2 weak cyls.
 

Ok, here is what I know. The car is running a little weaker than it should be and shaking a bit more than it should be. I dediced Id look for a weak cyl. with my infraed ther momater. sure enough, when the car is fully heated up all but 1& 6 primaries read 650-700 but the 1 and 6 primaries read 350-400 I dont have an accurate enough tach to do a cyl balance test but im sure tese are the problem cyls.

Here is what I have done...
Replaced plug wire with known good plug wire. no change
Swapped 1 &2 and 6 & 8 fuel injectors. problem still on 1 &6
Used a spark tester, It hit 25k volts no problem.
Visually inspected plugs, they look fine and are gapped right and still have the platnum discs.
I think Im going to get 2 new plugs and try em anyway, wouldn't hurt to have spares around for testing....
what else is left? computer problem with injectors? I doubt it.
Could the opti couse this? if so why would it pass the spark test?
or lastly, mechanical/. valves? bad grind?

any other tests that i could do?
I gotta dyno tune this thing monday so please give me some suggestions.

Do a leak down test compared to the other cylinders. Obviously the test will tell where the problem is if it is a leakdown problem. If it is, check the lifter preloads on those four lifters. If that doesn't help, the heads have to come off.

Who put the rings in? Were they checked for gap before the pistons were installed? What is the gaps on the top and middle rings?

That was done by the machine shop. they "said" that they were all put to spec (they told me but i forget) .010-.012 or somthing like that how aaare you shure its not valve related?????
I installed the lifters, by preload you mean rockers being too tight?

I do think it's valve related. The question was just to think while we wait for the leak down test results.

Yes preload is "tightness"

Do the test. Only way we're gona know what's going on.

ok I did a compression test. Im not sure how many pulses of the needle you are supposed to watch for but after 3 pulses both one of the problematic cylinders and the good cylinders read 90 PSI. I cranked it for about 15 seconds and got 145 PSI.

I also plugged the air hose into the cylinder and there was no sound inthe intake / exhaust oil filler cap whil i held it at TDC comoression and it was obviously holding pressure.

so why would those 2 cylinders only hit 350 degrees!?!?!
im goin to try to get a friend to put it on a sun 450 tomarrow, mabye that can clear somthing up.

I tried to respond yesterday but my post did not get through,
before you spend a bunch of money try putting a "Noid" on the
two dead cylinders fuel injector electrical plugs to make sure that
you are getting a pulse from the ecm, that would be my guess
after what you have already tried.


Dave B