No acceleration/power - Nissan Forum
 
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post #1 of 9 Old Aug 23rd, 2009, 12:05 PM Thread Starter
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No acceleration/power

Hey everyone
I'm newly registered to this forum but have been researching/searching archived posts for a few months now.
I'm working on my girlfriends 2000 Altima GXE - 2.4L 4cyl
There is no power at all low end, off idle to about 1500rpm's it has a real bad bog, and then above that it picks up fine. It does this in park, neutral, drive, etc so I do not believe it is transmission related.
It was throwing a code for the 02 sensor although that has been on since she bought the car about 8 months ago.
So far I've
- changed spark plugs, fuel filter, air filter
- removed both cats and ran it with just the exhaust manifold
- checked fuel pressure(46psi or so).

Anybody have any other ideas for me to check? I'm running short on ideas here and the car is still not any better, I need to get a run just to get the car onto car ramps even
thank you very much
Jamie
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post #2 of 9 Old Aug 27th, 2009, 08:18 PM Thread Starter
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alright, well I'm still working on this thing and still havn't gotten it fixed.
I've noticed that while idleing the ignition timing is around 15-20 degrees, then when i put the pedal to the floor it drops to about 4-5 and then once the rpm's come up it hits 45-50ish, so something timing related is definately not working.
I've replaced the knock sensor thinking maybe it was at fault with no improvements.

After doing some testing, the manual says the crank sensor should measure between 430-510ohms, and while testing mine I'm reading 570, so thats definately out of spec, although on top of that, while checking for reference voltage, while the manual says I should have 5V, I have 0.
Anybody ever ran into a problem like this? I'm thinking either broken wire from ecu to the crankshaft sensor, or maybe a faulty ecu?

sorry for such long posts, just trying to give as much info as possible

Jamie
1999 Pathfinder Chilkoot
2000 Altima(g/f's car)
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post #3 of 9 Old Aug 28th, 2009, 12:00 AM
jdg
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Quote:
Originally Posted by jamiestj View Post
I've noticed that while idleing the ignition timing is around 15-20 degrees
Normal...

Quote:
, then when i put the pedal to the floor it drops to about 4-5 and then once the rpm's come up it hits 45-50ish
Again...totally normal. Timing is inversely related to manifold pressure. The more the pressure, the less the timing advance.

Quote:
I've replaced the knock sensor thinking maybe it was at fault with no improvements.
Which would only show up if you were running entirely too much initial timing or crappy gas.

Quote:
After doing some testing, the manual says the crank sensor should measure between 430-510ohms, and while testing mine I'm reading 570, so thats definately out of spec
Yes, out of spec, but make sure your meter isn't adding an extra amount of resistance to the reading in the first place. Would suck to replace a sensor when the measurement was bad in the first place.

Quote:
although on top of that, while checking for reference voltage, while the manual says I should have 5V, I have 0.
If you didn't have a reference voltage, then you might've measured it wrong. Generally has to be checked with the engine running. And if you actually didn't have a reference voltage, you'd get a code and the timing wouldn't change at all.

If your resistance reading is correct, I'd shoot for a crank and/or cam sensor. Could be the gap between the sensor and the pickup teeth is too large also. Fire up the engine, check that reference voltage, and wind up the engine a few times, see if the voltage changes.
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post #4 of 9 Old Aug 28th, 2009, 12:30 AM Thread Starter
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Quote:
Originally Posted by jdgrotte View Post
If you didn't have a reference voltage, then you might've measured it wrong. Generally has to be checked with the engine running. And if you actually didn't have a reference voltage, you'd get a code and the timing wouldn't change at all.
If your resistance reading is correct, I'd shoot for a crank and/or cam sensor. Could be the gap between the sensor and the pickup teeth is too large also. Fire up the engine, check that reference voltage, and wind up the engine a few times, see if the voltage changes.
I had the ignition on while checking it, I checked the reference readings at other sensors(Intake air temp, egr temp, etc) and they all had close to 5V(4.8 or something like that), although at the crank sensor I am reading 0. I checked continuity between the black(ground) at the crank sensor and the intake air temp and there is continuity there, so the ground wire is infact good, its just that for some reason or another, that 5v reference is not there.
As for cam sensor, is the cam sensor not for timing the fuel, and the crank is for spark? or am I wrong there, I very well could be, but thats how I always looked at it. And the resistance reading was checked with two different meters, reading the same thing, it seems odd for it to be so close to spec which is why I dont really want to change it, but I've really got to get this car out of my garage, haha.
thanks for the help

Jamie
1999 Pathfinder Chilkoot
2000 Altima(g/f's car)
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post #5 of 9 Old Aug 28th, 2009, 12:57 AM
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Quote:
Originally Posted by jamiestj View Post
I had the ignition on while checking it
Ignition on and engine running = two different things!

Quote:
As for cam sensor, is the cam sensor not for timing the fuel, and the crank is for spark? or am I wrong there, I very well could be, but thats how I always looked at it.
Kinda/sorta...
Cam sensor is generally for figuring out when #1 cylinder is hitting. Crank sensor is generally for figuring out exactly where the engine is in it's rotation. If the car only had a crank sensor, you'd never know if #1 cylinder TDC was right before the power stroke or intake stroke. If it only had a cam sensor, well, the cam sensor spins half as fast as the crank sensor, so the computer gets better info from a sensor spinning faster.
They both work for both things. Might be able to lose one or the other and the engine will keep running in 'limp home' mode. Lose both of them and the thing won't run at all.

Quote:
And the resistance reading was checked with two different meters, reading the same thing, it seems odd for it to be so close to spec which is why I dont really want to change it
Good call on the 2 meters. I've been bit by a bad meter before which is why I mentioned it.
And I guess that's why they call it a 'specification'. It's either good or it's bad. Although in this case, I'd be a bit leery of that slightly high number also. In this case, too much resistance means that the current being generated by the hall effect sensor might be just a bit too low, low enough NOT to feed the ECU enough juice to tell it what's going on, until it gets gong faster. These crank and cam sensors (hall effect sensors) are basically AC generators so therefore, the faster they go, the more juice they make.
I think the first thing I'd try is cleaning the heck out of the connectors (wire brush to get the major stuff, q-tips and rubbing alcohol to get everything else) on both the connector itself and the sensor before going and swapping out sensors since it is so close to being out of spec.

Also, get your hands on a 'Haynes' or 'Chiltons' manual and check the fuel pressure with the engine running and when you blip the throttle and such. Fuel pressure should change. Might have a fuel pressure regulator problem. Check the vacuum line going to the regulator.
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post #6 of 9 Old Aug 29th, 2009, 03:31 PM
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Out of curiosity did you check the rotor/distributor cap? Did a bit of overhauling on mine when we were looking to see where mine was dumping oil and the points were horribly encrusted and was causing mine to bog down between idle and ~2000 rpms. Above that, it would be fine, but below it sounded like it was going through death throws. Also, did you fix your timing when you changed the plugs? Had to do that on mine as well.
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post #7 of 9 Old Sep 2nd, 2009, 08:05 PM Thread Starter
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alrighty time for another update
havnt had a whole lot of time lately to work on the car so took me a while to reply
as for cap and rotor, i ended up changing them both aswell, didnt look real bad, but figured it wouldnt hurt anyways, and there was no oil under there at all.

As for reference voltage, im still not seeing any there, i even went as far as to get a pin-out for the ecu and checked from the ecu pin to the crank sensor and there is infact continuity there(so there is no break in the wire from ecu to crank sensor). Also, with the harness plugged into the ecu, i back-probed the crank sensor wire and still no 5v reference voltage, i get roughly 0.2-0.3v or so, either with ignition on, or with engine actually running. Does anyone know for sure that there should be a 5v reference here and that my haynes isnt just throwing me off?
Also, I can unplug the crank sensor and the car runs the exact same, making me think theres definately a problem here, bad ecu perhaps not sending a signal to crank sensor??
thanks again
Jamie
(getting ready to light a match soon, haha)

Jamie
1999 Pathfinder Chilkoot
2000 Altima(g/f's car)

Last edited by jamiestj; Sep 2nd, 2009 at 08:08 PM.
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post #8 of 9 Old Sep 3rd, 2009, 12:11 AM
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Quote:
Originally Posted by jamiestj View Post
i back-probed the crank sensor wire and still no 5v reference voltage, i get roughly 0.2-0.3v or so, either with ignition on, or with engine actually running
If you had an o-scope, you should actually get a pulsing 5v signal, so if the car is running and you've got a normal meter hooked up to it, you probably won't read a full 5v. Try the AC scale and see what you get.

Quote:
Also, I can unplug the crank sensor and the car runs the exact same, making me think theres definately a problem here, bad ecu perhaps not sending a signal to crank sensor??
Does the ECU throw a code when you pull crank sensor plug and run the engine? I would think it should. Take it out for a test drive. If it drives exactly the same, I would say it's bad, maybe just not bad enough to throw a code(???). I would guess it would run like crap without a crank sensor hooked up.
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post #9 of 9 Old Sep 23rd, 2009, 12:27 AM
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Quote:
Originally Posted by jdgrotte View Post
If you had an o-scope, you should actually get a pulsing 5v signal, so if the car is running and you've got a normal meter hooked up to it, you probably won't read a full 5v. Try the AC scale and see what you get.


Does the ECU throw a code when you pull crank sensor plug and run the engine? I would think it should. Take it out for a test drive. If it drives exactly the same, I would say it's bad, maybe just not bad enough to throw a code(???). I would guess it would run like crap without a crank sensor hooked up.
Curious ...Have you checked for the notoriuos intake manifold gasket leak? Try spraying some carb cleaner or starting fluid along the intake to head area and see if the idle smooths out. Just to be certain its not a mechanical problem instead of electrical.
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