Well, I rechecked all of the intake manifold fasteners, they were tight. Did a
once over on all the fasteners near the knock sensor, they were tight too. I
went and picked up the new knock sensor and installed it. Took the Miata out
and left the Link pad where I could view the knock values. The values increase
from 1 to around 19 right around 4500 rpm but that's about it. So, it's a bit
better than before. I ran the car, hard 1st through 3rd, then went to 4th,
coasted until I was at 2000 rpm and then floored it. No knock, but the same
ramp up @ around 4500 rpm. So, I believe it was the sensor, however it still
ramps up some (it's still well below the knock limit). Is this normal? I
didn't check it with the original knock sensor that I got w/ the FM kit.
----- Original Message -----
From: M. Ybarra
To: Miata Power List
Sent: Friday, November 07, 2008 5:54 PM
Subject: Re: Obiwan Knock sensor acting up, any ideas?
The intake manifold brace was removed when the FM turbo kit was installed due
to the inclusion of the PWR Twincooler radiator/oilcooler. The oil hose
routing necessitates the removal of the intake manifold brace. The starter
bracket is secure. I haven't checked all of the lower intake manifold nuts,
but the ones I could readily reach were secure. I don't have any vacuum leaks
so this is a little less likely, but I will check tomorrow. Also I have stage
8 fasteners of the turbo, DP and exhaust manifold. These are secure as well.
I just ordered a new sensor (they are Bosch units from a 91 Porsche 944 w/
the 3.0 liter motor, bosch part # 0-261-231-006) locally and will go pic it up
tomorrow afternoon. Hopefully that's it.
Myron
----- Original Message -----
From: Ray Ayala
To: M. Ybarra ; Miata Power List
Sent: Friday, November 07, 2008 4:36 PM
Subject: Re: Obiwan Knock sensor acting up, any ideas?
The noise source may very well be on the other side of the motor. Peaking
in a fairly narrow rpm range certainly does suggest something resonating. I've
seen four such things over the years ... the intake manifold brace (loose bolt
at the top end), the intake manifold itself (brace missing and one loose
manifold bolt), the starter (front brace missing so the entire started acted
like a tuning fork), and a loose downpipe flange bolt.
----- Original Message -----
From: M. Ybarra
To: Miata Power List
Sent: Friday, November 07, 2008 11:45 AM
Subject: Obiwan Knock sensor acting up, any ideas?
Early this week, I was accelerating in 2nd gear on an on ramp getting
onto the freeway when right around 5000 rpm and I got a knock event, just 1. I
went to 3rd to about the same rpm and got another. The Link pulled a
substantial amount of timing as a result. I assumed I got a bad batch of gas,
so I kept out of boost and when I got home I put in some of my race fuel (about
2 gallons) and left the existing map alone as I have been running this ecu
street setting for about 3 years. Ran the car again and the same thing
happened. I got the car home again and went to the knock screen on the Link
pad and rev'ed the engine to about 5000 in blips. Since there is no load on
the engine I figured that it's shouldn't register anything. Unfortunately the
knock #'s rose to 40 really quickly then back down to 1.
Well, I figured that I have something loose near the sensor (which is
what Keith @ FM suggested as well) so I put the car up on my lift this morning
and checked every bolt or nut I could get my hands on; bell housing, motor
mounts, starter bracket, oil pan, ancillary brackets all the way up to the
valve cover bolts. Nothing is loose. So I figured that maybe the Quaife with
all of it's racket could be causing it, so I pushed in the clutch to quiet the
gear set and rev'ed the motor to 4500 rpm, the numbers shot up to 38 really
quick then came back down to 1 when I released the throttle just like the first
time. So, I'm at a loss. Could the sensor be going out or am I missing
something else?
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