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Josh, I dion't know whether it was an at or mt, the engine was stored in the junk yards storage rack area and all they know is that it is 90-94 compatible according to them. What I have is a 90-91 engine with 93 rail & injectors, and harness in a 93 automatic legacy wagon. It drives as good as my original engine, BUT THE DARN MILEAGE IS PATHETIC........15mpg city vs. 23 with my all 93 car. Highway is 21mpg now vs. upwards of 30 in the all 93 car. Absolutely no difference in seat of the pants feel from my 93 motor, great cold idle , idle goes up with ac and defrost, absolutely perfect except for the mileage. No flat spots, doesn't feel sluggish or rich running at all. What, other than the injectors do you think I should pull off my 93 motor? the sensors and emission stuff looks identical. Throttle body? idle valve ?, I drive up to 1000 miles a week so this mileage problem will hit me in the pocket book big time. I will reset the ecu tonite. Any idea if those 90-91injectors may help? I can't find any info, other than from you, as to what to try next.

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Does the IAC valve look like this?

http://www.main.experiencetherave.com:8080/subaru/images/injectors/DCP_2470.JPG

 

If it's exactly like that, the engine you got was from an automatic.

 

If the engine seems to be running good, I'm sort of at a lost as to your mileage.

 

Reset the ECU and report back.

 

Who rebuilt the tranny? Does it have any kind of warranty?

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the valve looks the same, it has these numbers on it

 

22650 AA032

A33-000-R10

OY21C

 

I reset the ecu by following the fuse instructions and the trannt has a 12,000 warranty and I'm 10,000 into it, I'll drop it off Tues. It was rebuilt in Aug. 04.

I drive alot, this is my work & personnal car, so I keep it in perfect shape. And check the mileage every fill up, this engine runs srtong but eats gas like crazy. I was thinking if the passenger side fuel injector wires were switched that would have maybe explained where the gas is going, but I think they are on the correct injectors. Really strong motor. Argh!!!

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have you tried swapping the injector connectors to double check?

 

Other thing you can do is pull one connector off while the engine is running. It will leave a code in the ECU. Check the code, and it will specify which injector it came from. If it doesn't correspond to cylinder # you pulled off, you know you got the wrong ones on.

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will try, when I switched injectors to the 93 ones, I only transferred the straight rail section, not the curved lines that snake their way around the engine, I don't think it matters. My 3rd tankful and still pathetic mileage.

No you don't need to swap the hard fuel lines that hook up to the rails.

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pulled the front passenger cord to the injector, got cyl#1 error code, so my injectors have the correct leads. Will drop car off to tranny place next week. Could it be a bad o2 sensor? I got o2 sensor error codes from when I was switching injector leads, but not since the leads & injectors match. absolutely no error codes now Even reset the ecu. I wonder if I should put my 372k throttle body on ( it looks old and alot "blacker" inside than the 65k one. Totally stumped.... PCV valve is fine, swapped it with my 93 engines. I'm assuming the cam shaft and crank sensors are the same, no error codes. Is the intake manifold identical between a 93 and 91? coil pack swapped also. Anyway the 2 lines right next to the line from the fuel filter can be switched? I swear I labelled them correctly. This is a doozy of a problem.

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pulled the front passenger cord to the injector, got cyl#1 error code, so my injectors have the correct leads. Will drop car off to tranny place next week. Could it be a bad o2 sensor? I got o2 sensor error codes from when I was switching injector leads, but not since the leads & injectors match. absolutely no error codes now Even reset the ecu. I wonder if I should put my 372k throttle body on ( it looks old and alot "blacker" inside than the 65k one. Totally stumped.... PCV valve is fine, swapped it with my 93 engines. I'm assuming the cam shaft and crank sensors are the same, no error codes. Is the intake manifold identical between a 93 and 91? coil pack swapped also. Anyway the 2 lines right next to the line from the fuel filter can be switched? I swear I labelled them correctly. This is a doozy of a problem.

You know that you have a problem with the transmission. I would wait to have the the transmission straightened out before I went any further with the engine. The problem could be in the transmission. And it's much, much tougher to troubleshoot two problems simultaneously.

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I thought of that, but the tranny was beginning to slip 2nd to 3rd with the 372,000 motor while I was getting the much better gas mileage with that engine. It's a few hundred rpm slip from 2 to 3 under heavy acceleration, not in normal city driving.

 

Frankly, there are people on this board more experienced on early 90's Subarus than me. But, I know that on the later Subarus the O2 sensors sometimes can be ineffective for weeks before they throw an error code. You can easily measure the O2 sensor output with a multimeter. Make sure the voltage is well within the specified values. It'll take just a few minutes, and then you will know for certain that the sensor is or isn't part of the problem.

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pulled the front passenger cord to the injector, got cyl#1 error code, so my injectors have the correct leads. Will drop car off to tranny place next week. Could it be a bad o2 sensor? I got o2 sensor error codes from when I was switching injector leads, but not since the leads & injectors match. absolutely no error codes now Even reset the ecu. I wonder if I should put my 372k throttle body on ( it looks old and alot "blacker" inside than the 65k one. Totally stumped.... PCV valve is fine, swapped it with my 93 engines. I'm assuming the cam shaft and crank sensors are the same, no error codes. Is the intake manifold identical between a 93 and 91? coil pack swapped also. Anyway the 2 lines right next to the line from the fuel filter can be switched? I swear I labelled them correctly. This is a doozy of a problem.

It might be the O2 sensor. You could try getting a new one. Especially if it's never been replaced and it has that kind of mileage on it.

 

You really can't test the O2 sensors too well. The voltage on them at idle will go up and down between 0v and 1v. If it doesn't oscilate then there's obviously a problem. Some multi-meters however don't have a fast enough sample rate to see the oscilation, which is why I'd say just replace it if you have more then 100k miles on the sensor.

 

The throttle bodies are the same, with the exception that some of the 90-91's had a little idle adjustment/bypass screw on the top of the TB. I found this out the hard way when chasing a high idle problem. However they are fully swappable. camshaft & crankshaft sensors should be the same. Intake manifold should be the same or similar enough not to cause an issue.

 

There's three lines coming from the fuel area. One is obviously a fuel supply, ones a return, and one's from the fuel separator vent system in the tank. The supply line should go to the bank of fuel injectors on driver's side. The return should come from the line on the pass side of the engine. Technically I guess you could swap them....

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will try the o2 test, where can I find the values? also is there a way I can post this whole thread on the older board.

Just post a new thread over there linking to this one. Tell them to try and keep all the technical replies/discussion in this thread so it's easier to follow.

 

I'd also recommend waiting on getting the tranny fixed so you're not trying to hunt down two problems at once.

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thanks Josh, taht idle screw is what I used to bring the idle down from 1100 to 800. Dealer wants 149 for an o2 sensor, autozone wants 89. Is one better than the other? can it be off and not throw a code? I'll try to link to the other board later tonite. Since I drive up to 1000 miles a week, and have my car memorized, I can tell by the time I'm halfway through my gas gauge how the mileage is going. Then when I fill up and do the math I'mpretty close. This darn thing goes through gas like a v8.

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sorry for the confusion again, I adjusted the top and bottom stop screws to lower the idle. It seems that there is either a cap plate on top of the screw in the throttle body or no screw at all. I adjusted the top stop screw (with the white paint) and then adjusted the bottom stop screw (with the nut around it) so that at idle bolt screws were up against the moving linkage at idle. Minor turns were needed. I once had a 90 legacy that had the O-ring screw in the throttle body, I'm assuming it is an air screw. I only had to lower idle by approx. 300 rpm when warm. After the adjustment, the cold idle and fast idle(for ac and defrost) still work fine.

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You're not supposed to touch those throttle stop screws ;) The TB is bench flow tested at the factory and adjusting that can mess things up.

 

As I mentioned before, adjusting those screws is trying to fix a symptom, not a problem. More then likely the high idle issue is/was related to your horrible gas mileage problems.

 

Unfortunately I really don't have any more suggestions as to what the problem may be. Other then testing all the sensors with a multi-meter and checking over everything....I'm sort of at a lost. That air bypass screw is what got me. I swapped TB's and the problem went away, I was like WTF? and finally found that screw. If you still have your other TB, you could try swapping it and see if the high idle goes away.

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will do, I also noticed if I disconnect the o2 (to see if there is a difference)sensor it appears as if I'm getting better mileage, at least on the 2 tankfuls I've gone through since yesterday. I figure 372,000 on the original o2 sensor was pushing my luck.

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mission Control: we have data coming in.

Fact 1.) 4mpg better highway mileage with o2 sensor unplugged, confirmed on last 2 fill ups. Same route, same weather conditions.

Fact 2.) 372k (from 93 motor) throttle body has 800 rpm warm idle on 65k 91 motor. 91 throttle body has 1100 rpm warm idle (before adjustment).

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Sounds like I'd definitely put in a new O2 sensor

 

On TB....is the 93 TB the one you adjusted or is it the 91? I think from your post, the 91 is the one you adjusted. So you swapped back on the 93 and all is good?

 

Other thought.....do you know how old the coolant temp sensor is? That may be something you might want to replace. it's 20 bucks from subaruparts.com and can affect how much fuel the engine is getting.

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the 91 tb was adjusted because it had the high idle, the 93(unadjusted) tb on the 91 motor had the normal idle. Now, do I keep the adjusted 91 tb on the motor, or the older, more worn 93? Yeah, I'll get an o2 sensor and a temp sensor. I just hope a new o2 sensor doesn't give me the crappy mileage back. ALSO....... my 372k motor had 20/50 oil in the summer and 15/40 rotella in the winter. On this "new" broken in motor I think I'll go 5/30 winter and maybe 15/40 rotella in the summer. OR synthetic.

 

THIS MAY BE THE CURE!!!!

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Keep the unaltered 93 TB on there.

 

The only component that really might need replacing is the TPS. If you want to swap TPS's you can do that. However you will need to adjust the TPS for the TB. You do that by setting the idle switch. Instructions are here:

http://www.main.experiencetherave.com:8080/subaru_manual_scans/FSM_Scans/TPS_testing3.jpg

 

I'd recommend a 10w30 for these motors. The owner's manual says not to run 5w30 if you're going to be doing extended freeway or "high speed" driving.

 

Hope we're on the home stretch here.

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