1994 Infiniti Q45 check engine light on

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94Q45Beast
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Car: 1994 INFINITI Q45t w/HICAS
1992 INFINITI Q45
2017 INFINITI Q70S AWD BLACK ON BLACK
Location: ATL GA

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This morning I was driving back from a friends house and my Q was running great (other than the fact that I need to change the brakes and suspension), and now (2 some hours later) I start my car and pulled out the driveway, and I noticed my car shaking a lot and barely hanging on like it was about to stall (at this point I was confused to why this was happening when it was running fine this morning), so I turned the car off (right there in the street of my neighborhood) and unhooked my battery for a minute to reset the computer, same symptoms when I started the car I got the same symptoms, so I kept the car running in "Park" position, and went out to the back of the car to check the exhaust and it wasn't blowing out a constant flow, it was chopping (best way I describe it) and then I brought my car straight back home, what can be the problem? every time there is a half tank of gas left of premium fuel, I add in some fuel injector cleaner. i'm about to go check my engine oil level.

additional information, my car idle's around 700 - 800 rpm normally (I don't know if that's normal, I don't think so) but now its idling around 400-550 rpm

Thank You in advance.


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Q451990
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If I had to guess, I'd say a bad mass air flow sensor or it's connection. I'd try wiggling it's connector, and all of the others you can reach easily to see if you can notice a change in idle. Another guess would be a failing fuel pump/controller.

Check your car's factory service manual for instructions on pulling the code for the MIL. www.infinitiservicemanual.com

Heath

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94Q45Beast
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one more bit if information, there is a clicking noise from the middle of the car to the back, somewhere there, its definitely not coming from the front of the car. and my car has no problem accelerating, and my car feels jumpy on the brakes, it feels like my car is applying the abs brakes. (I am changing the brakes in a few days, I bought my brakes online), I wiggled the MAS connection around and nothing changed. ima take it to a shop that does check engine lights for free

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goody90q45
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The clicking does sound like an ABS problem. For the engine issue ohm test the fuel injectors and knock sensors.

http://q45.org/ohminjectors.html

Chances are the shop that checks codes for free will not be able to check your Q since it's OBD1 and they won't have an OBD1 code reader. Read further at Q45.org and it will tell you how to check engine codes yourself.

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94Q45Beast
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lol. some more information, I drove to several auto shops and on the way I had some serious loss in power, like I could not accellerate ( I read goody90q45's post when I came back), it felt like I was driving a tractor, and the only shop that is able to pull the codes was the infiniti dealership for 300 bucks ( I didn't do it) I am going to look through Q45.org as goody90q45 suggested, I will check the knock sensors and fuel injectors but I have a feeling that it could be the o2 sensor....just a feeling

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Q451990
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I don't think an O2 sensor would cause what you're describing... is the clicking just when you apply the brakes?

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94Q45Beast
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no, it was clicking while in park position, also when the car was in "on" position, and I apply the brakes, there is a click noise coming from inside the car around the the right side of the dash/radio area, i'm currently looking for my volt meter, but I think it is my knock sensor, that should be a fun fix, btw. I do all car repairs on my own, no matter how big or small.

qship96
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you may indeed have a bad knock sensor or 2....possibly been bad for many miles/years,,,,,,,,but I guarantee you it has nothing to do with the symptoms you describe-nothing.

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94Q45Beast wrote:no, it was clicking while in park position, also when the car was in "on" position, and I apply the brakes, there is a click noise coming from inside the car around the the right side of the dash/radio area,
this sounds like the shift lock release solenoid. rest your hand on the gear selector and you may feel it go in and out as you step on the brake in park.

the chugging exhaust sounds like a bad misfire.
now the question is why.
ohming injectors is a good place to start.

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94Q45Beast
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its good to hear from The Doctor Jay, and qship96, and q451990, and goody90q45, I will do as the doctor prescribes, but I have a possible theory....since I'm doing all repairs on my own regardless of how big or small or cost of tools (I love the struggle of changing parts), I have a feeling it could be the timing chain, it is raining like crazy right here in Atlanta so I'll do it in the morning.

a list of things I am changing/going to do:
-shocks
- brakes
- knock sensors w/ harnesses
- clean the throttle body
- clean MAF sensor
- do a oil change (mines got dirty really quick, props for using a fram), while doing the oil change, pour in 2-3 quarts of gasoline, I heard this cleans all the sludge, and then flush it out with a quart or 2 of the oil your going to be putting, and complete the oil change using a k&n oil filter, basic fram filters are terrible for my Q (let me know if this cleaning method is ok or not).

3Q Jay
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family time is starting, so my views/responses may be a bit delayed.
i think you are on the wrong track with timing chain.
lot of other things to eliminate first.
is the symptom constant or does it smooth for a while, then start bucking again. you can (gently) try what we used to call power brake it.
put it in gear and hold at idle, what changes from park and idle? feed in a little gas (maybe up to 1800 rpm max) and see how it responds.
holding this condition too long (the power brake) will heat up your trans so keep that in mind also.
unless you have reason to believe that sludge is somehow causing your misfire (way down on the list of things that are suspect, imo) i wouldn't try the engine clean at this point.
focus on the symptoms, gather data volts, ohms ,etc. and share what you find.

PS- you said exhaust was chugging--what does exhaust smell like? both cold and hot?

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94Q45Beast
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will do as soon as I can...also with family.

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94Q45Beast
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ok, I finally got some time to gather data

- exhaust = neither hot nor cold, in between
- exhaust smell= sweetish
- a click noise from shiftier every time the brakes are depressed
- My Q started smoothly the way it always does
- idled in park position around 1250 rpm
- check engine light took a few seconds to come on after start up
- in park position a faint deep deep knocking sound was herd
- when put in gear (in "R" position to be exact) my Q starts bucking/shaking, the idle dropped to around 700-800 rpm,the chugging noise started which was in sync to the exhaust
- when put back in park, idled back to 1250 rpm, faint deep deep knocking sound
- revved to +/- 1800 rpm easily the way it always does, no issues there
- noise while revved = normal engine noise, the faint deep deep knocking sound was possibly masked by the engine's noise of being revved.
- really really high fuel consumption, I got 30-40 miles in the half tank that was left, still 4-5 gallons left in tank
- ac serpentine belt was cut off by my other brother in revenge, I did not turn on the ac at all and nor will I until my belt comes in.
KNOCK SENSOR:
- I could not get a reading from the pins of the plug, but on the socket side of it (where the pins go into) I got 5 ohms on only 3 of the six socket, (the first 2 in the first row starting from the left and the middle one in the second row)
- on the fuel injector pins, I got 15 ohms on all pins.

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94Q45Beast
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btw. I used a analog multimeter

3Q Jay
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Is the bucking 'rhythmic'?

did you do 1800 while in gear, or only in park?

with non-autoscaling multimeter you will need to me on the Mohm (mega-)
scale or 100k Ohm scale. Reading should be somewheres around 550k. (going by memory, not by the service manual right now).
measure on the side of the harness that goes under the intake spider.

research how to pull codes with a screwdriver on your ECU.
sounds likely will be an O2 sensor (observable, not the cause), but we need to be sure.

injectors sound electrically ok, if you measured correctly, and got the same reading on all 8 pins (we were looking for 1 or 2 to be somewhat 'different' from the others.

did you change spark plugs recently?

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94Q45Beast
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I am so sorry I have been gone for a few days, I wont be back to my Q in a few more, iv been out of town to take care of some unexpected business.

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94Q45Beast
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Sorry I've been away, I needed some down time, a friend past away. now back to life

I am changing the spark plugs, fuel filter, oxygen sensors, relays, all fluid flushes, transmission filter, all belts, and all hoses in about a week or so (some parts I ordered online), will give an update when I'm done. btw, My Q was just sitting there under a tree for around 6 years and I brought it back on the road a few months ago. and body wise, there are thin black and grey spots on top of my pearl colored paint. how do I get that off without damaging the paint? I am thinking of pressure washing it.

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94Q45Beast
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Location: ATL GA

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what I have changed so far...

Starter relay, a bottle of Lucas anti-slip (for the slip light was on but it still seems to be on), fuel treatment, and Oil changes

about the oil changes:

when bringing the car onto the road, I used a Fram High Milege Oil Filter with Casterol part synthetic 10W-40 which only lasted roughly 1000 miles,
then I switched to Bosch performance oil filter with Penzoil platnum full synthetic oil with pure plus tech. and added in a Slick 50 full synthetic engine treatment and the car is running way better.

as for the fuel treatment: I added in 4oz whenever I had a 1/4th of the tank left, my dad forced me to do it that way, I don't think its suppose to be done that way.

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94Q45Beast
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my Q is fixed, pulled codes for knock sensors and fuel injectors. its running like a dream. I also changed the valve cover gasket.

3Q Jay
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good, did you also do the plugs?

the only thing slick 50 will help is if your engine is completely wornout, rod and main bearings bad from oil starvation.
Otherwise, the slick 50 molecules are actually too thick for the very tight precision tolerances of the factory manufactured VH45DE.
you can do more harm than good with slick 50.

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94Q45Beast
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yes I did change the plugs, NGK double platinum which I believe is the PFR5G-11, I didn't have that much trouble with #7 and #8 cylinders. what really gave me a hard time was unscrewing and screwing the plastic cover to expose the coil packs. but that was because I couldn't stand for very long. I tore my lateral ankle ligaments in a tennis practice session. so one knee was on a rolling chair while working. as for the slick 50, I mainly used it to clean up my crank case (it was just sitting under a pine tree for 6 years). but I got faster acceleration when I used the Penz oil platinum full synthetic with pure plus technology. than I would with castrol edge full synthetic. now I had noooo idea what a big difference knock sensors made performance wise untill I changed them. :woot:

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94Q45Beast
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now I'm thinking about upgrading my ecu, and lowering it about 2 inches. but I am soooo lost on how to restore the paint. Iv tried buffing it and its working on reviving the paint color but its not bringing out the "pearl-ness" of the paint. I might just have to wrap it in pearl white.


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