MC gremlins

[Ken Keith]

Have you replaced the fuel filter yet?

Ken

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
> 
>