2000 Pathfinder runs rough when started

[cminor9]

Hey all, new here. Of course, I found this forum trying to figure out what's going on with my Pathfinder. Nice forum, good to see this.

I'll try not to ramble too much, but I want to provide sufficient info. The pathfinder: When I go to start it, it runs rough sometimes. It'll start bucking and sputtering and shaking (tach will jump around in the <500 rpm range) and then it'll either die totally or start running fine after I give it some gas and sort of gently force it to go. Once it's going, it usually runs good and smooth. Twice now (on hot days) it has refused to start again after being driven for a while and has left me stranded until I just let it sit for an hour or so. For the most part, it starts fine. I have been dealing with this for months now, and cannot correlate the rough start behavior to any particular weather condition (though the 2 outright failures to start have been hot days) or time of day. It's very intermittent.

A few months ago, the SES light came on. I read the codes and found a misfire and a bad o2 sensor. Guy at NAPA talked me out of the pricey sensor I was going to buy and advised me that o2 sensor probably was ok and to start with less expensive tune up items (hence plug wires, cap, fuel filter). His reasoning was that the o2 sensor was just complaining about a problem upstream, most likely bad ignition in a cylinder. It seemed like good sound logic to me. I did the tune up stuff. SES light went off, and problem kinda stuck around.

I have 145k on it, and had timing belt done at about 135k (had it done at 40k w/water pump). This year so far, it has gotten: new plugs, wires, fuel and air filter, distributor cap and rotor, transmission filter, front driveaxles, wheel bearings, tie rod. Lots of $ in other words. I am now too broke to keep randomly replacing sensors and more expensive parts.

Took it to mechanic today, told him all this. This place is a Nissan/Infiniti specialist and has a very good reputation here in St Louis (its THE place to take your Nissan). I don't know if he just didn't want to work on my car or what, but he said he probably wouldn't be able to figure it out being that the problem was intermittent and I'd just be wasting my money. He advised me to, hear this, try premium fuel for a while because of the high ethanol content in regular (ethanol vaporizes at a lower temp and could cause vapor lock in the cylinders he said). He also said he personally tested some gas from a local station and found it to be significantly >10% ethanol. The vapor lock theory sounds plausible and I am willing to try the premium fuel (though skeptical). Jury's out on whether he conducted an accurate test, but I'll give the benefit of the doubt.

Getting desperate. I generally don't think you can buy a mechanic in a can. Tried some lucas fuel additive at the request of three diff people. Hasn't helped after a few treatments. Again, I am skeptical of the premium fuel, but I'll try it.

I think I have shared every tidbit of info on the subject. Anyone out there have any ideas on what else I could check on this pathfinder? What do you think about the premium fuel? I would really appreciate your thoughts.

I am new here, and I hate to join a new forum and drop a heavy one like this. I have been scratching at this for about six months now, and could really use some help. I have been working cars for years now and can handle most stuff shy of a total rebuild (biggest job I have done is rebuilt the top half of a ford v6, fun fun) but I don't do it enough to really be able to troubleshoot well. I might not be able to diagnose Nissan problems like you guys here (been searching this forum for a while before posting, you guys are good) but I can post the result of my gasoline experiment in hopes it'll help someone else. I think it'll be an interesting experiment. Searching the intarwebs, I see a lot of debate on fuel grades for this type of thing.

[jpedderson]

On the times it wont start when hot... Does it turn over and not go? Or not even turn over? Do you have a code reader you can use to check sensor values? Hows the coolant level? I'm wondering if it's a coolant temp issue or coolant temp sensor issue.

[cminor9]

Thanks for the reply.

The two times it has failed to start: the engine will crank when I turn the key. Both times, it sputtered and bucked and died. Subsequent attempts to start, it wouldn't even catch. The engine would crank as long as I held the key in the start position but no ignition. Then after letting it sit for an hour or so, I went to start it and it worked. And, as I seem to recall, it started smoothly.

The first time I checked the codes (SES light was on) it said I had a misfire in cyl 2 and a bad o2 sensor. That's when I went to NAPA and the guy told me to try the tune up stuff before replacing the sensor. I did that, and rechecked the codes (the SES light was now off cause I cleared the codes after the first check) there were no new codes. Everything checked OK.

I tend to keep an eye on the temp gauge because I know how bad an overheat is. Last year I flushed the coolant and replaced it. Earlier this year (Jan) I took it to the Nissan shop (the one I mentioned in my post) to have the timing belt done. They of course had to take off the water pump and they refilled the coolant.

The rough starts, however, have happened on cool mornings in addition to hot days.

[jpedderson]

There are two separate items: the Engine Coolant Temperature Sensor which feeds into the ECM and the Coolant Thermal Transmitter that feeds to the gauge...so you wouldn't necessarily see anything on the gauge reading. It's a wild guess but it would be something to eliminate...and can cause hard start problems. Can also be caused by loose wiring connection or low coolant level - more likely than bad sensor.

[ARKQX33V6]

1st---your fuel rail pressure may drop feeding the injectors.
2nd---the fuel filter may be plugged
3rd---using premium fuel in a 87 grade car causes greater problems since high test takes longer for combustion to start and may carbon up the chamber.
Your stoichiometric ratio does get hammered with ethanol but this additive has been around a long time so I doubt that is too blame. At the mileage you have if your O2 sensors are still original they are lazy and their shifting from lean to rich and back again can cause the problem especially when a code related to O2 sensors and a miss fire are evident.

Your firing pattern of the injectors need to be examined.

Has your static timing been adjusted, check it and your advance mechanism since if you are too retarded similar things can happen.

[cminor9]

Thanks, jpedderson and ARKQX33V6.

I'll check out that sensor and the wiring. I didn't mention it in my last post, but the coolant levels are good. I do check that regularly (open the hood every couple of weeks to check that stuff).

I recently replaced the fuel filter, no difference. I am assuming the timing is fine since when the car runs it runs good and they did just do the belt not too long ago (I do know what a car runs like when the timing is jacked up).

It does seem that when the engine is under strain it runs worse (in N or P it'll sometime be OK when it starts, but when I move to D it'll sputter until I give it some gas). I wondered about fuel pressure lacking. I don't have a way of checking that, but I may try some of the coolant temp sensor troubleshooting before I switch fuels.

[ARKQX33V6]

The next time you start it and it runs put a timing light on each spark plug wire 1 at a time and see if they are all firing.

If the engine has difficulty running under a load or at off idle check the advance mechanism

[fleurys]

x2 for Engine Coolant Temperature Sensor

[cminor9]

You guys have given me a lot to try out. I think since several have suggested the coolant temp sensor and it's a $25 part I'll try that next. The timing light and code reader are easy to get ahold of, so I can try those too. I'll try those things as soon as I can and report back. I want to assure your time is not wasted, I do plan on trying your suggestions until I get this thing going right. It might take me a while though due to time and $ constraints.

Since I want to know what the root cause is, I am trying one thing at a time and observing the result. This also takes longer, but I learn more that way. I don't think the car will leave me stranded on the freeway and I don't think I am damaging the engine.

I have never checked fuel pressure, but I have read how to do it (I think in the haynes manual I have).

I hope it's not the temperature sensor. The implication of that failing is that the car may be overheating and that's what is causing this problem. If the car's truly overheating, then all of my money on this thing is maybe wasted. Had an 89 Mazda MPV with >200k miles on it. One day I lost a hose and it overheated. Had no temp sensor IIRC, just lights so I could not monitor the temp. Interesting, actually. The engine revved up and down when it overheated and that's what tipped me off that something was wrong. Didn't expect that on an overheat (mostly because I had never overheated a car!). Stopped it ASAP and discovered that all my coolant was on the asphalt. That engine was never the same after the overheat. The Pathfinder isn't acting like it overheated, so at least that is encouraging. But the mazda did run (just rough and loud) for another 15k miles until some uninsured turd hit and totaled it, but that's another story

[jpedderson]

Remember there are two separate 'sensors' for temp... A sending unit for the gauge and the coolant temp sensor for the ECU. You would still see it at the gauge even if the other one went tits up. So I don't think that's the case.

Also for that coolant temp sensor, it's just as likely to be a bad or loose electrical connection than a bad sensor...

[cminor9]

I checked the coolant temp sensor, and so far it is reading within spec (hot and warm, I'll check it in the AM when it's cold). I also checked that it is being supplied the correct voltage per my Haynes manual. Cannot find anything on the temp sending unit. I verified that I am getting a spark at all cylinders.

Also, I have definitely noticed a pattern. The car starts and runs fine when it's cold. After it's been driven for a while (45 min) and I shut it off and go to start it within an hour, it'll run badly. Really badly. The other day we had a hot day here in St Louis. Wife went to store, got groceries, drove to another store. When she left that store and went to start the car...it came home on a tow truck.

The engine light flashed the other day after starting the car and driving for a block or so (it ran badly from the start). I checked the codes and it was full of random misfires. I really don't want to drive it now, because if I have to replace the catalytic converters on this thing I think I'd rather sell/scrap it. It's only got 148k miles, I'll never buy another nissan again if it doesn't outlive my POS 1985 ford LTD wagon (180k miles).

I am renting a car this week so I can get into this and try to fix it. Given that the Coolant temp sensor seems to be OK, I cannot find any reference to the temp sending unit in my manual, I got sparks, and I now have some OBDI codes to go on, any further recommendations?

[fueler]

check oil level... also what weight oil are you using? what oil filter?

[cminor9]

Thanks for the reply, fueler. The oil has been changed 2 or 3 times since this problem started early this year (I make sure I keep it clean). I have been using mobil 1 synthetic and a mobil 1 filter. I think I used a few diff filters in the past few changes, whatever good quality filter was on sale (STP, maybe a FRAM). I have used other brands of synthetic in there too, but not recently.

[VG33QX4]

IGNITION COIL

[cminor9]

VG33QX4: this is a 2000 with the 3.3 V6. It has a distributor. I thought the coilpacks didn't come along until 2001. Am I missing something, are there coils on this model too?

[cminor9]

Been testing sensors, etc, and have had to unplug several things. One thing that really bothers me about this car is that the plug design on many components (distributor, coolant temp switch, etc) make the plugs VERY hard to remove w/o destroying the thing.

I spent ten minutes studying one after getting it unplugged. There is a green spring loaded tab on the side of these plugs, with an arrow that indicates it should be pushed in. But pushing it in doesn't seem to disengage the clip that fixes the plug to the component. In fact, nothing seems to work, pushing it, pulling it, squeezing it, etc. The only thing that seems to work is brute force, but if they were meant to be unplugged that way why would there be a spring loaded clip inside the plug? I think I may have to replace my cam position sensor in the distributor now, cause I nearly destroyed it trying to remove the plug. The plug which is supposed to be designed in such a way to allow it to be removed WITHOUT destroying the component it's plugged into. FAIL.

I generally have a good mechanical sense, after studying something for a few min I can usually figure out how it works. But this plug seems to have no functional release mechanism. Anyone else ever run into this on Nissans? I have worked on Mazdas, Fords, Toyotas...this is my first Nissan. I have never seen such an obstinate plug design.

[Towncivilian]

EL-5 and EL-6 describe some ways to disconnect some of the wiring harnesses. I also have difficulty with a lot of wiring harnesses, especially when I replaced my '01's camshaft position sensors. Those were extremely difficult for a friend and myself to disconnect.

[cminor9]

thanks Towncivilian. That is good to see. So I was doing it right, according to those illustrations. How dreadful that they'd make plugs that difficult to unplug!

[cminor9]

I just took the car to the dealer. Got sick of troubleshooting it. They did a full diagnostic on it and told me it seemed like it needed to have some carbon removed and so recommended an engine flush. A bit skeptical, I told em to go ahead with it. Whether this fixes it or is just a way to sell me a $179 service remains to be seen. Assuming they aren't totally shady (have had good dealings with them in the past) that means they could find nothing else wrong with it. That's comforting, in a way. That means there is nothing obvious that I just missed. Will follow up with the results.

[cminor9]

Got the car back from the dealer now. The did an inspection on it (100 point inspection, whatever that is, I guess I should have asked) and they found that my catalytic converters were going (due to the misfires, duh) and that my distributor was the fault. They also did the flush on the fuel system and on the valves. After reading up on the flush procedure, I found this: http://media.nbcbayarea.com/documents/H ... uments.pdf That's disturbing that a Nissan dealer would recommend this service in light of those documents. Anyhow, the car is running but for how long?

I really tried to press the guy at the dealership because I kind of got the feeling I wasn't being dealt with straight up. He was nice and all, but maybe a bit evasive. I asked him if they found anything else? Or did they just guess at the distributor? I never really got a satisfying answer other than "that's what the *experienced* mechanic thinks". Fair enough, I do appreciate the experience of a qualified mechanic (that's why I took the car there in the first place because clearly I am not an experienced mechanic). I guess I just had expected a bit more than a hunch, what with a shop full of top end diagnostic tools, the myriad sensors on this car, and my willingness to pay for a firm diagnosis. I guess some things are just beyond possibility. I'll replace the distributor (or at least part of it). If that doesn't fix it, well, I don't know what to do.

Does anyone think a distributor (as in, the whole unit) could cause the engine to run badly only when hot? That doesn't seem to make sense. Not that I am a mechanic, but I am an engineer who spends a good part of each day troubleshooting things. Now, I can see maybe the cam position sensor inside the distributor going bad, but the whole distributor? Seems a bit odd. It's a bevel gear, a shaft, and a piece of metal with 360 perforations on it that interrupt an LED/photocell "connection" in the sensor, and finally a cap/rotor. The cap/rotor are new, the metal disc with the perforations wasn't damaged or blocked, so that leaves the sensor and the mechanical pieces that turn the shaft. I'd deduce that if the shaft were faulty, it would totally fail, not just when hot. So that leaves the sensor. The decision I have to make is to replace the sensor versus the whole distributor. In terms of cost, neither option is excessively expensive. But replacing the whole distributor means I have to get the engine to TDC, and *carefully* insert the new distributor. I'd like to avoid that if it's not necessary. Anyone have any opinions?

[jpedderson]

Bad cats aren't going to do anything...mine are gone and the car runs fine. What other codes are you seeing?

Carbon flush, LOL. Scamola.

Distributor doesn't make sense either... A lot of the searches for "hard start when warm" are yielding results suggesting fuel pressure regulator...

Problems under load at idle (shifting transmission to D) sounds like IACV...

[ARKQX33V6]

Distributor can cause your problem, that's why I suggested a timing light to each plug wire. If the distributor is not distributing the HT voltage along to each plug at the right time a mis-fire shows up. Your catalytic converter should be OK , just gets a charge of raw fuel mixture that should evaporate with heat.

But with missed firing could come plugged plugs, excess carbon, EGR valve problems.

From what you say buy a can of seafoam treatment and do a minimal seafoam adder to help cleanse out some of the carbon, do not do a whole can or 1/2 can treatment yet, try to clean the engine gently. And before the next oil change drop seafoam into the crank case for about 100 miles or so then do an oil/filter change, read the can for instructions

[cminor9]

Got a timing light. I will check the timing. I did verify that I have a spark at each cyl but the timing could be off, for sure. If I see that off, I think that would be a pretty good indicator of the cause, or at least keep me out of the fuel system for now.

Along those lines, before they gave me the "final" diagnosis of what was wrong, the guy had mentioned something about the fuel pressure regulator / pump. VERY interesting to hear that recommended by jpedderson AND earlier by ARKQX33V6. I think I have my next thing to check if the timing checks out (fuel regulator). If I have to do that, I also have to pull the upper intake manifold. If I do that, I will use the opportunity to check the EGR and IACV. Of course if I do that and the car works properly, I may not know exactly what the root cause was.

Here's something interesting: the dealer replaced my fuel filter, said it was totally gunked. I told them I had just replaced it two or three months ago. Guy said it was totally gunked anyway and that they did it for free as a favor. Many people recommended Lucas gasoline treatment. Months ago, I skeptically tried some (of course it didn't help). I also tried some seafoam, again skeptically. Didn't help. But it makes me wonder what could have clogged that filter. According to what I found, the seafoam is mostly naptha and so I don't see the harm in that. I wonder if the Lucas stuff did that, because it is kinda oily? I don't know what else could cause that fuel filter to clog, but the Lucas stuff is a good suspect.

I really do appreciate you guys for sticking with me on this thread. I hope I can figure this out and that this thread can help someone else.

[cminor9]

started thinking about this problem from a fresh angle.

When I had started this thread I wasn't sure what was wrong with the car. I had never had a misfiring car before, because my younger, less busy self had always maintained my cars very well because I had copious free time. I didn't know that was a misfire. OBDI codes cleared that up.

The engine misfires when hot. That's the problem. The paragraphs and paragraphs I typed above could have just said that.

So I googled "engine misfires when hot". Guess what most of the results were for? Spark plugs. Now, I said above I had newish spark plugs. I seem to remember doing them last summer. But in actuality I cannot pin them to a specific date. So I bought some plugs. I am gonna try em out, let's see what happens. I have never really had to dig into any of my other, crappier cars this far. There is a first time for everything, but even though in my mind I eliminated the plugs, this stuff is almost always something simple. For $24 and a couple hours of time, if this fixes it the only regret I have is the wasted time (yours and mine) and the wasted money. Sure, I'll feel like an idiot for letting plugs get so bad, but at least the car will be fixed.

One more thing; The other day I pulled plugs just to make sure they were sparking. I compared that mental image with the plugs I just bought today. The ones I just bought have an almost needle-like tip on the electrode. The one I pulled out of the car did not. Hmm...might be onto something here.

I'll follow up with the results, even if they make me look like a moron.

[cminor9]

Changed the plugs. Ran the car for a while, restarted, and guess what? No misfire. Steady idle, right at 750rpm like the day I bought it.

As best I can determine, I did the plugs in Jan 2009, not Jan 2010 like I had "remembered". Time sure flies when you're living life. I did put ~25k miles on it since then. Seems like plugs used to last longer, but that could be just wishful thinking.

I'll post back in a week or so to confirm the fix. Thanks everyone, especially jpedderson and ARKQX33V6 for all of your advice. I did learn a lot in the process. Hopefully this thread can be a reminder to myself and others about never overlooking or assuming around the simple things before trying more complex and expensive things. I am a software engineer, I spend half my day troubleshooting stuff. You always try the simple things first. Always. Never assume anything is good until you test it. I incorrectly assumed those plugs were good and could not see past that. For the price of a set of plugs and an hour's time, I could have saved myself a lot of money and headache. Call it a life lesson, I suppose.

[cminor9]

when I started the car this morning and drove for a bit, the MIL turned off. That happens when the trouble condition no longer exists. That's good news. It certainly hasn't misfired again and it does seem to run better. Again, time will tell on that.

Now, though, I am left with a rough idle and when I accelerate it jerks and hesitates a bit (not as bad as when it was misfiring though). It seems like when I turn it off and the immediately restart it's ok (as I did last night) but if I leave it sit for a 30 min or so then it starts with the rough idle. That seems really odd. Not sure what would cause that.

Maybe these were two separate issues all along.

[cminor9]

I am beginning to suspect a vacuum leak. The symptoms are pretty consistent with that, a rough idle and the plugs looked like the engine was running lean. Also, checked my EGR and it isn't moving as the Haynes manual described. So I get to replace the EGR valve. Then it's time to check for vacuum leaks.

How do you all recommend checking for leaks? The methods I have heard are:
1) put seafoam into the vacuum system, usually through a brake booster hose
2) spray carb cleaner on hoses, listen for the engine to rev
3) open up a blowtorch with no flame, listen for engine to rev
4) spray water on vacuum lines, listen for engine to falter.

What would you recommend?

[cminor9]

Distributor can cause your problem, that's why I suggested a timing light to each plug wire. If the distributor is not distributing the HT voltage along to each plug at the right time a mis-fire shows up. Your catalytic converter should be OK , just gets a charge of raw fuel mixture that should evaporate with heat.

But with missed firing could come plugged plugs, excess carbon, EGR valve problems.

From what you say buy a can of seafoam treatment and do a minimal seafoam adder to help cleanse out some of the carbon, do not do a whole can or 1/2 can treatment yet, try to clean the engine gently. And before the next oil change drop seafoam into the crank case for about 100 miles or so then do an oil/filter change, read the can for instructions

yup, I tried the seafoam in the gas a while ago. Didn't help. I just changed my oil, but I might try that when its time to change it again. The plugs were pretty clean, definitely no excess carbon on them.

[cminor9]

It was the ignition coil. Found one here http://cgi.ebay.com/ebaymotors/NEW-96-0 ... 1489wt_941 Put it in, and ran it for a while. It's been a bit and the car is running great still. Thanks again everyone for your help.

[egg998]

i have some similar issues... but now my car won't start..

is the ignition coil you're referring to part of the distributor, or is it a separate part? and how did you figure out it was the ignition coil?