2007 Nissan Altima 2.5L, can't accelerate under load

Hi Everyone,

I have a 2007 Nissan Altima 2.5 with 175,000 miles on it and I’m the original owner. recently my car has an issue where it has trouble accelerating under load such as going up hills or trying to get onto the highway and I’m not sure what is wrong.

The first day that this happened was when I was going to work and getting on the highway it seemed to lack power and that I needed to step on the accelerator more to get up to speed, 65mph. On the way home from work I noticed the same thing on the back roads going up hills, when I got on the highway on ramp it was the same issue but worse and I could barely get it to 65 mph

I thought at first it might be the CVT dying on me, I read that getting the CVT fluid changed might fix the problem. I brought it to the Nissan dealership and had them change the fluid, but the problem is still happening.

-My car isn’t throwing any codes, I hooked up my BlueDriver scan tool and ran the full test and there are no codes on the car and no pending codes. Mode 6 also doesn't have any codes showing up.

-When I drive on a flat road I’m able to accelerate up to 50+ mph at a normal rate of acceleration. However if I try to accelerate hard or go up a hill, the engine bogs down and the car starts to slow down.

-If I try to accelerate hard the engine seems like its misfiring and the rpms don’t seem to go over 3400 rpm, the car will then start to slow down while its doing this.

-It’s still using the original transmission, I haven’t had the issue that many other people had with their CVTs in the past.

-My valve cover leaks around the gasket, I haven’t fixed it because of the engine design has an engine support mount that goes over the valve cover. I did do a half ass fix by applying permatex black silicon gasket maker around where it is leaking to some temporary success. Prior to this “fix”, a lot of oil did get into the spark plug cylinders 1 + 2 but I have cleaned it out the oil and cleaned the spark plugs and the ignition coils.

-About 3 years ago I replaced the manifold/catalyic converter(not oem), not sure if the catalytic converter could be clogged.

-One other symptom was that was happening. After about 10-20 minutes of driving I could hear a whining sound when I accelerated. I don't recall where the sound was coming from.

I attached copies of some live data I took with the Bluedriver. I drove the car around and several time I really floored it and you can see where the engine load is high and the rpms drop and so does the mph. I appreciate any help you can give me.

Thank you for your help!

My first thoughts are low fuel volume/pressure. Or, restricted exhaust.

Hi pole71, thanks for the advice.

I forgot one other symptom was that was happening. After about 10-20 minutes of driving I could hear a whining sound when I accelerate. I don't recall where the sound was coming from.

Could this sound be the fuel pump dying?

I have heard some pretty loud, whining fuel pumps. But, given that you only hear it after 10-20 minutes and while accelerating, makes me think of a power steering pump that is getting aerated or, possibly, an alternator. Does it whine at higher RPM's while in Park/Neutral. You could remove the fuel cap and have a listen. Do you have access to a fuel pressure gauge? I'm not sure if the Altima has a schrader valve for easy fuel pressure testing, or not.

Thanks for posting that data. I'd like to be clear on this - was the lack of power issue happening during this capture?

Initially, I don't see an issue with these numbers. The Load is going to 99%, the downstream O2 shows full rich under acceleration, and the fuel trims are reasonable. That suggests fuel delivery is good, the MAF is reporting accurately, and that there are no VE issues (plugged converters, timing, ect). I even put your highest MAF rate into a VE calculator for giggles:



On paper, this car should have no problem getting up to speed. :silly: Which is why I wanted to be certain that your issue was happening during this capture. Because if it is, I'd look towards a transmission issue. If not, I'd suggest retaking a capture with the issue happening.

do you smell a strange smell and have u checked the cat converter. if u have a vacuum gauge you can test it. snap throttle and vacuum should drop fast, then come back up fast. if it comes back up slow, the exhaust is restricted.

Pole71: If the power steering pump is going could that cause acceleration issues? I didn't notice the sound when I was in park. I currently don't have a fuel pressure gauge, I guess I could buy one that way I'd have one on hand for the future.

Tyler: Yes the lack of power was happening in the data. The lack of power in the data can be seen at time mark 307 to 345, you can see the engine load is around 99 most of the time (I was flooring it) but my speed wasn't going past 26 mph.

Wacoeagle: I don't recall smelling anything strange, but the valve cover has been leaking a little oil on my exhaust manifold so all I've been able to smell is burning oil. I don't have a vacuum gauge, but could I test it by removing the o2 sensor and see if it responds better when I try accelerating hard?

Thanks again for your help!

can u hear anything rattling in the cat converter?