Flaky 87 5000 SQ - non turbo

[Matt Ammann]

Hi All,

I wrote some time ago for help on my 87 5000 s q,no
turbo.  I received some excellent advice, which
unfortunately hasn't produced results.

Here  is the story.
It runs well,  but after runningfor some time, 
like between 15-30 minutes, will start to miss,
and some times be unable to rev from idle, or
even die.  If it dies, it won't restart for a while,
but then seems to run fine again.

I tried jumpering the fuel pump relay, but this did't
help.

Today, when it wouldn't rev from idle, I pulled
the oxy sensor lead, and it could immediately
rev, and I thought I had it knocked. But some time
later, it started to miss again, but didn't get
as bad as it had previously.

Other info-It sometimes doesn't return to idle
well, but instead hovers around 1800 rpm, and the
off/on idle response can be jerky.

Any tips before I either ship it off to the junk
yard, or pay someone lots of money to try to
diagnose?

thanks,
matt

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