well i happened to have a set of bosch cables in the basement... i installed those and drove the car on several errands tonight and not one acceleration stumble. i'll certainly follow up on the other great suggestions as i get the car ready for my son. good to be back here with all you great folks.

93 940 -- 342k
90 240 -- 328k

You could check the adjustment of the throttle position switch for "on idle to off idle acceleration."
The ECU needs to know when the change is happening.

Is the throttle body clean and the port to the FPR.
Make sure throttle plate shut so that "all the idling air" is going through the IAC's control range. A partial open plate messes with the transition.

Check "all hose" connections behind the AMM, including vacuum lines, to make sure they're in good shape. The AMM needs to control all the air to the engine.

Phil

thanks art,

i performed the pinch and feel test on the return line and am able to feel a good backpressure with my fingers when i pinch the line further downstream with pliers.

i did make another interesting observation.... as i was reving the engine via the throttle spindle i noticed a good size spark jumping from a spark plug wire to a bolt on the intake manifold. it has been extremely humid here and spark plug wires are 6 years old according to my records. is this just bad wires or is there another cause.

do you think this could this be causing the intermittant issues i'm experiencing. at this point i would like to insert a question mark but alas the shift key appears to be non-functional.

thanks,
matt

Hi Matt,

First, on the hot fuse... it is most likely a red herring. Of course a fuse does what it does by getting hot, and that does not work like a light switch (cool until it needs to melt) so yes a working fuse may burn your finger. But in that particular fuse panel, high resistance contacts are a well known trouble, and their result is heat. Check the current by using a multimeter in the 10-amp range; you should see about 3-5 amps with the oxygen sensor heater and tank pump together. If you hear the tank pump running you can pretty much rule out needing to go back in there.

On it being a fuel delivery problem like it feels... could be, certainly, and it wasn't 3 months into my 15 year relationship with Volvos that I realized I needed a way to measure fuel pressure. You do too. A fair substitute is a check of the return flow. Run the pumps by jumping fuse 4 to 12V (like from 6) and feel the flow through the hose exiting the fuel pressure regulator. If you trust the regulator and feel the flow, you can feel somewhat assured you have 43 lbs of pressure to the injectors. Then you can go on to be sure the intake vacuum is doing its thing.


--
Art Benstein near Baltimore

I wonder if other dogs think poodles are members of a weird religious cult.
-Rita Rudner