Another TPS question and FSM

[suprunner]

1998 OBW, 5MT 251/25D

 

Hi all, looking to test my TPS. Been getting some misfires, and when hooked up to an OBD II reader, the TPS position is not the most consistent when giving values, as well as it never achieves 100% when I put the pedal to the floor. I've gone through three FSM versions so far, and the instructions say to use the ECM. Cool. I have the ECM out and exposed. Problem is that none of the connector options given B84, No. 24 & 25, or No. 20 & 6 connectors will give me what I want. Either 25, or No. 6 don't even have wires going to them. I'm trying to diagnose a few problems, from another post. Following the FSM diagnostics page as best as I can, and would like to test things before just spending money to replace. And say I did replace the TPS, how would I adjust it? Is there a place to get a FSM that is tied to my VIN? Does subaru provide/sell such things?

 

Thanks for your time,

 

Greg

[suprunner]

[Rampage]

You need to count the pins from the other end of the connector. The picture of B84 is the Connector side Not the Wire side.

Pins 6, 20 and 21 are for the TPS. Pin 6 is the one you adjust the TPS to .5 (one half) volts. Key on, engine off, throttle closed. I use the center pin at the TPS connector.

My scanner live data shows 0 for the TPS at idle. Never checked it at full throttle.

[GeneralDisorder]

Misfires aren't caused by the TPS. You are barking up the wrong tree. Fueling is done by mass airflow and timing largely by RPM.... The TPS would have to swing a LOT to make considerable changes in timing enough to cause a misfire. TPS is largely used for acceleration enrichment and transmission kickdown, etc. Not achieving 100% isn't really an issue as anything over 80% is generally considered wide open for purposes of tuning (the point where the ECM enters power enrichment mode). 

Figure out what's wrong with your ignition or fueling or compression. TPS isn't your problem. 

GD

Edited July 25, 2020 by GeneralDisorder

[suprunner]

15 hours ago, GeneralDisorder said:

Misfires aren't caused by the TPS. You are barking up the wrong tree. Fueling is done by mass airflow and timing largely by RPM.... The TPS would have to swing a LOT to make considerable changes in timing enough to cause a misfire. TPS is largely used for acceleration enrichment and transmission kickdown, etc. Not achieving 100% isn't really an issue as anything over 80% is generally considered wide open for purposes of tuning (the point where the ECM enters power enrichment mode). 

Figure out what's wrong with your ignition or fueling or compression. TPS isn't your problem. 

GD

 

16 hours ago, Rampage said:

You need to count the pins from the other end of the connector. The picture of B84 is the Connector side Not the Wire side.

Pins 6, 20 and 21 are for the TPS. Pin 6 is the one you adjust the TPS to .5 (one half) volts. Key on, engine off, throttle closed. I use the center pin at the TPS connector.

My scanner live data shows 0 for the TPS at idle. Never checked it at full throttle.

Thanks for the clarification Rampage, and as always, thank you for the guidance GD. TPS appears fine. Measuring the resistance at the coil, I get 0.0 -0.4 ohms between terminals 1/2, and 0.4-0.6 ohms between terminals 2 and 3. According to an FSM, that's an issue.  Resistance between the secondary terminals are all right on the mark though.  I have an Import Direct-brand ignition coil hanging around (new) that gives me 0.9-1.3 ohms between terminals 1 & 2, and 0.7 ohms between terminals 2 & 3.  Just to be redundant, those numbers aren't correct, and I should be looking at purchasing a subaru OEM coil? 

Thanks for your help,

 

Greg

[Rampage]

4 hours ago, suprunner said:

Measuring the resistance at the coil, I get 0.0 -0.4 ohms between terminals 1/2, and 0.4-0.6 ohms between terminals 2 and 3.

With a fluctuation like that, I would blame the meter probes or cables or an electric motor or something running nearby producing a magnetic field that your meter wires are picking up like an antenna. Or, the windings in the coil could be picking up magnetic or RF signals. Been there a few times.

OHMS on a meter works with a small voltage applied to a circuit by the meter and the meter reads the resulting current flow and then displays it as OHMS. The best way to check any coil is with an Impedance meter, but a good one is not cheap. It uses AC and will show impedance and reactance of the coil. It will show if the coil has a shorted winding somewhere in it. An OHM meter will not show that, unless the short is real close to the two connectors.

Hold the two probe tips together and the meter should read 0 and not change. Wiggle the wires and see if it changes. Every so often I have to repair my probes because some of the strands of wire break. When they get too short I get a new set. You can also unplug the cables from the meter and jump the two sockets with a short wire and see if it stays on 0.

My multi-meter has probes with screw on alligator clips. They make better contact than using the probe tips. I use them a lot.

Hook one probe onto pin 2 and test 1 and 3. Then hook the other probe to pin 2 and test 1 and 3. Try to not move the meter wires while testing. You should get a reading that only changes by one digit if it changes at all.

[suprunner]

1 hour ago, Rampage said:

With a fluctuation like that, I would blame the meter probes or cables or an electric motor or something running nearby producing a magnetic field that your meter wires are picking up like an antenna. Or, the windings in the coil could be picking up magnetic or RF signals. Been there a few times.

OHMS on a meter works with a small voltage applied to a circuit by the meter and the meter reads the resulting current flow and then displays it as OHMS. The best way to check any coil is with an Impedance meter, but a good one is not cheap. It uses AC and will show impedance and reactance of the coil. It will show if the coil has a shorted winding somewhere in it. An OHM meter will not show that, unless the short is real close to the two connectors.

Hold the two probe tips together and the meter should read 0 and not change. Wiggle the wires and see if it changes. Every so often I have to repair my probes because some of the strands of wire break. When they get too short I get a new set. You can also unplug the cables from the meter and jump the two sockets with a short wire and see if it stays on 0.

My multi-meter has probes with screw on alligator clips. They make better contact than using the probe tips. I use them a lot.

Hook one probe onto pin 2 and test 1 and 3. Then hook the other probe to pin 2 and test 1 and 3. Try to not move the meter wires while testing. You should get a reading that only changes by one digit if it changes at all.

Okay, I may need a new multi meter or cables at a minimum. The probes don't appear to be serviceable, and when touched together the multimeter reads a 0.4 for resistance. 

[Mike104]

I've never had good luck with aftermarket coils on Subaru's.  My go to is a pull and pay yard or buy one from an online Subaru dealer.

[Rampage]

Check or replace the battery in your multi meter. The battery is used for OHMS and to power the display.

[suprunner]

4 hours ago, Rampage said:

Check or replace the battery in your multi meter. The battery is used for OHMS and to power the display.

Batteries were brand new. I jumped the terminals with a wire as you had suggested, and the reading was .4 ohms. It was a multimeter that I bought almost ten years ago, and didn't take very good care of. Thrown/bounced around a bunch in the back of a car/tool-bag... I just bought a new multimeter (shows zero when putting probes together) and tested the coil. First tested after pulling right off the car after sitting in the sun. Terminals read 1.3 ohms. Then I waited for it to get to room temperature, and I'm getting .9 ohms between terminals 1 and 2 and 2/3. Safe to say it's out of spec? Per FSM the highest resistance should be .803 ohms. Lowest .657 ohms. 

[suprunner]

7 hours ago, Mike104 said:

I've never had good luck with aftermarket coils on Subaru's.  My go to is a pull and pay yard or buy one from an online Subaru dealer.

Thanks, I will keep that in mind! 

[Rampage]

5 hours ago, suprunner said:

First tested after pulling right off the car after sitting in the sun. Terminals read 1.3 ohms. Then I waited for it to get to room temperature, and I'm getting .9 ohms between terminals 1 and 2 and 2/3. Safe to say it's out of spec? Per FSM the highest resistance should be .803 ohms. Lowest .657 ohms. 

It may not be out of spec. using OHMS.

Most everything expands with heat. Think about this a little bit. Copper wire of a certain gauge has an OHMS rating per foot. The longer the wire, the higher the OHMS reading. An ignition coil is made of a very long thin copper wire wound into a large number of coils for the primary that you are measuring. The secondary has way more turns. When heated the coils will expand basically creating a longer thinner length of wire which would read higher in OHMS. When it cools, it shrinks and the OHMS drops in value. One thing to consider is, the coils may have stretched and are not returning to their original size. "Maybe" when someone measured the first coil for the FSM, they were sitting in a clean, air-conditioned room and would get a low reading. The expansion and contraction will eventually break down the insulation ( it is like enamel or varnish ) on the copper wire and create a short between adjacent coils. That is what an OHM Meter will not show you because the difference in OHMS is very tiny. If that short occurs it will put extra load on the Ignitor that controls the coil and the coil will have less output voltage (less spark).

The only time I had to replace a coil on our 95 was when it developed a crack on the bottom and was arcing out to the metal core. That was a Diamond, so I got the same from a yard.

Did you pull any codes for the misfires or anything else?

[suprunner]

1 hour ago, Rampage said:

It may not be out of spec. using OHMS.

Most everything expands with heat. Think about this a little bit. Copper wire of a certain gauge has an OHMS rating per foot. The longer the wire, the higher the OHMS reading. An ignition coil is made of a very long thin copper wire wound into a large number of coils for the primary that you are measuring. The secondary has way more turns. When heated the coils will expand basically creating a longer thinner length of wire which would read higher in OHMS. When it cools, it shrinks and the OHMS drops in value. One thing to consider is, the coils may have stretched and are not returning to their original size. "Maybe" when someone measured the first coil for the FSM, they were sitting in a clean, air-conditioned room and would get a low reading. The expansion and contraction will eventually break down the insulation ( it is like enamel or varnish ) on the copper wire and create a short between adjacent coils. That is what an OHM Meter will not show you because the difference in OHMS is very tiny. If that short occurs it will put extra load on the Ignitor that controls the coil and the coil will have less output voltage (less spark).

The only time I had to replace a coil on our 95 was when it developed a crack on the bottom and was arcing out to the metal core. That was a Diamond, so I got the same from a yard.

Did you pull any codes for the misfires or anything else?

So the coil could be fine. I've had misfire codes for every cylinder pop up. Seems random. They mostly happen at highway speeds (even though this is when the car runs the best) and very hot (being in Vegas that is always right now), although misfire codes for cylinders 1 & 2 popped up with a P0183 (fuel temp sensor A circuit) while leaving a parking lot. I will be checking the voltage and resistance to/from the MAF hopefully soon. It's tough getting to work on the car consistently and juggle grad school too. The thing stumbles/surges when at operating temps and idling (always when hot outside, rarely/never when it's colder than 70 degrees), and feels very unbalanced at 1800-2500 rpm. The compression numbers are pretty good, with one cylinder being kinda high in comparison, but still within 10% of them all. . . The valves sound loud. Is it possible that the valve clearances are so bad that i'm causing misfires? GD mentioned that my Long Term and short term fuel trims indicate that the thing runs very lean, and I need to figure that out...which I'm assuming is the MAF... I've yet to test it via the FSM's guidelines, but i've swapped between two used oem MAFs and one aftermarket MAF, and symptoms stay the same. 

[Rampage]

Hopefully you have OE or NGK plugs and wires installed. Anything else would be questionable.

Have you changed the fuel filter?

I would check fuel pressure at the connection between the fuel filter and the engine. The FSM tells you what the pressure should be and to remove the vacuum hose from the fuel pressure regulator. Another test I do to see if the fuel pump is up to par, is momentarily pinch the return line with pliers and see if the pressure jumps up to 70 - 90 psi (depends on the pump max psi).

Our previous 95 had low power going uphill. I had checked the fuel pressure at an idle and it was right on 28 and 35. Then, after changing a few parts with no improvement I rechecked the pressure and when I pinched the return line, the pressure stayed the same it did not go up at all. That told me the pump could not provide the volume or pressure needed when under throttle. With a new pump it went to 95 psi and the engine had its power back.

On our 97 the MAF sensor will go bad and stall the engine without setting any code.

[suprunner]

On 7/27/2020 at 4:05 AM, Rampage said:

Hopefully you have OE or NGK plugs and wires installed. Anything else would be questionable.

Have you changed the fuel filter?

I would check fuel pressure at the connection between the fuel filter and the engine. The FSM tells you what the pressure should be and to remove the vacuum hose from the fuel pressure regulator. Another test I do to see if the fuel pump is up to par, is momentarily pinch the return line with pliers and see if the pressure jumps up to 70 - 90 psi (depends on the pump max psi).

Our previous 95 had low power going uphill. I had checked the fuel pressure at an idle and it was right on 28 and 35. Then, after changing a few parts with no improvement I rechecked the pressure and when I pinched the return line, the pressure stayed the same it did not go up at all. That told me the pump could not provide the volume or pressure needed when under throttle. With a new pump it went to 95 psi and the engine had its power back.

On our 97 the MAF sensor will go bad and stall the engine without setting any code.

OE spark plugs and wires, Brand new delphi fuel pump/strainer, and fuel filter is about 4 months old. I recently checked fuel pressure, and it was at spec. The pressure elevated as the engine went into its idle stumble, but I didn't pinch of the return line. The idle stumble/surge, and the unbalanced feeling at 1800-2500 rpm are symptoms that followed this motor from a different car. The motor (all onboard sensors) and the MAF, minus brand new temp sensor/sender and knock sensor came over into this current wagon. So, ignition coil(s), MAF(s), crank/cam sensors, fuel injectors, TPS are all implicated in my mind. I have checked compression, and it's 210-225 psi between all cylinders. Cylinder 3 has 225 psi, and the other 3 are sitting in the 210's. Is it possible to have intake valves stuck open causing a lean situation? I haven't serviced them, and the manual says that's an 80-100k job... if that is a possibility though, why does the motor purr when at higher speeds/rpms? 

 

 

[Rampage]

9 hours ago, suprunner said:

The pressure elevated as the engine went into its idle stumble,

If the fuel pressure is going up during the stumble one or two things are happening.

Lower than normal vacuum in the intake manifold that will affect the fuel pressure regulator. Less vacuum more fuel pressure. Could be any thing connected to the intake, including a sticky intake valve. Another oddball thing that happened to our 97 is, the pin for the roller (in the rocker arm) that rides on the cam lobe came out and the roller moved into the cup on the rocker arm and the exhaust valves on one cylinder did not opening completely to let out all the pressure from fuel detonation and then when the intake valves opened for the piston to pull in air and fuel, the excess pressure was pushed into the intake causing pressure instead of vacuum.

The other thing could be that something is causing the ECM to cut back on the fuel injectors and not letting enough fuel into the cylinders.

 

The coil could have a problem when it gets hot. The insulation could be breaking down. At higher RPMs you won't notice misfires like at lower RPMs. I would get one from a yard and see if it makes a difference.

It would be a good idea to check the clearance on the valves. They may not be opening all the way since they are loud. Maybe the rockers are not getting enough oil and starting to wear.

When checking compression I remove all the spark plugs. I write down the compression from 1 pump of the piston and then 3 pumps on each cylinder. My reasoning is when the engine is running, there is only 1 compression stroke in each firing cycle. Most testers have a check valve that keeps the pressure on the gauge and usually will show an increase with more pumps.

[forester2002s]

Long shot: In case the valves are sticking, try an oil+filter change.

[suprunner]

18 hours ago, Rampage said:

If the fuel pressure is going up during the stumble one or two things are happening.

Lower than normal vacuum in the intake manifold that will affect the fuel pressure regulator. Less vacuum more fuel pressure. Could be any thing connected to the intake, including a sticky intake valve. Another oddball thing that happened to our 97 is, the pin for the roller (in the rocker arm) that rides on the cam lobe came out and the roller moved into the cup on the rocker arm and the exhaust valves on one cylinder did not opening completely to let out all the pressure from fuel detonation and then when the intake valves opened for the piston to pull in air and fuel, the excess pressure was pushed into the intake causing pressure instead of vacuum.

The other thing could be that something is causing the ECM to cut back on the fuel injectors and not letting enough fuel into the cylinders.

 

The coil could have a problem when it gets hot. The insulation could be breaking down. At higher RPMs you won't notice misfires like at lower RPMs. I would get one from a yard and see if it makes a difference.

It would be a good idea to check the clearance on the valves. They may not be opening all the way since they are loud. Maybe the rockers are not getting enough oil and starting to wear.

When checking compression I remove all the spark plugs. I write down the compression from 1 pump of the piston and then 3 pumps on each cylinder. My reasoning is when the engine is running, there is only 1 compression stroke in each firing cycle. Most testers have a check valve that keeps the pressure on the gauge and usually will show an increase with more pumps.

Yeah, I was worried about needing to check the valves. I don't have a break from school until October, so making time right now is an issue. Not looking forward to pulling the motor and having it sit out for a while. I know it can be done in-chassis, but that also just seems like a PITA. . I think I will try to electrically diagnose all sensors/units this weekend and make a decision. I'm considering buying a newer wagon now. Tax return should be coming soon... 

 

[suprunner]

5 hours ago, forester2002s said:

Long shot: In case the valves are sticking, try an oil+filter change.

Yeah, I wish it was that simple. Oil and filter has been changed many times since symptoms first appeared. Thanks for the input. 

[Rampage]

Until you can check the valve clearance, replace a quart of engine oil with a quart of Lucas Motor Treatment and add "half" a can of Seafoam Motor Treatment to the gas tank(half to full).

In the summer I use 10w30 in our EJ22s and 5w30 in the winter. The FSM recommends thicker oil in hot areas.

[suprunner]

On 7/30/2020 at 4:51 AM, Rampage said:

Until you can check the valve clearance, replace a quart of engine oil with a quart of Lucas Motor Treatment and add "half" a can of Seafoam Motor Treatment to the gas tank(half to full).

In the summer I use 10w30 in our EJ22s and 5w30 in the winter. The FSM recommends thicker oil in hot areas.

Since I moved here, I've been running 15-40 in the motor. I need to put some heavier gear oil in the transmission too. I just got done connecting the single-wire green connectors under the dash to listen to all of the solenoids coming on/off. Everything seems to be working except the purge valve under the passenger intake. Could that be contributing to the idle bobbing? What is its job?

[suprunner]

On 7/24/2020 at 9:35 PM, GeneralDisorder said:

Misfires aren't caused by the TPS. You are barking up the wrong tree. Fueling is done by mass airflow and timing largely by RPM.... The TPS would have to swing a LOT to make considerable changes in timing enough to cause a misfire. TPS is largely used for acceleration enrichment and transmission kickdown, etc. Not achieving 100% isn't really an issue as anything over 80% is generally considered wide open for purposes of tuning (the point where the ECM enters power enrichment mode). 

Figure out what's wrong with your ignition or fueling or compression. TPS isn't your problem. 

GD

I've followed the FSM instructions to test the voltage and resistance for Ignitor and Ignition coil through the harnesses. Coil reads slightly high for resistance at its terminals and removed from the car. Now, following the guide to test the MAF, I found that voltage going to the MAF is good. Resistance though, I am stuck/lost as I'm less than a novice at electrical diagnostics. According to the FSM I need to fix a short in the harness? When testing between terminal #5, and ground, the meter doesn't read anything, as if the probes aren't touching anything. How do I find the short between the two harness connectors? Can I splice in a ground near the connectors? 

 

Edited August 1, 2020 by suprunner

[suprunner]

I found the purge valve under the passenger intake to be inoperable. Swapped it out for one from a junk yard. Has helped considerably. Now, the surging only happens for short periods of time during the hottest parts of the day. If I drive in the morning (cooler temps) the car is happy. So, something evap/vacuum related. Thanks for your input @Rampage, and @GeneralDisorder 

[suprunner]

On 7/24/2020 at 9:35 PM, GeneralDisorder said:

Misfires aren't caused by the TPS. You are barking up the wrong tree. Fueling is done by mass airflow and timing largely by RPM.... The TPS would have to swing a LOT to make considerable changes in timing enough to cause a misfire. TPS is largely used for acceleration enrichment and transmission kickdown, etc. Not achieving 100% isn't really an issue as anything over 80% is generally considered wide open for purposes of tuning (the point where the ECM enters power enrichment mode). 

Figure out what's wrong with your ignition or fueling or compression. TPS isn't your problem. 

GD

Hi, resurrecting an old thread hopefully I'm closer to an answer. 

I found that the Purge Valve under the intake manifold was faulty. Replaced it with a junkyard find. That helped until I'm assuming it died. So, I capped the line off from the top throttle body port, and have the gas cap slightly opened. Fuel trims are now (I think?) back to normal limits. Longterm Fuel Trim was 25.0 before capping off the line. See attached photo. Now, during the hot part of the day the idle bobbing is no longer present.

I just did a leak-down test as well. According to the gauges, I'm within 10% for each cylinder. ALTHOUGH, I do hear/feel air escaping through the intake, and the oil filler tube. (I followed this for instructions: 

 

Compression for #3 is about 225 psi, the remaining cylinders are between 210 and 215 psi. Can one cylinder being higher than the rest cause an unbalancing/misfire?

I'm still getting an unbalanced shake/hesitation from 1800-2500 rpm, and I'm getting random misfires for any of the cylinders every couple days and PO420 after the misfires. Even if the numbers are good, the fact that I have air coming through the oil filler tube and intake, does this suggest the motor is shot? 

Plugs, Wires are less than a year old. Fuel pump/filter/strainer within 6 months. Coil and ignition module are within spec according to an FSM that I read. 

Check my timing again? Can a light-weight flywheel cause the unbalanced feeling and misfires? 

@1 Lucky Texan

@Rampage