Code P0303

[xerexabante]

I have a tester, to check mine. see if can get away by an ohmeter.

[Qproject]

didn't some guy with a 99+ with same problems end up replacing all his coilpacks and end up not fixing the problem ?

[Q45tech]

Same problem or a problem that APPEARS to the untrained non engine engineer as a similiar problem!

Have you done a Consult power balance to view the condition of cylinder power production.

[UM97Q4.1]

I get a stall sometimes which triggers my "TCS traction control system" light to come on.

this happens very randomly.

I just noticed that I got this same thing today, when I got on the gas and looked down cause it was struggling to get up to speed, I noticed the "SLIP" light flicker about three times. Dont know if I have posted in this thread but I am having the same exact problems as others.

[Qproject]

wtf ? same problem that appears to the untrained eye as a similar problem ? are you on crack or something ?

anyhow let's keep at the top, it looks like we are gonna have to figure it out ourselves.

Same problem or a problem that APPEARS to the untrained non engine engineer as a similiar problem!

Have you done a Consult power balance to view the condition of cylinder power production.

[AlabamaDan]

It could be a bad plug.

It could be a bad connector from the wiring harness to the coil, or something.

It could be a bad wire in the harness.

It could be something not plugged in.

You said the problem started after plug changes. During that procedure you could have caused any of those.

[Q45tech]

When the misfire is only partial or below the threshold of OBD2 to register a code you must get scientific and utilize special tools.

If you can feel the misfire then it can be analysed with the proper test equipment. Dealers may not have everything they need or have expert engineers on staff to properly diagnose.

A useful tool is a storage digital oscilloscope:

http://www.picotech.com/auto/e....htmlh ... /a....html

The point is if you can hear the misfire from the [put'put] in exhaust pipe you can measure the time [electronically] between exhaust pulse and determine which cylinder is misfiring. You must have a working reference cylinder to trigger the sequence....................something like how a timing light works.

The engine firing order is known and thus 8 sequential and equal pulses [pressure/sounds] come out the exhaust pipes. Connect a microphone to/near the exhaust and view the sound with a suitable oscilloscope

Without a specific individual cylinder code the tests can take hours and hours or days of labor [depending on the genius level of tech] without the proper test equipment or engineer to evaluate other methods of arriving at the correct answer.............thus dealers want to change all the coils.

The other situation is they know that one bad coil means the others may fail within their 12 months parts warranty and the typical customer will demand warranty even if it is another different coil.

"Ever Since Customers" are the bane of automotive repair.

[wreid8409]

Okay I changed the sparkplugs in my car 1997 Q45 and the car is shaking and there is a general loss of power, I have changed the pcv valve and checked each plug for misfires, I cannot find the problem, don't know the next step???

[maxnix]

Are you certain no codes are being thrown?

[wreid8409]

I'm sorry I don't understand the question about codes being thrown? Could you explain?

[Q45tech]

Codes are read with an OBD2 scan tool or code reader, then code numbers [0001 -1000] looked up in FSM manual or googled.

[wreid8409]

The auto parts store put it on the diagnostic test machine and the codes that came up said mutlipy misfires. I am not sure what the codes were, I can find out if need be..

[bdijanni]

Ok, here's whats going on with mine, 99 q45t fy33... the car is stumbling during idle, excelleration, reverse, in park doesn't really have rhym or reason (that i have figured out yet) as to whats making it happen more or less, Again strange miss fire type feel, but more like a stumble... some days worse then others, seems to happen alot worse when its really hot and with the AC running or a load period... I have done the following: Fuel filter, plugs, cleaned coils, Front O2 sensors (upstream), I just replace KS' this weekend (which sucked *** by the way) Did it without removing the plenum... Did not replace the harness dont think that this is the problem... We could be having Coil issues, but what is happening to the people on the forum, makes me think other wise... This is going to be something dumb that we are all over looking!! We just need to figure out the fix... Also making me think, due to the fact that so many people are having the same problem... that it is something normal, but again is getting over looked... I am curious to know every one that is having this problem like I am, what are your miles, at?? My car has 102,000, is this just happening to the car's that have higher miles? or are we getting this same problem from car that are in the lower miles? and what about exhaust? has anyone heard sounds like maybe the cat or resonator cloggage? Someone has got to know what the fix is here? I just bought this car, I am not giving up yet!!

[wreid8409]

My care is a 97 with 145,000 on it, I have not had a problem until about three weeks ago as far as this is concerned, my car lost power big time one day, I filled the gas, put a treatment in and it was doing better, now recently did oil, brakes, plugs, and fixed a oil leak, which was disovered after removing the last plug and seeing the oil, now the car is still no running correctly.

[Q45tech]

We have repaired half dozen of these multiple misfires in our 3 locations. Eventually after new plugs and 1,2, 3 or more coils and an injector test and cleanup we solve the problem.

Usually involves some defective non standard gasoline but not always.

However gasoline in Georgia contains no ethanol and almost never causes injector problems so what works here may be useless elsewhere.

If you google: multiple misfire code ......... you will find 77,000 hits that cross every brand and model! Even Mercedes with 2 plugs per cylinder.There are 55,000 hits for P0300.

http://www.epa.state.il.us/air....html

The EPA even has a one day seminar on how to diagnose a P0300 CODE!

Any Nissan with this code may also have sluggish O2 sensor or sensors which are the sensors that ecu uses to determine P0300 and P0301-308 Codes.

[AlabamaDan]

So are you saying, bad gas is probably the issue. Can they add some type of octane boost to clean up this one tank or just suffer through it?

[bdijanni]

I'm not 100% sure that this is a bad gas related issue. Seems to me that this is going to be a carbon build up problem or multipl coil issue. I will give an example... I have tried numerous different things, and the only thing that seemed to work for a limited amount of time, was the bg44k which leads me to believe that this is going to be some kind of carbon build up issue or something like that..

[Q45tech]

Lean misfire can result from carbon build up on the rear of intake valves where the fluffy carbon absorbs some of the gasoline vapor idle squirt and makes the cylinder too lean to fire properly.

Bg44k and fuel rail injector flushes can remove this...............only to have it return if your driving style natches the worst case conditions:

Cold crank driving less than 10-15 miles in traffic then shutting off with multiple every day repeats.................failure to exercise the engine to blow the carbon out.

[bdijanni]

You think that this might be the issue that we are all dealing with? I am going to try a couple of tests to see if I can get the results that we are looking for, maybe we can gain some ground with this crazyness... Going to try and run another bg44k along with 50/50 100/93 octane fuel see if this will blow out some of the carbon. If drivablity gets any better at all then this will probably be the cause! The reason I'm leaning to the carboned valves or pistons theory, is that i had read in some past threads on infiniti online mechanic, that some people had some results with running cleaners through the intake plenum. Someone on there was saying that they had ran some household super cleaner through thier intake and had great result with the same problem we are dealing with. So I'm going to give this a try and sh*t I might give the old seafoam a try as well might help? We'll see

[Q45tech]

It is always STRANGE that people brag on the gasoline quality they use YET fuel injector cleaners [like BG44k] when they work [which on 17 years of Q they always do] PROVES my concept of poor fuel quality causing problems.

[bdijanni]

I guess I understand you point to a degree. I will explain: I have been using Shell V-power at newer stations since I've had the problem, so I dont think that my problem is contributed to a low grade or poor fuel issue. Again I'm going to conduct a couple of tests and see what I come up with. If this seems to help my problem, then I'm going to look into fixing the carbon issue for good. If you have an idea on something that I should try then by all means please. That would be better then throwing money at this problem, Your saying after changing out various coil packs and fuel injector cleaning you finally fix the problem. How long does that last and exactly which part is the problem? Is the problem really a carbon issue with valves or pistons and your temp fixing the problem with the injector cleaner? I dont know about you but I want to know exactly what the issue is so we can help everyone else out from here on out! Plus I want to do it with out having to spend $150+ for coils that probably aren't bad.

[Q45tech]

But that's just it you must throw money at the problem either in diagnostic time with the proper expensive test equipment or expensive parts - usually a comination of the two.

Just part of the prorated annual $3,000 per year old V8 lux car need to maintain as new operation. 12 hours of labor and $1800 in parts* and fluids.

* If something has a 6 year life you divide it's replacement costs into advanced prorated segements and save the money for the part. If a transmission lasts 8 years and costs $4,000 that's ~~$571 per year.

If you are lucky and over estimate repair costs you have that pile of money left at the end to use as a downpayment on the next one.

[bdijanni]

Look it man, I'm not trying to be rude to you because I value your knowledge, as an infiniti tech... But we are not talking about the issue at hand, I asked you a direct question.. and this is the answer you give me? This is the exact reason it is so hard to deal with the dealers, Honestly you sound just like a dealer or a dealer service tech, not really sure what the problem is and cant really give any good ideas on what to try first just wanting you to spend all kinds of money in replacing parts that really were never bad in the first place. Or it the old let me put it on the diagnostics machine but it will cost $50mil up front, and after paying your still left replacing parts that probably aren't the problem... But they will eventually fix the problem, but who wouldn't after replacing every single part that has to do with the problem, This is a do it your self tech forum, help me figure out whats going on with these cars, give me some ideas

Thanks

[99q45t_vl]

I've experienced the similar issues like stumble, rough idle, etc. In my case the coils or plugs were not problematic - bad injectors (#5 and #2) were. I've replaced the O2 sensors, KS, harness, PCVs. The IACV, Plenum, TB, EGR get cleaned every year. Run the power balance test at the dealer (they charge $80 for that) and make the informed decision.

[Q45tech]

I gave you 77,000 google hits to review and if you spent 10 hours reviewing them you will see that Code P0300 is the most difficult and time consumming to properly diagnose BECAUSE so many different components can cause the same code! Plus bad gasoline can cause the code.One can spend hours and hours and hours [all day] testing individual components and eventually find the defective one. If there is a defective component.

One can send the gasoline to a lab and study it's chemistry.One can tear the engine apart looking for carbon build up [20 hours of labor].One can examine spark plugs with a microscope.

My rule of thumb is if spark plugs have more than 30k on them replace them first.Use BG44k to try to clean carbon and injectors. But this takes 200 miles to get enough thru. {for the past 10 years I have used at least 4 cans of BG44k per year as a preventative...........just one thing less to worry about.

Same with primary [2] O2 sensors they fail softly and progressively with time/mileage and their sensitivity is a function of gasoline contaminents.

Hint with a Consult 2 you can read the conditions that occured WHEN the code was set by analysing data.

[bdijanni]

So your saying that I should bring the Q to the local Infiniti dealer for the 105$ per hour diagnosis, and let them tell me whats wrong?

[AlabamaDan]

No I don't think the dealer diagnosis is the answer. I believe it's just impossible to narrow it down to exactly the problem. Try Plugs, then bg44k, then....

Right Dennis?

[Q45tech]

Without personally knowing and observing a specific dealer technican doing any diagnostic process it is hard to make an affirmative decision.

After all techicans just follow the test proceedures outline in FSM and and TSB.

After they work on and solve a few dozen they can develop short cuts or clairovoyences.

As they say in Ghostbusters: "Who you gonna call".......................someone who works on your model 5 days a week is a good start.

[maxnix]

After they work on and solve a few dozen they can develop short cuts or clairovoyences.

As they say in Ghostbusters: "Who you gonna call".......................someone who works on your model 5 days a week is a good start.

And herein lies the problem - there are very few senior Infiniti technicians left in the field, and few owners will pay dealer labor rates to diagnose a non-warranty problem, so verrrry few dealer techs have the experience and sophistication required. Fewer independents do. We can name only 3 on this board. That is why instead of spending the money diagnosing each coil, the dealer replaces them all for about the same bucks. The owner gets new equipment, if not a cure, and doesn't get a large bill and a stumped technician with no cure for the problem.

Don't forget to tip your tech and service writer.

[Qproject]

hey guys,

could the problem be due to a bad throttle positioning sensor ?

when my TPS and Slip lights go on, the man symtoms are a harsh transmission shift and a harsh down shift. everything is fine when I shut off engine and restart, however it seems to be happening more often.