Fill 'er up...WOW!

[Bernard Littau]

Sounds like the "new" engine has some propensity to knock, and with low
octane gas the ECU retards the ignition, making the engine drive as if it
lacks power.  Shifting to the 93 octane appears to have overcome whatever is
causing it to knock more readily.

Check your plugs.  They may be too hot.  You may also be running slightly
too lean, have you checked the emissions, or can you check the O2 sensor
output?  The "new" engine may also have lots of carbon in the head --
spirited driving with 93 octane should eventually burn that out :-)  I'd
rule out plugs, and lean, and anything else anyone can think of before you
go for spirited driving.

Best,

Bernard Littau
Woodinville, WA
'88 5ktq
  The scenario:

  After putting a boneyard engine (88 5ksq, w/75k supposedly certified
miles) into my son's 88 5ksq he's noticed that the car was lacking the power
of his old engine.  I told him that, until I could get the weather/time to
go through it, to start using fuel injector cleaner every other fill
up...which I'm sure he did for the first month.  The performance did
increase very slightly (placebo effect I think) afterward.  Early last week
he told me that he had put a tank full of 93 octane in it and that it
[engine] suddenly had "unbelievable" power.  He's continued to use high test
and is getting great results!

  The question:

  What would be askew with the engine to prevent it from getting adequate
performance with a slightly lower octane rating?  TIA

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