5kt diagnostics

[QSHIPQ at aol.com]

A couple of things I'd ck here, you went backwards on diagnostics, but 
that'll make this easier:
*  block the holes in the fuel distributor boot, and try starting the car, 
before you even get there, you might find one of the following to be the 
problem
  -  vacuum ck valve at the bottom (ck this for proper operation or body 
cracks)
  -  decel valve on the fender side (intermittent stuck open, no vacuum 
pulling flap)
  -  PCV system at the back (hoses cracked or blocked)

*  Pull the dipstick, does the idle stumble and recover? (it should)
*  Pull the oil cap off, does it stall (it should)
  -  if the above don't ck out, then you have a vacuum leak somewhere

*  Ck the WG to manifold line underneath for cracks or leaks
*  Ck the michelin man hose (IC to tbody) for cracks or leaks
* Pull the rubber T off the top of the valve cover, ck for leaks 
*  Ck the IC end caps to make sure they are still sealed
then
*  system pressure and control pressure ok?

This sounds like a lean condition to me, usually related to the above cks.

HTH

Scott Justusson
QSHIPQ Performance Tuning
Chicago IL




On 15 Feb 2001, at 10:27, Matthew Beaubien wrote:

> I've had a problem with my '86 5kt for a while now, and seeing as how
> the weather has been warming up, I've been more inclined for work on
> it.
> 
> It all started a few months ago when I was driving home from work. 
> About 10 minutes into the drive, the engine started running really
> poorly.  I was only a couple of blocks from my house, so it didn't
> leave me stranded, but was very disconcerting.  It didn't want to idle
> and wouldn't make any power.  At WOT in first gear, it would maybe rev
> to 3k RPM.  Playing with the throttle while sitting outside my house,
> it cleared up and started running just fine.  I drove it to work the
> next day without any problems.  On the way home, it started acting up
> at almost the exact same spot.  This time, it didn't clear up, and I
> had a consistent miss.  Playing with the throttle, I could get it to
> rev up, but a lot of times it would backfire through the intake and
> the large pressure increase would case the I/C to hit the front of the
> car (not good).
> 
> Further diagnosis showed that pulling #1 plug made no difference.  I
> tried a couple of different spark plugs and verified spark.  No
> difference.  Fine, it must be fuel.  So I swapped #1 and #3 lines at
> the fuel distributor and fired it up.  It still had a miss, but it
> wasn't on #1 _or_ #3.  I pulled all the injectors and operated the
> flapper to see the injector pattern/flow.  They were all very close to
> one another, and if anything, #1 had a bit more fuel than the rest. 
> During the course of the diagnosis, I replaced the FP relay and pump,
> and I also tried swapping the warm-up regulator with no effect.
> 
> The next step (a couple days ago, and a couple months since the above)
> was to put a set of fresh plugs in and try to get a better read on the
> mixture.  It started ok, didn't have a miss, but was running so-so. 
> It seems lean.  As it warmed up, it was harder to keep it running and
> get it restarted when it would stall.  There may have been a slight
> miss after running for a few minutes.  I pulled all the plugs and they
> had a nice tan to them, aside from #4.  It looked like hardly anything
> had gone on in that cylinder.  Also, the O2 sensor was reading very
> lean during the entire time (even without the miss).
> 
> So, what is my next step?  Just swap out the fuel distributor?  I
> don't see how it would have caused the intermittent problem I started
> out with, and it seems like there is even flow to all the injectors. 
> It just doesn't make any sense.
> 
> Suggestions?
> 
> Thanks,
> 
> Matt Beaubien
> '86 5kt
> '73 911E
>