[jmjolley406]

Howdy,
I've got an '02, V6, 4x4 manual X that is losing power when I accelerate.
Upon starting it, it'll sometimes sputter a little bit like it's about to die. Then when I try to accelerate, the RPMs will go up but there is just no power when I hit the gas. I used to be able to go out of a full stop on a flat road from 2nd gear, but now I can barely get up and go from 1st gear, fearing my X will putter out and die. Hills and the highway are incredibly difficult to get up to speed.

I am asking for some trouble shooting ideas on what could be wrong. I'm not too sure about taking it to some of my local shops because I am a lady, so who knows what they'll tell me. Anyway, I was thinking maybe it is a fuel related problem, so I changed the fuel filter since it's pretty easy (had no effect). My X is also kicking out an O2 Bank 1 code, and a Knock Sensor code. My brother also mentioned maybe checking the fuel pump.

Anyway, any insight would be great! Whether it is a way to troubleshoot the issue, or if y'all might know what could be causing the issue.
Thanks!

 

[Arizona Pro-Photo]

Assuming that you changed the air filter, did you check and see if the fuel filter needs changing? A clogged fuel filter will cause this kind of problem because if there is not enough fuel reaching the injectors as the load increases then it will lean out and sputter from fuel starvation.

 

[jmjolley406]

Assuming that you changed the air filter, did you check and see if the fuel filter needs changing? A clogged fuel filter will cause this kind of problem because if there is not enough fuel reaching the injectors as the load increases then it will lean out and sputter from fuel starvation.

Yes, I changed both the fuel filter and the air filter which had no effect on performance.
So I didn't know if I should try the fuel pump, or if the O2 sensor would have any affect on the issue. I'm not even sure how to know that my fuel pump is defective besides just replacing it either.

 

[Arizona Pro-Photo]

Yes, I changed both the fuel filter and the air filter which had no effect on performance.
So I didn't know if I should try the fuel pump, or if the O2 sensor would have any affect on the issue. I'm not even sure how to know that my fuel pump is defective besides just replacing it either.

To my knowledge a bad O2 sensor won't make it stall or lose a lot of power, but you will have a rough idle and it will have bad MPG.
Plus a bad O2 sensor will cause the "Service Engine" light to come on.

However, if the fuel pump is going bad that would cause the symptoms you describe.
But I thought I would ask about the fuel filter first because sometimes it is the simplest things that cause big problems.

You never did say how many miles it has.
If it is over 100,000 has it ever been tuned up?
Worn out ignition parts can also cause power problems.

 

[Arizona Pro-Photo]

I forgot to mention in my last reply that if your X is over 105,000 miles the timing belt could also cause the problems you're having. The user manual says that it should be changed after 105,000 miles. As the belt ages it can stretch and cause the cam and ignition timing to get off causing the power problems you described.

 

[MeToo]

If you haven't yet, get the codes scanned.

Don't start throwing parts at it, either! Some folks see a code and determine that Part 'X' has to be bad. Codes tell you that a system has detected something that isn't right and you need to inspect the system, not just start replacing sensors.

I agree with @Arizona Pro-Photo suggesting that you schedule the timing belt replacement. The change interval is 105,ooo miles. Certain knowledgeable members on CX recommend that you also change it if it is 7 years or older. Whichever comes first, it would be good to do it.

But the first thing is to scan for codes.

 

[jmjolley406]

To my knowledge a bad O2 sensor won't make it stall or lose a lot of power, but you will have a rough idle and it will have bad MPG.
Plus a bad O2 sensor will cause the "Service Engine" light to come on.

However, if the fuel pump is going bad that would cause the symptoms you describe.
But I thought I would ask about the fuel filter first because sometimes it is the simplest things that cause big problems.

You never did say how many miles it has.
If it is over 100,000 has it ever been tuned up?
Worn out ignition parts can also cause power problems.

If you haven't yet, get the codes scanned.

Don't start throwing parts at it, either! Some folks see a code and determine that Part 'X' has to be bad. Codes tell you that a system has detected something that isn't right and you need to inspect the system, not just start replacing sensors.

I agree with @Arizona Pro-Photo suggesting that you schedule the timing belt replacement. The change interval is 105,ooo miles. Certain knowledgeable members on CX recommend that you also change it if it is 7 years or older. Whichever comes first, it would be good to do it.

But the first thing is to scan for codes.

So the codes it's throwing are the O2 sensor and knock sensor codes.

When I bought my truck in 2011 it had 100k+ miles on it and I had the timing belt replaced, but it is now 20 years old with 200k+ miles on it, so getting that checked wouldn't be a bad idea.

I can't say it has had a thorough tune up in awhile. Just routine maintenance.

 

[Arizona Pro-Photo]

So the codes it's throwing are the O2 sensor and knock sensor codes.

When I bought my truck in 2011 it had 100k+ miles on it and I had the timing belt replaced, but it is now 20 years old with 200k+ miles on it, so getting that checked wouldn't be a bad idea.

I can't say it has had a thorough tune up in awhile. Just routine maintenance.

I could be a combination of things.
If the knock sensor is getting triggered that could mean the timing is getting too advanced, which could be related to the timing belt.
If the belt has stretched a little then it might have jumped a tooth or two. Over advanced cam or spark timing will cause knocking when accelerating.
The O2 sensor could be just a coincidence, but if that code is showing then it should be looked into as well.

 

[MeToo]

Unless it's supercharged, the KS has little effect on the NA engines. (KS=knock sensor, NA=naturally aspirated)

Belt being stretched can lead to it getting a wee bit looser than is good for it, so it could skip a tooth. There are 3 sprockets: 2 cams and 1 crank. Which one it skipped would make a difference on how it runs. Each cam drives both the intake and exhaust valves for that head, but the crank turns both of them.

The O2 sensor reports things to the ECM, which uses that and other inputs to determine how to manage the engine. A bad sensor and/or a clogged cat could be part of the problem. If it's clogged, you need to figure out what clogged it, such as leaky fuel injectors, leaky fuel pressure regulator, EGR, or some other issue.

You say that it threw codes. Do you have the actual codes, not just their descriptions? That could be really helpful to the CX members who volunteer their time while at the same time wrench on vehicles for a living. (I don't, so I'm about at the end of my questions and input.) Hopefully they'll pop in and offer some input.

 

[Arizona Pro-Photo]

Unless it's supercharged, the KS has little effect on the NA engines. (KS=knock sensor, NA=naturally aspirated)

Belt being stretched can lead to it getting a wee bit looser than is good for it, so it could skip a tooth. There are 3 sprockets: 2 cams and 1 crank. Which one it skipped would make a difference on how it runs. Each cam drives both the intake and exhaust valves for that head, but the crank turns both of them.

The O2 sensor reports things to the ECM, which uses that and other inputs to determine how to manage the engine. A bad sensor and/or a clogged cat could be part of the problem. If it's clogged, you need to figure out what clogged it, such as leaky fuel injectors, leaky fuel pressure regulator, EGR, or some other issue.

You say that it threw codes. Do you have the actual codes, not just their descriptions? That could be really helpful to the CX members who volunteer their time while at the same time wrench on vehicles for a living. (I don't, so I'm about at the end of my questions and input.) Hopefully they'll pop in and offer some input.

A clogged Cat-converter is something I didn't think of since it is not as common a problem as a bad timing belt.
A clogged cat can produce some of the symptoms described, but there are other symptoms of a clogged cat, such as a rotten egg smell from the exhaust and black smoke when accelerating.
It might be worth checking just to be safe.

 

[jmjolley406]

Hmmm, I'll have to do a bit more digging it sounds like. But I do appreciate all the input. It helps me to see what I might be missing. I know the very basics of how engine stuff works, but I am pretty new to fixing my own stuff. I've really been enjoying it, but I don't have anyone to show me when I have questions.

Also the specific codes are: P0328 and P1143. They've since "cleared" them selves, as in the light goes on then off. I've also had these codes being thrown off and on for awhile now (maybe 6 or so months), but it wasn't until these past few weeks that I noticed my power declining. In case it's relevant.

 

[XT2015]

Hmmm, I'll have to do a bit more digging it sounds like. But I do appreciate all the input. It helps me to see what I might be missing. I know the very basics of how engine stuff works, but I am pretty new to fixing my own stuff. I've really been enjoying it, but I don't have anyone to show me when I have questions.

Also the specific codes are: P0328 and P1143. They've since "cleared" them selves, as in the light goes on then off. I've also had these codes being thrown off and on for awhile now (maybe 6 or so months), but it wasn't until these past few weeks that I noticed my power declining. In case it's relevant.

P1143 code showing an issue with the front O2 sensor on bank 1 (cylinder 1 engine side) is a code you don't want to ignore for six months. If it's caused by too much fuel getting pushed to the cat converter, the excess fuel will degrade the performance of the converter and eventually ruin it and create a expensive repair. Treat symptoms early to avoid extended damage.

 

[jmjolley406]

P1143 code showing an issue with the front O2 sensor on bank 1 (cylinder 1 engine side) is a code you don't want to ignore for six months. If it's caused by too much fuel getting pushed to the cat converter, the excess fuel will degrade the performance of the converter and eventually ruin it and create a expensive repair. Treat symptoms early to avoid extended damage.

Yeah, I know, pretty naughty. Unfortunately money, weather, work, and me being very pregnant deterred me from working on my vehicle.
Are there ways to check to see if the cat converter is bad? From a comment above, I don't have any black smoke or a rotten egg smell. And from experience with my husband's dodge, it gave us a code for the converter issue, so I was thinking my X would do the same with an issue there. I'm also in a state that doesn't require emissions testing, so most people around here cut out the cat and weld a pipe straight across. Also a naughty practice, but we're kind of in a red neck area.

 

[MeToo]

You can always consider replacing it with a pipe, and then set aside a few dollars here and there to get it fixed properly later on.

My experience is that most of the time, the rotten egg smell (sulfur dioxide) is from a new cat rather than one that's on its way out, but I don't know everything, so it's possible that a bad cat could smell like that. (Just ask any dog how bad a cat smells. )

At least you have a choice since you're in an area without smog testing!

 

[TalcomX]

Yeah, I know, pretty naughty. Unfortunately money, weather, work, and me being very pregnant deterred me from working on my vehicle.
Are there ways to check to see if the cat converter is bad? From a comment above, I don't have any black smoke or a rotten egg smell. And from experience with my husband's dodge, it gave us a code for the converter issue, so I was thinking my X would do the same with an issue there. I'm also in a state that doesn't require emissions testing, so most people around here cut out the cat and weld a pipe straight across. Also a naughty practice, but we're kind of in a red neck area.

Sometimes it can be as simple as a plastic bag obstructing your intake. Keep the Xterra running, the kid will love it.

 

[Paulsxterra4x4]

Howdy,
I've got an '02, V6, 4x4 manual X that is losing power when I accelerate.
Upon starting it, it'll sometimes sputter a little bit like it's about to die. Then when I try to accelerate, the RPMs will go up but there is just no power when I hit the gas. I used to be able to go out of a full stop on a flat road from 2nd gear, but now I can barely get up and go from 1st gear, fearing my X will putter out and die. Hills and the highway are incredibly difficult to get up to speed.

I am asking for some trouble shooting ideas on what could be wrong. I'm not too sure about taking it to some of my local shops because I am a lady, so who knows what they'll tell me. Anyway, I was thinking maybe it is a fuel related problem, so I changed the fuel filter since it's pretty easy (had no effect). My X is also kicking out an O2 Bank 1 code, and a Knock Sensor code. My brother also mentioned maybe checking the fuel pump.

Anyway, any insight would be great! Whether it is a way to troubleshoot the issue, or if y'all might know what could be causing the issue.
Thanks!

Check air filter, fuel filter, first

 

[Satito]

Check your Fuel Pressure Regulator. With the engine running pull the small vacuum line off the back of the intake manifold. There are two 1/4" OD lines towards the passenger side. it should be the one closest to the passenger, but pull em both off for good measure. If fuel dribbles out of the vacuum line you need to replace the FPR. This can cause both O2 and cat codes. It will also cause your cats to fail eventually.

Also check the EGR to make sure that it is not sticking. A stuck EGR can cause a vehicle to stumble/stall and have low power at idle and lower RPM.

Manual transmission...
You state that the RPM increase, but it has no get up and go. Are you sure that the clutch isn't slipping?

 

[Paulsxterra4x4]

Check your Fuel Pressure Regulator. With the engine running pull the small vacuum line off the back of the intake manifold. There are two 1/4" OD lines towards the passenger side. it should be the one closest to the passenger, but pull em both off for good measure. If fuel dribbles out of the vacuum line you need to replace the FPR. This can cause both O2 and cat codes. It will also cause your cats to fail eventually.

Also check the EGR to make sure that it is not sticking. A stuck EGR can cause a vehicle to stumble/stall and have low power at idle and lower RPM.

Manual transmission...
You state that the RPM increase, but it has no get up and go. Are you sure that the clutch isn't slipping?

Check all vacuum lines, could be dry rot leaks

 

[jmjolley406]

As always, thanks for all the input. Finally got a Haynes repair manual, which has been incredibly helpful. There's a troubleshooting section that outlines possible causes for the loss of power, so I've been doing some reading.

So here's a quick update:

• Air and fuel filter replaced.
• Already needed an oil change, so oil & oil filter replaced.
• For the Lols, we checked the spark plugs, saw they were a rust color and corroded, so we replaced all plugs and wires. (Indicating a lean fuel mixture)
• Had a small crack in one of the serpentine belts, so replaced all 3 belts.
• Noticed a crazy rattle coming from the passenger cat converter, but it was the heat shield separating at the seam. Noticed that the driver side had one of those metal pipe clamps on it, so we decided to do that to the passenger side to stop the rattle.
• O2 sensor is on the way, should be here tomorrow. Then Bank 1 Sensor 1 will be replaced.
• Fuel pump is here but we either need to siphon the gas out or let it get low. Then we'll replace that.
• (Engine itself is pretty loud; makes a sort of ticking sound. My bro suggests it might be the lifters. Sounds like it might be coming from the general area where the injectors are in the engine. Will probably try to post a video of the engine and sound to another thread to see if the community thinks it's serious or what have you. We just want to keep this thing running for forever...)

Anyway, still no luck on getting that power back yet.

As for the clutch slipping, we don't think that is the case. The RPMs don't go up abnormally when trying to accelerate and there is no burning clutch smell. My husband has also driven 2 other vehicles where the clutch was slipping, and he says my X feels nothing like those did.

We should do the line testing...not a bad idea there. The haynes manual details how to test the FPR and Fuel pump and stuff, but since we have the pump on hand, we'll change that and see how things pan out. If that doesn't help, testing the lines is probably a better bet than just replacing all these parts all willy nilly. I mean, the X is looking better because of it, but you know...time and money.
But yeah, as always thanks for the help. This community is awesome, just like our little trucks. Hopefully we get this resolved soon!

 

[XT2015]

As always, thanks for all the input. Finally got a Haynes repair manual, which has been incredibly helpful. There's a troubleshooting section that outlines possible causes for the loss of power, so I've been doing some reading.

So here's a quick update:

• Air and fuel filter replaced.
• Already needed an oil change, so oil & oil filter replaced.
• For the Lols, we checked the spark plugs, saw they were a rust color and corroded, so we replaced all plugs and wires. (Indicating a lean fuel mixture)
• Had a small crack in one of the serpentine belts, so replaced all 3 belts.
• Noticed a crazy rattle coming from the passenger cat converter, but it was the heat shield separating at the seam. Noticed that the driver side had one of those metal pipe clamps on it, so we decided to do that to the passenger side to stop the rattle.
• O2 sensor is on the way, should be here tomorrow. Then Bank 1 Sensor 1 will be replaced.
• Fuel pump is here but we either need to siphon the gas out or let it get low. Then we'll replace that.
• (Engine itself is pretty loud; makes a sort of ticking sound. My bro suggests it might be the lifters. Sounds like it might be coming from the general area where the injectors are in the engine. Will probably try to post a video of the engine and sound to another thread to see if the community thinks it's serious or what have you. We just want to keep this thing running for forever...)

Anyway, still no luck on getting that power back yet.

As for the clutch slipping, we don't think that is the case. The RPMs don't go up abnormally when trying to accelerate and there is no burning clutch smell. My husband has also driven 2 other vehicles where the clutch was slipping, and he says my X feels nothing like those did.

We should do the line testing...not a bad idea there. The haynes manual details how to test the FPR and Fuel pump and stuff, but since we have the pump on hand, we'll change that and see how things pan out. If that doesn't help, testing the lines is probably a better bet than just replacing all these parts all willy nilly. I mean, the X is looking better because of it, but you know...time and money.
But yeah, as always thanks for the help. This community is awesome, just like our little trucks. Hopefully we get this resolved soon!

Have you already checked the ignition timing advance at the distributor? If that is retarded and not set to spec you are going to be losing power for sure.