I recently purchased a 1998 S70 with 148,000 on it.
I notice that whenever I give it more than half throttle, it hesitates--kinda shuts off for a fraction of a second until I release the throttle.
Any ideas?

 

Have you checked all of your vacuum lines? Is your throttle control valve in good condition? Not sure how to check it. Also could be a fuel pressure probem but not likely.

 

Freq,

I just Bought a S70 t5 with 188,000km. When I am accelerating (anything over 3/4 throttle) at about 4500rpm and above the engine would cut out until I let up on the throttle a bit. I can't seem to make it do it at any less that 4000rpm, and when I go easy on the throttle I can easily bring it up to the red line. Up to 4000rpm the car has lots of power.
Maybe it's the distributor cap/wires/plugs?

Tony,

 

Ideas?

1. Stage 0 (full tune up)
2. Ck fuel pressure

 

I usually start simple and work my way up from there. Ignition cap (&/or rotor) corrosion is the most likely culprit, especially if the car goes to a place like Jiffy Lube for oil/filter service instead of the dealership.

But the symptoms you describe REALLY sound like they don't just affect ONE cylinder, which is usually indicative of an electrical issue. This sounds more like a universal failure (or at least a temporary drop below normal acceptable parameters) of an entire system. That is, if I'm understanding your issue correctly. I have 2 really obvious possibilities and one completely out of "left-field."

Obvious #1? Your fuel delivery isn't keeping up with the demand of the engine at high-RPM acceleration. Sounds like it could be a dirty fuel filter. but;

Obvious #2 (also the cheapest and most likely)? Your Throttle Body has a build-up of sludge on the latter 1/3 of the butterfly valve's open range, causing just enough of a disruption of airflow under hard acceleration that your injection mapping no longer fits the profile of what is needed. Pull the Throttle Body, clean it, hit the pivot points of the butterfly valve with some 3-in-1, and re-install it with a new $9 gasket. Should clear right up.

"Left-Field": Neutral Position Sensor/Switch in the tranny. Yeah, I know it sounds weird, but the rev limiter on these cars is set at 4,000 when the car is in Park or Neutral, and the coincidence is just too strong to ignore. I had this exact issue on an old Audi that drove me absolutely nuts until one of my buddies suggested this issue. Did exactly the same thing, and everything else was new on the damned car. Funny enough, it had just turned 150,000 miles on the clock, and we had dropped the tranny pan to change the filter. We had bumped the Neutral switch and knocked the lead loose. We plugged it back in and Oi-La!

None of these three items costs more than $50.