Ok , so my 87 Turbo has been having some problems with the AFR. It idles fine, at about 14-15. but if i slowly apply throttle it drops like a rock at about 2k its at about 17.5-18 and at 3k its usually below 18. The AFRs are just great under boost, so i'm not too worried about that. Ive adjusted my Super AFC to compemsate it for now by lowering the throttle point to about 40% low and 80% high. This helps fixes the problem while im crusing around, but the base problem still remains.

My Mods are:
Racing beat 3" turbo back with custom 3" bonez cat installed for emmissions. FCD and a SAFC. I use a PLX wideband to monitor the Air/fuel

My first thought was that maybe my stock o2 sensor wire came loose, but it is fine. So my second thought is the TPS.. Would this do it if it was outa wack?!?!?

Just looking for some ideas so if i fix the TPS (tomorrow) and it still is screwed up ill have something to check nex.

Any help appreciated.


AUGie

 

How does changing the throttle point on the SAFC help AFR's while cruising though? When I'm on the highway at 75mph the throttle (according to the SAFC) in my s4 N/A usually reads 100%.

 

ever think about ur car not getting enuff fuel? ic uhave an fcd and if u start raising boost levels ur gonna start to lean out the higher u go..

 

I've experienced an issue where right around 3k RPM's there's a 'flat' spot under mid-level acceleration... I can feel the hesitation as well as monitor it on my (narrow-band) A/F gauge.

But yeah, at WOT/boost my problem would go away. It's like there's no transitional period. I would trace this to the TPS. Have you checked the resistance/specs on your TPS?

Don't know if that's ANY help at all, but I can tell you--you're the man Dogie.

 

AFRs are find under boost its only at the "normal" setttings that it is runnig lean.
at 2k rmp it is showing 27% wich is way below the low settings that i have. there for it is running on the stock fuel maps as i havn't changed them for the low setting.

 

Well crusing on the freeway at about 60 my tps was listing about 78% (???) i had my SAFC set to pretty much be on or off with low at 95% and high at 96%. By lowering the low tps setting it kicks up into the high fuel settings and gets more fuel

I also have played with the fuel settings in the low setting but i need to adjust the fuel ALOT to get it to read an AFR in the yellow about 23% correction at 2k just do get it at about 14:1 that seems like its WAY too much .

Im kinda worried it my be my AFC. I had it mounted up at the base of the windsheild at it was really hot last night with the defroster on full. Plus its been acting a little strange when i turn on the car. It will go to settings when i hat it set to display.

I think that i will bypass the fuel control parts to the AFC and go back to the stock ECU controlling the fuel and see if that helps first. (no boosting though) then check the TPS if that doesnt yeild any results.

 

Your WOT is fine, right? Whats wrong with it? Your AFR looks correct to me.
You DO NOT want to cruise at 11 AFR.

It is listing 78% throttle when you are crusing because you have a narrow band TPS.

You need to leave the S-AFC at 0%, because you are a bit confused about how AFR works.
Stop messing with the low throttle map. You do not know what you are doing.

If it worrys you that much... take off the wideband...

 

slpin:
the reason i am concered about my A/F ration is much lower then it was one month ago. On the low setting it would stay right in the stoich range while crusing. This stayed constant though the the rpm range at 2k it would show 14-15 and at 3k and 4k etc. It would drop on deceloration to 19 like it was supposed to and then go right back to the stoich range. The only time it was up into the rich range was under boost ie WOT which is also just fine.

I know about the narrow band TPS on my series 4 it makes it tough to tune with the AFC and I was going to be changing over to running off of the boost sensor soon. HOWEVER the current problem has put off that idea because it doesnt seem to be running properly at stock settings (which is what my low throttle map is set at)

The only settings i change on the low throttle map are to make tests. Otherwise i run at stock levels on it.

I do understand how AFRs work. In an ideal world my car would always be showing stoich. whether at idle or under 10 PSI of boost. but i know that for safety. i have to run it ruch under boost, and that running lean is not good.

I worry when my oil light goes on, should i remove that too????

I really am not trying to be rude i am just asking for a little help.

 

1. I'd suggest to disconnect the 02 sensor. It plays no part at idle or acceleration, but does during cruise. During cruise it will fight the inputs of the SAFC.

2. I"ve never seen a RX-7 that would idle at 14-15 afr at idle unless the airpump and ACV are working, then the afr IS NOT 14-15 because you have the airpump air exiting at the exaust ports prior to the wideband and you can figure out what that means. So at idle disable the airpump by pulling the Relief Solenoid plug off.

3. If you do not have a airpump and acv and have 14-15afr and the idle is smooth and whatever...............then I'd say the wideband is corrupt.

4. I'd have the SAFC throttle input coming from the boost/pressure sensor instead of the TPS since it's a series four tps and it's at 100 percent at MAYBE 20percent throttle travel.

 

My GTU will idle at 14.1-14.3afr around 780 without jumping all over the place.


When I ran my wideband's narrowband output into the ECU I got some disturbingly nasty AFRs under light throttle/cruising, around 16-19AFR.

89GTU without any emmissions so its not the AP dumping fresh air into the exhaust, I have no AP.

 

so is the method for testing the TPS out of the car the same as in. Mine was acting funny so i pulled it. it shows .97 ohms and goes DOWN when i push in the button. in the car i couldn't get it to read better then 1.5 ohms and 5.4 ohms at WOT

One last question... .is the narrow range TPS from a Series 5 interchangeable with the series 4???
cause i hava a spare S5 TPS

 

The ECU wont be able to use the signal.

 

I notice you don't have an upgraded fuel pump?

 

Where are you measuring afr from? If its the end of the tail pipe you may have a gasket or part of a gasket that fell out.

 

eternal gamer: no upgrade yet. its next on the list. Havnt had problems befor now.

Greg: wideband is at about 2 feet from turbo just before my cat.

Fortunaltly IF i have a extra tps its from my spare 87 t2 (i forgot i had that one) so im going to do some more testing and If i can find it maybe swap out the tps with my other one

 

*****One last question... .is the narrow range TPS from a Series 5 interchangeable with the series 4???***********

The last time I looked, the series four TPS was held to its bracket with four little bent over ears. So it can be seperated from its bracket if you bend them up. So look at your series five narrow range and compare the two narrow range and see if they can be swapped.

Resistance on the tps is measured in K ohms.

Again, pull the 02 sensors wire off if you want to see what a SAFC is doing to the mixture. The ECU will fight any changes made by the SAFC if you leave the 02 sensor connected. Common sense.

 

well i finnally got my tps adjusted with the volt meter method. Reads just under 1ohm (.98 or so) at rest and about 5.5 at WOT just like its supposed to. BUT it hunts really bad when i start it like that. i know i can adjust it with the test light method, but then my tps voltage will be like 1.3, WFT??? going to play with it some more tommorow. Get it adjusted with the lights, and pull the O2 sensor to see what happens.

So could this be a bad O2 sensor causing all this?? I got lots of those *******. so it should be easy to test.

Any way thanks for all the help so far guys. i'll keep you posted

Augie

 

The 02 only works during cruise. Steady throttle is what I mean. Any time you accelerate or go wide open throttle it's not a player. So if your talking about wot and acceleration, then it's not the 02 sensor.

If your cruising at a steady rpm, the 02 and ECU will try to maintain something close to stoic. If you pull the plug on the 02 and drive the same steady rpm, then you'll see what your SAFC settings are doing at those steady speeds. That's if you've put inputs to the SAfc for low throttle.

And you know that the 02 sensor has no input at idle so it can't be the 02 being a problem at idle.

 

Well the tps is back to set by the light method, it just wouldnt hold idle if i adjusted it to 1 ohm at the tps itself. soooooo

I pulled the o2 sensor like hailers recomeded and it doesnt change anything. I Checked the voltage on the o2 sensor and it stayed pretty low, like at .08 voltage. I checked the narow range output on my wide band and it reads double that. Swaped out with another o2 sensor i had( very few miles... its a long story) and it is about the same. voltage seems really low. Im going to check the continuity of the wire to the harness, and maybe attach the narrow band output from my wideband to my ecu and see if that does anyting.