Tuning without the TPS?

[m4xwellmurd3r]

So i've been trying to get my 280z to pass emissions (last time tested, it was wicked low across the board, but the HC idle was through the roof due to it being lean i think (co% load was 1.4, co% idle was .27)

i've been trying to get this afm adjusted (it's from an 80's MR2 ) and i've found that it runs WORSE when i have the tps hooked up, and way better with it unplugged. I think the afm is just adjusted to rich, and the full throttle position causes it to start flooding?

is it possible to tune it and never use the tps?

(btw the reason why it was so lean, was because the afm idle adjustment was set too lean since it was ment for a smaller car)

[sblake01]

i've been trying to get this afm adjusted (it's from an 80's MR2 )

Well, as Jamie from the Mythbusters would say, "Well, there's your problem right there". I don't know of any benchmarks for tuning a 78 280Z with an AFM designed for a 4 cyl Toyota with or without a TPS. The TPS changes the mixture during the different stages of throttle opening. If you get it right in one stage, it will be off in the others without it. But the real problem is that the AFM you have is not designed for that car. You're just going to have to tinker with that until you get it right if that's possible. Or find a proper AFM for that car. What was the reason for swapping the OEM AFM?

[m4xwellmurd3r]

that's the one that it had when i got it.

im gonna guess the oem somehow died sometime over the years

it runs fantastic as it is, i actually got the mixture right whenever i brought it to get it tested, but it failed cause it overheated and had nasty idle missfiring because of it.

[sblake01]

Do you have a way of testing the exhaust gas? I have a CO analyzer that I use while making adjustments. My Z has never failed a smog test during my ownership and my 810 failed one right after I bought it due to a bad TPS.

[m4xwellmurd3r]

nope, i don't have a way to test it T_T

i think i might have it adjusted to rich, so it causes the tps to flood the car. i'm going to try leaning it out a bit and see if i can get it running correctly WITH the tps hooked up.

here's the weird thing. at load it says it's richish (co% is 1.4, limit, 1.5) and the HC is down at 120ppm (limit 240-250ish) BUT the idle, says it's wicked lean and missfiring (hc is 1000ppm, co% is .24)

[TomoHawk]

It sounds like your TPS is wired backwards!

Did anybody mention checking over at HybridZ.com? They do a lot of swapping there, so maybe there's a work-around for your stuff.

thxZ

[sblake01]

Or it could be that the Toyota AFM meters air differently than the proper one for his car would. He's attempting to pass smog rather than going for performance. (I think) I don't know if he'd find any info on that at Hybrid. Even amongst the Datsun AFMs and ECUs, the manuals warn about mixing years. He's mixed manufacturers. And without a meter to test his adjustments, he's just guessing and using the failed smog tests to see his results. I'd be looking for a correct, stock AFM if it were me.

[TomoHawk]

You're right Stephen,

To know if the Toyauto AFM would even work on the Datsun, you would need to check some things like the resistance values for the different openings of the flapper ( assuming it is that design,) and probably some of the other things like the fuel pump switch. On the extreme, it might be possible to add a resistor to adjust the resistance range on the AFM to work. The engine should run reasonably well with only the AFM connected, and even better (for daily driving and performance-wise) with the TPS connected.

Just because it fits, doesn't mean it'll work properly, and maybe another swap with the 240SX AFM should be considered.

Don't forget a proper tune up too.

[m4xwellmurd3r]

it's in the shop right now, they found 2 leaky injectors so idecided to replace them all before the rest start going bad

the afm on it works pretty well actually, it's just i don't have a good way of tuning the car with it (no o2 sensor with a guage.....) what kind of work in involved with swapping in the 240 afm? just plug and play type deal? (i'm going to search that tommorow XP

[KDMatt]

...they found 2 leaky injectors...

Hrm... the elusive culprit at last?

[sblake01]

Throughout this thread, I've wondered if we were really discussing an AFM or a throttle body. The 240SX swap Tomohawk mentions that is more commonly done is a throttle body. I've never heard of anyone using a 240SX AFM on a 280Z. At any rate, neither one of those items, being from different vehicles, will help you pass an emissions test. I don't understand what you're trying to accomplish by steadfastly refusing (seemingly) to put the proper AFM on your car. For whatever performance gain, if any, these items will provide, it's just not worth the hassle, to me, if I have to screw with it every two years or whatever your state mandates to pass a smog check. My cars, both the Z and the 810, have the stock AFM and throttle body. They've never failed a smog check during my ownership.

[m4xwellmurd3r]

the problem is FINDING one where i don't have to spend 200 bucks for a new or used one. i mean, if someone in my area had a spare they'd be willing to give up for pretty cheap or somethin i'd be more than happy to swap it out.