P0300 misfires on 3 different Q's now

[QCumber]

Holy pumpernickels....

97, 98 and 2000 Q45 all with the same issue...

This is a veritable epidemic: first my old lady's Q then a friends and now a customer's all with exactly the same symptoms:

* Runs rough at all speeds but it's even more perceptible between 45 and 60* Blatantly misfiring (enough to rock you in your seat a bit)* Chugs through gas like a v12 in Reagan's white house

- Plugs are clean- leakdown only showed a very minimal (hardly noticeable) drop in pressure- no specific codes other than the P0300 (no help whatsoever, P0300 might as well be translated to: "it's broke man..."- Ran injector cleaner thru - no change whatsoever- Knock sensors recently replaced- O2's checked and in range

Scratching head...

[maxnix]

Maybe you need a better OBD II reader? Should inciate specific cylinder misfire, then you can switch coilpacks to diagnose.

[Q451990]

The Y33 series weakness is the coil packs. Brian is right, more diagnosis is in order, but for the most part members have found that replacing all of the coil packs tends to resolve the issue.

Heath

[Mopar]

Yes Q45 is correct

I had this problem. SAME exact problem. Drinking gas. shaking while idle etc. I fixed it by changing all 8 coil packs from a 2000 Q. Runs fine for almost a year now.

Also make sure you have the OEM spark plugs. They are called NGK something.

Good Luck!

[bullittandy]

Coils, coils, coils. If you get a code for specific cylinder than you can save some money by only replacing that coil but with no code then you have to replace all 8.

I had same problem and no CEL, waited and waited for the light to trip and finally gave up and order 8 coils and guess what-1 day later the coil went and the CEL lit-pissed me off but I know that replacing all 8 coils made the problem go away "forever."

[elwesso]

no free lunch baby, 90-96 get to replace injectors, 97-01 get to replace coils!

Andy, did you go through the FSM procedure to test the coils? I think theres various resistance tests you can do to verify them...

[QCumber]

Thanks so much for all the replies. I was starting to think about the coils but have limited ways to test them individually.

Elwesso, what is this FSM method you speak of?

[bullittandy]

I'll have to go back check the FSM to see those tests-I haven't seen anything like that but I also haven't been looking for one. I'd be great to figure which was bad so that i can keep the good ones for reuse.

Thanks for the tip!

[QCumber]

INDEED, at roughly $140 per coil, it would be fabulous to figure out which one is the culprit.

Two thoughts: how long would it take for the borderline failing coil to completely fail and therefore give me a P030x where X will point me to the exact cylinder?

Second: is it possible that once one coil fails the others are soon to fail also? (This is not a trick question, I really am just looking for odds).

[Q45tech]

Remember 7years and 100k is design life by agreement.

Every car made by every manufacture has to have a weak short life component.

What happens when you assign a team of accountants to double check and cost analyse an engineers work.

Common on V6 [of 2000 and newer] also same coils same failures.

Car already last too long and some of that is why the industry is in bad shape....................6 year tradeins and 15 year average life means bad things for the union and non union workers.

http://www.1aauto.com/1A/Ignit...72228

has them for $155 so you know they are special vs the $50 generic aftermarket type for Ford or $89 Hitachi coil for I4 Sentra.

[elwesso]

I'll have to go back check the FSM to see those tests-I haven't seen anything like that but I also haven't been looking for one. I'd be great to figure which was bad so that i can keep the good ones for reuse.

Thanks for the tip!

EC-375.

Check it out.. It'd be interesting to test a few bad ones and good ones and see if you can get bad ones that test good, or if the FSM is a good test.

[bullittandy]

INDEED, at roughly $140 per coil, it would be fabulous to figure out which one is the culprit.

Two thoughts: how long would it take for the borderline failing coil to completely fail and therefore give me a P030x where X will point me to the exact cylinder?

Second: is it possible that once one coil fails the others are soon to fail also? (This is not a trick question, I really am just looking for odds).

I had the stumble for about 3-4 weeks before it lit the CEL, I think IOS, (parts sponser) has them for about $75 a piece-or did a couple months ago.

Good question on do the coils fail in succession-I DK but I'd think that several must but maybe not all 8 in a 6 month period-but just a guess with no facts to support.

[Q45tech]

The coils don't fail per se, otherwise you get a hard code for a fully dead coil. The random misfire is usually a bad insulation [sensitive to temperature and humidity] resulting in a lower than ideal voltage.................all depends on plug condition, dielectric constant of new vs used oil etc leaking into plug well.

RPM [dwell charge time] even atmospheric pressure are possible varibles along with the cars particular religion and political affiliation

[97 Q45insocal]

Hi QCumber,

I've got a 97 Q45t with 140k. Over the past 6 months I have replaced all of my coils. At first i received specific codes and replaced the appropriate coils then I started getting the dreaded p300. Over this time I consistently researched coils ( the local dealer was listing at $280.00 and aftermarket around $150.00.) I found a Dealer ( OEM nissan parts) that was selling for $75.10 plus shipping (around $10.00) so I ordered the rest of my coils and installed them. The consistent misfire and the loss of power ( felt like a 4 cyl) disappeared.Its been about 6 weeks and it drives like a dream and runs like a racecar.I dont Know if this is relevant but my p300 started showing up when my knock sensor (bank 1) began to pop up on my obd II reader. I purchased the KS but realized that it is in a difficult place to reach and have not ventured there yet.

Good luck

[elwesso]

RPM [dwell charge time] even atmospheric pressure are possible variables along with the cars particular religion and political affiliation

I wonder if a similar test jig to what deatschwerks does to electrically test their injectors (voltage drop and waveform) could be adapted.

[Q45tech]

How would one compensate for external variables of installation, positioning, oil in plug well and spark plugs....................not to mention temperature and humidity.

Again an individual code tells you the coil is bad! A 300 misfire code tells you its enviroment is bad.

[maxnix]

Again an individual code tells you the coil is bad! A 300 misfire code tells you its enviroment is bad.

That is useful information, but I think the propr condition could also indicate a bad spark plug if not a bad injector.