Hi all,i have a 2001 xterra with the 3.3l v6 and an automatic trans.This only happens if we're at the store and engine is already warmed up.We'll be backing out of the parking stall and it will drive reall rough like its hesitating so bad.Then when we put it in drive it will do it until we get past about ten miles an hour.It doesnt do this if the car is cold though.We have 87,000 miles on it and havent had any problems before.Also the check engine light comes on and then sometimes gos off.Ive changed the fuel filter and pcv valve.Any advice would be much appreciated.thanks in advance.

If its showing a ses light have the truck scanned for trouble codes. Sounds like something electronic is acting up, with the trouble codes you can narrow down your search.

Thank alot.Where can I get the codes checked and do they do it for free?

Alot of the parts stores will do it no charge. Depends on where you are, here on the east coast we have autozone, advance auto parts, both of which will read codes for free.

ok thanks.Im gonna go to autozone on my day off and have them check it out.In the mean time what could it possibly be?Just want to get an idea of what it could be and if ill be able to fix it myself.

The last time I dealt with this problem it was an 89 Escort, problem was the throttle position sensor. Easy to replace, just make sure its lined up right.

ok thanks again for your help.I hope its the throttle position sensor.Ive read other guys saying theyve had to put in a new intake manifold gasket.I dont wanna do that lol.

You should do spark plugs, plug wires, distibutor cap and rotor as well. And run a can of BG44K through the fuel system. Get the codes checked. I think it could be a bad fuel injector myself. They act up intermentitly then take a dump. Running on a bad injector can fry your catalytic convertor. Let us know what it is. So many guys ask for advice and then never get back to us.

Ok I went to AutoZOne today and had it checked out.There were two codes that came up,here they are p0325 and p0300.
The first code p0325 has a list of probable causes
1-knock sensor defective
2-check connector and wiring to sensor
3-engine mechanical condition-knock or rattle in engine
4-low fuel pressure

ok and the other code p0300
probable cause

1-ignition system fault-spark plug(s)ignition wires,coil
2-vacuum leak
3-Injector fault
4-High or low fuel pressure

So theres alot of stuff to look at here.I really need some advice to what I should do.Ive thought about doing the basic stuff first like chaning the spark plugs,wires and distributor cap and rotor.But my maual says the plugs should be changed at 100,000 miles.I currently have 85,000 miles.
If it is a bad injector are those easy to replace or should I have a shop do it?Or should I just take it to a shop now and let them find the problem and fix it?Im pretty mechanically inclined just dont wanna waste any money.Thanks in advance for any advice.

The air plenum has to come off to get to 3 of the injectors. The other 3 are easy to reach and they are easy to replace. Each injector needs to be ohm tested to see if they are in spec. But if it's intermittent as you say, they they might be ok when you ohm test them. So you might pass over the faulty injector. At minimum for this check you'll need the air plenum gasket.

It might be worth replacing the knock sensor yourself since it seems to be a common failure. And inspect the wire harness / connector at the sensor.

Replace the plugs, wires, cap, and rotor. The dealer is going to want to do these anyway if you take it to them because of the mileage on the plugs.

It's darn near free to inspect any rubber vacuum hoses in the intake system for cracks causing vacuum leaks.

And lastly, I'd test the fuel pressure at the fuel rail to see if it's in spec. Are you sure the fuel filter was installed in the right direction of fuel flow? My expierence is a fuel pump either works or doesn't. Not as sporadic as you describe.

Hi Chubby,well with regards to the fuel filter i put it on in the same direction as the old one.its a weird coincidence but it seems the problems happened right after i changed the fuel filter.I mentioned this to a friend recently because I thought maybe I did install it the wrong way.My friend used to build diesel engines and really knows his stuff.He told me that fuel filter have a valve to keep them from flowing the wrong way so if i did put it on wrong no gas would get through so i did put it on correctly.im going to change the plugs,wires and distributor cap and rotor first and then Ill repost here to update my progress.Thanks for the help so far.

U mentioned the injectors have to be ohm tested.Do you mean if i buy new injectors they need to be ohm tested or do u mean the injectors on there now have to be ohm tested?

You can bank on the new injectors would be good from the Nissan dealer. But I meant ohm test your current injectors. I can get the ohm specs for them if needed. Meaning if your willing to take the plenum off and check each one. I've got the shop manuals for the 2001 Xterra that will give the ohm ranges.

sweet chubby,just another question.How do I ohm test the injectors?ive never heard of doing that.Thanks

There are actually 2 electrical test on an injector.

A.) Check the ohm resistance w/ an ohm meter. This test the injectors coil windings for shorts or opens in the windings. You need to write down your data for comparsion amongst all 6 injectors.

B.) Coil testing. This test checks the condition of the coil windings while in a "powered up mode."

Most shops only do the first because they don't have the proper equipment to benchtest the injector under power. But the first is going to isolate for sure a "shot" injector.

Ok I had new plugs put in (NGK Iridiums) and the rough take offs have gone away.I also changed the wires.I had to have a mechanic take out the last plug cuz I just couldnt get to it.But my hands are tore up from trying.He showed me the plug and it was different than the other five.It was also damaged so it leads me to believe it wasnt changed as often as the others.Im just glad its running good and I dont have to do anything else to it right now.Thanks for all the advice guys.

Thanks for letting us know what you found out. So many people come here for advice and never give feedback. Glad it's running better.