Still diagnosing the stumble....... Now possibly fixed

Uncle Arthur · Postby **Uncle Arthur** » Mon Feb 04, 2008 11:53 am

I'm still

trying to properly diagnose the stumbling problem I'm having with Max at low throttle cruise.

I have swapped leads.

I have tried swapping the coilpacks (Thanks AdamJP - they are on their way back to you via Aust Post).

I swapped out the plugs and tried a new spare set.

I have fiddled with most of the additional connections I made when fitting the Emanage and replacing the motor.

One thought keeps coming back to me - is it something to do with the readings from the O2 sensor?????

The car seems to stumble most over smallish bumps - corrugations, etc - when it does stumble, the stoichmeter shoots straight over into rich, and jumps around even more than on closed loop - almost lighting up the entire light band....... My first thoughts were that something is causing it to cut spark, but what if there is an intermittent connection fault between the O2 sensor and the ECU?

I vaguely recall reading/seeing somewhere that if the O2 sensor cuts out, the car defaults to rich? Is that true? Because that would explain (with bigger injectors etc) why it reads/runs rich on stumbling, and why as soon as I put my foot down, the problem disappears (turbos like it a bit rich).

I've tried taking the car to a dealer service place but they were unable to use their diagnotic computer (apparently it wasn't working that day), and I'm yet to take the car back to a dyno tuner (thinking of using Sheck's tuner cause of the Emanage).

But if it is a loose wire connection, and I can find it, it will obviously solve the problem much cheaper.

Does anyone have any furter thoughts or possible insights?????

AJ · Postby AJ » Mon Feb 04, 2008 12:01 pm

not that i'm overly well versed in this stuff UA, i'd think it would be natural that if something that controls the air/fuel in any way like the o2 sensor actually stopped working, that the ECU would default back to full rich to protect the motor from pre-ignition, better to have too much fuel than no fuel, if i was a Mazda software personage, i'd err on the side of caution

if it's intermittent on your car, it follows that the ECU would pick it up & adjust accordingly in nothing flat, reversing that once the fault disappeared........causing the stumble

JBT · Postby **JBT** » Mon Feb 04, 2008 1:41 pm

It's going to be a process of elimination UA. Try the O2 sensor circuits....makes sense.

However, it could be anything - cracked wire, loose/intermittent connection, intermittent earth, intermittent short circuit etc.

Sheck · Postby **Sheck** » Mon Feb 04, 2008 1:42 pm

my car runs the same with the O2 sensor connected or not - dont know if that means its stuffed and was tuend with it stuffed or it actually doenst do anything. Try checking the eManage wires, something could be loose.

lowmiata · Postby **lowmiata** » Mon Feb 04, 2008 2:10 pm

JBT wrote:It's going to be a process of elimination UA. Try the O2 sensor circuits....makes sense.

However, it could be anything - cracked wire, loose/intermittent connection, intermittent earth, intermittent short circuit etc.

Just unplug it
that will give you a better idea
I did this to prove that my 02 sensor was the problem

car runs fine without it it just runs in the start up mixtures ie when cold
just doesn't change to normal runnig procedure

Uncle Arthur · Postby **Uncle Arthur** » Thu Feb 07, 2008 5:37 pm

Looks like I may have cracked it - I rewired the connections between the O2 sensor, the stoich gauge, ecu, EManage, etc last night. Found a less than perfect connection, so it's all re done.

Driving the car today was a pleasure again - it behaved itself - no apparent stumbling, although the drive out to work tomorrow will definitely reveal how successful I might have been.

Uncle Arthur · Postby **Uncle Arthur** » Fri Feb 08, 2008 1:48 pm

IT'S FIXED!!!!!!!!!!

:mrgreen:

Richee · Postby **Richee** » Fri Feb 08, 2008 2:43 pm

Uncle Arthur wrote:IT'S FIXED!!!!!!!!!!

Well done UA, so it wastn Jules' fault after all :mrgreen:

Tezzax5 · Postby **Tezzax5** » Fri Feb 08, 2008 2:44 pm

Are you sure it wasn't catching on speedbumps and driveways..?

Also what is the beer quota on getting a couple more tags polished up..

PLEASE..?

Uncle Arthur · Postby **Uncle Arthur** » Fri Feb 08, 2008 3:01 pm

Tezzax5 wrote:Are you sure it wasn't catching on speedbumps and driveways..?

Also what is the beer quota on getting a couple more tags polished up.. PLEASE..?

I haven't received the beer for the first ones yet

Perhaps a tag for me might be a suitable lasting memento.....

Just call me 'Uncle Dodgy' :mrgreen:

Postby **Okibi** » Fri Feb 08, 2008 3:14 pm

I remember one S13 coming into Speedwok with issues, it had every known jaycar style kit and pixy piggyback wired into the already modified ECU, lots of flashing lights and LED bar graphs :roll:

they had to keep removing each item until they found out which bit of dodgy wiring was causing the issue ... the joys of car modification

I've been nervous about replacing my 02 sensor with one of those DIY generic ones for this same reason, I don't know if I should trust my own skills.

JBT · Postby **JBT** » Fri Feb 08, 2008 3:25 pm

Uncle Arthur wrote:IT'S FIXED!!!!!!!!!!

Well bring it out on Sunday :!:

Uncle Arthur · Postby **Uncle Arthur** » Fri Feb 08, 2008 3:34 pm

JBT wrote:
Uncle Arthur wrote:IT'S FIXED!!!!!!!!!!

Well bring it out on Sunday

Can't - flying to Syndey for a conference (8.00am flight)

jules · Postby **jules** » Fri Feb 08, 2008 4:34 pm

Richee wrote:
Uncle Arthur wrote:IT'S FIXED!!!!!!!!!!

Well done UA, so it wastn Jules' fault after all

OI! Back in yer cage you NA traitor...
Glad to hear Arthur. Now just need Max to pay a visit to Uncle Jules for a final test drive up Springbrook :lol:

Purely for a 2nd opinion mind you.

Jules