How much shop time to replace plugs '92 Q45?

[kdkrone]

I decided that I just didn't have the time to work on trying to solve the issue about why I had developed the intermittent, then constant, missing that I have posted about so I took the car to my mechanic. He pulled the plugs and said that they did not look like they had been changed at 60K miles as they should have been (the Q has 85K). He also gave me the bad news that the shop time is 3 1/2 hours per side to pull the plugs and that until 95 or 96, there was no printout available to help diagnose whether the issue might be the plug or coil.

I thought that 3 1/2 hours sounded like a bit much, although when I looked at what is involved with the plenum and read how difficult it was to reach some plugs that perhaps it was not totally out of reason.

Does anyone know why that amount of time is necessary? I know my mechanic and he is a hard-working fellow who has been quite honest in the past when working on my Jeep.

ThanksKen K

[squeefoo]

Ken, I can do mine in about 2 hrs., but, I've done it before.Only use the NGK double Platinum! it just won't run right otherwise. Squee

[DougQ45]

Did my 1st set in 3 hours, and my second set in 2 hours. 7 hours is crazy ridiculous.

[elwesso]

Took me 7 hours, including tool hunting, lunch, back breaks, bathroom, etc........

4 hours is the book time........

[Q451990]

I think book time is 3-4 hours for plug replacement. I doubt your miss is a bad coil or plug (although it's possible). More likely a bad injector. One old plug should look different than the others (maybe black) indicating the bad injector.

Heath

[kdkrone]

Isn't there some more sophisticated way to diagnose a bad injector than looking for a plug that looks different?

One would think....

Regarding shop time: my local dealer says their shop book says 5 hours

[Q45tech]

5 book hours is standard unless the car is a Q45a or has TCS then add 1 hour.

"Just plugs" is not very profitable since the 5 normal hours would correspond to $400 in parts resulting in $170 gross profit vs $50 [for just plugs].........why they are bundled with 60k service where there is some profit in the fluids, sprays, etc.

But then again there are lots of jobs you don't make averages.

[kdkrone]

Thanks, Q45tech.

Do you have any thoughts on Denso Iridium plugs versus the NGK?

And is there any more sophisiticated way of diagnosing coil failure versus injectors than testing each one individually? Is there any computer readout available?

Thanks,Ken K

[Q45tech]

Brain power works well in diagnosis, only if you have test equipment not normally found at dealers. Sun ignition analyser or similar to view the waveform of the spark after the coil. Possible to glean information by looking at each coil input with an oscilloscope........looking for differences.OBD2 does it for you.

Other than a power balance, injectors can be mesured for flow on a special bench, the pintle lift point can be seen with a current probe and oscilloscope.

The problem is even master techs are so spoiled with the Consult that they may not have thought about or don't have the equipment or the time to develop non Infiniti proceedures.

Why waste money on a more expensive non standard plug, the oem NGK work well and that has been proven in 100,000 Q.

The reason you change plugs every 4 YEARS or 60k is to see the plug, make sure it doesn't/hasn't galled in the heat, and to evaluate any valve cover leaks that may need resealing.

The is no measureable differences in power for various plugs [that are satisfactory].Be a test case for us and after you report success in 4 years members might consider a more expensive plug.............we"ll leave the light on for you"

[paintwgn]

Just had the plugs in my 91Q replaced yesterday. The mechanic said the shop time was 3.2 hours. He is very good so it probably took him less time. I took the car in for state inspection here in PA and expected it pass with flying colors. No way - it was way over the limit on hydrocarbon emissions. He suggested changing the plugs because its the most common cause of high hydrocarbons. I had the plugs replaced about a year ago at a different shop and recall telling the mechanic at that time to specifically use NGK's. Guess what - he used Bosch instead. With the new NGK (PFR-5B-11) plugs it easily passed the emissions test. BTW, the car ran great with the Bosch plugs. I really don't understand how a different plug could make that much of a difference in hydrocarbons which is essentially unburned fuel. One more reason to stick with NGK.

[DAEDALUS]

1 month later, and I still have a pastrami sandwich riding on a bad coil. If it's not too late, by all means do what Heath said and get the old plugs and look at them carefully. Compare them all side by side and look at their condition all over. Ideally you would want to number them as you pull them, so you always know which cylinder appears to be running rich/lean/missing.

[kdkrone]

Daedalus, you may get your sandwich yet. I may know at the end of the day today. I stopped in today and watched my mechanic swearing at the limited access of the plugs. The first three looked fine to my eye.

q45tech, what is "OBD2"? Also, in the 92 Q is there any equipment that records problems that can then be hooked up to some analyzer to help figure out what is wrong?

ThanksKK

[maxnix]

q45tech, what is "OBD2"? Also, in the 92 Q is there any equipment that records problems that can then be hooked up to some analyzer to help figure out what is wrong?

You can search this site (might try OBDI and OBDII also), or the web.

The analyzer is called a Consult, and you have OBDI on your 1992.

[kdkrone]

DAEDALUS,

No sandwich. The number one injector was bad. The coils and other injectors checked out OK.

Thanks all for the education. I must say that for as wonderful as all of the engineering is for this model, there really could have been more sophisticated equipment built into the car to diagnose things.

Thanks all,Ken K

[Q451990]

I must say that for as wonderful as all of the engineering is for this model, there really could have been more sophisticated equipment built into the car to diagnose things.

It's easy to forget everything was developed 16 model years ago in 1987 or 1988 - I think I was using a Commodore 128 or maybe an XP with a 20MEG hard drive at that point.

Heath

[Q451990]

I doubt your miss is a bad coil or plug (although it's possible). More likely a bad injector.

Do I get a sandwich? Does a bacon cheeseburger count as a sandwich?

Glad you got it fixed...

Heath

[DAEDALUS]

How did they diagnose the bad injector, and how did they confirm the good coil?

[kdkrone]

I am not sure yet. I just received the phone call this AM. I leave for Italy for 3 weeks in a couple of hours so when I come back I will attempt to remember to post how Sherlock solved the mystery (for an outrageous amount of money. I think I should have taken it to the dealer....)

KK