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EJ25 Conversion Driveability Problems. IAC? O2? Please help!
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luceronator
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PostPosted: Wed Nov 02, 2016 5:57 pm    Post subject: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

Hey everybody.
I'm looking for help and info on an '86 Weekender that I recently bought from a friend.
The van has an EJ25 motor from an automatic Legacy, I am told.
The wiring harness was made by Jeff Robenolt, who recently told me that my ECM is from a Forester (based on part # on the ECM).
There are driveability issues that cropped up shortly after I acquired the van. It suddenly had poor acceleration, the engine would stall when load was applied, the rpms take a long time to go back to idle.
I quickly figured out that the van ran much better when I unplugged the upstream 02 sensor, it drives nicely but idles very high.
A new 02 sensor did not fix the problem, however that is when I found out that the van is running an 02 sensor spec'd for a Manual, while this engine is an auto.
I just replaced the MAP sensor, no change.
Checked for vacuum leaks and couldn't find any.
Running codes, several IAC codes keep popping up, P1507, P1510, P1512, P1514, and P1516 have reoccured.
So that brings me to a question.... Jeff Robenolt told me that my o2 sensors (for a manual) are correct, but the ECM is still throwing IAC codes that only apply to an Automatic. (I was thinking I should be running the o2's from an auto)
So I am wondering what o2 sensors are others who have installed EJ25's off of autos using. And do you have to do anything to the IAC to make it happy?
(I have tested the IAC motor and it is good, swapped it for a known good unit and problem persisted.)

Some extra info... my friend that I bought the van from ran it as he sold it to me for quite a while without issue. He say that the problems I am having are new, and I believe him, as it's basically undriveable as is, and I trust him. So it appears something changed.
Also, I recently cleared the codes, then drove the van about 100 miles with the upstream 02 unplugged, and then rechecked codes. What I got (besides the ones listed above) are P1133 and P0141. Unplugging the downstream 02 doesn't seem to make a noticeable change.

I appreciate any insight and suggestions. I spent a fair amount of time trying to search info specifically about running an EJ25 from an auto and didn't find answers to what I was looking for. I apologize if I'm re-asking something that has been covered already.
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AKWesty
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PostPosted: Wed Nov 02, 2016 7:57 pm    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

If it were my van the first thing I would do would be to check compression on each cylinder. Once you know you have good compression on all 4 then you can problem solve from there.

Next I would check fuel pressure. Gauge the fuel and make sure you have 30 psi coming from your pump.

The high idle problem you are having is most likely a gummed up IAC or your TPS is out. You need to get a Chilton and and Haynes manual for the subaru. Each have testing procedures for the TPS. Meter bench ohms testing and in vehicle voltage testing.

The symptoms you are describing are beyond the symptoms of the O2 sensor. It sounds like TPS to me because of your poor acceleration as well as the high idle. You have to make sure your TPS is good before you work on your IAC.

After that you can go to your injectors. Assuming your plugs are good and tested you may have a cracked or clogged injector.

Compression, Fuel, Spark.....I suspect your TPS
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wesitarz
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PostPosted: Wed Nov 02, 2016 11:05 pm    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

Did you do any work on the engine or wiring harness prior to this happening? I recall that driving while having the two green test connectors connected results in multiple codes.
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luceronator
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PostPosted: Thu Nov 03, 2016 6:56 am    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

Thanks for the replies.
AKWesty, I have been using an AllData subscription for an '01 Legacy, I will try their procedure for bench testing/troubleshooting/adjusting the TPS. And pulling the IAC will happen this morning.
I hadn't given much thought to compression or fuel delivery because when the upstream o2 is unplugged the Van runs with plenty of power, it just wants to idle around 3k rpm.

Wesitarz, the green test connectors are not plugged in.

Thanks!
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dobryan
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PostPosted: Thu Nov 03, 2016 7:53 am    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

Also be sure your exhaust system is tight with no leaks. An exhaust leak plays havoc with the Ox sensor and mixture...
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luceronator
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PostPosted: Thu Nov 03, 2016 10:18 am    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

Thanks dobryan. I'll check the exhaust, haven't done that yet.

Pulled the whole throttle body off this morning to be sure the IAC is clean. Everything was pretty spotless.

So I'm really curious what o2 sensors other people are using. Subaru specs a 5 wire upstream o2 for Auto's, and a 4 wire for manuals. So those of you with Auto EJ25 conversions, which upstream o2 do you have?
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Howesight
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PostPosted: Thu Nov 03, 2016 10:37 am    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

A functioning Intake Air Controller is considered by Subaru to be a safety item when the vehicle has an automatic transmission. The limp home mode raises the idle to prevent stalling on, say, railway tracks. The ECU also limits RPM to force the driver to address the IAC problem. Your oxygen sensors are not the problem. Do you have a VSS and is it working?

There is likely a problem in the IAC itself or in the wiring between it and the ECU. This is a conversion harness, after all, so it is worthwhile testing.

Regarding the TPS, Subaru Throttle Position Sensors are not very robust and do fail and/or go intermittent. You need an analog VOM with a sweep needle to check for drop-outs in the signal when moving the throttle. From personal experience, I can also vouch that a Subaru TPS that is in the process of failing is often sensitive to temperature, working poorly when the engine is cold, but returning to mostly functional when warm. I mention that they do fail because it may just be simpler to replace the unit and consider it preventive maintenance.

By the way, for the benefit of others trying to learn from this thread, the codes you quoted, and the malfunctions they identify, are as follows

P1507 - Idle Control System Malfunction (Fail Safe)

P1510 - Idle Air Control Solenoid Signal 1 Circuit Low Input

P1512 - Idle Air Control Solenoid Signal 2 Circuit Low Input

P1514 - Idle Air Control Solenoid Signal 3 Circuit Low Input

P1516 - Idle Air Control Solenoid Signal 4 Circuit Low Input

P1133 - ?

P0141 - Rear Oxygen Sensor Heater Circuit Malfunction

Hope this helps.
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pantone149
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PostPosted: Wed Nov 23, 2016 5:07 pm    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

luceronator I went through very much the same frustrations. My Subaru engine is from a 99 Outback automatic, but my VW is manual. I am using the Subaru ECU and wiring harness, modified/stripped plus the SmallCar circuit board. Any time I drove it even moderately hard I would get many of the same codes as you. I learned that all ECU's are essentially the same, the difference is either an automatic versus manual wiring harness. My solution was really easy. Ground the ECU pin that normally goes to the manual transmission. This is going to take some research on your part to find which pin would normally go to a manual trans. Get a small connector and run a wire to ground. The ECU is getting very unhappy thinking your transmission is in neutral as you rev up the RPMs. Grounding that pin makes the ECU think you are in gear and it's OK to rev up then. Good luck. This worked for me like a dream.
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tates1882
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PostPosted: Wed Nov 23, 2016 5:44 pm    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

pantone149 wrote:
luceronator I went through very much the same frustrations. My Subaru engine is from a 99 Outback automatic, but my VW is manual. I am using the Subaru ECU and wiring harness, modified/stripped plus the SmallCar circuit board. Any time I drove it even moderately hard I would get many of the same codes as you. I learned that all ECU's are essentially the same, the difference is either an automatic versus manual wiring harness. My solution was really easy. Ground the ECU pin that normally goes to the manual transmission. This is going to take some research on your part to find which pin would normally go to a manual trans. Get a small connector and run a wire to ground. The ECU is getting very unhappy thinking your transmission is in neutral as you rev up the RPMs. Grounding that pin makes the ECU think you are in gear and it's OK to rev up then. Good luck. This worked for me like a dream.


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luceronator
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PostPosted: Tue Jun 20, 2017 7:08 am    Post subject: Re: EJ25 Conversion Driveability Problems. IAC? O2? Please help! Reply with quote

Hey everyone,
I left this thread dead in the water, even after helpful advice was given, so I thought I should come back and give my solution to the problem.
So my problem seems to have started when the PO and his mechanic were doing two EJ25 swaps at the same time. One was from a manual and one from an automatic. They mixed up the wiring harnesses a bit, and I ended up with the harness for the o2s from a manual, but my engine and everything else is from an auto. Manuals run 4 wire o2s and autos run 5 (or 6? It's been a while). So that where the trouble came from. The PO and his mechanic got the harness straightened out, the ECM got the info it wanted from the correct o2 sensors, and it ran perfectly.
So, probably not a problem that's likely to come up again, but thanks for all the help!
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