90 Q45 misfiring

[gbiehal]

The car fires up strongly but then misfires persistently. I've had two injectors and all the plugs replaced but it makes no difference. I've noticed the following:1. The car works much better when the air/engine are very cold. As soon as it warms up, tho, it starts misfiring.2. On warm days, the engine always misfires.3. When this problem first started a few months ago, the car would drive badly for about 15 minutes, and then suddenly start to run smoothly. Now it runs badly all the time.4. I have warning lights that the rear tail light is out - but it isn't.The car has only 65k on it, is always fed premium, and has been garaged in winter. I'm wondering whether this is the "end of the line," or whether putting $$$ is worth it, so any help or suggestions would be much appreciated. Thanks,Gabe

[Q45tech]

65k in 17 years is definitely owner abuse..............why because I suspect the oil wasn't changed every 90-180 days [68 - 34 oil changes].

Sounds like corroded connections or internal sensor circuit board connections [MAF, CAS, coolant temp sensor, coil or injector harness, KS etc.How many times were the plenum hoses totally changed [heat and age].

What does your expert technican advise after a Consult evaluation.........observing the running hot vs cold parmeters.

A Q engine is never done until there is a hole in block or bent valves stopping rotation.

BG44 k treatment and a BG Quick Clean for engine treatment can be thought off as paramedic emergency care before you get in the ambulance.

[gbiehal]

You're right about the oil changes, only twice a year. And the plenum hoses have never been replaced. Guilty as charged. My repair guy doesn't say anything about the problem other than change more injectors - which didn't help - so I've lost faith there. And I dread going to the dealer. But that may be what I have to do in the end, to get a better handle on what's going on. Car went great for many years, no problems at all, and then "boom."Based on what I've read at this site, MAF sensor problems seems to cause many misfiring problems... I'll suggest that to the dealer!Thanks for your comments.

[carfrk666]

try your engine coolant temp sensor, that changes your fuel ratio from when the engine is cold to when it is hot, more fuel when cold, less when hot, if temp is sayin cold but engine is hot, its dumping too much fuel in, this sensor isnt the same as the one your gauge runs off of. try that tho

[maxnix]

Timing Chain Guides?

[Q451990]

A Q engine is never done until there is a hole in block or bent valves stopping rotation.

If that's not quote-worthy for somebody's signature line, I don't know what is.

[Q451990]

I'm wondering whether this is the "end of the line," or whether putting $$$ is worth it, so any help or suggestions would be much appreciated. Thanks, Gabe

Gabe,

Welcome to NICO! It would be awesome if you could post some pics of your car... as you can tell I'm a huge fan of low-mileage Q45s.

I absolutely think your car is worth saving if it's in good cosmetic condition. Timing chain guides are a must... as well as a lot of other deferred maintenence, I suspect. Any maintenence history you can provide... as well as reviewing all of the old threads by Q45Tech, and the FAQs at http://www.q45.org will help you learn more. The good news is that you found the absolute best resource anywhere to help you maintain your Q.

Good luck!

Heath

[gbiehal]

Thanks for the suggestion. Is the timing chain guide something I can see by inspection - if I remove some of the engine covers for example?

[Q451990]

Nothing easy... you have to pull the front engine cover to check. How long have you owned the car? Do you have the dealership service history for the car? If not, you may be able to get a copy at a dealership (by VIN) or by calling Infiniti consumer affairs if it was archived - to have them pull it.

Heath

[carfrk666]

i dont mean to sound as if im going against your judgement or anything, but timing chain guides wouldnt make a car only run when hot, either they work, they make a loud clicking noise, or they make a rediculously loud noise and engine goes boom. but i would definatly look into replacing your guides and chains and all that fun stuff, if your even going to bother to look at them, might as well just replace them. .

[Q451990]

i dont mean to sound as if im going against your judgement or anything, but timing chain guides wouldnt make a car only run when hot, either they work, they make a loud clicking noise, or they make a rediculously loud noise and engine goes boom. but i would definatly look into replacing your guides and chains and all that fun stuff, if your even going to bother to look at them, might as well just replace them. .

You're partially right... I absolutely agree that failing guides aren't the problem Gabe asked about. It's just that those of us who have experienced failed guides or have seen the devastation, don't want it to happen to someone else... especially on such a low-mileage Q!

As far as noises... not really. For the most part it's a working great one second / dead engine the next type of deal.

Heath

[goody90q45]

Sounds like corroded connections or internal sensor circuit board connections [MAF, CAS, coolant temp sensor, coil or injector harness, KS etc.

Gabe- A loose or corroded MAF connection is a common problem and very simple to check and clean yourself. There's no need to take it to the dealer since a very small screwdriver is the only tool you need.

Pull the MAF plug (use the screwdriver to remove the clip) and clean off any corrosion with an old toothbrush and any type of oil (WD40, 3 in 1, PB Blaster, etc.). Do the same to the pins on the MAF. If there's corrosion on the MAF plug there's probably corrosion on all the other connections Tech mentioned above.

How did the MAF plug feel when you pulled it off? Loose? If you can wiggle it up and down (free play, don't force it) more than about 1/8" the 3 female connector pins need tightening. Use a push pin or small finishing nail to press down the tabs on the 3 pins in the connector. Grease up the connector with dielectric grease and plug it in.

If corrosion was present and cleaning the MAF plug helped then move on to the CAS, throttle body connections, and at least injector #1 and #2 (easy to get to). Good luck.

[DrewQ45]

Gabe- A loose or corroded MAF connection is a common problem and very simple to check and clean yourself. There's no need to take it to the dealer since a very small screwdriver is the only tool you need.

Pull the MAF plug (use the screwdriver to remove the clip) and clean off any corrosion with an old toothbrush and any type of oil (WD40, 3 in 1, PB Blaster, etc.). Do the same to the pins on the MAF. If there's corrosion on the MAF plug there's probably corrosion on all the other connections Tech mentioned above.

How did the MAF plug feel when you pulled it off? Loose? If you can wiggle it up and down (free play, don't force it) more than about 1/8" the 3 female connector pins need tightening. Use a push pin or small finishing nail to press down the tabs on the 3 pins in the connector. Grease up the connector with dielectric grease and plug it in.

If corrosion was present and cleaning the MAF plug helped then move on to the CAS, throttle body connections, and at least injector #1 and #2 (easy to get to). Good luck.

If the steps Goody outlined aren't helpful, take the car to the dealer and ask them for a diagnosis only with an estimate. They'll put it on the consult. Once they tell you the problem, fix it yourself or take it elsewhere.

...Drew...

[gbiehal]

This is very helpful info, as are all the other replies! I don't think it's a guide rail problem because (1) there's no engine noise and (2) I don't see how that would differ as a function of hot versus cold weather. But it's definitely something to keep in mind for later. In the meantime, I'll work on the MAF per your and other folks' comments and then see how it goes. Then depending on that, off to the dealer for an estimate. Problem is, in the DC area there aren't any good independent Infiniti repair places - I've looked and looked. It's almost an "orphan" brand when it comes to non-dealer service here (if anyone knows one, pulhleese let me know!).Thanks everyone for all the great comments!Gabe

[gbiehal]

Thanks for the suggestion - it makes sense to me, and it's definitely something I'll check out with the MAF.

[maxnix]

This is very helpful info, as are all the other replies! I don't think it's a guide rail problem because (1) there's no engine noise and (2) I don't see how that would differ as a function of hot versus cold weather.

Problem is, in the DC area there aren't any good independent Infiniti repair places - I've looked and looked. It's almost an "orphan" brand when it comes to non-dealer service here (if anyone knows one, pulhleese let me know!).

1) is irrelevant as there may be no warning before failure. Don't ignore them!

You have Vanmeter in NJ and T-3 in Smyrna.