1996 Infiniti Q45 Showing a mis-fire on cylinder 7

[bigdog76]

My car started running yesterday like it was missing. Gradually it got worse threw the day. I ran the codes and it said a mis-fire on cylinder 7. My buddy and I changed out all the spark plugs and sure enough number 7 was really bad. Assuming number #7 is back right side.

Now the car is running way better but I notice I still have a rumble when I am at idle. My buddy says he thinks my Catalytic converter is shot out.

What would cause this rumble that I am getting. The car has 230,000 miles on it I would guess the cats are toast. I dont have the money for the OEM catsI could just take them out for now til I have to smog it.

After market is a ideal for me. Also the Harmonic pully in the front is wobbling at idle could that be an issue with this?

[maxnix]

#7 is back left (1-3-5-7).

Pulley is probably the growl.

Aftermarket catalytic converters are crap and don't last.

Be sure to read your trunk sometime.

http://www.jerrytucker.net

might work on it if there is no y.

[qship96]

What did the plug look like that you replaced? Possible it was not getting spark to fire?{wet looking?} could be poor connection to plug or coil problem. I would replace all plugs if it has not been done w/i the last 60-80K.

Wobbling crank pully? sounds serious- any work done in that area recently that could have caused this, like front oil seal replacement?

[Q451990]

Your miss is likely an injector issue. Visit Q45.org to see how to ohm test your fuel injectors. Make sure you do the test with your ignition switch on but with the engine not running.

Heath

[elwesso]

Yeah, check the injectors and report back... Cat failures are rare but they can happen especially on 94-96.

[jimbyjimb]

Rumble is a broad description. Be more specific. Is it a popping sound? Does the engine shake noticeabley?

[bigdog76]

I think the #7 or #8 plug was noticably bad burnt and oil wet on it.

The car runs fine when I am driving. The problem is when I come to stop at idlethe car has a noticable change in the idle it rumbles RPM moves slighly but we can all feel the change in idle from smooth to like hiccups in the idle when the change happens.

When I first notice the problem before I changed all the plugs I could feel a total miss fire as I drove and came to stops. After replacing the plugs driving is smooth but idle is still having these rummbles. I feel it right under my seat.

Now when I punch the gas in park I can hear a pop sound from the exhaust which my friend believed is coming from a bad catalytic converter

I am kinda sratching my head on this one.

[maxnix]

Sounds llike a possible bad coilpack. Have youtried swithing them?

FR 2-4-6-8O <=N 1-3-5-7T

RTFSM!
Modified by maxnix at 10:55 AM 5/31/2009

[bigdog76]

What do you mean switching them?

I dont smell gas at all do you think one of the fuel injectors is bad or would I notice that right away on driving?

[bigdog76]

Now that you showed me the break down it was #7 that was the bad plug back right looking at the car from the front.

All plugs are replaced still rummble on idle

[bigdog76]

When I put the plugs in I didnt use platinum plugs this time would that cause a problem? I went with copper standard this time NGK BKR5ES-11 I dont see a different on driving at all.

[maxnix]

RTFSM!

PFRG are specified! heat range 5 or 6 depending on location and driving style.

[bigdog76]

so what is the worst case scenario then? with theses plugs

[maxnix]

They won't perform as well as the specified ones.

At least you didn't install the AC, autolites or Bosch. They have been known to destroy VH series engines when the electrodes break.

Please read the FSM before you continue to "maintain" your Q45. It will run better and last much longer. And if you read the previous posts, you will spend much less money on the long run.

You can start by reading your trunk.

[Q451990]

Have you ohm tested the injectors yet?

Having one injector down will cause the ECU to try to rectify the lean condition on that bank (no fuel from the bad injector) causing the the other three to run rich. I haven't experienced the pop in the exhaust you mentioned, but who knows...

Heath

[bigdog76]

I am hearing a popping when I accelerate really fast.

[bigdog76]

I have 230,000 miles on the car I dont really know how much longer it can last.

I was trying to buy me sometime. I agree I should have probley went with the platinums I will next time for sure.

I did notice a slight crack in one of the vaccum hose that connects to the big throttle body hose. Could this be letting air in after the MAF cause issues?

[qship96]

Cracked vacuum hose WILL cause running problems!!! fix at once.

[bigdog76]

I will ohm the fuel injectors and fix that crack and see what happens

[bigdog76]

what is the heat range of the spark plugs I put in the BKR5ES-11 verus the PFR5G-11

I hope theses last me a while. I dont thing this would be causing my car to stumble at idle.

I ran the Platinums for 60,000 miles and they number #7 went bad that is when I pulled them all.

What would cause one of my spark plugs to go bad like that?

[qship96]

"5" is the heat range, so the plugs you put in are the same heat range as the ones you pulled out. The plugs you put in will work fine, but the platinums advantage is they have a much longer lifespan than the plugs you put in. Not sure why your one plug was bad, could be a problem with the plug itself, or the coil/wiring for that plug- did you have the engine light illuminate?, if so did you read the codes that caused it?

[bigdog76]

Yes it throw the code for the number #7 cylinder mis firing.Turned out to be a bad plug when I pulled it out.

That solved the missing I was feeling when I drove.

Now I am still trying to track down the rumbling at idle I am experiencing.

I have that crack on one of the hoses and I am going to ohm the fuel injectors later today.

[qship96]

As a temporary fix, clean the hose real well and wrap it tightly with electrical tape to seal out air leaks

[maxnix]

I am hearing a popping when I accelerate really fast.

Are you certain your plugs are installed (torqued) correctly?

Fix all plenum.

Well maintained G50 should go 300K no problems. Well maintained = correct parts and timely preventative maintenance services. By then you might learn which marque you are driving?

I ran the Platinums for 60,000 miles and they number #7 went bad that is when I pulled them all.

What would cause one of my spark plugs to go bad like that?

60K is the recommended service limit. Were all the old plugs identical in appearance? Ever clean the plenum, lower runners, throttle body, EGR and IAC valves? Replace PCV?

[jimbyjimb]

Popping in the exhaust indicates a rich mixture. If the plug were fuel fouled rather than oil fouled it would seem to be the case. Are you sure the plug in question was oil fouled and not fuel fouled? Black and wet doesn't mean oil. A plug in a rich cylinder will have a soft, black coat, or, if excessive, will be wet from fuel either clean or blackened. This could be caused by no or low spark. In the event this happens again the plug may be reused after a wire-wheeling and using compressed air to dry plug. I would suggest a spark check and replacing those non-plat. plugs with proper units.

[bigdog76]

Today the engine light came back on.

It feels like it is missing when I rev the car at idle.

I dont know what pounds my buddy torque them.

[bigdog76]

All the plugs where identical in appearance except Number's 7 & 8 looked bad.Plenum cleaning no, Lower runners no, Throttle bod yes I cleaned. EGR and IAC values no No on the PCV.

I was running fine up intil the check engine light that came on last week threw a code of mis firing on cyclinder 7. Now the engine light is back on and I have not ran the check yet on it.

60K is the recommended service limit. Were all the old plugs identical in appearance? Ever clean the plenum, lower runners, throttle body, EGR and IAC valves? Replace PCV?

[Q451990]

http://www.q45.org/ohminjectors.html

[bigdog76]

Ok I want to throw an update out here.

I checked all the fuel injectors by ohm them.

We followed the directions key "on" for a 1996 and new but we could not get correct readings (All of them were only showing 400 or so) We had the positive probe to the the battery and the negative probe to the to the individual pins. Nothing not sure why.

So we put a screw driver to them to listen and all of them sounded good (Nice clicking) I could not get to the back #7 one to hear that one which was the one throwing a mis fire code.

So then we glued up the crack in the throttle body pipe (Big Black plastic pipe) No Change on idle.

Then we pulled out the AAC Idle Control (Auxilary Air Control) and took it apart and cleaned it up it looked real dirty and that it might have been sticking. We test the terminal and that was good and we also tested the Re-installed that and this didnt change the stumble in the idle still.

Then we pull the number 7 spark plug and switched it with #3 and also switched the coil packs re-installed it all and the problem seems to have went away. Knock on wood. The car is idling right at 650 and is running smooth.

My two buddys were leaning toward a bad fuel injector but all is ok for now.

We ran the codes when the check engine light came on before we started to pull the plugs and coils.

PO15 Engine Collant Temp Circuit Malfunction (Not sure what that is)PO505 Idle Control System Malfunction (Probley caused when we pulled it out and tried to start the car)PO307 Cylinder 7 Mis-fire (This was before we switched the coil and plug)

All an all I dont know if it was the AAC that did it or what? We were trying to see if the number #7 misfire would jump to number #3 by switching the coils but when were all done it started to run fine with no check engine light.

My buddy is going to run it with his scanner at work some $3,000 scanner that tells you everything we will see what that one says this weekend after running the car a few days with no check engine light on.

Chime in let me know what you think?

[qship96]

could have just been a loose or dirty connection on #7 coilpack/sparkplug connector- sometimes just unplugging and replugging solves this-good luck,and hope your issue is solved!!!!!