1994 Lumina APV 3.8l -lacks power

[Lumina94APV]

Congratulations on a great site! I am going thru other posts on this subject but thought I would add mine for any suggestions.

My current problem started last year - lack of power/misfire/hesitation/ difficulty going up hills.
The sparkplugs had heavy deposits- mainly from age and short trips. Replacing them (and the back 3 wires which broke) cured some of it - but it still lacks power/trouble going up hills.
It runs good when accelerating and above about 100km/hr (60 mph). and picks up around 120-130 (72-78mph). I assume it's running "open loop" under acceleration and at higher speeds??
80 km/hr(50mph) going uphill is bad. It doesn't unlock the TCC or downshaft and loses speed.. Of course, the computer doesn't mind - no CEL or trouble codes!
The 3 front plugs were white/lean.
A dealer suggested the catalytic converter might be restricted - but I don't think it would accelerate as well if it was....
They changed the O2 sensor, fuel filter, cleaned the injectors, IAC valve and throttle body.
I had high hopes for the throttle body cleaning as it had worked miracles before...
There was some improvement - more at lower speeds and it improved the downshifting under load.

The front plugs still are lean, idle is rough and still has a lack of power "choked or restricted" feel to it.

I built an ALDL cable (and it works!). there are no DTC's - but cyl #3 misfires at idle. I need a portable computer (or a long extension cord...) to run it at higher speeds.
My plan is to start with the basics- new plugs and wires (both not old), PCV valve.
Then check TPS, clean EGR valve and passages, clean MAF sensor,check grounds and for vacuum leaks.

Any suggestions are appreciated!!!

Thanks
Allan

[maxwedge]

How do you know #3 misfires?

[Lumina94APV]

The software program from www.pontiac-interface.de showed #3 cyl as misfiring but did not indicate any weak cylinders - if that makes sense??
I will check again after changing wires and plugs.

Allan

[maxwedge]

Do you feel a misfire?

[Lumina94APV]

It does have a rough idle but no detectable missfire at higher speeds. I haven't played with the software enough to be confident in the data-- figure I'll check it again after changing plugs and wires and see if it's ok then. I removed the plugs today and they all look lean - except cyl #1 which looks rich. This is after mostly city driving - they were all white/lean looking after 6hrs of highway driving. I'm thinking maybe a leaky injector on #1?


Allan

[maxwedge]

I'd be careful with the #3 misfire info. A weak o2 sensor can cause this, so can low fuel pressure. Dirty injectors, nboard injector cleaning doesn't always work. White insulators on the plugs is normal on modern pcm controlled efi systems.