Thread: RPMs Shoot Up When Accelerating From ~40mph ???

If the rpm go up w/o you moving, the engine isn't falling on it's face, the trans is.

If at 40ish if you give it some throttle it should be in 4th and try to downshift to 3rd. Put the shifter in third and get up to 40mph give it enough throttle to get power but not downshift. Does it slip?

Turned out to be a bad fuel pressure regulator. And I JUST fixed this a few days ago. Problem's been going on for a long time. It would drive fine off the line but it was VERY noticeable when going into heavy boost from part throttle/ cruising. I realized that it had nothing to do with the trans since I got a trans swap done like 3-4 months ago & even with that newer trans, the same symptoms persisted. Rented a fuel pressure tester from AutoZone & KEY ON was fine. It was about 48 PSI. However at idle, it would dip down to 40 PSI which is no good. Bought a Sorensen brand one from AutoZone for $35. Everything works better now. Around 50 PSI at idle. That Actron tester is a piece of sh1t with inconsistent readings but you get the idea. FINALLY able to get my GTP to act normally when trying to get into the high RPM range from a cruising speed. The RPMs now smoothly & gradually rise instead of shooting up midway through. Guessing the A/F mixture was severely leaning out with the clogged FPR. Funny thing is that I never noticed any fuel in the vacuum line attached to it but I read that the diaphragm can rupture OR - in some cases, probably like mine, clog up & just end up sitting there and doing nothing.