98 Sentra code P0301 - stumbles at 2000 RPM - need help!

[Ridge Racer]

The distributor cap came from Autozone, so I'm sure it's not the best in the world. I still have the original Nissan cap that I took off. I didn't notice any change at all from one to the other, in terms of the hesitation problem. Is there some way I can test either of the caps? If it would help to know- I can pull off that new cap and see if it says where it was made.

So far, at least this evening - I haven't seen the SES light come back on. I assume that if it's going to - it probably will tomorrow driving to or from work. If it does come back on, I'll get it scanned.

[NISTECH]

Based on you saying it hasnt changed at all from one cap to the other I would say its likely not the cap. but the way to check them is visually see if there is any carbon tracking inside them or if there are any cracks, the cracks wont be big, they will be small and almost hard to see unless you look closely around the terminals inside the cap.

[Ridge Racer]

I think the cap's ok, then. I drove the car to work this morning (about a 20 minute drive) and the SES light still has not come on. I am hoping that the NGKs took care of that.

The hesitation / stumble is still there, though. Assuming that the P0301 has been cured - where would you start looking for a culprit on the remaining problem?

I thought it might be the timing, so one day I got out the timing light and messed around with it a little. I'm not sure how to read the timing marks on this car. I saw 3 marks that were closer to each other than the others, so I turned the dist. until the middle of those 3 marks lined up with the pointer thing. Where is it supposed to be set?

Thank you!

[NISTECH]

one mark should be colored and the rest will be white. The colored one is TDC I suspect that is the gap you see in the marks and where you have set it. you need to adjust it to spec , each mark away from the colored one is 5 degrees BTDC. The one mark on the other side of the colored one is 5degrees ATDC

[Ridge Racer]

OK - I'll look and see if one mark is colored. What is the correct timing spec. for that car?

Thank you!

[NISTECH]

Ugh that I dont know off the top of my head, should be on the hood, probably 15 or 20 degrees BTDC like most others.

[Ridge Racer]

OK - It was on a sticker under the hood. It's 15 degrees. I will take a look at that when I get home.

Do you have any other ideas on things that might cause the hesitation at light throttle? EGR or something?

Went for a quick ride to the store and the SES light came back on. Will get it scanned on the way home and post the results...

Thank you!

Modified by Ridge Racer at 11:41 AM 6/17/2005
Modified by Ridge Racer at 1:32 PM 6/17/2005

[Ridge Racer]

Surprise, surprise! Had the car scanned and got P0301 twice. Same damned thing.

Any ideas on what else I can check?

Thank you!

[NISTECH]

I think at this point its safe to say the ignition system is ok, I wish it were easy to swap injectors but its near impossible to remove one with out damaging it. I am hesitant on this but am really starting to lean toward that injector and something going on with it. but that sir is a guess at this point, I dont know what else to tell you to check, nothing else can really only effect only cyl 1.

[Ridge Racer]

OK - well I guess I will do some research on replacing an injector. If you have any advice in that area, please let me know.

Do you think that BG44K stuff would be enough to clean out the injector? Is there any way to know that - to test to see if an injector is clogged?

I really appreciate your help!

Thank you!
Modified by Ridge Racer at 7:54 AM 6/18/2005

[Ridge Racer]

I called around to get prices on a new injector as well as on a cleaning service. Sounds like I can get a cleaning on a Daytona machine (some 3 part cleaning service comparable to a BG service) for about $130, which is about the same price as a new fuel injector.

Any recommendations?

Thank you!

[NISTECH]

As I said at this point it is a guess as to what is wrong. The point of failure[hesitation/miss timing] does not really indicate an injector. typically when one goes it is either high end drop out or poor idle quality. your problem is in between. basing all you have done I am shying away from the ignition as being a problem that leaves fuel supply and cyl integrity [compression] I know its not the cyl integrity or it would be a constant failue. there is no variable in its operation other then speed of piston movement. meaning the problem would get worse the slower it moves, at idle it would be dead as a doornial if that was the problem. The fuel injector varies its dump so this is my reasoning for going for that. If you had a poor idle but aon accel it improved but was still present I would recommend the cleaning, in this case I think it would be a waste of money to try the cleaning.

[Ridge Racer]

I called around to get prices on a new injector as well as on a cleaning service. Sounds like I can get a cleaning on a Daytona machine (some 3 part cleaning service comparable to a BG service) for about $130, which is about the same price as a new fuel injector.

Any recommendations?

Thank you!

[Ridge Racer]

OK - so assuming I was going to replace the fuel injector, is that a part that I should definitely get from Nissan - rather than from an auto parts store?

Also - it sounded like you don't think the possibly bad injector would cause the problem I'm having. (hesitation/stumble) Is that what you were saying? Should I test the fuel pump or something?

Since I had already tried most of the things that made sense to try - I took the EGR stuff (EGR valve, BPT valve and EGR pipe) off yesterday and cleaned it all out w/ carb. cleaner. The pipe really wasn't very dirty. Slapped it all back on with a new EGR gasket. Problem still there. Not that I expected it to go away, mind you - but I thought I'd give it a shot.

I don't know if this will help narrow anything down - but it seems to happen mostly when the car is in overdrive (4th?). I will give it a little gas and the rpm's on the tach. will drop suddenly about 200-300. Then with a little more gas, the rpm's jump up about 400-500.

I looked at the timing marks again, but I couldn't see one mark that was a different color than the others. They all looked white to me. I am wondering if having the timing set incorrectly would even cause this kind of a problem. Seems like I would have a problem across the rpm range if the timing was set wrong.

Well man - I know I'm getting pretty damned tired of working on this car, so I'd imagine you are getting tired of reading these posts! I'm one of those people who will try to solve a problem until it's solved, completely ignoring things like my wife, work, eating, bathing, etc. If you have any suggestions or ideas at this point - please let me know. If you have reached the end of your willingness to help, or are out of ideas - I can completely understand. I am getting to that point myself!

Thanks for all your help!

[NISTECH]

No I dont give up that easily. The thing with it at cruise in od may or may not be related to the miss problem. That sounds like the tps issue we were dealing with origianlly but I know the TPS problem will NOT cause a cyl 1 misfire. I am focusing completely on that code by itself and what ever is causing it. That leaves only cyl 1 related componets in this diagnosis. For that cyl not to miss it needs correct fuel supply,fuel pump feeds all the cyls so that wouldnt be it since the code does not move around.The injector is the only fuel supplying component restricted to that cyl. Another cyl 1 component is the spark plug, as you said replaced with quality part with no effect. The wire going to cyl 1 spark plug too has been replaced. The number 1 electrode in the cap again another cyl 1 isolated component. the rotor is not isolated to it so that rules out anything before it. Now to what controls both the spark and the fuel supply.ECM decides to fire the injector and the coil to ignite the plug in that cyl. IF the ecm does not see the signal to fire both it wont. It will look at the crank angle sensor[the wheel in the distributor] to determine when to fire it. If that signal doesnt make it to the ecm it wont fire. Now the wire it travels on is used for all for cyl so that rules that wire in the harness out. That leaves the crank angle sensor as a possibility, the only way to check the integrity of that signal is to use an oscilliscope[very expensive tool] better to pay someone to do that.On the out put side the ecm sends the signal to the coil to fire at the specific time. Again the wire in the harness the ecm uses is the same for all 4 cyl's that eliminates that wire.Now the ecm uses a signal to fire the injectors from the distributor as well same wire for all 4 so that wire is out. BUT the wire going from the ECM to each injector is independant to each injector so that wires integrity could be the problem. That is pretty much all that could be wrong with the system to cause JUST a misfire on number oneThe list basically looks like this. in order of probablility

PlugWireCapInjectorCylinder compressionWiring to #1 injectorCrank angle sensorECM.

[Ridge Racer]

OK - so I talked to the owners of this car earlier today. I suggested that they might need to buy a new injector, but that there might still be a few more free or relatively cheap things I could try. From what's left on that list of probable cuplrits that I haven't addressed, it looks like I might be able to test the compression (although it sounds like you said that's probably ok, or it would fail constantly) and/or the signal wire from the ECM to the injector.

What could I do to test the signal wire? Also - is your gut feeling that there's probably just something mechanically wrong with the injector?

I have looked at a few posts about replacing injectors and it sounds like a big job. It seems like you would just have to remove the top of the intake (probably easier said than done) and then pull the old one out (also - probably easier said than done), but I've never done it.

Thanks again for your tenacity and free knowledge!

[NISTECH]

yes my feeling is possibly the injector component wise, the things you have replaced are pretty much ruled out I dont think its the crankangle sensor, but I am leary of the ECM too. with out an oscilliscope its hard to say weather or not the ecm is sending the signal to the injector to fire at that point. The problem only occurs off idle which is when the engine torques so if you can find the wire on the ecm that goes to injector one disconnect both the ecm connector and injector and hook your ohm meter at either end and watch it while you wiggle the harness from the ecm to the injector. See if the circuit goes open at any time, if so you have a broken wire somewhere in the harness, I have yet to see this on a sentra but at this point anything is possible. this would be an inexpensive check that can take a little time to do.

Yes the injector can be a bit tough to get out but I dont believe removing the intake is neccesary as it is right next to the valve cover. You have checked for any oil or fluid of any type in the injector connector right?

[NISTECH]

also you dont have any oil or water in the spark plug well right?

[Ridge Racer]

Nope - no water or oil in the connector or in the plug wells.

When I was testing the resistance on the injector, I was looking at possible ways to get the thing out, and it looked like I would have to remove the metal thing above it at the very least. I'm not sure what it's called (see pic. below) but it looks like it might be a little work getting it off...

[NISTECH]

I believe you can snake them out with out removing the plentum[upper intake] but you need to remove everything between the valve cover and plentum.

[Ridge Racer]

I found a guy who said he'd send me an injector for $10 (to cover shipping). He said it's a red 259cc injector, so hopefully that's what I need. Assuming he's not just taking my $10 - I should have an injector to try in a few days.

Now - to learn how to remove the old one and put in a new one. Any tips and or tricks anyone knows would be greatly appreciated. I'll do a search on here to see what's out there.

Thank you!

[Ridge Racer]

So, it rains like hell out here (Tennessee) for about 2 hours. I get in the car to go home, start 'er up and - no SES light. Made it all the way home, with one stop and still no light. Weird! Could the water have made or improved a ground or something? I put some marvel mystery oil in with about 5 gallons of gas on Saturday - might have cleaned the injector out (though I seriously doubt it!). I expect the light to come on again tomorrow - will post again after I get to work.

Not all is lost however, as the stumble/hesitation/whatever-the-hell-you-want-to-call-it is still there. I've read some posts about re-grounding the MAF sensor. What - if anything, would a poor ground do there? Also - where exactly is the MAF? Is that the electronic thing just past the air filter? (see pic. below)

I looked again for a timing mark that is a different color than the others, but they all look white to me. Is there any other way I can tell which mark to line up with the pin?

I forgot to mention this, and it may not mean anything. As I was taking things apart to get the EGR stuff off the car, I notice a couple of vacuum lines with nothing connected to them. One of them was right next to where the BPT connected via rubber hose to a brass line. The line right next to where the BPT was connected had nothing on it. Also - there's what looks like a vacuum line that was clipped to the air cleaner box that has a hooked-looking metal end on it, and it wasn't connected to anything either. Any ideas or questions on those?

Thank you!
Modified by Ridge Racer at 7:15 PM 6/20/2005

[NISTECH]

The maf is the device by the air cleaner. It would usually make the car run rich if grounded poorly. If there is no clored timing mark then all the marks would be spaced evenly with no gaps and the first mark would be TDC.

[Ridge Racer]

Got the car to the office this morning - still no SES light...

Still have the hesitation, though. I will ask my wife to look at the timing marks and see if one looks like a different color to her. I'm a little color-blind, so that might be why they all look the same.

So - if I do wind up needing to remove the plenum - is there any trick to it, other than just taking out all the bolts? Is there a gasket I'm going to have to replace, or any weird technique to getting it off?

Thank you!

[Ridge Racer]

SES light back on when I went to lunch. I am now wondering if the fuel additive might have temporarily helped, or if the rain somehow helped. I will test the rain theory tomorrow morning by spraying the car down before I leave the house...

[Ridge Racer]

I'm still waiting on the fuel injector to come in the mail (should be here tomorrow). I've been reading about some people who have linked the stumble/hesitation at light throttle to the TPS sensor. Some have suggested replacing it or making sure it's calibrated correctly.

I just disconnected the one on this car, and drove around for a few minutes. There was no hesitation or stumbling. It shifted like an old automatic Mustang with a shift kit, but I assume that's b/c I unplugged that sensor.

Would you suggest getting a new sensor? Is there a way I can check the calibration? I checked the voltage last week, and it sounds like it was ok. Is there anything in the physical part of that component that could go bad, but still give proper voltage?

Thank you!

Modified by Ridge Racer at 11:13 AM 6/23/2005
Modified by Ridge Racer at 11:56 AM 6/23/2005

[NISTECH]

The voltage check was the calibration process.

[Ridge Racer]

Well, my friends want their car back, so they are coming to get it tomorrow. The fuel injector didn't come on Friday like I thought it might, so I'll have them come over sometime afer I get that and see if I can swap a new one for the old one without destroying humanity! Hopefully that will at least clear the misfire code.

Thanks again for all your help! I'm sure I will probably call on it again soon.

[Ridge Racer]

I was able to remove the #1 fuel injector without removing anything but a couple of hoses and the electrical connector. The hardest part was getting the screws out of the cover thing that was over the injector. I used a tiny wrench and a screw-drive bit from my drill. Took forever! Anyway, I pushed a flat-blade screwdriver between the edge of the injector and the engine and turned it - popped right out.

I put the new injector in (after oiling the o-rings) and started the car back up. SES light was still on, but I know that wouldn't go off right away. Car still stumbles like before. I'm going to leave the battery disconnected for a few hours and see if the SES light stays off. I can't think of anything else to try...

Thanks for all your help!