Looking for Q45 Stumble Solutions

[donflamenco]

Hello All: I have spent the better part of a whole week searching this site about my Q45 stumbling problem, and have theories, but in some threads, I don't see solutions so either people have driven their Q45's off a cliff or they have solved this problem. I'd like to solve this.

Background--I have a 1999 Q45 that stumbles slightly at a stop and will stumble badly either under a load while driving (ie up a hill) or when pressing the accelorator after coasting (especially around 40 mph). The check engine light has come on suggesting bad o2 sensors which have been replaced. New spark plugs, intake cleaned, premium gas--I take care of the car well. It has 105K miles on it, I purchased it at 92K miles. I replaced the battery as well.

OK, with that being said , I have read numerous posts here and after looking at some of the same theories I have had, I have come down to this, that it is either the MAF or the coils or both.

My question here is this: Some members have suggested that if you are stumbling at idle, that it is indeed a coil problem.

1) Is it a truism that it is a coil problem if you are stumbling at idle?2) On a 99 Q45 is it possible to test coils on a Q45? Is there any other way to determine which coil is bad without doing them all and guessing that that is the case? 3) If it is the case that the coil problem is responsible for the stumble at idle, would that be responsible for the stumble while driving? If not, what is?

I think those are the three main questions I have based on the theories i have seen on this site. Unfortunately. my guess is htat if a person has solved this problem, they are no longer coming on this site. Please let me know if there are any universal truths that have been discovered?

For what it's worth, I am glad to have found out that this problem is not unique to me, and more importantly, i am not crazy.

I love the car, but these mechanics are looking at me like I'm nuts when i describe the problem. I have read almost every thread here with regards to stumbles, and the two that stand out to me are the MAF and coils, and i might add I have seen everything from knock sensors, altenators, battries, plugs, etc as the culprit.

Any help would be appreciated before i spend more on it correcting this than i spent on the car.

thanks

[Q451990]

The coil pack issue on the Y33 (97-01) is pretty common, and the ulitmate solution appears to just replace all of the coil packs... Do you have codes for a misfire showing in the ECU?

Heath

[bullittandy]

MAF problems seem to be related to earlier cars-90-96.

Stumbles on 97+ cars are almost always coils which is not a big deal except that for some reason the car will stumble for a long time without throwing a code which has lead to this becoming a mysterious problem. If the misfire code tripped as soon as the idle stumbled then there would be no mystery to discuss on this board.

So, you have two options: 1. Live with the misfire until it trips a code and replace only that coil. pros-much cheaper ($75), cons, you have to live with the stumble for a bit or maybe even a long time.2. Replace all 8 coils. pros, problem solved now and into the future. Cons-much more expensive ($600).

I have a 99 that stumbled for maybe two months and I got tired of waiting for CEL and ordered 8 new coils and while they were being delivered the CEL came on-yeah!!!

My wife drives a 97 and just reported a stumble but I am determined to wait for a light on this car.

[Q451990]

I was under the impression that it's not unusual for the stumble to move from coil to coil? Is the ECU smart enough on the later Q to narrow a misfire down to one cylinder?

Heath

[oldmako]

Has anyone ever cross referenced the part number to see if the identical coil us used on other models? Might help in finding replacements, and perhaps at a better price.

I'm just sayin.....

Andy, did you go ahead and replace all of them after the code came up which identified the bad one?

[maxnix]

I was under the impression that it's not unusual for the stumble to move from coil to coil? Is the ECU smart enough on the later Q to narrow a misfire down to one cylinder?

Heath

Yes, OBD II will indicate the misfiring cylinder. Switching coils can help tracing the defective ones.

But, if the intake path, EGR and IAC systems, and TB are not clean, tougher to isolate. Same for high mileage plugs.

[donflamenco]

I knew I would forgot things. The codes it was throwing this last time were P0138 and P0159 and P0158 which led to us replacing the o2 sensors. Prior to that, it has thrown codes p0300B, P0300 and P0325 and U3FFF which from what I understand are mostly just random misfire codes and the knock sensor.

BullitAndy--yours was one of the stories that I was following on a number of different threads. It seems that you a) have to wait until it throws a code and b) get lucky that it throws a code to the faulty coil. I think it makes sense to just replace all of em. Andy, was your car also stumbling while driving under a load or after coasting when re-accelerating as well? The stumble at idle doesnt bother me near as much as the stumble at 40mph. I just want to be sure to correct that.

Thank you everyone.

[miata007]

I too replaced all 8 coils at once and solved the stumbling issue. As yourself how long you are going to keep you car?

If for some times, replacing all coils with OEM is a good idea. Be sure to get OEM!!!

Coils are wear and tear item and I read somewhere on this site that they are rated for 100K miles so is time for you. If you can do it your self, atleast you only have to pay for parts. Make sure you take your time and not over-tighten any bolts on the valve cover.

Good luck!!007

[maxnix]

It seems that you a) have to wait until it throws a code and b) get lucky that it throws a code to the faulty coil. I think it makes sense to just replace all of em.

Fault codes (all in the FSM) point to cylinder misfire only. Why one must switch to determine if it is coilpack, spark plug, injector, wiring, .....

[donflamenco]

Thanks, and that reminds me. It seems that the consensus is that it is the coils, but I have also read a number of posts here (albeit older posts) that the injectors on Nissans and Infinitis are notoriously bad.

I had the mechanic check the ohms on the injectors and everything seemed to be inline both hot and cold. He said he did the same on the coils, but since this is a problem that seems to appear most when on a load, it seems like a very hard thing to duplicate and test at the same time.

I dont have the time or know how to change these myself (I used to work on my old 74 Dodge Dart, but these days everything is so compact, I dont know where to begin--and just getting to the coils seems complex. The dealership estimated parts and labor on a coil replacement to be 1500. Seems a tad high.

I guess it is about time for the switch anyway, so might as well do it. Thanks All and i will follow through if it helps and will be sure to make sure it is OEM.

[maxnix]

Changing coilpacks is pretty easy. If you are doing them all, might as well do plugs too. Check the valve gaskets for leaks above the exhaust manifolds.

[bullittandy]

Thanks, and that reminds me. It seems that the consensus is that it is the coils, but I have also read a number of posts here (albeit older posts) that the injectors on Nissans and Infinitis are notoriously bad.

I had the mechanic check the ohms on the injectors and everything seemed to be inline both hot and cold. He said he did the same on the coils, but since this is a problem that seems to appear most when on a load, it seems like a very hard thing to duplicate and test at the same time.

I dont have the time or know how to change these myself (I used to work on my old 74 Dodge Dart, but these days everything is so compact, I dont know where to begin--and just getting to the coils seems complex. The dealership estimated parts and labor on a coil replacement to be 1500. Seems a tad high.

I guess it is about time for the switch anyway, so might as well do it. Thanks All and i will follow through if it helps and will be sure to make sure it is OEM.

To answer the previous questions:-My car was not stumbling under load (that I could tell)-only at idle.-Like a dumbass I did not check the codes when the CEL finally came on, I figured "It doesn't matter, I have eight new coils-they are all gonna be replaced." Well, now I have seven good coils and one bad one all mixed together in one indeterminable pile on the backseat of my partscar. I will wait for the code on my 97 and blindly stab at my pile of used coils and pray to God I get lucky and grab a good one-I have about a 89% chance of success.

Parts would be about $700 for coils and plugs (since you're there) and any tech can replace those so figure about $200-$300 for labor so dealer is a little high.

[KoupeDaVille]

Im having the same issue, but its hardly noticable. Im glad to know that its an easy fix.

If you have any troubles installing the coils, maybe I could fly down to the cities and help a fellow Q45er out. Im from St. Cloud, but Im in the cities once or twice month.

Good luck with the fix.

[GThreat]

Andy,

Are any of those coils up for sale? I need one to fix my problem, but would buy 2 to make sure I get a good one.

Thanks

Craig

[donflamenco]

UPDATE

I did want to provide an update to this for future reference to someone going through the same thing, because FOR NOW (I dont want to jinx anything) the problem seems to have been corrected. Changing the coil packs seems to have made the difference. I am not experiencing the stumble at idle or during acceleration at all.

Thanks to all on this board for helping me figure this one out saving countless hours and experimenting.

Also, Koupe, thanks for the offer to help out. I was travelling quite a bit so I just had a local mechanic do it. Here was the final tally:

Eight Coil packs (and plugs): about $650 from Ifiniti parts in Scottsdale

Labor: about $175

The dealership quoted over $1500 just to replace the coilpacks.

thanks again, and hope this is the fix! It does seem from talking to others that at about the 100K mile mark the coils go bad.

[qship96]

Yea!!!!!!!!!!!!!1 Should be good to go for the next 100,000 miles without stumbling re-occurring with brand spanking new coils and plugs!!!! Much, much better to do it the way you did than to change one coil at a time, or worse yet, use used old tired coils from a junkyard or other parts car.......

[KoupeDaVille]

No problem, glad to hear your Q is running good again!

[Q45tech]

I like the honesty of GM/DELCO right in the specification sheet for coils they warn that their operating life is ~~ 100,000 miles!

Here are some explanation and pictures of the insides of generic coils:http://www.standardbrand.com/u...5.pdf

http://www.generalcable.com/NR...S.pdf

http://www.equiserv.com/Produc...a.pdf

http://delphi.com/shared/pdf/p...s.pdf