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Discussion Starter · #41 ·
was the code you pulled for the upstream,downstream or both 02 sensors? cod also have a melted down cat . a vacuum snap test would verify if or if not . if you disconnect the problematic o2 sensor with it running does it smooth out ? have you checked voltage outputs from the sensor or input voltage ( if it's a heated type ) ? those things arnt cheap just to be guessing .
No, I havent done any of those things. As for the code being for upstream or down, I dont know that either but I bought the upstream sensor today from NAPA, 81 bucks. From what I've read online though, it is most likely the upstream and if not, at least the downstream one is supposed to a good bit less expensive and easier to replace. I am no longer able to crawl around under cars so I am going to have to pay a man to replace this one for me, maybe the downstream one I can do myself.
 

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No, I havent done any of those things. As for the code being for upstream or down, I dont know that either but I bought the upstream sensor today from NAPA, 81 bucks. From what I've read online though, it is most likely the upstream and if not, at least the downstream one is supposed to a good bit less expensive and easier to replace. I am no longer able to crawl around under cars so I am going to have to pay a man to replace this one for me, maybe the downstream one I can do myself.
in my experience lots of times 02 sensor codes being set is really just an after effect of something else being out of kilter . the only way to tell is to take a voltage sample directly from the sensor and see if it's switching between a high and low voltage reading ( closed loop ) or if it's not switching at all ( dead sensor ) . otherwise your just guessing.. I guess you will know soon enough .
 

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it
in my experience lots of times 02 sensor codes being set is really just an after effect of something else being out of kilter . the only way to tell is to take a voltage sample directly from the sensor and see if it's switching between a high and low voltage reading ( closed loop ) or if it's not switching at all ( dead sensor ) . otherwise your just guessing.. I guess you will know soon enough .
it's easy to check this with an obd2 system and a graphing data logger BUT since your car is obd1 you have to unhook the sensor and use a meter to check it , kind of a pain especially if you can't crawl under the car . let us know what happens . good luck !
 

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Discussion Starter · #45 ·
in my experience lots of times 02 sensor codes being set is really just an after effect of something else being out of kilter . the only way to tell is to take a voltage sample directly from the sensor and see if it's switching between a high and low voltage reading ( closed loop ) or if it's not switching at all ( dead sensor ) . otherwise your just guessing.. I guess you will know soon enough .
Yep! Now I know. Changing the sensor did not make it run a bit better. Would you take time to tell me again, kinda like you would a child, how to do that test you speak of? I would appreciate any help!!

On this car, you cannot readily see any wires that come out of the sensor, even the mechanic who replaced it for me could not make me a price to do the job cause he could not see from the top side what he would have to do. Luckily for me, he is a very trust worthy person and did not attempt to take advantage. Charged me 40 bucks to do the job.

Things have really changed on vehicles since I turned wrenches! Back then, you put in new points plugs and condenser, Adjust the carb and check the timing. If you managed that without dropping the screw down thru the distributor, and I did more than once, it would run right.
 

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Discussion Starter · #46 ·
Sure glad I have an OBD1 test can and scanner.
I did find a good way to check codes on this one, just hook a volt meter to numbers 1 and 12 on the plug where you would usually plug in the OBD1 tester. Turn the key on, and the meter will read a wide arc on the dots, and just a blip on the dashes. It leaves no doubt that you are getting it correctly.
 

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Yep! Now I know. Changing the sensor did not make it run a bit better. Would you take time to tell me again, kinda like you would a child, how to do that test you speak of? I would appreciate any help!!

On this car, you cannot readily see any wires that come out of the sensor, even the mechanic who replaced it for me could not make me a price to do the job cause he could not see from the top side what he would have to do. Luckily for me, he is a very trust worthy person and did not attempt to take advantage. Charged me 40 bucks to do the job.

Things have really changed on vehicles since I turned wrenches! Back then, you put in new points plugs and condenser, Adjust the carb and check the timing. If you managed that without dropping the screw down thru the distributor, and I did more than once, it would run right.
do a vaccum snap test first . this will tell you if the cat converter is clogged or melted ( likely if you had a bad maf and it was running rich ) 1. connect a vacuum gauge to NON ported vacuum like where the brake booster feeds from . 2. start engine and note vacuum , should be around 14hg on a healthy engine , if it's really low you have valve timing or compression problems . 3 . OK now watching the gauge with the engine running snap the throttle quickly , when you do this you should see the vac gauge go to zero and return to 14 . if it does not do that I'd suspect a clogged converter which will throw off the 02 sensor readings and set an 02 sensor code . try that first and post back the results.
 

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1993 obd1 tech is old and simple compared to what's out there now. now you have air/fuel ratio sensors , variable valve timing , variable turbo trim , self adaptation , cylinder deactivation , can/bus networks . all very complex , have to have an i.t degree just to diagnose new stuff .
 

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Discussion Starter · #49 ·
do a vaccum snap test first . this will tell you if the cat converter is clogged or melted ( likely if you had a bad maf and it was running rich ) 1. connect a vacuum gauge to NON ported vacuum like where the brake booster feeds from . 2. start engine and note vacuum , should be around 14hg on a healthy engine , if it's really low you have valve timing or compression problems . 3 . OK now watching the gauge with the engine running snap the throttle quickly , when you do this you should see the vac gauge go to zero and return to 14 . if it does not do that I'd suspect a clogged converter which will throw off the 02 sensor readings and set an 02 sensor code . try that first and post back the results.
THANKS! I will try that.
 

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Discussion Starter · #50 ·
do a vaccum snap test first . this will tell you if the cat converter is clogged or melted ( likely if you had a bad maf and it was running rich ) 1. connect a vacuum gauge to NON ported vacuum like where the brake booster feeds from . 2. start engine and note vacuum , should be around 14hg on a healthy engine , if it's really low you have valve timing or compression problems . 3 . OK now watching the gauge with the engine running snap the throttle quickly , when you do this you should see the vac gauge go to zero and return to 14 . if it does not do that I'd suspect a clogged converter which will throw off the 02 sensor readings and set an 02 sensor code . try that first and post back the results.
I have found my vacuuam gauge but it has been raining for the past couple days so I havent tried that test yet. I have another question though since you seem to know more about mitsus than most. Is there any chance that the harmonic balancer has been off, and put back on so wrong so that checking timing will give a wrong reading?

I ask because I checked the timing again and it was set correctly, so I advanced it again, this time up around 20 before. It ran MUCH better, does not spark knock and the trouble light has not come on.
 

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I have found my vacuuam gauge but it has been raining for the past couple days so I havent tried that test yet. I have another question though since you seem to know more about mitsus than most. Is there any chance that the harmonic balancer has been off, and put back on so wrong so that checking timing will give a wrong reading?

I ask because I checked the timing again and it was set correctly, so I advanced it again, this time up around 20 before. It ran MUCH better, does not spark knock and the trouble light has not come on.
I'm not a mitsubishi guru or anything . I went through tech school for automotive and been working on import cars for 28 years though so I consider myself "seasoned". my tractor is a mitsu diesel is why I got the avatar .

I've never seen a balancer that wassnt keyed so unless the key got leftout or broke its unlikely its not where it should be .
on some efi engines they have to be put into what's called " base timing " meaning a connector has to be jumpered then the timing set , then remove jumper ... I'm not certain the details if that particular engine but you should be able to find it somewhere , if you set ign.timing without It being in base time mode its not going to be correct .
something else you might want to check is the valve timing , if it's jumped a tooth or slipped that would make sense why it smooths out when you advance the ignition timing so much . once again I don't know where the timing marks are on that particular engine but easy enough to lookup online if you know the exact engine model number , the mitsu 3000gt's had several variants over the years . emissions decal on the hood should tell you exactly which one you have . hope this info helps you .
 

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Discussion Starter · #52 ·
on some efi engines they have to be put into what's called " base timing " meaning a connector has to be jumpered then the timing set , then remove jumper ..

Yeah, thats how you do this one. I appreciate the help!!

I had thought about jumped timing, but seems like that would set off the check engine light, and it has not come back on after I replaced the 02 sensor and then unhooked the battery to clear it.
 

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on some efi engines they have to be put into what's called " base timing " meaning a connector has to be jumpered then the timing set , then remove jumper ..

Yeah, thats how you do this one. I appreciate the help!!

I had thought about jumped timing, but seems like that would set off the check engine light, and it has not come back on after I replaced the 02 sensor and then unhooked the battery to clear it.
You know the system has to run throw a few run cycles for check engine light to come on. That requires some road time.
 

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on some efi engines they have to be put into what's called " base timing " meaning a connector has to be jumpered then the timing set , then remove jumper ..

Yeah, thats how you do this one. I appreciate the help!!

I had thought about jumped timing, but seems like that would set off the check engine light, and it has not come back on after I replaced the 02 sensor and then unhooked the battery to clear it.
I don't think that engine monitors valve timing since there is no cam/crank sensors right ? doesn't the distributor have the sensor in it ? if so it's dumb and can't sence an out of time issue , worth a check at least . gotta go back to the basics sometimes to find the root problem .
 

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Discussion Starter · #55 ·
Im an ASE Master Tech and a mitsubishi fan. I have a few mitsubishi vehicles, although some are projects that havent been started on yet. Running: 87 Montero, 02 Diamante. Not yet: 97 3000gt, 1980 Plymouth Arrow Pickup (read Mighty Max).

I've also had the 3.0 Sohc v6 in several FWD dodges including a Dodge Dynasty that I converted to a manual trans. I even have two different styles of rare custom-made turbo manifolds for 3.0s in Dodges.

All this to say, you shall not take the Crazy Crown from me!! lol
I asked Wrenchturner this question, but I had you two mixed up thinking that he was the mitsu fan. Is there any way that the harmonic balancer could have been taken off this engine and put back on wrong? Are they splined, or do they have a key?
Cause as I told him, when I went back and set the timing way high, according to the light, it runs much better. More power, doesnt sputter, and the engine light has not come back on, Cranks good, does not spark knock, just seems like that is closer to where the timing should be. Set it where it is supposed to be, and it wont hardly pull off, finally starts pulling good after you get above 3000 RPMS. Seems like it catches its breath there and takes off.
 

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Time to find out a few things.
1. Is this an interferance engine. ( If the timing belt or chain goes will it self distruct).
2. You checked cam to crank timing?
3. What type of timing light are you using?
 

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Discussion Starter · #57 ·
Time to find out a few things.
1. Is this an interferance engine. ( If the timing belt or chain goes will it self distruct).
2. You checked cam to crank timing?
3. What type of timing light are you using?
The only one of those questions I can answer is, the timing light is the same kind I used 35 years ago. 2 connections to the battery and one to the #1 cylinder.
 
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