I've got my '97 vdp running well. New O2 sensors last summer cleared the CEL. The only issue I currently have is with acceleration from about 30 mph to 50 mph when stepping on it to get on the highway. It takes about 6-7 seconds. I know the car is heavy but this seems a little excessive. My gas mileage is a little lower than expected too. What should I be looking for to maybe get a little more oomph. I've run fuel injector cleaner a couple of times but I haven't pulled them. I have replaced plugs a couple of times. I suspect maybe an exhaust issue? I ran Cataclean through it a while back, before I changed the O2 sensors. Has anyone deleted the rear cats, the ones further back in the exhaust? Replacing the front cats is an option but kind of pricey.

 

The engine will not be in closed loop optimal regulation until the engine coolant temp sensor sees 165 C / ECT sensor , it can be calibrated on car against a chart in the 801s doc

Open loop may be your issue

The O2 sensors will not be used until closed loop but I have faint inclings from reading others the O2 sensors are tested ( ? ) before closed loop

There is 1 fuse for all 4 sensors to heat them to read correctly , fuse 10 , 12 , 14 , or 16 as only 1 , right engine bay fuse box , notice the papa indy 61 connector position 12 as the white / green wire , the blue arrow points to the fuse , there is a TSB on this connector corroding because of it's position behind headlight that lets rain pass through headlight surrounds

Clean O2 sensor installation with no anti seize on tip of sensor ?

 

Is your transmission downshifting when you give 'er the boot?

Or, for that matter, are you giving enough boot to make the transmission downshift?


What is your actual MPG and what is your expectation?

Cheers
DD

 

The downshift signal should be from the " spread ' between the throttle position sensor and the mass flow rate comparing that to a no load condition

there will also be a spark timing retard or advance one or the other

So that notion begs for a very very slow TPS check for no open on the variable resistance resistor ( what a TPS is )

MAF will read 1.2 volts DC ( 4 grams / sec air mass ) at the proper idle climbing toward 5 volts on throttle up on the middle wire connector still installed

All this can be seen on a ELM - 327 live date device plugged into the OBD 2 port as you drive

If the TPS has an open spot on the throttle range the ECU sees the return signal as out of range ( error ) and will after a certain amount of time reject the signal not using it , ECU revert to a less than optimal set of maps without TPS , when the TPS comes back in expected range the ECU will revert back to optimum using TPS , all this takes time lag or time dampening

 

Acceleration should cause the fuel system to go Open Loop (i.e. the O2 sensors are ignored and inbuilt fueling map is used) - so you can discount O2 sensors.

I would be checking whether kick-down is happening as @Doug suggested, rather than an engine power issue.

 

Kick down would be indicated by RPM jump higher dropping into lower gear

The transmission shift point ( s ) in normal low load driving is ..................................4000 ?

Real time on the spot gas milage from instrument cluster button should be an indication of open / closed loop with caveats

 

Plug in OBD scanner, with the key in position 2(engine not running) see what's the TPS range by pressing the gas pedal fully. Its either in %(11%-~95%) or V(0.7V-5V) depending on your OBD scanner.
Often the cable stretches over time, its never adjusted and if yours showing low, with the foot down, it will feel like you're running 4 or 5 cylinders only and the car will be extremely sluggish.

 

There was someone in New Zealand that had the throttle cable mis routed at the final bellcrank not allowing full 100 % opening , this was on the supercharged throttle body

put back in place and got his power back