Newbie-intro

[John Hess]

Five and seven on the small block fire consecutively.  It is generally 
advised NOT to run these two wires adjacent to each other due to 
cross-fire considerations.

You will find that the MAP sensor engine is rather sensitive to engine 
changes (much more so than the MAF, which is why I recommended the MAF 
with the '89 chip).  I will not pretend to try to diagnose your engine 
from my desk, but this is a consideration.  If the distributor looks 
funky, replace it!...AND the coil...AND the wires.  The injectors 
might be suspect, but I would look at the connections before I pulled 
the injectors (much easier).  Also listen for air.  This system is 
famous for air leaks.

Good luck.


----------
From:  jforbes at primenet.com[SMTP:jforbes at primenet.com]
Sent:  Thursday, January 09, 1997 3:28 PM
To:  'DIY_EFI at coulomb.eng.ohio-state.edu'
Subject:  RE: Newbie-intro

At 11:14 AM 1/9/97 -0600, John Hess wrote:

>You might find out that the engine won't run at all!  Your '86
>(assuming you are using all the original stuff off it) is a MAF
>engine, while the '91 is MAP.  The best option would be to assemble
>the package WITHOUT the cold start enrichment injector and use the 
'89
>PROM.

Well, actually, I finally finished the harness and put it in last 
night, and
the engine fired right up!!!!  Surprised the daylights out of me   :)

I forgot to mention, that when the guy put the 90 engine in his 86 
Vette, he
used his 86 runners and upper plenum, so the 90 runners and plenum 
came with
the 86 and are on the car I'm working on....no cold start injector. 
 No MAF
sensor.

The thing runs pretty bad, seems to have two cylinders not firing 
right or
at all, misses quite a bit.  I just did a compression check, 150# 
across the
board.  The distributor cap looks funky, it had some water in the coil 
area
while in storage, and the coils all rusty, but I didnt see any 
evidence that
this is causing the problem.  On my old Sun tune up scope, cylinders 2 
and 5
have a different spark pattern than the rest, there's kind of a second 
spike
at the end of the firing period.  Those plugs are wet, also.  Might be 
a
couple bad injectors, they were supposed to have been cleaned and 
tested by
a shop, but perhaps they didnt really test them....I might switch a 
couple
and see if the misfire moves around with the injectors.

The misfire doesnt seem to be a mixture problem, the exhaust analyzer 
shows
about 1 to 2 % CO and about 100 to 200 PPM HC while running, which are 
good
numbers for an non-catalyst engine.  Very odd...usually an ignition 
missfire
will send the HC level thru the roof, which is what leads me to 
believe the
injectors might be acting up.  If there's no fuel, then there's no 
HC.


Jim
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Jim and Janet Forbes                          jforbes at primenet.com
Sierra Vista, AZ             URL= http://www.primenet.com/~jforbes
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