RPMs jump but MPHs slow to increase, engine shakes, help!

[drc4423]

2003 g35, car only has 60,000 miles on, previous owner kept really good care of it, but recently when driving and hitting the gas the rpms jump, but the mphs aren't catching up and when it hits 40mph the speed just stays. Even when you press the gas as hard as you can the engine revs but nothing happens, the front of the car shakes and jolts a little bit. You have to let go of the gas pedal and keep trying. Seems like the gas isn't reaching the whole engine, too much oxygen, computer chip problem? Anyone else have this problem?

[joe603]

sounds like a throttle body issue to me...take it to a dealer to verify.

[kmckis1029]

if the RMPs are going up the car is getting fuel...

sounds like the transmission is slipping or the ECU has the car in a "limp mode" limiting the speed... maybe a sensor on the throttle????

that is very wierd

[zozoka1212]

Is it Auto or manual? From your post it sems like auto. Did you try shift in DS or manual? What does it do?

[drc4423]

automatic, not sure what you mean by DS.

[g35808]

i have a 06 coupe,auto, and the exact same thing happened to me a year ago. it was the valve body in the transmission. the dealer replaced it. check the recall's thats what mine was. not sure if its the same for the 03. it was free for me, hopefully you too.

[smockers83]

Mine does the same thing and I've tried to figure this out. At first I thought it was the transmission slipping, a friend suggested the VDC cutting power to the wheels (accelerating over bumps). The valve body, can someone else confirm there was a recall on this? Not that I don't believe you, I just like confirmation.

[drc4423]

what year is yours? I need to get this fixed, I can't get it about 40 without this happening. The Infiniti dealership checked the computer chips, found nothing, and they said replace the whole transmission, are you serious lol. HELP, I need my car to go fast again, especially with summer.

[tollboothwilley]

are you throwing a CEL? Have you read any codes? Its difficult to tell what your problem. We need more information.

2003 - Coupe or Sedan ? Auto(5AT) or Manual(6MT) ??

If 6MT and your RPMs are increasing but speed is not = then you most likely have a clutch issue.

If you are 5AT and your RPMs increase but speed isn't = you could have an issue with your Valve Body (most likely a solenoid is clogged or stopped working) or else you could have mechanical issues with the gearing.

Has anything been done to the car? Mods? Any changes lately?

[tollboothwilley]

Mine does the same thing and I've tried to figure this out. At first I thought it was the transmission slipping, a friend suggested the VDC cutting power to the wheels (accelerating over bumps). The valve body, can someone else confirm there was a recall on this? Not that I don't believe you, I just like confirmation.

I've heard of this happening to a few people now. Although it doesn't seems all that commmon, it happens. I believe it is just a faulty solenoid in the Valve Body but it should be covered under the 5 year 70K mile Powertrain Warranty.