^Zircon248

iTrader: (5)

Hi all,

I'm having an issue with the car at the moment. While I'm cruising there is a moment where my wideband slowly goes from 12.5 AFR to no reading in the lean side if I'm slowly pressing on the throttle to keep car's speed constant. If I gently retract my foot, it come back to 12.5 AFR but car's is decelerating slowly and if I press the throttle for normal acceleration (or hard one) there is no problem what so ever.

I'm leaning toward the TPS having a broken spot but coud'nt find it with my multimeter. Also the car does'nt have any power and stutter when it happen.

Here is car's details:

-S5 TII Engine
-Rtek 1.5 (no omp) N374 ECU
-AEM UEGO Wideband
-Rat nest removed, still have the BAC for idle control
-Ajusted the TPS recently and did'nt change anything

Any help is welcome !

GrossPolluter

iTrader: (1)

I would def see what is going on with the tps. My wideband read super rich when my tps wire was hanging by a few strands. When I would snap the throttle, the af ratios went all over the place

^Zircon248

iTrader: (5)

AFR are at 12.5 Idle and around 13.2-13.5 on hard acceleration. But while cruising depending on throttle position I've seen 10.5 AFR (and full lean too) some times.

I'll take the TPS and AFM out for testing this afternoon and report my findings.

^Zircon248

iTrader: (5)

So, I took out the complete UIM and fully cleaned the throttle and the TPS. Also I resistance tested the AFM, the IAT and the TPS. Each of them tested good. I reassembled everything back, adjusted the TPS to 1kohm and went for a drive. Beside the idle that need to be tweaked out, the lean issue is still there.

Tomorrow I'll readjust the Idle and TPS and report my finding if any.

In the mean time, if anybody have suggestion about a possible place to check, let me know.

misterstyx69

iTrader: (142)

What injectors are you running?

^Zircon248

iTrader: (5)

Fuel system is composed of a Walbro pump, modded S4 rail with -6AN fittings and hoses, Aeromotive FPR set to 35PSI and 4 stock 550cc S5 injectors (driven by an Rtek 1.5'ed N374 ECU)

wthdidusay82

iTrader: (15)

35 psi seems low , iirc stock pressure for idle is 38 on a t2.

Is your afr going lean during the secondary Injector transition? I have the same problem

^Zircon248

iTrader: (5)

I originaly set the fuel pressure at 38PSI but at this point it was way too rich across the board sitting at around 11.4 to 11.6AFR. Now at 35PSI it sit at 12.4 to 12.6AFR and goes a bit richer by 8000RPM.

I have no hesitation while accelerating, secondary injector transition occur around 3600RPM with the Rtek but there is no leaning at this point. My issue occur at cruising RPM so between 2500-3000RPM.

I just finish adjusting idle and TPS correctly (1.04KOhm at 850RPM idle), so I'll go for a road test and report more detail about the stated issue I'm having.

Craze8

Set the fuel pressure to spec. If spec is 38, set it to 38. If you set it too low you will run into lean spots, if you set it too high, you will run into rich spots set it to spec. Either that or have a way to tune the injectors

^Zircon248

iTrader: (5)

I just checked in Mazda's shop manual (F2-9) and the spec is between 34.1-39.8PSI. So I'm still in the spec's range but I'll bump it up a bit to see what it does change.

Also I've taken a video of what happen with the wideband. Here's a quick description:

At first, you can see the AFR go full lean slowly and this is my trouble.
Second time, I lifted my foot off the pedal so it naturally goes full lean.
Last time, the AFR went lean the same way as the first time but I did accelerate a bit faster. (Well you can clearly hear the car accelerate slowly)

Engine was between 2200RPM and 2800RPM

Here's the video, just scroll down a bit to see it. Sorry for the shaky video, roads are **** in here...and coud'nt fit my tripod in the car properly...go figure why

^Zircon248

iTrader: (5)

Got the time to check fuel pressure and it was running around 30PSI at idle so it was out of specs. I bumped the fuel pressure up a bit to 36PSI so its back in the range. But there was no much change beside the AFR being a bit richer across the board.

Still no much idea of where the problem is comming. Anyway if there is any update about it I'll post here.

Can't wait to get full EMS...

Thanks everyone !

^Zircon248

iTrader: (5)

Did a good ride with the car yesterday, went on the freeway too. I took some more time to think about the problem and realized that the fuel is probably cutting on the rear rotor. The problem I see with this hypothesis however is that I'm not in boost condition and got a build in FCD with the Rtek. So I don't think it is boost related.

What leaded me to this was when on the freeway in 5th gear, if I try to keep speed constant at 65mph It slowly goes lean but does'nt fall on its face. When this happen, the car slow down a little bit like there is way less power than usual. If I move the throttle (retract my foot a tiny bit) to get AFR's back to normal, I feel a suddent increase in power (rear rotor coming back online perhaps).

If I'm at the same speed but in 4th I don't have any issue, I've played with the throttle a lot to see if it would lean out at some point but i did'nt. I guess since I'm rev'in pass 3600RPM (or near that does'nt remember exactly) the secondaries are on and there is no fuel cut for some reason.

I've eliminated the LIMP mode since I have the Rtek 1.5 no OMP, I have a build in FCD too...I tought about knock sensor giving knock reading to the ECU that could cause fuel cut on rear rotor, would that be possible ?

Well if anyone could chime in with advises or idea on the issue, it would help me a lot !

satch

iTrader: (1)

You have a 5th gear switch which increases gas mileage by leaning out the fuel mixture some.

^Zircon248

iTrader: (5)

Thanks for the info but as I stated earlier in the thread, it happen while in any gear while around 2200 to 2800RPM, not only when I'm in 5th gear. It seem like it only happen to a certain position of the throttle.

^Zircon248

iTrader: (5)

Little update, I replaced the TPS and adjusted it and the issue is still present. So I'm pretty much lost right now.

Just a tought about something, is a bad injector could stay closed at a certain duty cycle ? Since all this happen while the secondaries are off (under 3600RPM) I guess these could be the issue.

Anyone could confirm or have any imput about it ?

^Zircon248

iTrader: (5)

Additional information about my issue if someone can give inputs here.

While the car is cold, it drive perfect. But as soon as it warm up, the issue is starting. So would the water temp sensor at the back of the water pump could be doing all this ?

satch

iTrader: (1)

What reading does it give at the ECU?

^Zircon248

iTrader: (5)

Went out to check on this and got those readings:

Water thermosensor: read: 1.35K Ohm @ 20 C ----> Spec: 2.5K Ohm @ 20 C

CAS: read: 156 Ohm on both side ----> Spec: 110 - 210 Ohm on both side

Injectors: At ecu read: 613Ohm all 4

Not too sure about injectors readings I got but the Water thermosensor could be the bottom of the issue.

satch

iTrader: (1)

You should check the voltage reading at the ECU pin associated w/the sensor. Cold engine should read 2 to 3 volts w/key to on and close to .5 volts when fully warmed.

^Zircon248

iTrader: (5)

Did that second ago and when cold (about 22 C) the reading was 2.34V and warmed up was around 0.5V. S4 gauge around 1/4 up. Normaly the issue is present as soon the car is starting to warm up.

Craze8

If its spec is 2.5K, and your only 1.35k Thats 1150 Ohm difference cold. Now, theres a plus and minus to the spec but I don't have that info handy... While the motor is cold its won't care what other sensors are doing, its going to go off a set map. But once it reachs X temp, that X being when it switches from open to closed loop or vice versa (I'm not thinking clearly on which way it is at the moment.) if the temp is off then you will run into issues as it attempts to give X fuel thinking the motor is warm/too hot when its not.

^Zircon248

iTrader: (5)

Specs are 2.5K Ohm at 20 C (+-0,2K Ohm) So its kinda off specs. The lowest voltage reading I got at the ECU is 0,37V when fully warmed up if that could help.

My only concern is that its leaning only around a certain RPM (2200-2800) when I'm trying to keep speed constant like 4th gear around 60kph.

When accelerating lets say from 30 to 60kph, is the car goes back to open loop ? when cruising it would go back to closed loop and check water temps to give fuel based on temperature and others sensors ?

Craze8

Correct, after x reading on tps, it switches and goes to its own map, but at cruising speed and throttle angle its watching all the sensors and doing what it needs to do to be happy. Since you have rtek watch what the factory o2 sensor is doing.at that time as well, it should switch from lean to rich and do so quickly. If not or it hangs you can have a lazy o2 sensor. I have one on my 7 and it will cause odd things to occur since it wants to see things switch back and forth

^Zircon248

iTrader: (5)

I don't have an o2 sensor, it been replaced with AEM's Uego wideband. But I have the narrow band signal off the gauge/controller plugged into the ECU o2 input. Last time I got a failed o2 sensor (on an other car), the only issue I had was her running bit richer that usual.

Just to illustrate the issue one more time..

Lets say I'm in 4th gear and (trying to cruise since I can't) at 60kph. If the speed is slowly going down and I want to get back to 60kph, I push the throttle just a little but as I do so the AFR's goes leaner and leaner until there is no more reading on the wideband.

There is a video a couple post earlier of what the wideband is doing.

^Zircon248

iTrader: (5)

Its time for a thread revival ! My issue is still present and this winter I started to read on Megasquirting my FC. While doing so I tought about this everlasting issue I have since last summer about having the engine leaning out while atempting to keep speed constant in any gear while under 3600rpm (secondaries stagering).

What I'm thinking is maybe the throttle linkage coud move a bit but the tps cannot see it and make up with fuel for the extra air input. This leading to leaning condition. What you guys think about that ?

On the other hand, like I've stated earlier in this thread, when the engine is cold I'm able to accelerate slowly without any stumbeling or lead condition. But as soon as it warm up the issue reappear. So it lead me to ask, what sensors are used to calculate fuel requirement and load when cold ? And when hot ?