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How (and why) to Ramble on your goat sideways

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Old Feb 28, 2013 | 11:05 AM
  #16021  
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Originally Posted by Godless Commie
Oh, and my tailpipe test?
0.00 CO, 0.00 HC. Oh yes. Thanks, Reverant!
Lemme see dat MSQ, son.
Old Feb 28, 2013 | 11:12 AM
  #16022  
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Cant tell if he's talking about me or Techsalvager.
Old Feb 28, 2013 | 11:54 AM
  #16023  
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Originally Posted by Braineack
Cant tell if he's talking about me or Techsalvager.
Neither.

And it's all the Federal Reserve's fault.
Old Feb 28, 2013 | 12:07 PM
  #16024  
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Originally Posted by Godless Commie
Joe, have you checked your VE table for anything unusual at the low end?
You may inadvertently have created peaks and valleys in the table as you were slowing down for the light.
Originally Posted by Braineack
Jow, how much spark is in your cruise rows now?
I'm pretty sure this isn't software. After that drive, I reverted the tune back to my previous save point, and no change at all. Visually inspected the VE table, and it looks fine to me.

And this change was sudden, like someone threw a switch while I was driving. One moment it's all happiness and kittens, and the next, *BAM*- no torque.

Here's a datalog showing when the event happened:



At point A, I'm idling at a light at the bottom of the hill. Idle is rock-steady at ~940 RPM, MAP is steady at 29-30 kPa, AFR is normal (AEM miscalibration, 15.3 = 14.7), spark is steady at ~14° BTDC, fuel PW is steady at ~ 2.7, PWM idle duty is steady at ~ 31.

Then the light turns green and I run through first, second and third, and come to a traffic signal at point B. I *think* that's when it happened (during the space between point A and B), however I hadn't quite come to stop, so I didn't notice anything wrong. Ran through the gears again and came to a full stop at point C.


At point C, everything is wrong. MAP is 60, RPM is unsteady and a tad low, IdleDC is WAY up at 45, fuel is way up at 4.8 and yet AFR is still right where it ought to be. And when I tried to take off again, I almost stalled the engine. Had to slip the clutch to keep it above 2,000 RPM.

Drove it again this morning, and it's exactly the same. No mechanical noises, no smoke, good oil pressure, and above 2,000 RPM it runs just fine.

The VE table:

Attached Thumbnails How (and why) to Ramble on your goat sideways-log.gif   How (and why) to Ramble on your goat sideways-ve.gif  
Old Feb 28, 2013 | 12:46 PM
  #16025  
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TB jump tooth?
Old Feb 28, 2013 | 12:51 PM
  #16026  
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Based purely on the map at point B, I think you are correct in assuming that things went south between A and B. Other than that, I have no idea what may be your issue.
Old Feb 28, 2013 | 12:55 PM
  #16027  
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Originally Posted by Braineack
TB jump tooth?
That's what I'm assuming.

I know the intake cam is fine, as I verified the ignition timing last night (I'm still using the stock CAS on this engine.) Could well be that the exhaust cam skipped a tooth or two and is now retarded relative to the crank, which from what I understand would cause this exact symptom. Probably won't have time to pull the cover and check it until this weekend.

On the plus side, I already have a full timing belt kit (including water pump, crank bolt and woodruff key) lying on the shelf. Anybody know the correct torque for the main crankbolt on a shortnose engine? The earliest FSM I have is '92.
Old Feb 28, 2013 | 01:45 PM
  #16028  
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Do want.

7mgte 1984 celica supra
Old Feb 28, 2013 | 01:52 PM
  #16029  
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Originally Posted by Joe Perez
That's what I'm assuming.

I know the intake cam is fine, as I verified the ignition timing last night (I'm still using the stock CAS on this engine.) Could well be that the exhaust cam skipped a tooth or two and is now retarded relative to the crank, which from what I understand would cause this exact symptom. Probably won't have time to pull the cover and check it until this weekend.

On the plus side, I already have a full timing belt kit (including water pump, crank bolt and woodruff key) lying on the shelf. Anybody know the correct torque for the main crankbolt on a shortnose engine? The earliest FSM I have is '92.
I find it very funny that on a miata forum Joe decides to post his miata problems in the Ramble On thread, not make a new thread in the correct section of the forum describing his problem.
Old Feb 28, 2013 | 01:54 PM
  #16030  
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Originally Posted by Joe Perez
Anybody know the correct torque for the main crankbolt on a shortnose engine? The earliest FSM I have is '92.

In 1990, the correct torque is 80 - 87 foot pounds. For 1992 and later, the larger crankshaft uses 116 - 123 foot pounds.¹


¹ Miata Crankshafts
Old Feb 28, 2013 | 01:58 PM
  #16031  
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Originally Posted by shuiend
I find it very funny that on a miata forum Joe decides to post his miata problems in the Ramble On thread, not make a new thread in the correct section of the forum describing his problem.
I described the problem in the form of a bohemian freestyle poem. How does that not fit into the Ramble On thread?
Old Feb 28, 2013 | 02:04 PM
  #16032  
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Originally Posted by Joe Perez
I described the problem in the form of a bohemian freestyle poem. How does that not fit into the Ramble On thread?
Finger snaps.
Old Feb 28, 2013 | 02:38 PM
  #16033  
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Originally Posted by Joe Perez
I described the problem in the form of a bohemian freestyle poem. How does that not fit into the Ramble On thread?
Originally Posted by mgeoffriau
Finger snaps.
Attached Thumbnails How (and why) to Ramble on your goat sideways-fingersnap1.png  
Old Feb 28, 2013 | 03:01 PM
  #16034  
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Also want this, even though it's not an All-Trac.

1990 Toyota Celica Turbo 3sgte
Old Feb 28, 2013 | 03:05 PM
  #16035  
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With the valve cover doffed
And a few beers quaffed

Joe Perez will try to discover
the woes of his red miata lover

He'll tug on her bolts
and measure her volts

And compress her valve springs
until her pipe sings

Wearing his homage to Hawai'i
while he's aligning her I and E

The belts will be tight
The shafts will be right

With a spark in his eye and her high tension lead
Joe'll eventually get her back up to speed.
Old Feb 28, 2013 | 03:07 PM
  #16036  
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This thread couldn't even be more complete with cheerleaders and ice cream.
Old Feb 28, 2013 | 03:09 PM
  #16037  
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Attached Thumbnails How (and why) to Ramble on your goat sideways-beat.jpg  
Old Feb 28, 2013 | 03:24 PM
  #16038  
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Originally Posted by Braineack
This thread couldn't even be more complete with cheerleaders and ice cream.
you can haz. with jimmies.
(unrustled)



VIP-5!
Attached Thumbnails How (and why) to Ramble on your goat sideways-20130222_202116.jpg  
Old Feb 28, 2013 | 03:25 PM
  #16039  
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bonus of brain getting his cheerlead* on.



*ice cream not shown.
Attached Thumbnails How (and why) to Ramble on your goat sideways-20130222_190255.jpg  
Old Feb 28, 2013 | 03:28 PM
  #16040  
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that's a cowlick, not a bald spot.



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