New guy with problems

[Ryno317]

Hi everyone. I recently purchased a 08 Cx7 with 95k on it. For the past week whenever I drive it jerks and hesitates on acceleration. It doesn't lose power and shifts thru the gears fine. It continues to build power and speed, but it feels like a nurse pumping the blood pressure cuff ball while I press on the petal. If I let go, it stops.

I checked tranny fluid. Good level. Added a fuel injector cleaner, seems to help alittle. So I purchased a new in tank pump thinking the pump wasnt building enough pressure fast enough. Going to install in next few days.

Does anyone have any other ideas what it could be if the pump doesnt help?

[MSMS3]

Welcome!

The symptoms are vague and could point to many things. Since it is a new to you car, maybe start with the basics. New spark plugs and new air filter would be good to do anyway.

Check all hose clamps and hoses from the turbo to intercooler and intercooler to throttle body. Check vacuum lines.

Maybe get some spray MAF cleaner and carefully remove the sensor and clean the element, being careful not to let anything touch it except the cleaner. Let it air dry and reinstall.

Maybe your ECU is cutting fuel or boost. Do you have a check engine light on? If so, get the car scanned for free at a local auto parts store and post the code numbers here.

[Ryno317]

Sorry, I was a but vague and rushed in my original post.

No check engine light to get checked to point me in a general direction. Hasn't come on at all to even hint at something. Did the loose vacuum lines and hoses check already.
Sprayed MAF. Air filter is clean. Didnt do spark plugs, according to Carfax they were replaced in April, plus no code for misfire either. No obvious loose connections of plugs or grounds.

It starts and idles fine and smooth. Rev it in park, no issues. Its when its driving and accelerating. Rpms dont go sky high like its slipping.

If normal acceleration is Raaaaaaa, mine is Ra ra ra ra ra, but still increasing speed and shifting, until I let off the petal.

Thanks

[Ryno317]

Ok, so I threw in a new In-tank fuel pump. Acceleration problem has stopped. I'm thinking it was original fuel pump, becuase the screws were old and stripped out easily. I had to drill the heads off and spin out the threads. Grabbed new screws from hardware store to re-install metal ring.

[Ryno317]

Update, so the jerky acceleration started again yesterday. Wife and I went for some early Black friday shopping. Car ran great, on our way home stopped and filled the tank up. Fast forward 5 hrs, wife leaves, car is running like crap, same jerky acceleration. So we assume bad gas, so i siphon out 12 gallons. Leave about a 1/4 tank and i dump in a Techron gas treat and a bottle of Heet water remover, all directly into the tank and on top of pump. Button it and go for a spirited drive around the neighborhood. No issues, yes. But wait, i clean up, go out again, highway speeds, nothing, park, hour later, leave and the issues start. During this whole time, no CEL, nothing.

So I'm think high pressure fuel pump, spark plugs, coils. But with no CEL, I dont know where to start.

Help

[Bertospeed3]

Spark plugs would be the cheapest and most practical start. Even though it says they were replaced in April, i'm sure they weren't gapped correctly.

[Ryno317]

Sorry, I didnt update, but after more internet digging, I came across another person having similar issues and they replaced the upstream 02 sensor. They had said that the dealer put it on a scanner and the upper 02 sensor was reading off, but not enough to throw a code. I replaced mine and problem seems fixed as of now. If not, then its going to be spark plugs and coils next.

Undoing the connections is a PITA.

[MSMS3]

Originally Posted by Ryno317 Sorry, I didnt update, but after more internet digging, I came across another person having similar issues and they replaced the upstream 02 sensor. They had said that the dealer put it on a scanner and the upper 02 sensor was reading off, but not enough to throw a code. I replaced mine and problem seems fixed as of now. If not, then its going to be spark plugs and coils next. Undoing the connections is a PITA.

Thank you for reporting the solution. Too many users post problems, seek advice, find a solution, and selfishly never come back with that solution so it can help others. No one else learns anything when they do that. I appreciate your contribution to the community.