Problem Stalling out
Thread Starter
Racer
Joined: Jul 2006
Posts: 343
Likes: 0
From: Denver, CO
Problem Stalling out : TPS PROBLEM- Throttle Linkage
1986.0 928 5-spd.
When I rev the engine past approx. 3K and then
put in the clutch the car stalls occasionally.
When the AC is on and I do this the car stalls every time.
The problem is worse when the temperature is high.
I've tried spraying WD-40 into the ISV. No change.
I also suspect I have a vacume leak associated with my AC.
Because it never really gets very cold so I think it's not recirculating.
Is this problem most likely the ISV or a vacume problem or maybe
something else?
Thanks in advance,
When I rev the engine past approx. 3K and then
put in the clutch the car stalls occasionally.
When the AC is on and I do this the car stalls every time.
The problem is worse when the temperature is high.
I've tried spraying WD-40 into the ISV. No change.
I also suspect I have a vacume leak associated with my AC.
Because it never really gets very cold so I think it's not recirculating.
Is this problem most likely the ISV or a vacume problem or maybe
something else?
Thanks in advance,
Last edited by RichS 1986928; Aug 22, 2008 at 11:31 AM.
Supercharged
Rennlist Member
Rennlist Member
Joined: May 2002
Posts: 18,926
Likes: 88
From: Back in Michigan - Full time!
It could be the ISV, but I doubt it. To me, it sounds like it's your throttle position switch. You should test it at the LH/EZK connectors to ensure it's working. If it is, then you might consider checking the ISV.
Your suspicion of a vacuum leak may or may not be warranted. The only way to tell for sure would be to apply vacuum to the system and see if it holds vacuum or not. A vacuum leak usually will not cause your symptoms - but rather manifest themselves as high/erratic idle. But if you have a vacuum leak, you should fix it.
Your suspicion of a vacuum leak may or may not be warranted. The only way to tell for sure would be to apply vacuum to the system and see if it holds vacuum or not. A vacuum leak usually will not cause your symptoms - but rather manifest themselves as high/erratic idle. But if you have a vacuum leak, you should fix it.
Thread Starter
Racer
Joined: Jul 2006
Posts: 343
Likes: 0
From: Denver, CO
Ok,
2 questions then,
how do I test the throttle position switch?
where is it located? I don't recall seeing it in there. I couldn't find
a pic at 928intl or 928specialist but I found one on ebay assuming it's
correct.
I do have the WSM, is there a testing procedure in there?
thanks
2 questions then,
how do I test the throttle position switch?
where is it located? I don't recall seeing it in there. I couldn't find
a pic at 928intl or 928specialist but I found one on ebay assuming it's
correct.
I do have the WSM, is there a testing procedure in there?
thanks
Race Car
Joined: Dec 2006
Posts: 4,089
Likes: 6
From: Tampa Florida
Unhook you 25 pin connector, (Ecm of far right) to the LH and put one lead of the meter, black in the Ohms position and connect to car ground and check the following:
Red lead of meter: Wot to pin 12 when gas is to the floor meter should be 0 ohms.
Red lead of meter: Idle Pin 3 when gas is off meter should be 0 or so ohms.
Red lead of meter: Wot to pin 12 when gas is to the floor meter should be 0 ohms.
Red lead of meter: Idle Pin 3 when gas is off meter should be 0 or so ohms.
Nordschleife Master
Joined: Jun 2006
Posts: 6,297
Likes: 63
From: ɹəpun uʍop 'ʎəupʎs
If its faulty, have a read of this thread:
https://rennlist.com/forums/928-forum/367546-wot-throttle-switch.html
I tested mine using the WSM procedure, and then took it apart and soldered - now works just fine
(they're not that expensive, but the week+ lag time for ordering to here Australia wasn't something I wanted to wait for).
https://rennlist.com/forums/928-forum/367546-wot-throttle-switch.html
I tested mine using the WSM procedure, and then took it apart and soldered - now works just fine
(they're not that expensive, but the week+ lag time for ordering to here Australia wasn't something I wanted to wait for).
Race Car
Joined: Dec 2006
Posts: 4,089
Likes: 6
From: Tampa Florida
You have an 86 so I can tell you you will need to remove the intake tubes at least the front one's, get a gasket set from Roger and or a used switch you will need this if you pull it. If you need to replace it I'll send some pictures and tools you will need.
Mark
Mark
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Thread Starter
Racer
Joined: Jul 2006
Posts: 343
Likes: 0
From: Denver, CO
Ok, sorry for the delay, I finally got some time to work on her last night.
4 pictures.
2 showing where I checked pin 3 and 12.
Pin 3 was .17 ohms, Pin 12 was 800 ohms. Neither changed
at idle or WOT.
So this means the TPS is dead right? Next question is how do I get it
out of there. From the picture you can see where I'm at.
Mark, you said I'll need to order up the gaskets and maybe need some
speical tools? You also mentioned pictures on how to do this, That would
be great!
2 other questions while I'm at it. What do those brown and green wires
coming from the LH/EZK connectors do? They were wrapped off in electrical
tape.
Last: How do I check the Temp II switch?
ThankS!
4 pictures.
2 showing where I checked pin 3 and 12.
Pin 3 was .17 ohms, Pin 12 was 800 ohms. Neither changed
at idle or WOT.
So this means the TPS is dead right? Next question is how do I get it
out of there. From the picture you can see where I'm at.
Mark, you said I'll need to order up the gaskets and maybe need some
speical tools? You also mentioned pictures on how to do this, That would
be great!
2 other questions while I'm at it. What do those brown and green wires
coming from the LH/EZK connectors do? They were wrapped off in electrical
tape.
Last: How do I check the Temp II switch?
ThankS!
Last edited by RichS 1986928; Aug 21, 2008 at 04:26 PM.
Thread Starter
Racer
Joined: Jul 2006
Posts: 343
Likes: 0
From: Denver, CO
Ok, Still at it.
I reworked the intake and replaced the following.
TPS
ISV
Injectors
Fuel Lines
Rear Temp Sender
Heater Valve
And the result was.... Nothing! Well, maybe a little worse than before.
Vacuum lines are in good shape. Vacuum is good.
MAF was rebuilt last year.
I just checked the Temp II sensor and it's OK too.
Again the problem is stalling out. Runs fine until I take my foot off the gas and put the clutch
in. Would only start this time by pumping the gas. The problem gets progressively worse as
the engine temp goes up.
What should I check next???
Thanks,
Rich
I reworked the intake and replaced the following.
TPS
ISV
Injectors
Fuel Lines
Rear Temp Sender
Heater Valve
And the result was.... Nothing! Well, maybe a little worse than before.
Vacuum lines are in good shape. Vacuum is good.
MAF was rebuilt last year.
I just checked the Temp II sensor and it's OK too.
Again the problem is stalling out. Runs fine until I take my foot off the gas and put the clutch
in. Would only start this time by pumping the gas. The problem gets progressively worse as
the engine temp goes up.
What should I check next???
Thanks,
Rich
Last edited by RichS 1986928; Aug 21, 2008 at 05:16 PM.
Rennlist Member
Joined: May 2007
Posts: 323
Likes: 0
From: Not that far from the Jersey Shore
Rich - the O2 wiring harness connection is at the CE panel. You most likely have a 3-wire O2 sensor. One wire is the signal wire, another two are for the internal O2 sensor heater (one is + and the other -). The voltage range of the O2 sensor is 0.1 to 1.0 volt. You will need to backprobe the signal wire connector to read the voltage while the engine is running.
You can locate the wiring harness at the lower left of the CE panel - it goes through the floorpan at the torque tube hump.
I do not have pictures of the O2 connection but there are some here on the 'list.
Also, have you checked your fuel pressure? And the fuel dampers for internal leakage (do they hold vacuum or gas residue when the vacuum hose is removed)?
Adam
You can locate the wiring harness at the lower left of the CE panel - it goes through the floorpan at the torque tube hump.
I do not have pictures of the O2 connection but there are some here on the 'list.
Also, have you checked your fuel pressure? And the fuel dampers for internal leakage (do they hold vacuum or gas residue when the vacuum hose is removed)?
Adam
Thread Starter
Racer
Joined: Jul 2006
Posts: 343
Likes: 0
From: Denver, CO
I will check the O2 Sensor tonight.
Is there a way to check the fuel pressure without a fuel pressure gauge?
How do I check the fuel dampers?
Are you saying pull the vacuum hose and see if gas comes out? And
apply vacuum and see if they hold it? I will check that tonight. How many fuel
dampers are there?
Is there a way to check the fuel pressure without a fuel pressure gauge?
How do I check the fuel dampers?
Are you saying pull the vacuum hose and see if gas comes out? And
apply vacuum and see if they hold it? I will check that tonight. How many fuel
dampers are there?
Rennlist Member
Joined: May 2007
Posts: 323
Likes: 0
From: Not that far from the Jersey Shore
Rich,
The best way to check your fuel pressure is to hook up a fuel pressure gauge to the test port on the passenger side fuel rail.
Do you have the shop manual? If so, there are diagrams that show the vacuum hose routing and the location of the fuel dampers. They may also be a vacuum line routing decal under your hood as well.
On my '86.5's there is one regulator and two fuel dampers. They are located in the driver's side front and under the air box on the driver and passenger side. Look for the devices with fuel and vacuum lines hooked up to it.
I've tested the dampers with a MityVac.
Adam
The best way to check your fuel pressure is to hook up a fuel pressure gauge to the test port on the passenger side fuel rail.
Do you have the shop manual? If so, there are diagrams that show the vacuum hose routing and the location of the fuel dampers. They may also be a vacuum line routing decal under your hood as well.
On my '86.5's there is one regulator and two fuel dampers. They are located in the driver's side front and under the air box on the driver and passenger side. Look for the devices with fuel and vacuum lines hooked up to it.
I've tested the dampers with a MityVac.
Adam