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

Uncle Arthur · Postby **Uncle Arthur** » Fri Feb 08, 2008 5:00 pm

Test drives for both - this time I get to be in the car with you AJ so I can hear you giggle. :mrgreen:

Fatty · Postby **Fatty** » Fri Feb 08, 2008 5:09 pm

Okibi wrote: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 .

hey! i resemble that remark!! :evil:

Tezzax5 · Postby **Tezzax5** » Fri Feb 08, 2008 5:32 pm

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:

[/quote]

On its way :mrgreen:

jules · Postby **jules** » Sat Feb 09, 2008 8:45 am

AJ wrote:Mikey rang me today & gave me first dibs on a drive Jules........nerner

I love an NC driver who's not afraid to admit he still likes to slum it :lol:

Jules

AJ · Postby AJ » Sat Feb 09, 2008 9:54 am

you've SEEN me drink cheap & nasty Jules :lol:

jules · Postby **jules** » Sat Feb 09, 2008 12:54 pm

Yeah, at my place :lol:

Jules

Uncle Arthur · Postby **Uncle Arthur** » Thu Feb 14, 2008 2:39 pm

So much for a damn fix :evil:

Friday was perfect.

Travel to Sydney - no driving.

Back to Brisbane - Wednesday afternoon - worse than F^&%ING ever.....

Welcome to square 1 - population - Me.

JBT · Postby **JBT** » Thu Feb 14, 2008 3:01 pm

Hmmm.....might be worth re-visiting the areas that you fiddled with to see if there is anything deeper there perhaps. You may have temporarily disturbed something back into its rightful place which is now not...again.

Uncle Arthur · Postby **Uncle Arthur** » Fri Feb 22, 2008 9:00 pm

JBT wrote:Hmmm.....might be worth re-visiting the areas that you fiddled with to see if there is anything deeper there perhaps. You may have temporarily disturbed something back into its rightful place which is now not...again.

JBT - you are a bloody legend - you actually fixed the car without lifting a spanner.......

The stumble has been happening over bumps - corrugations, cracks, manholes, potholes, bitumen joins - basically any short sharp jolt has been enough to trigger it.....

The car would feel like it was dumping fuel, or dropping spark.....

The last time I tried a fix, I redid connections in the O2 sensor wire - thinking if it dropped out, perhaps it would read lean and dump in fuel - too much for the revs, but perfect for when I came on boost, at which point there was no hint of the stumble.....

So I revisited those wires - checked them time and time again..... forgetting that I had looked at one other thing during my last (successful) intervention - I had pulled the top off the AFM, and had checked that it was moving smoothly, and that all the solders were still holding. They were.....

Fast forward to this afternoon - I'm thinking to myself that this vibration thing has to be affecting a sensor somewhere - I couldn't find any broken wires, and I hadn't ever touched the throttle position sensor. I had however rebuilt the AFM... could it be the issue? So I pulled the top off again - moved it left and right all good - then I pulled up v...e...r...y slightly almost by accident..... off pops the sensor mechanism from its shaft. So I pushed it down hard, did my best to tighten it up, and drove home - all OK

So how did all this happen???

Well the AFM is pretty much resting right on the top of the shock tower. I have placed a sleeve of oil hose on it to absorb vibrations, but it does move around..... so every small sharp bump transmits vibrations through to the AFM. Question - what do heat cycles and vibration do to fasteners - they loosen them. Particularly if that fastener (in this case the tiny bolt that holds the sensor to its shaft) was only just interference tight in the first place - being very awkward to do up when installed.

Turn the clock back to October 07 when Jules had the car........ a hot day, and hard driving, up Springbrook - great corners, but $hit road surface. Perhaps the bumpiest, roughest road the car had been up since I turbo'd it. Heat + vibration = loose bolt. In a sensor which drives the whole thing. It was sporadic because sometimes the sensor was sitting just right, and other times it would bounce up and down, disconnecting. When the car was sitting idling - no vibration meant no stumble. Smooth flat road meant no vibration and no stumble - but how often was that? And when it stumbled, it vibrated more, making the effect worse. I seriously doubt a workshop would have even found it, without knowledge that I had completely gutted and rebuilt the AFM with an RX7 housing and MX5 internals.

So when I pulled it open last week and fiddled with it - I moved it just enough for it to hold for the drive out to Cleveland and back, but not enough to stay there after the expansion/contraction of the drive had loosened it again, and the car had cooled and sat for a couple of days.

SO JBT - that's why you're a bloody legend

- you made me wonder what I'd done, think really carefully about what I've modified, how it might affect the running of the car, then retrace my steps over the most and least obvious elements until it made sense and I fixed it. I owe you beer.

(and that tip for young players is why if you're going to mod your car you shouldn't be scared to do it yourself, otherwise you won't know what you've done and how to diagnose it).....

JBT · Postby **JBT** » Fri Feb 22, 2008 10:19 pm

Eeeeexxxcccccellent UA. Never mind the beer, I'll take you up on the offer of a drive in Max next time :mrgreen:

Postby **Okibi** » Fri Feb 22, 2008 11:46 pm

Great news UA, fingers crosssed.

Uncle Arthur · Postby **Uncle Arthur** » Sat Feb 23, 2008 12:39 am

Problem definitely seems sorted - a quick and enthusiastic blat up Mt Gravatt and not a hint of a stumble.

jules · Postby **jules** » Sat Feb 23, 2008 9:03 am

Uncle Arthur wrote:Turn the clock back to October 07 when Jules had the car........ a hot day, and hard driving, up Springbrook

Ummm.. it might not have been just "that" run up Springbrook when I had Max :oops:

Glad to hear it's fixed though! Next question, Boags has a stumble. Is he using an RX-7 AFM too?

Jules

AJ · Postby AJ » Sat Feb 23, 2008 9:08 am

thank god it was stumbling before i drove it

...............definitely your fault jules

UA??............piccys???.....maaaaaaaaaaate :mrgreen:

Uncle Arthur · Postby **Uncle Arthur** » Sat Feb 23, 2008 9:38 am

jules wrote:
Uncle Arthur wrote:Turn the clock back to October 07 when Jules had the car........ a hot day, and hard driving, up Springbrook

Ummm.. it might not have been just "that" run up Springbrook when I had Max

Glad to hear it's fixed though! Next question, Boags has a stumble. Is he using an RX-7 AFM too?

Jules

BAH

It was probably a cumulative effect - those 12 days with you were just enough th shake things up a little. I told you to use her like the little red tart she is.

Don't know about Boags - its not just that I'm using an RX7 AFM, but that I pulled the whole thing apart and rebuilt it. I do know Boags has his AFM sitting upside down - perhaps he is having a similar problem? He'll know when he pulls it off and checks it.