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  #1  
Old 11-07-2012, 07:00 PM
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Misfire and TPS adjustment issues

I have a couple of issues here that may or may not be related. Car is a stock 1997 LSI.

Issue #1: For some time now I've had issues with the torque converter locking and unlocking when cruising around 70 mph (randomly), and also a hard 1-2 shift (all the time). I've been suspecting the TPS may be bad.

Issue #2: I've got a major misfire at idle while cold that started Monday evening. Car runs fine during acceleration, cruising, and just general driving. But at idle, when cold, it misfired very badly. By the time the car was warm, the misfire had gone away.

I've checked the coils/plugs and they look great. Plugs were done this year with OEM plugs. I've also checked around all of the vacuum lines, grounds, and cleaned the MAF sensor just for the heck of it. Everything looked good. When I started the car up after taking the coils off and checking them, it misfired worse… so bad that the whole car was shaking. I triple checked the coils and everything I took off. It’s all back together properly.

I figured I'd check the TPS adjustment while I was in there since I've been suspecting it to be bad anyway due to issue #1. The document in the how-to section states that with the key on and throttle closed it should give .5 volts through the white wire on the plug. I measured mine and the volt meter shows 5.14 volts. My first thought was that I have my volt meter set incorrectly, but when I measure the battery on the same setting, it shows 12.2 volts. When I loosen the screws and adjust the position, the voltage doesn't change at all, but I get a loud buzzing sound that sounds like it's coming from the trans while I rotate it. Do I have a bad TPS, something else, or am I doing something wrong here? Could the TPS be the cause of my massive misfire/rough idle? Or completely unrelated?

Recent work that was done: Last weekend I changed the accessory belt and the front right axle. I took the black plastic intake off while doing the axle thinking it would be the easiest way to access the axle pin, but apparently it was unnecessary. My first thought after the misfire came was that bumped something when taking the intake off, but everything is connected properly and I cannot see anything out of place.

Edit to add: There is no CEL on.
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1997 SVX LSi Bordeaux Pearl
1995 SVX L AWD Polo Green - 277k miles
1986 Pontiac Fiero 3.4L Twin Dual Cam V6

Last edited by Coan; 11-07-2012 at 07:03 PM.
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  #2  
Old 11-07-2012, 08:49 PM
oab_au oab_au is offline
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Re: Misfire and TPS adjustment issues

Quote:
Originally Posted by Coan View Post
I have a couple of issues here that may or may not be related. Car is a stock 1997 LSI.

Issue #1: For some time now I've had issues with the torque converter locking and unlocking when cruising around 70 mph (randomly), and also a hard 1-2 shift (all the time). I've been suspecting the TPS may be bad.


I figured I'd check the TPS adjustment while I was in there since I've been suspecting it to be bad anyway due to issue #1. The document in the how-to section states that with the key on and throttle closed it should give .5 volts through the white wire on the plug. I measured mine and the volt meter shows 5.14 volts. My first thought was that I have my volt meter set incorrectly, but when I measure the battery on the same setting, it shows 12.2 volts. When I loosen the screws and adjust the position, the voltage doesn't change at all, but I get a loud buzzing sound that sounds like it's coming from the trans while I rotate it. Do I have a bad TPS, something else, or am I doing something wrong here? Could the TPS be the cause of my massive misfire/rough idle? Or completely unrelated?


Edit to add: There is no CEL on.
Excuse the chopping but this bit is odd. 5.14V on the white wire is not right, you would get that voltage across the supply and the ground. But when you rotate it, it may not change your voltage, but it is changing the TPV at the TCU as you can hear the solenoids responding to the change.

The lock-up clutch acting like that is a sign, so no idea what it is but the TPS would be suspect.

Harvey.
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  #3  
Old 11-07-2012, 10:11 PM
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Re: Misfire and TPS adjustment issues

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Originally Posted by oab_au View Post
Excuse the chopping but this bit is odd. 5.14V on the white wire is not right, you would get that voltage across the supply and the ground. But when you rotate it, it may not change your voltage, but it is changing the TPV at the TCU as you can hear the solenoids responding to the change.

The lock-up clutch acting like that is a sign, so no idea what it is but the TPS would be suspect.

Harvey.
Talk about odd... after reading your response I went out and moved the pin from the white wire to the red wire (the middle one). I was able to measure the voltage and adjust it to .50 volts exactly. The solenoids were constantly buzzing at .50 volts until I turned the car off and back on again. I assume this is normal?

So is my TPS wired incorrectly? It looks 100% original...

Also, I drove it around the block again and the misfire is still there. Not as bad at idle, but it's now hesitating severely during acceleration. The good (or maybe bad) news is that the CEL light finally popped on. I guess I'll be picking up an OBDII scanner tomorrow...
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1986 Pontiac Fiero 3.4L Twin Dual Cam V6
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  #4  
Old 11-08-2012, 05:00 AM
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Re: Misfire and TPS adjustment issues

If you have an Auto Zone near you, you can borrow one free of charge.
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  #5  
Old 11-08-2012, 07:19 AM
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Re: Misfire and TPS adjustment issues

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If you have an Auto Zone near you, you can borrow one free of charge.
Not any more at least in Ca some new law saying it was taking customers from repair shops by loaning the scanners out. So now they only sell them
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#1 1994 Ls ebony parts car-rip
#2 1994 L laguna blue - sold
#3 1992 Lsi pearl white - sold
#4 1992 Lsi pearl white -Ate two engines - Rip
#5 1994 L Laguna Blue fwd - Now Awd and manual - 03 wrx 5mt - 18's stern warp st4s - totaled hit a tree
#6 1992 Lsi custom orange parts car
#7 1992 Lsi green 4.44 swap. Currently for sale
#8 1992 Lsi custom pearl white. Project car... sold
#9 1992 Teal 4.44 swapped... sold
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#11 1994 Laguna Blue. Came with #10 engine and trans are out but plan to put it back on the road. Willing to sell it at any time! 😂
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  #6  
Old 11-08-2012, 08:01 AM
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Re: Misfire and TPS adjustment issues

Wow that sucks, but kinda funny. Around here you can go to any auto parts store and they will scan it for you, but I'm not sure if they let you take them home. I think it's time I just buy one, it would be nice to have...
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1997 SVX LSi Bordeaux Pearl
1995 SVX L AWD Polo Green - 277k miles
1986 Pontiac Fiero 3.4L Twin Dual Cam V6
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  #7  
Old 11-08-2012, 08:14 AM
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Re: Misfire and TPS adjustment issues

The girl at Auto Zone said they can only scan 2000 or newer. Maybe she was lying cuz she did not know how or lazy , but did not get my 94 done.
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  #8  
Old 11-08-2012, 02:25 PM
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Re: Misfire and TPS adjustment issues

Yes and no lol they can for 96 and newer as it would be obd2 system
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#1 1994 Ls ebony parts car-rip
#2 1994 L laguna blue - sold
#3 1992 Lsi pearl white - sold
#4 1992 Lsi pearl white -Ate two engines - Rip
#5 1994 L Laguna Blue fwd - Now Awd and manual - 03 wrx 5mt - 18's stern warp st4s - totaled hit a tree
#6 1992 Lsi custom orange parts car
#7 1992 Lsi green 4.44 swap. Currently for sale
#8 1992 Lsi custom pearl white. Project car... sold
#9 1992 Teal 4.44 swapped... sold
#10 1995 Laguna Blue. Sti 19 wheels,
#11 1994 Laguna Blue. Came with #10 engine and trans are out but plan to put it back on the road. Willing to sell it at any time! 😂
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  #9  
Old 11-08-2012, 06:20 PM
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Re: Misfire and TPS adjustment issues

Picked up a scanner today and checked the code.

"P0120 TPS/Pedal Position Sensor A Circuit Malfunction."

Of course, this didn't show up until after I adjusted the TPS... anybody got a used one laying around they want to get rid of?
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1997 SVX LSi Bordeaux Pearl
1995 SVX L AWD Polo Green - 277k miles
1986 Pontiac Fiero 3.4L Twin Dual Cam V6
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  #10  
Old 11-08-2012, 06:33 PM
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redlightningsvx redlightningsvx is offline
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Re: Misfire and TPS adjustment issues

just ohm test the tps it shoud read 5 ohms i believe.
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Soon to come:Fiberglass hood, upholster ALL suede to black leather
Past subies:

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Old 11-08-2012, 08:12 PM
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Re: Misfire and TPS adjustment issues

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Originally Posted by redlightningsvx View Post
just ohm test the tps it shoud read 5 ohms i believe.
When removed from the car, mine reads about 5.80 ohms with a fairly consistent change throughout the range of motion.
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1997 SVX LSi Bordeaux Pearl
1995 SVX L AWD Polo Green - 277k miles
1986 Pontiac Fiero 3.4L Twin Dual Cam V6
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  #12  
Old 11-09-2012, 12:33 PM
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Re: Misfire and TPS adjustment issues

Checked it again this morning, moving it very, very slowly. It starts around 5.80, and when rotating it, it will reach about 5.4 ohms and then jump back up to 5.9, to 6.0, to 6.5, to 7.0, to 7.8, to 14+, and then back down to 5.0 and consistently smooth the rest of the rotation down to .05 ohms...

"Well there's yer problem!"
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1997 SVX LSi Bordeaux Pearl
1995 SVX L AWD Polo Green - 277k miles
1986 Pontiac Fiero 3.4L Twin Dual Cam V6
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  #13  
Old 11-09-2012, 07:40 PM
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redlightningsvx redlightningsvx is offline
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Re: Misfire and TPS adjustment issues

Check the ground strap behind the dog bone on the bellhousing to see it its connected also.
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Seth
94' Barcelona Red w/ Tricoat black 2-tone AWD Ls -Sold
Mods:AWD conversion/4.44 swap by Budfreak, Custom red interior lights, Custom Satin black dash, Power mode switch, Cold air intake, Permecool tranny filter,Sony xplode 10" sub, Sony xplode 1000w amp, Blitz in-line driver, DDM Tuning 6000k HID's, New paint job/body work by me, 97' Grill, QC shift kit, 17'' MB Motoring rims, 15&20 min mod, front & rear urethane swaybar bushings, Custom fiberglass sub box, Custom red led a/c control unit, perrin lightweight crank pulley, Black wrinkle finish powdercoated intake manifold w/ clear hoses , 02' outback heated/power black leather seats
Soon to come:Fiberglass hood, upholster ALL suede to black leather
Past subies:

92' Pearl White/black top LS-L-SOLD
96' Legacy Outback-TOTALED
99' Legacy Outback Limited 30th anniversary edition-TOTALED
98' Forester L -Totaled
Other toys:
99' Forester S -WRX brake upgrade, soon an 04 wrx motor swap
06' B9 Tribeca-Stock
1982' Yamaha xj650 Maxim
Mods:
work in progress
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  #14  
Old 11-09-2012, 08:21 PM
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Re: Misfire and TPS adjustment issues

That's the kind of thing I was hoping someone would come up with - something that I likely bumped when removing the intake. But nope. I just went and checked it and it looks good.

Replacement TPS on the way from Nate...
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1997 SVX LSi Bordeaux Pearl
1995 SVX L AWD Polo Green - 277k miles
1986 Pontiac Fiero 3.4L Twin Dual Cam V6
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  #15  
Old 11-13-2012, 10:19 PM
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Re: Misfire and TPS adjustment issues

I installed the replacement TPS (used) today and still have issues, but they've changed slightly... No CEL but now I have a high idle (1300 to 1500 rpm) in Park and Neutral, slight hesitation under very light throttle right off idle, and a random misfire at idle. But it's much better than it was before...

Car drives fine once you get past the slight stumble at take-off.

Also, the replacement TPS did not change the hard 1-2 shift.
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1995 SVX L AWD Polo Green - 277k miles
1986 Pontiac Fiero 3.4L Twin Dual Cam V6
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