Mombodogs

90 Vert n/a check engine lite again, code 12 & 18 . TPS. In checking everything again, I'm showing the BAC valve is out of specs also. Is one more important than the other as far as idle? I've read that the BAC must be "disabled" for TPS, so could someone point me to a thread, or a chronologial order of which to check, and when.

Idle was dead nuts for so long, now its surging and carrying on.

Thanks in advance all!

PEACE THE DOG

13b4me

The TPS ultimately controls the idle... The BAC is just there to compensate for the accessories that are turning... So if it's not working, and you have AC, PS, etc, your car won't idle...

Turbonut

iTrader: (1)

Welcome back:
I would check both as the task is not difficult.

BAC-Make certain the valve will activate when 12 volts applied. Pull the BAC and check for an inner seal that's leaking. Blow through the end and see if air passes through the seal, or spray WD40 in there when vertical and see if lubricant leaks past the inner seal. If it leaks, replace as cleaning is only a temporary fix.

TPS-Narrow Range (A - B): Closed: 0.8-1.2 Kohms --- Full Throttle: 4.0-6.0 Kohms
Full Range (E - D): Closed: 0.6-0.9 Kohms --- Full Throttle: 3.4-5.1 Kohms

1. Disconnect the throttle sensor connector.
looking at the pins, the order is:
E - C - A
F - D - B

2. Measure resistance of the throttle sensors when opening/closing the throttle. Watch for any deviations as the resistance rises, and as usual check full throttle readings.

If adjustment is needed, get engine warm, set TPS to 1kohms, then do a final adjustment using the Mazda checker using 1 or 2 multimeters.

Many threads on the subject if you need more info.

Mombodogs

Thanks guys, I've done the TPS check, and I know the high range is above limits, but it seems odd that the TPS and BAC went bad at the same time, realatively speaking. I will pull the BAC and check it out. I see that some BAC's have adjustments, the reading I get is 13.8 ohms, is this adjustable on my vert?

PEACE THE DOG and it is good to be back! Thanks Turbonut!!!!!!!!

13b4me

A bad BAC can cause the TPS to go bad due to the increased load placed on it...

HAILERS

Your kidding.

RXxtraquick7

Were you referring to me about kidding Hailers? If you were, I'm not. I have read so many threads and posts on TPS, I would be surprised if the actual designer of this system weren't high when he came up with it. I know its simple for electronic wizards to understand, but that is what I am not.

I have a spair ECU I am taking apart to prepare me for testing of all this great information that has been provided. If someone actually had gone step by step in explaining it, there wouldn't be 50 new threads a day on it.

Haynes Manual Simple steps for idle-BAC ,AWS ,ASV, throttle cable, throttle valves, fast idle, water thermo valve, VDI, Solenoid Valve, Auxillary port valve, pulsation damper, injectors, EGI, Boost Sensor, Atmospheric sensor, Hot start assist, air pump, Cat converter valve, air valve, switching solenoid, relief solenoid, intake valve, and then the TPS. I mention these, cause my car is still stock with all that crap.

Sorry, I truly am. I'm frustrated, confused, and would like for someone to tell me how to adjust the fast idle cam screw, under the thermowax, while in place. I have tiny hands, and I can barely see the SOB with the hood off. See my pictures.

Again, I'm sorry. I have every TPS adj. thread from Wozz, to Geocities, to RXster, and so on imprinted on my brain. They are all great, just don't always work. And I do not have a vaccum leak.

Appologies again, I'm done venting.

PEACE THE DOG

NeCr0mStR

iTrader: (3)

OK so I used this method to adjust things... and I need to know if closed also means at rest? like the tps is closed or no throttle pressure on it at all right? Because I get

A-B closed 2.40kOhms
Full 5.35kOhms

E-D closed 1.22
Full 4.88


Now the A-B sweep is kinda choppy and hits 5.35 way before it is fully open.

Also I can get wthin specs if I push my TPS plunger closed but I have to force it to go all the way in kinda deal, if anyone can tell me if this is wrong it would be greatly appreciated.


Oh one more question when referring to reseting the TPS to 1kOhm how do you reset it? What is the procedure for reseting it? I am sure its obvious but someone please help me clarify.

Thank you

RotaryEvolution

iTrader: (30)

i would replace the TPS and recheck it, the BAC is affected by the TPS and will cause surging is the TPS is faulty of mis-adjusted so start with the TPS before moving on to the BAC testing.

NeCr0mStR

iTrader: (3)

I assume I should try for a used TPS since a new one is SUPER expensive?

NZConvertible

Completely wrong. The TPS does not control idle speed. The ECU controls idle speed by altering the duty cycle of the BAC valve, which alters the amount of air bypassing the throttle. The TPS simply tells the ECU whether the throttle is closed. If the ECU gets incorrect throttle position info then it can't control idle speed properly.

Like Hailers said, you're kidding right? Exactly how do you think that could happen? The TPS does not have any load on it from anything (except the throttle linkage). It's a very simple potentiometer that receives a fixed voltage from the ECU and sends a reduced voltage back depending on throttle position. It is not connected to the BAC valve in any way, mechancially or electrically.

13b4me

Thanks for clearing that up for me... I was under a completely different impression of how that worked... Electrical systems pwn me...

Fitness Stain

i dont have a BAC valve on my ride and i idle just fine

the car will idle as long as the other idle control mechanisms are functonal ...
actually the only idle control i have is the idle set screw on the back of the TB

you WILL notice the idle dipping from time to time .. FOR SURE while using the AC, but i never use that anyway ...

i have my idle set to around 1300 on purpose (while warm)

that way when i first start it up i only have to give it throttle for a few seconds and it will hold itself at around 500-800 rpms

i used to have the idle set to 800-900 when warm, but this caused the cold idle to be pretty damned low and forced me to have to keep it alive for a minute or so ...

however if i did it all over again i would leave the bac intact ... its not really in the way of anything and you gain nothing from removing it ... unless its faulty of course .. but i've read on here alot of people just cleaning them out and they work fine again after that ....

NZConvertible

Am I the only person to notice the completely contraditction in these two statements?

Aaron Cake

iTrader: (1)

No, I see it too...All the time I hear stuff like "I pulled my BAC valve and my car idles just fine! Of course their definition of fine is 1200 RPM that drops to 700RPM when the A/C turns on...

My5ABaby

iTrader: (7)

What's A/C?

Fitness Stain

what i meant is that the car still holds an idle ... as in doesnt die when the cars accessories are on .... because the person i quoted said the car WONT idle ... untrue

i know its "supposed" to idle around 750 but who cares?
when i jack up my idle a wee bit like this i can run everyting and not worry about the car stalling out ... it also keeps my oil pressure above the 30 mark on the stock guage while idling.

when i first removed the BAC years ago it was by accident basically while removing all the other emissions stuff ...

if you notice in the same goddamn post that you are quoting i said i would keep the bac valve if i had to do it all over again ...

My5ABaby

iTrader: (7)

Unless someone can come up with a reason to NEED to idle at 750, I agree. It's not like I sit at idle much. I don't do a huge deal of stop/go, so I probably sit at idle about 5% of the time.

HAILERS

Try taking that car with the 1300rpm idle to get it emissions tested and they'll reject that puppy so fast it'll make your head spin.

A little off topic, but I saw something related to the a/c that I didn't know about nor have read about. When the a/c compressor comes on, the timing advances. Now I know the bac duty cycle should bump up with the a/c compressor on, but I'd no idea the timing would also bump up

My rpms rise when the a/c is turned to ON but only to about 800rpm or so (meaning it's not the rpm going over 1100 rpm causing the ECU to bump the timing up).

And it's not related to the fan causing the bac to go to a higher duty cycle, because I turned the fan full blast with the a/c off, and the timing did not change. Turn the a/c to ON and the timing goes up. Just a little FYI.

I watched the timing on my Palm thru the RTEK2.0.

Aaron Cake

iTrader: (1)

Removing the BAC is a pointless "mod" that gains you nothing but looses you a lot. That's my main issue. All it does is make the car harder to live with and require other hacks to make the car operate close to as it should.

Fitness Stain

no emissions



and aron i understand your point for sure ... like i said i didnt know enough about it when i first took it off ... and thats why i recommended keeping it

My5ABaby

iTrader: (7)

Gotta love TN and no emissions testing.

Fitness Stain

indeed ... well parts anyway

most of middle tn has emissions, but i registered my car in roane county ... my home town of kingston

My5ABaby

iTrader: (7)

I have 0 testing period. Good old redneck counties

NZConvertible

"Holding an idle" at 1300rpm and idling "just fine" are not the same thing. Unless you have a bridgeport anything over 1000rpm is just ridiculous.

1300rpm is not "a wee bit", it's nearly double the normal idle speed! I'd be embarrassed to drive around with an idle like that. If you need an idle that high just to stop it stalling there's something seriously wrong with your engine. A warm, unloaded engine does not need a BAC valve to idle at 750rpm, it just won't be able to react to changing conditions. When I had my BAC valve temporarily bypassed (it was leaking past the valve) my warm idle was never higher than 800rpm.

Again, this is a sign that something is wrong. Probably the gauge...

Whether or not you have a BAC valve was not my point, what you consider a "fine" idle was. Adding a BAC valve isn't going to help whatever's wrong with your engine.