Engine missing under load - Please Help!

[nutsaboutbolts]

2000 Patfinder 170k miles- Try to keep this as brief as possible but I have tried almost everything.

Car cut off on the way home from work and would not start back. Had it towed to my local mechanic who I trust with my kids. I usually do most of my own work but my garage was full at the time. He chalked it up as a bad distributor and replaced it. I picked the car up and noticed it wasn't running as well as before (just seemed to lack power and surge under acceleration). I took it back to him and recommended plugs and wires - so he did those. Still had the same issue. He was now getting a P304 - #4 Cylinder misfire code.

He put his scope on the #4 injector and said it sounded like it wasn't firing correctly, so he replaced it. Still having the same issue. He has checked every vacuum line and everything seems good. He even went as far as swapping out the distributor 3 different times thinking he may have gotten bad ones. He basically gave up and said he could not find the problem so I picked the car up (He didn't charge me any labor only parts as he couldn't fix the issue.)

Here is what I notice about the car now. I cleared all codes. The car runs like a top when its cold. Once it warms up it runs ok but you start to notice a slight bump in the idle. If you turn the A/C on the idle drops a couple hundred RPMs and then begins to idle very rough. Turn the A/C off and it smooths out again. I also notice a bad skip when climbing a hill at low RPM or around 1/4 throttle. Give it gas and it goes away. I just replaced the fuel filter this morning and didn't notice any change.

Any ideas

To this point here is what has been replaced:

Distributor (aftermarket) Tried 3 different ones
Plugs and Wires - Swapped plugs around as well as the wires to make sure none of them were bad
#4 Injector Changed
Fuel Filter replaced
All vacuum Lines Checked
Cleaned MAF
Ran a bottle of fuel system/injector cleaner through a full fuel cycle

The only issue seems to be under a low RPM load -

[jux]

Went through similar issues with my 237K pathfinder a few weeks ago. The idle was rough after warming up, turned out to be the idle air control valve however it did throw a code.

[nutsaboutbolts]

Went through similar issues with my 237K pathfinder a few weeks ago. The idle was rough after warming up, turned out to be the idle air control valve however it did throw a code.

Did you notice the same hesitation anytime while driving as well? Like pulling up a hill? I wasn't sure if the IAC controlled anything other than idle.

[nutsaboutbolts]

Can someone tell me the location of the IAC valve? Does the plenum have to be removed to get to it? I am thinking of cleaning or replacing it as the next step.

[Leo1998]

I cleaned mine backyard mechanic style so i wouldn't have to remove the intake manifold (it is under the intake on vg33 engine) What i did is pull the front hose ( the one going under the intake) off of the air/intake and poured/sprayed throttle body cleaner or similar down the tube until it filled up, reconnected hose and started the rig. May have to do more than once. You will see some smoke out the exhaust but it's just the cleaner being burned up in the combustion chamber. What happens is carbon builds up in the valve and it effects the "on/off" cycle of the IACV, so you are just trying to clean it out. Also clean your throttle body opening along with the butterfly plate by spraying cleaner into it and wiping out. Here's a youtube video showing the hose, the only thing i didn't do was do it while the rig was running, maybe better...Idk? I did mine kinda as a maintenance because it turned out to be my MAF sensor and the idle was doing way more crazy s*** than the hesitation you have.

http://www.youtube.com/watch?v=2wz70IEr2I0

[nutsaboutbolts]

I cleaned mine backyard mechanic style so i wouldn't have to remove the intake manifold (it is under the intake on vg33 engine) What i did is pull the front hose ( the one going under the intake) off of the air/intake and poured/sprayed throttle body cleaner or similar down the tube until it filled up, reconnected hose and started the rig. May have to do more than once. You will see some smoke out the exhaust but it's just the cleaner being burned up in the combustion chamber. What happens is carbon builds up in the valve and it effects the "on/off" cycle of the IACV, so you are just trying to clean it out. Also clean your throttle body opening along with the butterfly plate by spraying cleaner into it and wiping out. Here's a youtube video showing the hose, the only thing i didn't do was do it while the rig was running, maybe better...Idk? I did mine kinda as a maintenance because it turned out to be my MAF sensor and the idle was doing way more crazy s*** than the hesitation you have.

http://www.youtube.com/watch?v=2wz70IEr2I0

Definitely sounds much easier. Does anyone have any objections to cleaning the IAC this way?

[jux]

Did you notice the same hesitation anytime while driving as well? Like pulling up a hill? I wasn't sure if the IAC controlled anything other than idle.

It would stall occasionally but didn't notice serious hesitation. That happened 2 weeks later when my distributor decided it was going to join the failure club followed by an 02 sensor 5 days later.

[nutsaboutbolts]

Ok so I just ran 3 cycles of carb cleaner through the IAC with no noticeable change.

I am almost leaning towards an issue with the A/C compressor. As soon as I turn on the AC the idle gets really rough. Could the bearing be trying to lock up and adding too much load to the engine? I checked the pulley temp with no load and it read around 130 - 135 degrees. Once I turn on the air and load is applied the temp climbs up to over 200 degrees and holds.

[Leo1998]

I think you may be on to something...Here's this http://www.nicoclub.com/FSM/Pathfinder/ ... der/ec.pdf
Page 581

and HA=19 http://www.nicoclub.com/FSM/Pathfinder/ ... der/ha.pdf

and your service manual to download http://www.nicoclub.com/FSM/Pathfinder/2000_Pathfinder/

[Leo1998]

http://www.nicoclub.com/FSM/Pathfinder/ ... der/ec.pdf

Page 416 shows what IACV covers

[nutsaboutbolts]

I think you may be on to something...Here's this http://www.nicoclub.com/FSM/Pathfinder/ ... der/ec.pdf
Page 581

and HA=19 http://www.nicoclub.com/FSM/Pathfinder/ ... der/ha.pdf

and your service manual to download http://www.nicoclub.com/FSM/Pathfinder/2000_Pathfinder/

Awesome information. Thank you. I am going to do some reading through there and see if I can eliminate this one way or the other. I am really wanting to replace the IAC. Quite a bit of work and an expensive part if that doesn't fix the problem. After reading a little here I think it's either IAC or an issue with the Compressor.

[Leo1998]

If you decide you need to pull the intake and need advice, I have taken mine apart twice. It's pretty simple and a good time to replace a few small coolant hoses that are at the back of the engine and under the intake. Goodluck!

[jux]

Ok so I just ran 3 cycles of carb cleaner through the IAC with no noticeable change.

I am almost leaning towards an issue with the A/C compressor. As soon as I turn on the AC the idle gets really rough. Could the bearing be trying to lock up and adding too much load to the engine? I checked the pulley temp with no load and it read around 130 - 135 degrees. Once I turn on the air and load is applied the temp climbs up to over 200 degrees and holds.

If you get to the point you decide it's the bearings on the A/C compressor give a shot at replacing the bearing instead of the compressor. I would assume you have the same compressor I have (1999.5 vs. 2000) and if so you can get the bearing here.

Kit9534: 6004ZZE Nachi Bearing Shielded C3 Japan 20x42x12 Ball Bearings
Sold by: VXB Bearings
Quantity: 1
$8.95 each

[nutsaboutbolts]

If anyone here has an infared thermometer or a heat probe would you mind checking the temp of the pulley on the front of your AC compressor? I checked them with both A/C on and off to see how much it increases under load. I am just curious to see what someone else gets in comparison. Thanks guys.

[nutsaboutbolts]

OK, so I am now positive that I have 2 completely separate unrelated issues.

I removed the AC drive belt - just to ensure when I turned on the AC that the rough idle was not coming from some sort of vacuum or electrical related issue. I turn on the A/C and the idle stays as smooth as silk. - Solution: Replace Compressor bearing or complete compressor if I find one cheap enough.

Secondly - I am still getting an engine skip when I get into a pull. Most noticeably around 50 mph at 2K rpm. I can be driving a long at 45 and go to increase my speed to 50 and I start getting the miss. It doesn't have to be on a hill but that seems to be where I hit that sweet spot between speed and rpm on the back roads. Anybody have any thoughts........

[jux]

OK, so I am now positive that I have 2 completely separate unrelated issues.

I removed the AC drive belt - just to ensure when I turned on the AC that the rough idle was not coming from some sort of vacuum or electrical related issue. I turn on the A/C and the idle stays as smooth as silk. - Solution: Replace Compressor bearing or complete compressor if I find one cheap enough.
[/b]

Hate to bring this up but just because you removed the belt and the idle stays smooth doesn't necessarily mean it's the compressor bearing. By removing the belt you removed the compressor load so turning on the A/C does nothing as far as the engine is concerned. You could still have some other low idle issue that only shows up when the compressor is on because the engine has to work harder at idle due to the compressor load.

With the car off try turning the compressor pully by hand with the belt off and see if you hear a pronounced grinding noise or if the pully is hard to turn. You can use a stethoscope if you have one. It should turn freely since the compressor clutch is not engaged.

[Leo1998]

I would think if a bearing like that were to go bad, it would make some high pitch squealing and/or rattling noise, like a clutch fan bearing makes when it's done.

How old is your distributor and what brand, could the timing be slightly off?