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

[Ridge Racer]

I'm working on a friend's '98 Sentra SE (2.0 liter, automatic). Once you get going about 45-50mph with the engine turning about 2000 rpm's - if you give it a little bit of gas, it stumbles. If you get on it, it will drop a gear and go like hell - but then stumbles again if you barely give it gas.

The SES light is on - had Autozone check it. Code P0301 is on there twice. Not sure how it's coming up twice, but that's what he said. I have replaced the spark plugs, wires and distributor cap and still no change. Still stumbles around 2000 rpm's and runs crappily at low rpm's (only when in gear).

It sure seems like it would be an ignition issue to me, but what else is there to change out? Would a bad coil do this, or a bad rotor button? Maybe a bad injector?

Please let me know any suggestions/questions you guys have.

Thank you!

[NISTECH]

I would say ignition as well. When you changed the cap did you notice any oil in it at all? Also when you pulled the spark plugs did you notice any moisture or oil in the plug well this will cause a misfire as well. P0301 means cyl 1 misfire. The reason it shows up twice is there is a hard code in there and a 1t code in there. The hard code is what is turning on the CEL the 1t code is it happened during the current warm up cycle. It could be the number one injector but you need to evaluate The items I mentioned and you should have put a rotor in it as well. The cap and rotor should be of good quality i.e. not made in italy.

[Ridge Racer]

I did not notice any oil on the cap, nor any oil or moisture around the plugs or wires. I bought the cap and a rotor button at Advance Auto Parts. The rotor button they sold me didn't fit, or I would have replaced that too.

Assuming those are both ok (cap and button) - is there some way I can start ruling out or testing the coil and/or the injector?

Thank you!

[NISTECH]

On the cap inspection for oil, you have to really look for the oil in there, usually under the plate below the rotor.

I really dont think its the coil since your misfire seems to be limited to 1 cyl. To test your injector you would need an ohm meter. You need to compare its resistence to the one next to it. If they are the same then it is likely not your problem. You could also have a wiring issue. try wiggling the harness at idle and see if it effects the idle.

[Ridge Racer]

Actually, now that you mention it - there was a little rubber thing under the rotor button. I do remember wiping a little bit of oil from it - but I think the oil was only around the outside of it. It might have just been engine 'gook' that had gotten on it.

I have a multi-meter, but am not sure exactly how to check the injector's resistance. Do you think that the rotor could be the problem, since it's only saying cylinder #1 has a problem? I only ask because to get a rotor button that fits, I'll have to order one.

Which harness are you talking about wiggling at idle, and where is it located?

Thank you so much for your help! I think it's great that you are sharing your knowledge with 'destroy-it-yourselfers' like me!!

[Ridge Racer]

OK - so I got out my multi-meter and poked around a little bit. Does this sound like the correct (or at least an acceptable) procedure?:

I pulled the electrical connector off of the #1 cylinder injector and put the test leads on the 2 posts of the injector. It read about 13.7 ohms. I could not get to the injector directly to the right, but I could get to the next one (3rd from left). I tested it the same way and got the same reading - 13.7 ohms. If that's the correct way to test them and that resistance sounds ok- I guess it's electrically sound?

Last night I pulled the negative cable off the battery hoping to reset the ecm. This morning when I started the car - no SES light. I drove it around for about 20 minutes and the light came back on. I haven't had it scanned - but I will, and I suspect it will come up with the same code.

Can anyone think of any other things I can check that would make the car stumble at low rpm's (only in gear) and/or cause that P0301 code? The idle seems fine - good and steady, and the egr valve seems to be working ok (after warm-up the diaphragm flutters when the engine is revved). Could loose throttle cables cause this?

Thank you!
Modified by Ridge Racer at 5:33 PM 6/12/2005

[NISTECH]

You tested the injector right and electrically it is OK . mechanically you just have to listen to it and hear if it is always clicking, I suspect it is ok as your symptoms dont really point to a bad injector but it is always worth checking. the harness I was refferring to is the one that comes off that injector. I wouldnt go right into replacing the rotor just yet but pull it out and remove the plate underneath it and have a look inside around the crank angle sensor and see if it has and oil inside. also look closely at the little wheel with all the slots in it. see if there is anything in the holes in the wheel near where the larger of the 4 inner holes are. at thatr point on the wheel check both the outer ring and the inner hole for anything in the holes.

[Ridge Racer]

Well, I pulled the cap off and looked at everything I could see inside. It all looked pretty pristine. I couldn't see any gunk or oil or dirt.

I replaced the fuel filter (thought it might be a possibility) - but no dice. Problem remains.

Something I forgot to mention that may or may not relate to this... My friends who own this car are not very conscientious about car maintenance. I'd say it went many many thousands of miles between the last oil change it got before they bought it (about 4 years ago) and when I changed it (about 3 months ago). They had ridden around with the oil light on for about a month. When I looked into the hole where you pour the oil - I could see LOTS of sludge. I ran some Gunk engine flush, drained the oil, pulled and cleaned the oil pan, and took off the 'oil sender thingy' (the part that has the screen and the neck that sucks the oil out of the pan) and cleaned it as best I could. I put it all back together and put in new oil (Castrol GTX 5W30) and a new filter.

I have the car again (to replace an axle and hopefully fix the stumbling problem) and when I looked in the oil filler hole, I can still see some deposits. I put some solvent in the crankcase (Marvel Mystery Oil) to hopefully dissolve some of that stuff, and plan to change the oil again while I have the car.

Is there any way having had so much sludge running through could have caused this stumbling? If so - what can I do?

Any other ideas anyone has about things to check are most welcome.

Thank you!

[NISTECH]

No I dont think the sludge is the cause as it wouldnt be isolated to one cyl. When you pulled the cap and rotor off did you remove the gold plate below the rotor?

[Ridge Racer]

When I pulled the cap off, there was the rotor button (which I also pulled) and then a rubber cover-looking-thing. It was white on one side and maybe gold on the other side. Is that the plate you mean? If so - yes, I did take that off. Under that was a plastic wheel that looked fairly delicate so I stopped pulling things off there.

This morning, I drove the car to work and had my first chance to drive it at highway speeds. It seems to stumble when I push the pedal down about 1/2 to 1 inch - even if I am turning higher rpm's - 2500 or so, still does it. If I give it more gas, it works fine. Could this be something more related to the throttle cable or some sensor?

I saw in one of your old posts that you recommended that someone pull the vacuum line off their egr valve to see if their hesitation went away (and showed that the valve was bad). Is this something that you'd recommend I try?

Thank you!

[NISTECH]

You looked in the right place that little wheel is metal by the way. It should have had a bunch of little slots in it, if thats what you saw you got in far enough, if there was no oil resting inside at the bottom that was not your problem.

The thing with your failure is its limited to CYL 1 ,as far as I can tell. This pretty much narrows it to a few things, If it were the TPS it wouldnt be limited to that cyl it would be a P0300 code [multiple cyl misfire] or more then one cyl misfire codes like P0301 thru P0304. Some holds true for EGR but if the EGR did create the misfire and it were to throw a misfire code, it would more likely be cyl 4 as that is the cyl its closest to on the intake.

The odd thing is,in most cases, when you get a misfire it typically becomes worse the more throttle you give it and yours isnt doing that. Yours is an off idle miss [light accel]. Take it in and have the codes scanned again and see if the same code came up.

Will it do it if you are in neutral and you gently give it gas?

[Ridge Racer]

I unhooked the battery last night (to clear the SES codes). After about 20 minutes, the SES light came back on. I took it to Autozone about 10 minutes ago - had it scanned again. Same code in there twice again. P0301 - cyl. #1 misfire.

I was able to make it stumble in neutral but only with the A/C on. It stumbles when I am driving whether the A/C is on or off.

Should I try to replace the plug and swap wires on that cylinder? Both are practically brand new.

Thank you!

[NISTECH]

yea for the hell of it swap them to cyl 2 ,but you will need to have the code checked again to see if it moved. unless you have the old part. use cyl 2 plug wire and plug that way if it still happens there is no need to get the code scanned again. You would know cyl 2 parts were good. I seriously doubt thats the problem though since they are all new.

Do you have and know how to use a volt meter?

[Ridge Racer]

I have a multi-meter that has a DC volt setting. I know how to use it to some degree, but would not say that I'm proficient. Is there something I can check with it?

[NISTECH]

For fun your are going to check your tps. With the car not running but key in the on position back probe the tps [all three wires] one should be 5 or 12 volts this is your source voltage to the tps, one should be 0 volts[must be less the .2v] this is your ground for it. then the important one should be right around. 5 volts this is your signal to the ECM telling it exactly where your throttle is. When I say about .5volts I mean no less then.45v and no higher then.55v this is as close to properly set as possible. with out foling the actual ohm check procedure using feeler guages and you hard idle contacts. I thing your TPS connector is grey IIRC. The brown one is you hard idle contacts. You back probe the connector while its plugged in. If you tps is out of that range loosen the screw holding it to the throttle body and rotate it till you obtain that voltage. then resecure it and check to be sure it didnt wander out of that range when you tightened it down.

[Ridge Racer]

OK - The connnectors you are talking about: Are they just behind where the air intake hose connects to the intake (assuming you are looking at the engine standing at the front bumper)? It looks like there is a brown connector directly above an identical gray one.

It sounds like you are saying to test the connections with the plug still connected. If so - how do I do that? The tester I have just has a red and a black probe with pointy metal tips on the ends. I have only ever tested plugs when there were disconnected.

[NISTECH]

place your negetive probe[black] one on the batteries negetive post. use a t pin if possible if not a files down paper clip works too and shove it in the back of the terminal in the connector till it bottoms out[this tells you you made contact with the metal terminal inside the connector]. Then test that wire. Then pull it out and move to the next one. Your using the red lead to test them.

The lower grey connector is the TPS. If I am wrong about which one it is you wont get any where close to what I described, instead you will see voltage then when you turn the throttle drum the voltage will simply vanish, or the oppisite will occur depending on which wire you probe, but it will not hurt anything if I do have them mixed up, you just need to test the other connector. set your meter on the 20volt scale to perform these tests.

[Ridge Racer]

OK - I will try that when I get home this evening.

So when I test the connectors, I should have the key turned to 'On' but not running. Is there anything I should do other than test the voltage (move anything around, etc.)?

Thank you!

[NISTECH]

correct on the ignition switch.

once you have established your voltage readings, when you locate the signal wire to the ecm slowly rotate the throttle and watch that voltage it should steadily increase to just over 4 volts at wide open throttle.It should not at any point jump to 5 volts. Pay particular attention to the reading when you just start cranking the throttle open as that is where your problem seems to be when driving. If all the tests come out as I stated your TPS is ok.

[Nismo_Freak]

LOL @ this thread.

If your EGR valve (left-most disk shaped object behind valve cover) is disconnected, hook it back up. Reach up under the EGR valve and touch the diaphragm while the engine is fully warmed and running. Lightly rev the engine between 2000 and 3000 rpm. If the EGR diaphragm flutters or moves erratically instead of opening and closing smoothly then I've got your solution.

Remove both vacuum hoses from BPT (right-most disk shaped object behind valve cover). Remove the two philips screws on its top. Push the BPT back toward the firewall. You should see a rubber hose running between the bottom of the BPT and a metal tube. Remove the BPT and rubber hose from the metal tube and set them aside.

This metal tube is connected to the EGR passage and, ultimately, to the exhaust manifold. Exhaust manifold pressure, via this metal tube, operat es the BPT valve which regulates the vacuum to, and the opening of, the EGR valve. The less exhaust manifold pressure - the more the BPT valve opens - the more the EGR valve opens. The more exhaust manifold pressure - the less the BPT valve opens - the less the EGR valve opens. Carbon may block this metal tube which causes the BPT to not operate properly (if at all) which causes the EGR valve to operate uncontrollably.

I waited until the car was cold, then I sprayed about a half can of carb and choke cleaner into the metal tube to soften up the blockage. I used a stiff piece of wire (a long chunk of 8 or 10 gauge wire left over from the big car stereo install will do) to ream out the tube. Please note: DO THIS WHEN THE CAR IS COLD!! Carb cleaner and a hot exhaust don't mix well.

Wait about 10 minutes for the chemicals to evaporate. Start the car and hold your finger in front of the metal tube. You should feel a steady stream of exhaust coming from it. If not, try cleaning it again.

While you're waiting for the chemicals to evaporate, now would be a good time to remove your EGR valve and clean the carbon deposits from the plunger and seat. I find that the carbon build up eventually gets bad enough to hold the EGR valve slightly open. This changes your base idle speed (TPS disconnected) and can also cause a rough and wandering idle. And GUESS WHAT!!?? If the build-up gets bad enough it can cause your SR20DE equipped ride to stall when you push in the clutch!!

Reassemble the system, hook your EGR valve back up and take your SR20DE out for a ride. You should find that the problem is gone and your local smog police will give you an award for being a law-abiding smog free citizen once more.

I make checking the metal tube and cleaning the EGR valve a part of every tune-up and/or oil change.

[NISTECH]

Well, I pulled the cap off and looked at everything I could see inside. It all looked pretty pristine. I couldn't see any gunk or oil or dirt.

I replaced the fuel filter (thought it might be a possibility) - but no dice. Problem remains.

Something I forgot to mention that may or may not relate to this... My friends who own this car are not very conscientious about car maintenance. I'd say it went many many thousands of miles between the last oil change it got before they bought it (about 4 years ago) and when I changed it (about 3 months ago). They had ridden around with the oil light on for about a month. When I looked into the hole where you pour the oil - I could see LOTS of sludge. I ran some Gunk engine flush, drained the oil, pulled and cleaned the oil pan, and took off the 'oil sender thingy' (the part that has the screen and the neck that sucks the oil out of the pan) and cleaned it as best I could. I put it all back together and put in new oil (Castrol GTX 5W30) and a new filter.

I have the car again (to replace an axle and hopefully fix the stumbling problem) and when I looked in the oil filler hole, I can still see some deposits. I put some solvent in the crankcase (Marvel Mystery Oil) to hopefully dissolve some of that stuff, and plan to change the oil again while I have the car.

Is there any way having had so much sludge running through could have caused this stumbling? If so - what can I do?

Any other ideas anyone has about things to check are most welcome.

Thank you!

Repost of earlier one??

[Ridge Racer]

Not sure what happened there!

I didn't get a chance to do anything to the car last night, but will try swapping out the plug and wire, as well as back-probing the TPS today.

[Ridge Racer]

I did try that test

"If your EGR valve (left-most disk shaped object behind valve cover) is disconnected, hook it back up. Reach up under the EGR valve and touch the diaphragm while the engine is fully warmed and running. Lightly rev the engine between 2000 and 3000 rpm. If the EGR diaphragm flutters or moves erratically instead of opening and closing smoothly then I've got your solution."

and the egr valve seems to be working ok. I lifts and lowers pretty smoothly with the rpm movement.

Thanks!
Modified by Ridge Racer at 1:39 PM 6/14/2005

[Ridge Racer]

I just remembered - the last time I worked on this car, I put a set of Bosch Platinum spark plugs in it. I have read, since then - that a lot of people have had problems with those plugs and have had better luck with plain-jane NGKs.

Is that something that could cause this, or is all the talk about plugs just wishful thinking?

[NISTECH]

yes it is true about the plugs. You need to swap to NGK's

[Ridge Racer]

I bought a set of NGKs after work and hoped to put them in and see if the stumble went away. However, replacing the front passenger side CV axle (another undertaking I really shouldn't have undertaken!) took a bit longer than I had expected. It took some doing to get the splined part of the axle free from the hub.

Anyway - I'll swap the plugs tomorrow and see what happens. Keep your fingers crossed!

Thank you!

[NISTECH]

For future reffrence on your axle. when you pull the hub cap or wheel if they are custom immediatly spray the axle and hub with rust penetrate[PB blaster is good stuff] before doing anything else. While that is soaking start pulling everything else apart you need to to get it out. then remove your axle nut and shoot another shot of penetrant at the splines. I then put the nut back on the axle shaft till the head of the nut is flush with the end of the shaft. Then proceed to beat the livin hell out of it with a 2 or 3 lb sledge till the nut reaches the hub then remove the nut and the axle should slide right out.

[Ridge Racer]

I then put the nut back on the axle shaft till the head of the nut is flush with the end of the shaft. Then proceed to beat the livin hell out of it with a 2 or 3 lb sledge till the nut reaches the hub then remove the nut and the axle should slide right out.

Hilarious! I will try that the next time. I just sprayed some WD-40 at the splines. I tried whacking the shaft (huh huh, I said 'whacking the shaft!') - first with a large ball-peen hammer, then with a hand-held sledge and finally with a 2-handed sledge. The car shook, and I was able to do some good, healthy anger work - but that little mother *%#!er didn't budge. I finally had to go to Autozone and rent a 5 ton 3 jawed puller. Even with that and my 1/2 " drive socket, I still had to put a 3 foot length of cast iron pipe over the socket (home-made breaker bar) before I could get enough force to move the axle shaft through the hub. The front of the puller was starting to drive itself into the end of the shaft and split it open before it finally relented and backed out of the hub. I was worried that I was going to bend or break the hub!

So, once I get all the brake stuff I took off back together, I'll try out the NGKs and hope they solve the problem. Since I have already replaced a bunch of other, much more expensive stuff - it will probably turn out that $8 worth of spark plugs will be the solution!

Thank you!

[Ridge Racer]

OK, so after I finally finished with the axle job - I swapped out the Bosch spark plugs for a set of NGKs. Drove the car around for a few minutes, and the problem was still there. I had left the battery unhooked overnight - so no SES light at this point.

Back to the garage. I noticed that the throttle cable itself was a little bit loose, so I tightened it up a little. Drove around for 15 minutes or so and it seemed like the problem was gone at first, but it wasn't. It almost seemed like once the car got good and warmed up, then the hesitation was at its worst. Still, no SES light at this point.

I got it back in the garage and tested what I think is the TPS connector. Looking at the engine from the driver's side - there is a brown connector and a gray connector (brown on top) on the right side of the intake, right next to where the rubber air hose clamps to the intake. Each connector had 3 wires. I think the brown one was the TPS. Here were my readings. Top wire - 13.9 mV (no change with movement of throttle cable) ; Middle wire - .503V (increased to 4.09V at WOT) ; Bottom wire - 5.10V (no change with movement of throttle cable). Sounds like that part's ok? It made a noise when I would move the throttle cable - a quiet sort of 'I'm trying to pump something, but can't' kind of sound. Is that the fuel pump?

I will drive it to work tomorrow and see if the SES light comes on. It's gone longer tonight without coming on than it has the past couple of times I've reset the codes, so maybe that particular issue was just the plugs.

Any other ideas? Should I try to take that metal tube from the EGR valve to the exhuast manifold off and see if it's jammed up with crap? Would that cause a problem like this?

Thank you!

[NISTECH]

The noise you heard when you started cracking the throttle was a solonoid, that is normal, and it also tells you your hard idle contacts are working. your readings where good.

If you EGR passage was clogged it would be on multiple cyls.

What quality is your distributor cap, does it have a "made in" stamp on it somewhere?