Q45 Lumpy running and idle then popping sound

[pahrding]

My 91 Q45 suddenly started to shake at idle and accelerating like it was firing on 6 cylinders. The following day it started to run a little smoother butwas making popping noises which were coming from somewhere at the back of the engine on passenger sideOn blipping the throttle it sounded like a machine gun. If I held the throttle open slightly the noise would go away. This was accompanied by a strange smell from the exaust andwhat seemed like more heat from the rear wheel well close to the exhaust.

Before the popping noise, I thought it was another fuel injector acting up,but the subsequent popping noise and smell had not been present on previous occassions when I had fi problems. I have looked for loose Idevac hoses and gas leaks but can't find any.Ideas please.

[qship96]

maybe the popcorn is ready?

[Q451990]

Sounds like it's running extremely rich for some reason. Either leaking lower injector o-rings, or something with the fuel mixture - maybe the MAF?

The only time I ever heard any of my Q's backfire was during Q1's guide failure...

Heath

[5zigen]

sounds like the popping noise may be an exhaust leak?

[pahrding]

Finally got it diagnosed by dealer. They tell me that the problem is caused by a spark plug blowing out. I've only had them in for less than 15K, but apart fromthat I have never had a spark plug that blew out. It must surely have destroyed the threads in the head. I am not happy about the $500 or so cost to replace it as I am very concerned as to how it happened and what damage it could have done besides. zer...15647#http://forums.nicoclub.com/zer...15647#:

[qship96]

Who installed the plugs 15K ago? They may have cross threaded it upon installation .

[pahrding]

I was suspecting that not only had they crossthreaded it, but that they may have repaired the thread with a helicoil insert. I had the car into them for fuel injector replacement and thought it a good idea to replace the plugs at the same time. That outfit had a real bad attitude and I would not go back there because of it, plus I could not even drive it off their lot without it shaking all over the place due to various hoses not having been connected so I refused to drive it away until it was fixed, which they did very reluctantly with the inference that I was being unreasonable. After paying over $2000 to have the shaking stopped I don't think I was unreasonable. Anyway, you probably get the point. I would not get anywhere by complaining now.

[qship96]

Was it a Infiniti dealer or an independent shop?

[pahrding]

independent shop

[qship96]

How is the current repair shop going to fix the problem?

[pahrding]

They quoted just under $500 on the phone to replace a plug. I shall visit them tommorrow and get it in writing as the head may be damaged. It is a main Infiniti dealer and it is difficult to talk to a mechanic. The service advisors know very little about car mechanics, Infiniti or anything. I dn't see how they can quote a price without tearing into it.

[pahrding]

Problem now resolved. Turned out to be a spark plug where the center part had literally blown out. That set of plugs was less than 15k miles! I have never even heard of that problem - ever but have the plug to prove it.

I had had such bad experiences with service where I had originally purchased the car in 93 that I had not been to another Infiniti dealer in years but because of the noise the car was making I was looking for any shop nearby where I livedand the closest shop who had diagnostic equipment was a relatively new Infiniti dealer. I have to say that their attitude and professionalism was night and day different to that original Scottsdale dealer, so much so that I would even entertain the idea of buying another Infiniti. The name of the dealer where I received such impressive service was Infiniti of Supetrstition Springs

[3Q Jay]

NGK plug?

[maxnix]

NGK plug?

I'll bump. Never have heard of this with OEM specified NGK plugs. Or any NGK for that matter.

[GseaQ]

Hey Brian,

I changed the plugs in the bike last spring at my friend's shop who services the Q's. 4 new NGK's. Well, when he was tightening the plugs he felt something odd with one. This was even before the final torqueing - at the "snugging" stage. He took the plug back out and discovered that the plug had a radial crack halfway around the plug just above the top thread. If it had sheared completely it would have been a HUGE repair. Pull the engine and then the head. It came out of a sealed box with no marks or damage. Is NGK heading into some sort of cost-cutting thing that's affecting quality control?

Glenn

[maxnix]

Man, that's not good. Could it have been dropped, thus damaging it?

[GseaQ]

Man, that's not good. Could it have been dropped, thus damaging it?

There was no sign of it on the box it came out of. The threads are wrapped in a hard paper collar so I doubt if even a drop to the floor would hurt it. No, I'm sure it left the factory that way.

[pahrding]

The plug that blew out was Champion, not NGK which I believe was the original plug. Now I wished I had not bothered having them replaced. At the time I would not have cared which brand just so long as the reach and heat range were correct.

I have never had this problem on any plug regardless of brand most of which has been Champion.

[Jeff Williams]

In my experiences with the VH engine, the NGK are the plug to go with. I have not had any problems with them, and have put in 4 sets, each giving me flawless operation. I can't say that for the 2 sets of Bosch +4 plugs which burned up and caused poor performance.

$500 for one plug is steep, but the labor to replace one is about the same as the labor to replace all 4.

If i were you, I would replace all 8 as soon as you can. It takes about 4 to 8 hours to do it yourself, depending on your skill level.

I just paid $504.00 for my 105,000 mile service on the wife's I30t. I have always let the dealer do the service on her car, since I bought it new. They do a great job, and let me drive around in a new Infiniti every time I bring it in for an oil change. They also do a great job detailing the car before they call me to pick it up. It doesn't hurt that the service writer is a hot blonde, either.

[maxnix]

The plug that blew out was Champion, not NGK which I believe was the original plug. ... At the time I would not have cared which brand just so long as the reach and heat range were correct.

There is your problem. Autolites and Bosch are known to have destroyed VH45DE.

Use the factory specified plug. It was engineerd for the car. 6 heat range for hot or sustained high speed (standard on early VH45DE) or 5 heat range for N of Mason Dixon (standard on late model VH45DE).

RTOM and RTFSM or else!