VQ35 Poor WOT performance

Discuss topics related to the VQ series engine.
bigdirty
Posts: 9
Joined: Wed Dec 08, 2010 1:36 pm

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I have a 2003 Maxima VQ35 in my 2002 Altima SE. It starts and runs great. When I floor it (WOT) it runs pretty good but at about 3000 rpm it runs out of power and accelerates slowly. Doesn't seem to misfire; it just doesn't go. I've checked the fuel pressure and it stays at 55psi all the time.
I don't drive it that hard normally, but I would like to have more power when I need it.


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jbracy7
Posts: 1039
Joined: Sat Jan 13, 2007 8:39 pm
Car: 94 GTS TYPE-M in a dozen pieces
Location: S.A. TX

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So u swapped a vq into a alti,with out a good amount of info we can't help much.

bigdirty
Posts: 9
Joined: Wed Dec 08, 2010 1:36 pm

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My Altima had a VQ35 in it with 234,000 miles on it and the cam timing was off when I bought it. It wouldn't start or run.
I bought an 03 Maxima VQ35 with 86,000 miles on it. I replaced all three cam chains and tensioners (all genuine Nissan). I replaced the valve stem seals and piston rings. (There was quite a bit of carbon on the pistons. Number 4 had so much carbon that I couldn't turn it over by hand past a certain point.)
I also had the transaxle rebuilt.
As I said it starts and runs great excempt under WOT.
I checked it with a scanner and there are no codes.
I have been using regular unleaded, but I ran a full tank of premium which didn't make any difference.

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jbracy7
Posts: 1039
Joined: Sat Jan 13, 2007 8:39 pm
Car: 94 GTS TYPE-M in a dozen pieces
Location: S.A. TX

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Hook up the consult

bigdirty
Posts: 9
Joined: Wed Dec 08, 2010 1:36 pm

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I don't have a consult II. The Nissan dealer charges a min of 1 hour of shop time at $115. I may have to do that.
Any other thoughts??
Thanks

fat3oy
Posts: 305
Joined: Wed Aug 31, 2011 1:09 am
Car: 07 M35X, 06 350z, 06 RSX, 99 Dajiban
Location: Charlotte, NC

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Sounds rich... can you manually change gears on your tranny? Anyhow... do a WOT run up to redline in 5th, check for gas smell...

Any gurgle or backfire when letting off the gas after WOT pull?

Could be lean too... even if you are running at 55psi... any lurching or is the power band pretty smooth top and bottom? Do you see the tach smoothly progress, or does it jump around?

Any other issues? Smells? Troubles downshifting? No lights? Is daily driving not an issue, just under WOT?

If the rest of your chassis is 212k in, there could be a slew of other issues as well...

bigdirty
Posts: 9
Joined: Wed Dec 08, 2010 1:36 pm

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Thanks for the reply fat3oy!
I haven't had it to redline. It just doesn't accelerate well at higher rpm.
NO lights; no smells; it downshifts fine. At highway speed, 60-70mph, if you stand on it, it downshifts and tries to go , but just doesn't do well.
It starts and runs very well at lower rpm; up to about 3k.
Tach is steady.
It acts like it runs out of gas.
I pulled the fuel pump and looked at it. Intake screen was pretty clean. I flushed the outside of the intake screen with clean fuel to remove the what little dirt was on it.
Fuel economy is about 20 mixed and 22.6 on a 250 mile trip.
Daily driving; it runs pretty well except when I want to accelerate like on an on-ramp. Then if I use about half throttle it runs well up to about 3k or so; then I need to get into another gear. I've been using Premium fuel for the last couple of months.

bigdirty
Posts: 9
Joined: Wed Dec 08, 2010 1:36 pm

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Here's an update:
I borrowed a scan tool and hooked it up and went for a test drive. While accelerating, at about 2600 RPM, the O2 sensors on both banks drop to 0.01 and 0 volts. As a result the fuel trim takes a dive and goes to zero also. Could this be caused by a restricted exhaust? Number 3 cat or muffler?
This does not create a check engine light or code!

bigdirty
Posts: 9
Joined: Wed Dec 08, 2010 1:36 pm

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OK guys here's the long awaited answer - - -
The third cat was plugged. Some time back it had a code that indicated the bank one cat was bad. So, I replaced it. The old cat was empty! Nothing inside of it!
Well all the insides of that cat went downstream and plugged the third cat. I cut the third cat off and what a mess of junk in the pipe on the engine side. I put a "test pipe" back on and my Altima is a hot rod; it runs great and the mileage is much better as well. Now I need to replace the third cat. Anyone have a good recommendation for a good low restriction cat that I can put on?


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