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

[TheYanz]

Looking for some member input...

I've been experiencing some strange stuff at times when cruising then I try to accelerate. If I ease it REAL slow on the gas pedal, I won't notice it as much. But if I push down the gas a little faster than completely easing it, the RPMs'll shoot up with a with noticeable lack of power/ acceleration & the car will just make a reving noise & it feels like the engine just fell on its face.

Now off the line, I don't notice any symptoms. Most of my driving is normal street driving to & from work & running errands & going out around where I live. From a dead stop, I can ease it off a stop/ light to about 20 then just lay into it & get it up to about 40-45mph. It'll go through most of 2nd gear with none of the above symptoms until I have to let off due to posted speed limits.

Any thoughts about the symptoms described in the 1st part? Is this normal? Could this be a trans issue? Traction/ tires issue? Belt slip? Spark blow out? Fuel pump fueling issue? Boost control?

Lol I know I just listed 10 diff things but I dunno, what do you guys think?
Look in my sig for my mods. I had an engine swap done ~2 years ago. Using the same rebuilt trans from before the swap. It doesn't ALWAYS do the above. Just at times. What about that torque converter part? Could that possibly also be the culprit?? From what I recall, my car did the same thing in the past even BEFORE the engine swap.

 

[dsmuts]

Sounds like your trans slipping

 

[TheYanz]

Hey Smut : D U know, I considered that but IMO that's not what it feels like. I was thinking about what I had written last night today while I was driving. I've had a bad trans before & the way the RPMs shoot up w/ that obvious trans slip feel seems completely diff than what I'll notice from time to time on my car. With my situation during those times, it kinda feels like there's too much boost generated too quickly & the engine can't keep up w it or the fueling's off/ spark blow out, belt slip, etc. The fact that it everything shifts flawlessly & with bite off the line when I go through the gears kinda makes me scratch my head.

It's just those part throttle situations from a cruise when I try to accelerate w/o giving the PCM a second or two to adjust. But then again, maybe I've been driving my car for too long & I don't recognize it as, indeed, a trans issue.

 

[Scottydoggs]

it sounds like 3 rd gear is gone.

 

[BillBoost37]

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?

 

[TheYanz]

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.