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SuperWhiteNinetyTwoMeat
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Discussion Starter #1
I heard something about the jdm motors running lean when using a usdm ecu, and lately I think my car is running lean. A few people told me that if the car makes popping sounds in the exhaust while idling that is because its running to lean. Yet the temp guage has not moved. I have got some of the best mileage on this last tank could it be a fuel pump thats dying or something else? Thanks for any advice.
 

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///M3 > MKIII
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if you are hearing a poping in the exhaust its missing... make sure your cam sensor is timed properly.. I had to set mine once just by how the engine sounded cause I didn't have a timing light at the time.. and I would get little misfires here and there only at idle.. and turned out I had the timing way overly advanced.

Also.. that sounds like a bunch of bs to me about jdm engines running lean.. I don't know of any differences between them and us engines
 

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SuperWhiteNinetyTwoMeat
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Discussion Starter #6
No codes, just rechecked my new plug gaps and they were fine, timing at 10degrees.
 

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when this baby hits 88mph
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1QwikMK3 said:
Also.. that sounds like a bunch of bs to me about jdm engines running lean.. I don't know of any differences between them and us engines
yeah i gotta raise the bs flag. for some reason people think japan has this awesome gas thats so much better than ours. its just RON which is just a diff way to calculate gas octane. for the most part our high octane pump gas is better than theirs actually.

something else that might be worth a look is the Vf signal. use a voltmeter to see what it is doing (can hook into it at the diag block under the hood).

here is a link to translate your findings in case you are unsure how it works:

http://www.supras.com/04/resources/index.php?id=80&q=vf+voltage

btw, what plugs are you using? ive tried sev diff plugs and some idle a lot better than others. bosche were def the worst idle/performance

good luck

dave
 

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SuperWhiteNinetyTwoMeat
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Discussion Starter #9
Thank you toyota supra 1988 and Dave for the links, that will definently help me out. Im not sure if the article suggested taking it for a drive while keeping an eye on the the voltmeter, but I guess that might not be a bad idea if I had someone to help me.

As for the plugs I'm using Autolite coppers.

I think what the guy was trying to say is the JDM motors are not equipped with a egr unit, so at idle the USDM ecu will lean it out a little to compensate for the exhaust that is recirculated. I didn't think there was any difference in the ECUs, but now I'm not sure.
 

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7M POWAH! baby ;)
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jdm = japanese domestic market
usdm = us domestic market
edm i guess is what europes is hehe
 

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suprra_girl said:
jdm = japanese domestic market
usdm = us domestic market
edm i guess is what europes is hehe

ahh thanks, thought it was japanese developed motor but somehow all supra engines should be JDM then :)
 

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SuperWhiteNinetyTwoMeat
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Discussion Starter #14
Okay I measured it and it was jumping around between .5 volts and 3.5 volts during idle, so I am now confused.
 

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I have a similar problem... 3.5 volts is rich, 5 volts is pig rich. Have you resolved your problem yet?

Mine will run rich most of the time, except when I get in the gas, about two or three seconds after the turbocharger kicks in, sometimes it will lean out -- it'll drop to 2.5 and then 0.

I'm guessing I have some kind of restriction or leak somewhere that's keeping my fuel system from being able to keep the engine fed at high load -- I'm thinking that when it leans out, the motor is detonating a little bit, the knock sensors are picking this up, and then the ECU is panicking and pulling timing, and generally doing everything it can to make the motor run rich. I really have no idea, though. *shrug*

I'd be curious to see how you've fared.
 

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BTW, when your car is running rich, it is dumping unburnt gas into the exhaust, which will occasionally fire in your cat or in your muffler -- which would explain the popping sound you're hearing.

Mine does that a lot.
 

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when this baby hits 88mph
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Eriol said:
I have a similar problem... 3.5 volts is rich, 5 volts is pig rich. Have you resolved your problem yet?

Mine will run rich most of the time, except when I get in the gas, about two or three seconds after the turbocharger kicks in, sometimes it will lean out -- it'll drop to 2.5 and then 0.

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nosir. reread that link i posted. you have the voltages backwards.
 

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The article contradicts itself in regard to the Voltages. 1st its stated that 0v is rich to 5v max lean. Into the wright up its stated that 0v is max lean & 5v is max rich. I'm a bit confused (Not unusual :) ) but since the rest of the article reflects 0v (Max lean)-5v (max Rich) that Eriol has the correct voltage reading.
 

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0v [ max lean(ing) is what the computer is doing ] because the o2 is seeing pig rich condition
and visa versa
5v [ max rich(ening) is what the computer is doing ] because the o2 is seeing max lean condition
 

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Huh, weird... I woulda swore I read it the way I said somewhere.

Simple way to figure it out: what does a computer-controlled, fuel-injected car do when you let off on the gas or you're compression-braking? Does it dump unburnt gas, or does it stop feeding gas? When I do either of these things, the reading drops to 0.

Either way, I still have no idea what's wrong with my car... I suppose the next logical step is to take a pressure reading at the fuel rail.
 
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