[DeTomaso] more evidence I'm a not much of a mechanic...

[Thomas Tornblom]

Christopher Kimball skrev:
> I had my motor built to a 408 stroker not long ago, but lately, it doesn't "feel right."  It feels as if it may be missing on once cylinder, but I'm not sure how to test that.  Will this work?:
> 
> Let the car idle, and while it's running try disconnecting the spark plug wires, one at a time to see if it makes a difference in how the engine runs.  My logic would say every time I disconnect a wire from a firing cylinder, the motor would run a bit rougher.  If I disconnect the wire to the cylinder that isn't firing, it wouldn't make any difference, since that cylinder wasn't firing in the first place.
> 
> Of course, the problem could be something else; once before, with my old motor, I thought the same thing was happening, but it turned out it was an exhaust gasket leak.
> 
> Thanks for your thoughts on this.

This is very much like the built in cylinder balance test in the Ford 
EFI I have in my car (from an early 1990:s mustang).

When I enable the cylinder balance test, it starts by raising the idle 
to 1050 rpm (iirc), locks the timing and idle air and let it stabilize. 
It then starts to cut out one injector at a time, measuring the rpm drop 
for each cylinder, and if the drop is not within about 50 rpm per 
cylinder, it will indicate which cylinder(s) are not contributing 
properly. If I blip the throttle after the first test, it will re-run 
the test with a narrower drop, and it can be run with yet a narrower rpm 
drop.

Very cool! Good job Ford!

It did properly indicate that #3 and #7 did not contribute properly with 
my original motor, and that turned out to be due to glazed bores, which 
let oil past the rings, fouling the plugs. It also properly indicated 
the cylinder when it had wiped a cam lobe on #5 in Italy.

> 
> Sincerely,
> 
> 
> Chris
> #3846

Cheers,
Thomas

>  		 	   		  
> _______________________________________________
> 
> Detomaso Forum Managed by POCA
> 
> Archive Search Engine Now Available at http://www.realbig.com/detomaso/
> 
> DeTomaso mailing list
> DeTomaso at list.realbig.com
> http://list.realbig.com/mailman/listinfo/detomaso
> 
> 
> !DSPAM:4b7f0cbb5296312568212!
> 


-- 
Real life:   Thomas Törnblom             Email:  Thomas.Tornblom at Hax.SE
Snail mail:  Banvallsvägen 14            Phone:    +46 18 444 33 21
              S - 754 40 Uppsala, Sweden  Cellular: +46 70 261 1372