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90 Legacy - What sensors are use in open loop mode


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I've got a 1990 Legacy that is having trouble starting when cold. The car will start rev to about 2k and then quickly drop down, try to idle and then die because it is cold.

 

Here's what I've replaced:

  1. Timing belt
  2. Air Idle Control Valve (used and cleaned)
  3. Tempature sensor
  4. PCV
  5. Oxygen sensor
  6. Spark plugs
  7. Cleaned MAS

 

Other issues: I've got jerking on the freeway at 2750 RPMs. This goes away if I slow down or speedup.

 

I'm wondering what other sensor I should be looking at or areas.

 

I'm thinking about pulling a used MAS and ECU to see if that helps.

 

Thanks so much for your help!

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Hi Everyone,

 

Thanks for the advice. The check engine light does come on from time to time. The current code is for the oxygen sensor but I have seen a code for the MAS as well.

 

I've cleaned the MAS but that didn't seem to help. Also checked for vacuum leaks and didn't find anything.

 

What's the best way to check the coolant temperature sensor's connector?

 

I also took my car to a trusted mechanic yesterday and he was unable to find the problem. He said he hooked it up to the computer and didn't see anything odd. He also checked the ground connections but did not find any problems there.

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UPDATE: I took a closer look at the spark plug wires yesterday and found a small hole in one of them. I think they might be the original factory wires. Each wire is custom sized for the calendar and labeled. The part number of these are "Yakaki 1989 R-16-AIPS".

 

I picked up a new set of BWD wires from O'reilly Autoset and put them on today. I'm not really happy with the fit of the new was as they are much longer then the old one but the car is running much better now. I no longer have the jerking on the freeway at 2750 RPMs.

 

I think I would like to find another set of the Yakaki wires because they fit so much nicer than these BWD but I'm not sure were to get them.

 

I haven't been able to test the cold start issues yet but I will tomorrow when I go to work.

 

I also pulled a ECU and MAS from a junk yard today. I tested the ECU in my car first didn't seem to make a difference, I'm still getting a code for the oxygen sensor.

 

I then tried the MAS but as soon as I put it in and started the car I got a code for the MAS. I think it might have to do with the model. The MAS from my car has the model number 22680AA160. The one I pulled from the yard was 226680AA160F. So either the MAS I got from the junk yard is bad or its' not compatible with my car. Some other post seem to indicate that it should work so maybe I just got a bad part. Guess i'll be taking that part back.

 

What should I do about the 02 sensor code? I've already replaced the sensor with a universal sensor from bosch. The one that came out of the car was also from bosch but not a universal one. I'm starting to think maybe my MAS is ok and I just need to get a factory 02 sensor.

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What should I do about the 02 sensor code? I've already replaced the sensor with a universal sensor from bosch. The one that came out of the car was also from bosch but not a universal one. I'm starting to think maybe my MAS is ok and I just need to get a factory 02 sensor.

 

When you say "universal" did you get the one that had the plug-in on it already, or did you have to cut the plug off your old one and splice it on?

 

if you got the one you have to splice the plug on yourself - go get the other one with a new plug on it already. My 90 lego threw an o2 sensor code, i bought the bosch replacement that has the plug on it and have had no further problems from that.

 

I suppose it is possible that your cold starting issues are causing the continued o2 problems tho...

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Uploaded a new video of the car starting cold. This time with the new spark plug wires and the replaced ECU. A little better but still not right. It's still stalling out. The check engine light did come on and the code was for the 02 sensor. I think this was the first time I've seen the the 02 code when I start the car cold. Most of the time it just comes up on the freeway.

 

Here's the link:

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NGK plug wires from http://www.rockauto.com are a great fit and high japanese quality. I would RETURN the BWD's and get my money back. That is a load. I would replace the O2 and go from there

 

 

Thanks Olnick. Looks like I can get these delivered for around $40. I called the dealer and they want $50 for the OEM ones. Not sure which one to go with. I can get the dealer one tomorrow or save $10. Also the dealer one might fit a little better?

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When you say "universal" did you get the one that had the plug-in on it already, or did you have to cut the plug off your old one and splice it on?

 

if you got the one you have to splice the plug on yourself - go get the other one with a new plug on it already. My 90 lego threw an o2 sensor code, i bought the bosch replacement that has the plug on it and have had no further problems from that.

 

I suppose it is possible that your cold starting issues are causing the continued o2 problems tho...

 

Thanks heartless. I've read in other places the same thing but was hoping to save a few bucks and the parts store near me didn't stock the bosch replacement with the plug on it.

 

I went for a drive after work today and picked up the OEM one from bosch with the plug. Put it in, cleared the old code and took the car for a drive. I didn't get half a mile before the check engine light came on. Checked the code an it was once again the oxygen sensor.

 

At this point I'm thinking maybe it's a wiring problem. I'm not sure what the best way to find where it is though.

 

Any other ideas what it might be?

 

Thanks again for all the advice!!!

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well darn - sorry to hear you are still having issues with the o2...

 

where to start? start by physically inspecting the wires for chaffing or melted spots beginning at the o2 sensor and working your way back - also make sure the plug is clean and making good contact.

If you have a multi meter you can use that to check continuity and such...

I have most of a set of FSM's for this year - I can try looking up spec numbers for you...

 

edit - well cant find any specific numbers for the o2 sensor ... i tried...

Edited by heartless
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Do a compression check on the engine.

 

Sounds like you have a burnt valve.

 

The O2 is reading off from the unburned fuel, then trying to lean the rest out to get to the proper mix.

 

Of course the mixture isn't the problem, it's the dead cylinder.

 

Easy fix with a valve job and a set of headgaskets.

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Thanks for the help everyone. Looks like I'll be spending some more time under the hood this weekend. I'm hoping it's just a wiring problem. I'll keep you all posted as to what I find.

 

How hard is it to do a valve job? Also if it was a valve problem wouldn't the car run bad all the time?

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Doesn't sound like a valve problem to me. Looks to me like it's only running on 2 cylinders. Which could be fuel related, bad coil, igniter module maybe.

The O2 sensor does not make a reading until warmed up to about 550-600°F. Cold start issues are almost never O2 sensor related.

 

Exactly what codes are you getting? Any misfire codes?

Other than the stumble on the highway, how does it run when warm?

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Doesn't sound like a valve problem to me. Looks to me like it's only running on 2 cylinders. Which could be fuel related, bad coil, igniter module maybe.

The O2 sensor does not make a reading until warmed up to about 550-600°F. Cold start issues are almost never O2 sensor related.

 

Exactly what codes are you getting? Any misfire codes?

Other than the stumble on the highway, how does it run when warm?

 

So the O2 sensor is not used when the car is warming up?

 

The stumble on the highway was fixed with new spark plug wires. Once the car is warm it seems to be ok for the most part. Some times it feels like its lacking in power.

 

The only code I get is a 32 for the 02 sensor. I don't think these older cars with OBDI will give codes for a miss fire. Also my gas mileage is about 2/3 of what it was before this problem.

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yes, the DO give codes for misfire - been there, done that.

 

If it is still throwing an o2 code there is something going on with it that the ecu doesnt like - and it will affect fuel mileage.

 

just out of curiosity - have you changed the knock sensor at all?

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I'd replace all the spark plugs, too. Running around with a bad plug wire will short out a spark plug. It prolly needs new spark plugs anyway.

 

Thanks Mark. I replaced the spark plug a week or two before I found the problem with the wire. When I do the compression test I'll be sure to check them as well.

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Poor gas mileage, rough cold idle, loss of power, O2 sensor code even though it has been replaced, have you checked the fuel pressure regulator? Check the vacuum line that goes to it for gas.

Do you have or have access to a fuel pressure gauge?

Have a spare regulator you can swap in?

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I think a good possibility is that the idle air control solenoid is sticky and needs to be cleaned. It starts well, then when it tries to idle down it drops to <500 rpms, chuggs and stalls. Giving it throttle keeps it running, so I would think it's a lack of air issue.

 

There's a 1" diameter black hose that runs from the air intake tube to a thing next to and below the throttle body. That's the IAC, and it's held on with 4 10mm head bolts. Pulling it off and soaking the valve inside with carb cleaner and gently wiggling the valve back and forth with a pokey object until it's clean and moves freely should fix it. Use a fresh gasket if the old one tore, or lightly smear O2 sensor safe RTV on the surface before you bolt it back down.

 

Spark plug wires, if they were red and had 1989 printed on them, are factory ones. Blue NGK's are good, as are OEM ones from a dealer. 2.2l are not nearly as picky about plug wires as the 2.5l, so don't worry about the BWD or whatever wires you put on.

 

O2 sensor code as soon as you start it means the circuit is open so there's no connection. Either you pulled a wire partway out of the back of the plug when you were taking it apart, or you bent a contact pin when you put the plug together, or the wire got broken/chewed through somewhere further up the harness.

 

99% of the time, replacing the ECU won't fix a problem. They very rarely fail.

Edited by WoodsWagon
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I took back the MAS that didn't fit my car today and the ECU that didn't help. I pulled another MAS from the car in the yard that was the same year. This time I made sure that the model numbers were the same.

 

I put it in and the car ran great for half an hour! The idle was steady and the pickup was clean when I accelerated. Just when I started to gain confidence that this was going to fix my problem the car stalled out when I was approaching a stoplight. When I restarted it and it was running really erratically. It would almost die and then recover and then do it all over again. Luckily I still had the other MAS and was able to quickly swap the new one out for the old one and drive home.

 

So I'm thinking that maybe my MAS is going bad and that maybe the one that I got from the yard is either bad as well or needs a good cleaning.

 

So here's my weekend laundry list:

  1. Clean the new MAS
  2. Check the wiring to the 02 sensor
  3. Compression test the engine and check the spark plugs
  4. Check the fuel pressure

 

I'm really hoping cleaning the new (used) MAS will fix my problems. The car ran so well for that half an hour!

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I cleaned the MAS I got from the junk yard, installed it, and took the car for another ride. It started up cold and ran great...for about half an hour and then the car just died. I tired to restart it but it was running really bad. The car sounded like it was running on 3 cylinders and smelled like it was running rich. There was no power and I could not drive, so I put the odd MAS back in and drove home.

 

I think my MAS is going bad and the one that I picked up from the junk yard is good for a short time and then goes out. This is the second time I've tried the MAS from the junk yard and it has preformed exactly the same both times.

 

I'm still going to try the other items on my list, but so far, I think the problem is most likely my MAS.

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Jerking reminds me of when my MAF when unreliable.

 

So, MAF electronics could be going bad, such that cleaning won't help.

 

I suggest pulling another used one from pick and pull; hopefully a better on.

 

Other possibilities?? crank position sensor? plug wires or plug?

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