5kCSTQ very sluggish

[Doyt W. Echelberger]

Hello Dennis.........When my 87 5ktq displayed the 'Lost Power Syndrome,'
it was due to the progressive failure of the oxygen sensor.

I learned that sensors are good for about 30-40k miles, and sometimes start
progressive failure beyond that. As they get less capable of fine tuning
the mixture, the air-fuel ratio creeps toward 'rich' and then 'very-rich.'
This rich mixture doesn't combust efficiently, and power loss gets worse
and worse. And eventually mine arrived at an emergency condition in which I
couldn't keep up with traffic and had to get off onto the shoulder to avoid
getting hit.

Sounds like your car's condition is moving in that direction.

I noticed that I could get temporary improvement in power by dropping to 2d
gear and slamming open the throttle. The rich mixture then got more air
than usual, and the car surged ahead like a jack rabbit for about 3-4
seconds, until the RPMs got past 4k. Then, as I chickened out on the
throttle, the car coasted with the clutch disengaged, until it slowed to a
pace that allowed another burst.  I moved along the highway in this
jackrabbit manner, and eventually got to my mechanic, who replaced the
oxygen sensor.

The new sensor totally cleared up the problem.

You might try flooring it in 2d gear and see if it behaves better. That
could be a clue as to the cause.

Other causative conditions that come to mind are a clogged catalytic
converter, in which the broken pieces are bouncing around and randomly
blocking the exhaust flow.  Or, the air filter could be plugging up or
maybe wet, and impeding induction.

Doyt Echelberger


 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
At 08:56 AM 5/14/2002 -0600, you wrote:
>"Speedy" is now extremely sluggish under load after cold start-up. It's been
>5 months and we can't figure it out. So sluggish she has trouble getting
>into traffic and climbing any kind of incline. Sputters and even backfires.
>
>After warming up, it will run around town, but misses and has very little
>power. Running noticeably rough. Down-shifting's required on hills.
>
>At first it always snapped out of it eventually, usually within an hour, and
>then ran like a top. For the last few weeks it has run consistently poor.
>Snaps out of it only rarely, and for just minutes when it does.
>
>Fuel system's been checked -- distributor, pump, warm up regulator. Filter
>is new and lines ok. Vacuum hoses ok, temp sensor's been changed, ignition
>and timing ok. Spark looks just like that on a comparable, but healthy TQ.
>It idles just fine.
>
>Would an old timing belt cause this trouble? What are we missing?
>
>
>Dennis Unsworth
>Helena Montana
>'86 5kCSTQ; 220k hard miles
>(vanity 222TQ)