5kt diagnostics
QSHIPQ at aol.com
QSHIPQ at aol.com
Thu Feb 15 14:30:15 EST 2001
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
>
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