No Power/Check Engine Light

[Entropy]

Hi guys, I hope you can help me out here, because I can't seem to figure this out.

I have a '94 Pathfinder, automatic. A couple months ago, the check engine light came on, though it ran fine, so I wasn't concerned. After a while, it started to lack power, though only rarely. So I checked the codes, and it came back with code "33" - the O2 Sensor. So I bought a new one (Bosch I think) and replaced it. It didn't help at all. The check engine light still comes on (even though I clear the codes). As soon as the light comes on, I have absolutely no engine power. I can put the throttle down to just before it downshifts, and I can't accelerate. Sometimes the engine light will turn back off, and it's all back to normal, though lately the lights seems to be on more than it's off.

 

I checked the catalytic converted (I read if it's plugged it can cause this), but it's clean.

 

As some background (since this may help someone help me), my power door locks started behaving funny. All the doors lock automatically when either of the front doors are closed, just as iff I hit the lock switch. It's an inconvenience, but I don't know if the two issues are related (computer or something?) Plus, last year I had the Knock Sensor replaced because the engine was knocking really bad in the summer heat. Replacing that helped, though I have to run mid-grade gas now if the summer still to prevent pinging. I'm just throwing this bit in incase someone thinks these are related somehow.

 

Any help you guys can give would be really appreciated.

 

Thanks.

[andreus009]

Ok, I'm gonna throw you one idea I know from some experience. If your rubber intake tube that runs from the air filter box to the intake manifold is dislocated or has leaks (i.e. cracks) you can lose power and will cause check engine light.

[Precise1]

Ditto. I just replaced this on someones truck since it was on the way out.

 

Check all you hoses and EGR for vacuum leaks and clean the MAF (write up in the How To section)

 

B

[Alkorahil]

Hi guys, I hope you can help me out here, because I can't seem to figure this out.

I have a '94 Pathfinder, automatic. A couple months ago, the check engine light came on, though it ran fine, so I wasn't concerned. After a while, it started to lack power, though only rarely. So I checked the codes, and it came back with code "33" - the O2 Sensor. So I bought a new one (Bosch I think) and replaced it. It didn't help at all. The check engine light still comes on (even though I clear the codes). As soon as the light comes on, I have absolutely no engine power. I can put the throttle down to just before it downshifts, and I can't accelerate. Sometimes the engine light will turn back off, and it's all back to normal, though lately the lights seems to be on more than it's off.

 

Without driving the vehicle I would look at the following for lack of power problems:

1) Did they get you the correct O2 sensor? If you replaced it and the O2 sensor code is still coming back on after replacing it I am wondering....

2) As silly as it may sound....did you plug the new one in?

3) Air leak in the exhaust system before the O2 sensor allowing O2 into the exhause throwing the O2 sensor off.

4) As pointed out, Mass Airflow and vacuum hoses. Check all the vacuum hoses for any leaks/cracks/holes/frayed ends. The wiring harness connector to the Mass Airflow Sensor is notorious on these vehicles for giving intermitant problems, there are many threads on here about it.

5) Bad Distributor cap/rotor

6) Clogged fuel filter

7) Engine Timing off

8) Improperly gapped spark plugs/Damaged or fouled spark plugs.

9) Bad/loose spark plug wires

10) Engine Temprerature Sensor

11) EGR valve or EGR control Solenoid

less likely problems:

11) Bad pickup module in the distributor

12) Fuel pressure loss from fuel pressure regulator or fuel pump.

13) Stuck Idle Control Valve

 

I checked the catalytic converted (I read if it's plugged it can cause this), but it's clean.

 

This would be more of an all the time constant lack of power.

 

As some background (since this may help someone help me), my power door locks started behaving funny. All the doors lock automatically when either of the front doors are closed, just as iff I hit the lock switch. It's an inconvenience, but I don't know if the two issues are related (computer or something?) Plus, last year I had the Knock Sensor replaced because the engine was knocking really bad in the summer heat. Replacing that helped, though I have to run mid-grade gas now if the summer still to prevent pinging. I'm just throwing this bit in incase someone thinks these are related somehow.

 

The power door locks are on a completely different circuit and not tied to the engine computer. The engine pining is due to engine age.

Edited August 12, 2010 by Alkorahil

[Entropy]

Without driving the vehicle I would look at the following for lack of power problems:

1) Did they get you the correct O2 sensor? If you replaced it and the O2 sensor code is still coming back on after replacing it I am wondering....

2) As silly as it may sound....did you plug the new one in?

3) Air leak in the exhaust system before the O2 sensor allowing O2 into the exhause throwing the O2 sensor off.

4) As pointed out, Mass Airflow and vacuum hoses. Check all the vacuum hoses for any leaks/cracks/holes/frayed ends. The wiring harness connector to the Mass Airflow Sensor is notorious on these vehicles for giving intermitant problems, there are many threads on here about it.

5) Bad Distributor cap/rotor

6) Clogged fuel filter

7) Engine Timing off

8) Improperly gapped spark plugs/Damaged or fouled spark plugs.

9) Bad/loose spark plug wires

10) Engine Temprerature Sensor

11) EGR valve or EGR control Solenoid

less likely problems:

11) Bad pickup module in the distributor

12) Fuel pressure loss from fuel pressure regulator or fuel pump.

13) Stuck Idle Control Valve

 

 

 

This would be more of an all the time constant lack of power.

 

 

 

The power door locks are on a completely different circuit and not tied to the engine computer. The engine pining is due to engine age.

 

Wow, thanks guys for all the suggestions.

 

I cleaned the MAF, and it did seem to help, though the check engine light still comes on/off sometimes (and still shows error code 33); however, now when the light comes on, I don't lose nearly as much power as before.

 

And thanks Alkorahil, I'll check out all those things you suggested this weekend, though one more question. You ask if I was given the right O2 sensor. It sure looked the same, though I've thrown out the old one now. I've read (after I bought my current O2 sensor) that some guys run into problems if they don't use a 'Genuine Nissan' O2 sensor. I just bought mine at Lordco (it was Bosch or NGK). Do you know if there's any truth to this? I don't really want to buy another one (especially at dealership prices), though if you think there's some truth to this, and your other ideas don't help, I'll try that too.

 

Thanks again guys. Maybe I'll finally get this solved this weekend.

[Dowser]

And the answer to the Door lock problem is here. "Problem Solver"

 

Good luck and keep us posted on what the results are if you sort out the power loss issue.

[Alkorahil]

nice write up on the door lock timer.

 

As to the O2 sensor.....

I will say that I have had many people call in the past and say they got an O2 sensor at auto parts store X and that their vehicle runs worse, they get the OEM one from me and it cures their problems.

Then again, I dont know if they got the correct one from the auto parts store in the first place, I happened to give them the correct Nissan part their second time and thats why it worked for them.

[Entropy]

And the answer to the Door lock problem is here. "Problem Solver"

 

Good luck and keep us posted on what the results are if you sort out the power loss issue.

 

Thanks, I picked up a new Timer at Pick and Pull, and it fixed the door locks right up.

I'm still having no luck with the loss of power/intermittent Check Engine Light problem though. I'll keep trying, and let you guys know.

[Entropy]

Sorry it took me so long to respond back to this post. I just want to add to it in case it helps someone else.

It turns out it was a missing vacuum line. It goes from (I think) the back of the intake manifold to some fuel-thing which is pretty much right below it. It runs right up against the firewall, so I couldn’t even see the connection points. Once I got a new hose on there, it’s much better. The check engine light still comes on every couple of days, and it’s still the same error code, but it clears itself up after a few minutes. It also never loses power like it did before. I’ll probably take another look at it in the spring when it’s a little nicer outside.

Thanks for all the help guys.