Rpm's Jumping, Car stalling.Infiniti Q45 91 (SOLVED!)

[Noobius]

Car: Infiniti Q45 (G50)Year: 91Features: HICAS (which is linked to the Power steering unit)

I Just wanted to let you all know, That the easiest Diagnosis of this problem is the M.A.F. But in my case, this wasn't so... The solution to this problem is answered with a simple one, It was my alternator that was the culprit.

The car will hint to a multitude of problems, but the test you should run before you rule the alternator out, is run it off a higher output alternator, As in one for a truck, if you see no problems while testing, you can rest assured that your alternator is to blame, as it usually is in the 91. So, all you who think you're MAF is to blame, or a connection with it, test this first, you may not be cranking enough Power to support the system... Get a high output alternator as a replacement, because you always want to go a grade up, and never a grade down from stock.

try to get an experienced mechanic on this one... because this is not an easy task to do, you will be spending hours just trying to turn the bolts because a ratchet won't fit everywhere even with joints and extensions.

The reason I labeled this mass airflow sensor is because I have noticed a lot of people ruling it out for this exact problem.

Anyways, hope this helps some people!
Modified by Noobius at 5:31 PM 3/8/2010

[goody90q45]

Tell us more Noobert.

Welcome to NICO.

[Noobius]

It Turns out that that car doesn't have a distributor cap like most cars, that it all runs on alternator, and so... The electronics in the MAF sensor have failed, And all the Electronics stedily fail, leading to an eventual stall of the car, The Q45 Cannot run without the alternator for very long unless you manage to keep the rpms up, and even then, the ECU fails also, and you cannot rev it correctly. haha, it was funny what happened, now it is anyways, but not back then.I thought it was dead forever..

[qship96]

It Turns out that that car doesn't have a distributor cap like most cars, that it all runs on alternator, and so... The electronics in the MAF sensor have failed, And all the Electronics stedily fail, leading to an eventual stall of the car, The Q45 Cannot run without the alternator for very long unless you manage to keep the rpms up, and even then, the ECU fails also, and you cannot rev it correctly. haha, it was funny what happened, now it is anyways, but not back then.I thought it was dead forever..

Send some more time reading and learning about electrical systems and the q45. The time and money you will save is worth it.

[lino]

Get a high output alternator as a replacement, because you always want to go a grade up, and never a grade down from stock.

Lucky for me I've replaced my MAF and alternator both new from the dealer. I'm curious what upgraded alternator you suggest to buy?

[Noobius]

Well, basically, I do a search on Google for a High output Alternator for my specific car. I got my alternator from another Q45, and the person said it was a high output alternator, I trust his word, but yea... as far as brand names, I have no clue.

And as for the electrical system, I notice that the motors in my sunroof and some of the chair adjusters have failed. The guy i bought the car from thought he was a "wiz" at the electrical i guess... NOT. he installed some Crudy Power cables for a sound system, so I am due to replace those... I already gutted all the crap he did in the dash with the Stereo... just useless junk, I did keep it all though, in case it is needed for when i replace the head unit. it was a freaking mess in the dash with all those useless little boxes and junk.

[Q45tech]

One must match the oem rpm and amperes. High output alternators frequently do not!

The point being at idle the high output units may provide LESS than oem while providing more at cruise [2000 rpm].

Nothing not thought of is suddenly brand new on a 20 year old design.

Those of us who have owned and maintained our Q45 for 20 years know this. Neebees think they have discovered the wheel. Especially those without engineering degrees.

The FSM is a specification for oem alternator at different rpms of course this depends on air temperature passing thru alternator cooling the semiconductors, diodes and regulator IC plus of course the copper field windings.

"the person SAID it was a high alternator" The church use to say the sun revolved around the earth.

Here is an excellent Berkeley Physics [with no math] review [probably the finest teacher in the US no ifs and buts] that can be watched [podcast] in 27 - 1 hour lectures:http://muller.lbl.gov/teaching/Physics1 ... htmlSearch utube "Physics 10 Lecture 01" to begin

[Noobius]

Yea, Now that I have driven it, i have seen no difference between the old alternator, and the new one, aside for the fact the old one failed. So it seems like "high Output" was just a tag and had no real impact on if it outputted any more power. It looks exactly the same, so I am guessing it is a refurbished OEM. and Not a high output I was thinking it was. I will make the changes to my main post, thank you.. I will just pack an extra battery or something for reasons I won't get into on this thread.

[ShortSeason]

From the TSB the G50 requires a Group 27, 675 CCA Batt. Higher than any other Inifiniti ever built to date.

If link below does not work... see Paul Wall signature with links to docs. Thanks Paul

https://docs.google.com/leaf?i...ex=24

[Q45tech]

"Cold cranking amperes (CCA) is the amount of current a battery can provide at 0 °F (−18 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures.

The problem is a 10-12-15 year old starter [may not rotate at sufficient rpm with 7.2 volts!............to deal with old worn spark plugs/dirty injectors or restricted carbonized intake valves.

Early 90-96 VH45 need a new battery every 36 months +-3 months as shown by 20 years of historical data.

[qship96]

[QUOTE=Q45tech

Early 90-96 VH45 need a new battery every 36 months +-3 months as shown by 20 years of historical data.[/QUOTE]

Yes, but this historical data is based off of old fashioned flooded wet cell type batteries......wonder if the newer AGM type batteries will extend this, and if so, by how much?????

[Infinitiguy19]

From the TSB the G50 requires a Group 27, 675 CCA Batt. Higher than any other Inifiniti ever built to date.

If link below does not work... see Paul Wall signature with links to docs. Thanks Paul

https://docs.google.com/leaf?i...ex=24

Wow I never thought anyone paid attention to that link that too a while to put together. That really couldn't be done without Brian's AKA Maxnix And Q45tech help and NICO of course.

I just got a new battery from Costco rated at 800 CCA and 1000 regular AMPs, I dare the Q too kill that.

[Noobius]

Thanks q45 tech, even though my initial diagnosis was correct, I made a mistake with the installation of the new alternator, and i killed it, It was not a high output alternator to begin with, just a refurbished one. so, I bought a refurb alternator from ebay, put it in correctly this time, and it has worked like a beauty ever since, Now, my challenge is, Fuel injectors, Spark plugs, and rack and pinions, and the daunting elimination of the Hicas, and a power steering pump replacement when I get to it. Maybe I should just buy another q45 I thinks....

[Infinitiguy19]

And the daunting elimination of the Hicas, and a power steering pump replacement when I get to it. Maybe I should just buy another q45 I thinks....

Indeed I would buy another Q45 rather than destroy a Q45t especially from what I have heard from Q45Tech, That they do not cost much more to maintain than a base Q45 unless abused/neglected.

[lino]

Thanks q45 tech, even though my initial diagnosis was correct, I made a mistake with the installation of the new alternator, and i killed it, It was not a high output alternator to begin with, just a refurbished one. so, I bought a refurb alternator from ebay, put it in correctly this time, and it has worked like a beauty ever since,

Happy to hear that you resolved your issue. When my alternator failed, I looked at many options and very quickly realized after reading in here that genuine oem was the way to go. It cost me more but I at least I didn't have to do the job twice which was the case with quite a few people and I was up and going immediately.

Now, my challenge is, Fuel injectors, Spark plugs, and rack and pinions, and the daunting elimination of the Hicas, and a power steering pump replacement when I get to it. Maybe I should just buy another q45 I thinks....

Don't think that any other Q45 is immune to repairs and service. They all require work. If the previous owner didn't do it, then chances are very likely it will be you who will. There hasn't been a day since I owned my car that I wasn't planning the next repair or service. I'm forever planning the next thing. No one said it would be easy to keep up .