and use electrical tape to keep the plunger close to the middle. Got the EGR sensor, held the plunger about the center of the stroke and wrapped it with duct tape and then electrical tape. Plugged it in and cranked the engine... Idle problem solved. If the computer doesn't see the EGR position it causes the computer to do some funny stuff and it will cause the engine to idle like crap.

Mike
FFR 2335
 

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FFCobra Craftsman
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Can you say Potato?

4 wires and two go to ground!
 

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Discussion Starter #11
hhmmm potato, not a bad idea. I'd probably smell the same. Mike. do you think the egr would cause it to run rich? As far as I can tell it idled great, that was kinda funny when I removed the tps and the engine still idled fine.
All these problems are after it goes to closed loop. I'll go pull the egr off the old motor and plug it in and see what happens.
Let you know tommorrow.

thanx for the ideas.
chris.
 

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I'm pretty sure the EGR will cause it to run rich (and naturally cause it to idle like crap).

"Engineer Ed" could spend some time and figure out what resistor or pot will replace the sensor.


Have you tried resetting the computer with the engine Hot?

Mike
FFR 2335
 

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Discussion Starter #13
No. I haven't. Would that be to let the engine warm up, shut it off and disconnect the neg. for 20 mins?
What's really wierd about all this is the idle is great, but then again who knows what the computer is thinking.
I will be going to the car after work and then back at it early sat.
chris.
 

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Discussion Starter #14
[email protected]#$#%$n car.
No voltage to the tps with just the key on.
In the morning I will do a continuity check to the computer and if that checks out I'm getting the hammer.
Also plugged in the egr with no difference.

[ August 30, 2002, 06:39 PM: Message edited by: thunderball ]
 

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Discussion Starter #15
Hi all, this is what I found today.
The o2 harness got melted on the pass side during engine break in, I spliced in a new harness.However the wires may have shorted against the header.
I also replaced my tps with no change. I checked continuity to the comp. and all is good.
I think I may have fried something in the eec that is related to a ground, any ideas how to check this?
I also have 5v on the red/ grey wire and the brwn/wht.

thanx, chris.
 

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Chris,

Have you checked #47 at the computer for 5v (with the switch on)?

Are you using the Mustang ign. swith or a after market switch?

Mike
 

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Discussion Starter #17
oops no I didn't. I ckd #47 for continuity to the plug. I'll run off and do that tonight and ck back in later.
Yes I am using the stang switch.
 

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Discussion Starter #18
ok, been to the car.
No voltage on #47 ignition on, engine off. BUT, with the engine running I have 12v.
Just for giggles I unplugged the ect and it didn't change the engine at all, soooo... I'm wondering if this thing is even going into closed loop.
Right now I could get rid of the tps, and computer sensors in the engine bay and really clean it up!!
Next logical step it seems is use another computer seeing as everything worked great before the swap, then I fried the o2 harness which may have grounded something. The two wires which appeared to melt were thegrn/blk and beige/ylw.
I think those were ground and sensory from the o2.
 

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Chris,

I think you need to clean the two connectors behind the intake. From the Mustang site there's been some pretty good problems caused by a bad connection in one of the plugs.

I'll check my TPS voltage Sunday with the switch on and with the engine running and let you know what mine is doing.

Mike
 

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Discussion Starter #20
Thanx mike. I'll post the results in the am about 8 or 9 from the computer swap. I sure hope it's this simple.

chris.
 
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