At hwy. speed engine stumbles when letting off accelerator

[theWIFES_S70]

Hey dos, how's your throttle cable? Is it old, rusty, and unresponsive? Can you recreate this scenario by revving the car up to 4000RPMs, or does it only happen in fifth gear?

[mrbrian200]

Thanks, mrbrian. The MAF is genuine Bosch two years old so pretty confident it isn't involved. So will continue on the same repair track. I'll post back if resolved.

These can be really troublesome in my experience. The replacement sensors never seem to last as long as the one that originally came with the car. At this point with 2 2.5t P2s in the driveway I have a spare MAF I can pop on either one of them...Just because these can be so troublesome and it's one of the first things you want to rule out when 'not running quite right' and no CEL. With all other vehicles I've owned over the last 20+ years that used a MAF I ended up with a spare hanging around at some point, usually sourced from a salvage vehicle. Once either it and/or the one on the car was determined to be 'known good' one of them got bagged in a ziplock to protect from contamination and shelved for future use during diagnostics. Early thin film bosch type were especially prone to failure/frustrating.

[dosbricks]

Hey dos, how's your throttle cable? Is it old, rusty, and unresponsive? Can you recreate this scenario by revving the car up to 4000RPMs, or does it only happen in fifth gear?

Southern car is always garaged so not rusty, but this sounds plausible and easy to sound out. I'm here in Houston tonight and the car ran almost perfect on a fresh tank of fuel. So possibly got some bad gas. But I have supplies here so I'll take the cable loose and give it a good shot of Dri-Lube, the liquid bike chain stuff that dries right out and leaves a graphite film.

I'll also check vacuum hoses/fittings at idle with some starting fluid.

Thanks!