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Power Loss During Warmup
My 87 5kcstq at 150k miles starts on first crank, runs fine for 1-2
minutes, and then begins losing power and running so badly that I can't
keep up with traffic. This condition continues for about 18 minutes, and
then gradually gets better and finally the car runs just slightly off its
After about 20 miles on the turnpike, the car runs normally and gets better
and better the longer I drive it. Tonight, after 2 hours at a steady 65
mph, engine management was very stable and power was satisfactory. The
engine did not cycle up and down at stoplights and toll booths, and did not
stall out and refuse to start for a few minutes, as it did during the
initial 20 minute warmup phase.
WHAT HELPS? During the loss of power-RPMs falling off-going to stall out
pretty soon-phase, I can drop down into 2d gear and tramp the accelerator.
The engine grabs, the neck snaps, and the car races off like it had wings.
In traffic this lasts about a second and I have to let off and coast out of
gear, with the engine reving about 3k. Then I can put it back in gear and
drive a few more seconds and do the floor-it again. Sort of like the Easter
Bunny hopping down the highway. WOT works great during the warmup phase.
WHAT ELSE HAVE I DONE? Ran through a half tank of new high test gas laced
with gas dryer and Techron. Tried to blow out the carbon by running in 2d
and 3d gear at about 5k-6k for a few minutes. Engine runs great at high
RPMs and light load. Refilled tank with Sunoco Ultra 94 octane and another
bottle of Techron, ran 4 hours on turnpike at legal speeds. Came home,
parked it, and sat down to write this up.
WHAT'S NEXT? Car goes into mechanic at 8 AM Monday, with this report, as
you see it. I want him to have it sitting in front of his shop, engine
cold, at 8 AM. (So he can experience the power loss during the warmup
DATA POINTS: Ran fuel pump fuse test and got 4444 readout. Dash showed 'OK'
at startup. Used voltage tester (cheap neon bulb thing) and found current
at all sensors but no current at either terminal of the ISV while the
engine was running. Pulled fuel pump relay and popped off cover, insides
looked fresh and new. One plug blade of the fuel pump relay appeared
bluish, like it had been heated and cooled down. Two weeks ago the fuel
pump could be heard briefly from an open driver's window. Then it quieted
That's about all I can tell you.
I am hoping something in the story will ring a bell in the memory of a
fellow lister, and you will tell me enough before 8 AM tomorrow that I will
not have to pay my mechanic several days wages while he takes the entire
system apart and swaps every sensor and relay and module and ECU while
blindly searching for the cause of the condition. He drives a 5kcst
automatic, and is very familiar with the car, but BTDT would be very much