Is it dead Jim???? Low compression cylinder 3...

[kevinis]

Well it's only been about 8 years since my last post.

2000 Q; back in 2008 I posted about cylinder 3 misfire (the infamous misfire).

Whenever this happened since, replacing the coil has always fixed the problem.

So now a variation.

Sitting at a stop light I get not a misfire, but entire body shuddering....then that rotten egg your cat (yikes didn't know until this week there are 4 on this car) is going bad smell.

Take it to a mechanic with new hitachi coil in hand and long story short am told that I have low compression in
cylinder 3. Sorry I can't remember the numbers, but cylinder 3 was way lower than the other 7.

Fuel injectors all cleaned working proper, o2 sensors cleaned, MAF cleaned and tested; numbers good, coils moved all around to check if maybe the new coil is somehow the problem and still the same answer, cylinder 3 comes up way out of balance in compression numbers in relation to the other 7 cylinders.

Okay, the plugs, there were the proper NGK plugs in there with only about 20K miles on them and the mechanic changed them out with the dreaded iridiums (I told him not to and to save my plugs; not sure if he saved them).

So, tomorrow (Wednesday) a mechanic friend of his that works at a Nissan dealer is bringing a proper NISSAN box to scan the car.

Is this car dead??? Only has 135K miles on it.

Help.

[94Q45Beast]

does it burn oil

[kevinis]

Well, it wasn't.

When I picked it up today, it blew out some serious blue smoke; so before today no, but for at least ten minutes today, yes.

I only drove it about 2 miles and once up to temp sort of gunned it; lotsa smoke.

Seriously, it wasn't doing that before I took it in.

So, just for fun, the compression numbers:

Cylinder:

1 - 140
2 - 135
3 - 104
4 - 140
5 - 140
6 - 145
7 - 125
8 - 125

I pondered putting in some "Engine Restore" but the mechanic said it would be a waste of $$ because the problem is on the top end and engine restore would pretty much only affect the lower end of the engine.

[94Q45Beast]

from what I've read, it could be worn piston rings....again that is just what I've read.

[kevinis]

So; anyone have any thoughts about me putting in "Engine Restore"???

http://www.restoreusa.com/index.php

The mechanic is saying that the engine computer is gushing fuel into the #3 cylinder which is not burning (causing the cat smell) and is also saying the plug was fouled already after installing the new ones.

[94Q45Beast]

I thought blue smoke was oil.....

[kevinis]

Yeah,

I have always understood blue smoke to be oil burning; hence my answer; yes it appeared to be burning oil AFTER I picked it up and for about 10 minutes when I drove it. But, again, NEVER saw smoke before that, so maybe they
poured some oil in that cylinder which then burned off. At this point I haven't driven it since
feels a bit like a diesel truck now) though I did start it last night, let it run and after warm revved it;
no smoke, just nasty idle with shake.

[94Q45Beast]

now you sparked my curiosity.....I wanna know what the problem is also

[94Q45Beast]

bad fuel filter?

[Q451990]

I wonder if you have a bad injector, or leaking injector o-ring on that cylinder. If it's flooding, that could cause low compression due to the oil film being washed off of the rings on that cylinder. You should have been given "dry" and "wet" test numbers from your compression test. Dry being, how they read on a first run just hooking up the compression tester, and wet being after squirting oil into the cylinders. A higher wet test number normally indicates worn rings - but in the case of flooding, fuel washing the oil film off of the rings and cylinder walls could cause the same type of readings.

An injector would also explain the dead miss you're experiencing. Unusual on a 97+ Q45, but certainly possible with any 16+ year old engine. I would avoid engine restore or any other "fix in a bottle" snake oil until you've eliminate all other possibilities.

[kevinis]

Q451990, thanks for your great response; I don't know the answer to those questions; I've e-mailed them to the mechanic and will call him Monday (they're closed on weekends) to get specifics. But he did say he cleaned and tested the fuel injectors and that they were all functioning properly, so I don't know if he or the guy from the Nissan dealer that looked at it would have a leaking o-ring on their radar if they perceived the injectors to be injecting.
I would really like to keep this car but my diy efforts are limited to checking and adding fluids, changing a battery every 4 years and reprogramming the driver positioning system when it gets confused and stops working (you know, open the door 3 times and all that...). To hear the mechanic talk, the engine either needs to be replaced or rebuilt; don't even know where to start with that concept.

Not sure if that was a wet or dry test on the compression or if he even did both.

[Q451990]

The mechanic is saying that the engine computer is gushing fuel into the #3 cylinder which is not burning (causing the cat smell) and is also saying the plug was fouled already after installing the new ones.

Unless the newer Q got a much more advanced ECU (and I don't think they did) the ECU is not able to control each injector's pulse width (how long they're open spraying fuel) independently. On my Q, and I suspect yours as well, the ECU can change the pulse width for a bank of injectors to compensate for readings it's getting from the O2 sensor on that bank.

Here is a TSB from Nissan on performing an injector leak-down test. http://maxima.theowensfamily.com/tsb/NTB95-021.pdf A normal drop would be about 20 psi in two hours. If you have as big of a leak as it seems, you would probably see total loss of fuel pressure in 10 minutes or so. At least I assume the numbers would be similar for the Q. A more labor intensive test would be to pull the plenum and rails, and look for fuel squirting out around the lower injector o-ring when you turn the key on and the pump primes. Or if injector 3 is accessible without too much trouble, just pull it and put new O-rings on.

[kevinis]

Okay, so I sent the comments/questions from this post to the mechanic that worked on the car; haven't heard back from him. Drove it to Walmart to return the "Engine Restore" snake oil; about 2 miles from my house.

Yikes; blue smoke all the way, you can feel the misfire (feels like an angry diesel) the smoke becoming more intense when you hit the pedal enthusiastically. The Mercedes behind me didn't much appreciate that (he changed lanes and hung way way back.....can't blame him).

In Walmart about 20ish minutes, and when I go to start, she's cranking and cranking but not starting.
Turn the key off wait a second or a few and try again; it starts. Never had a starting problem with this car until now either.

Well, no more (test the car) errands for me as I don't want to be stuck somewhere, so back home; blue smoke all the way
same as to trip to...

So, I call Brian...Brian is the guy who bought "Jerry Tucker Automotive" way back when and has been servicing Q's alot of years. His shop (All Import Service) is about 25 miles from my house; freeway driving required.

Not sure if it would be a good idea to drive it that far/fast, but would love to have Brian look at it for a second opinion from someone who knows Q's.

[3Q Jay]

injector leakdown is a good place to start. beeee careful. dumping fuel in the cylinder can hydro (petro) lock and bend a connecting rod.
low compression may also be a sticky or bent or burned valve.
if leakdown passes, I'd start with some BG44K to properly clean the injectors and lower intake runners/back of intake valves.

[Q451990]

Ditto on the hydro locking comment. If you know and trust Brian, it's worth the $$ to have it towed to him.

[kevinis]

No response from the other mechanic; last I spoke to Brian, I thought I'd be able to drive it to him; (before the Walmart
drama). Will ask Brian next week what he thinks and then check into towing. Wiffee does not want me to spend any more $$ on this car; will have to check into towing charges.

Thanks all for your input/expertise....

[94Q45Beast]

insurance should cover a tow