1990 Q45 vibrating engine

[Q451990owner]

I had 2 bad injectors 1,8 I replaced them. The car ran fine . I notices some slight vibration at idle. So I cleaned MAF sensor and the air intake system , the MAF had a corroded connector that I cleaned.
Car is still vibrating on idle, as I rev up to 1,800-2,200 RPM there is a slight vibration getting worse as if the engine is missing.
My thoughts are as follows
1) I may have dirty injectors ( 6 old ones) I did one tank of Lucas injector cleaner. Should I get a second bottle and keep cleaning? Is it going to ruin my catalytic?
2) could it be the spark plugs? The car has 87,000 original miles but was sitting for 12 years...

Any recommendation ?

[Q451990owner]

I cleaned the throttle body too

[kevindanielk]

Pull a few of the plugs and check their condition. After 12 years and 87k miles, they may have seen better days.

[Q451990owner]

I Wonder how hard it is to pull out the plugs.

[db_autotek]

dude I just did a full writeup on changing the plugs lol.

Here, it's easy if you have some time. The first time changing anything is always difficult, but it's easier than most things. guide-change-spark-plugs-paint-plug-covers-t578673.html There

[Q451990owner]

Do you think the vibration is from the plugs ?

[Q451990]

I think it's more likely that more injectors failing or are dirty. I would ohm test them again, and have a pressurized rail flush done to eliminate any dirt in them. Gas tank additives won't do much except maintain an already clean system to some extent.

Heath

[Q451990owner]

I had a computer hooked up an only #1 and 8 were dead. The rest were fine. Do I still need an ohm test?

[Q451990]

It depends on what they tested and with what kind of test computer. I think the ohm test is going to be your best bet in terms of knowing if you have more injectors failing. In my experience they would drop out for a few seconds (causing a dead miss - or "injector death bounce" as I like to call it) and then come back - but I could always find a high ohm reading after feeling the bounce.

I would have injectors ohm fine one day and the start failing the next once ethanol 10 fuel was introduced here in 2008. Your car probably got real gas 10 years ago before coming out of moth balls, so unfortunately it's very likely that you'll see multiple injector failures using today's fuel.

http://www.q45.org/ohminjectors.html

Heath

[Q451990owner]

I think that a rail flush is the correct next step. I do not want to remove the planum. I don't think it's the spark plugs, although it may not be a bad idea to change them anyways to improve detonation and smoothness and increase gas mileage. Ideally, I would replace all injectors. But they are not bad, they were tested with a Nissan computer, and produced 75-80 rpm on the test. 2 tested zero. They were replaced.

[db_autotek]

Oh that's right your car is just now seeing ethanol haha! Oh :/ Heath is right you may suddenly start seeing crazy things from your injectors. If somebody suddenly replaced my morning milk with cheap vodka, I would be vibrating too lol. What you should do is review the injector ohm testing procedure, its easy and takes just a couple minutes after you get it figured out, and test them many times over a few days. Write down the numbers and after a few days you might have a good picture of how the injectors are behaving.

I doubt it is the plugs, but if they haven't been changed since being in storage, that should be near the top of the list of things to do. Good luck!

[OwnerCS]

It depends on what they tested and with what kind of test computer. I think the ohm test is going to be your best bet in terms of knowing if you have more injectors failing. In my experience they would drop out for a few seconds (causing a dead miss - or "injector death bounce" as I like to call it) and then come back - but I could always find a high ohm reading after feeling the bounce.

I would have injectors ohm fine one day and the start failing the next once ethanol 10 fuel was introduced here in 2008. Your car probably got real gas 10 years ago before coming out of moth balls, so unfortunately it's very likely that you'll see multiple injector failures using today's fuel.

http://www.q45.org/ohminjectors.html

Heath

It seems like my 2nd injector failure happened while I still had the first tank of fuel with injector cleaner that I used after I changed the plugs a few days after I got the Q. I've always thought that if an injector is close to the edge of failure, injector cleaner will soon finish the job.

[BCC93QT]

I would put $$ on that it is the injectors failing. "dirty injectors" I just don't see this happening with the ultra refined gas and all the bullcrap additives now adays. The pindle tips are getting/have been eaten and are not spraying correctly an probably dripping.

I am amazed you have not replaced the plugs as it sat for 12 years. That is one of the most inexpensive things to do to this car. Gloves, band aids, time, and beer.

2 options

A - If you want to keep the car for a reasonable amount of time. The 1990 is the most desired model i have heard. SO Remove the plenum and replace hoses, gaskets, and everything along with the 6 non replaced injectors. (upgrade all 8 to disc/port for longevity) Replaced my stock injectors when failed have seen over 120k flawlessly with the deatschwerks injectors.

B - Run it into the ground and continue on without the Q

[Q451990owner]

Re spark plugs, I called the manufacturer, and they told me that the mere if sitting 10 years will not have any effect on plugs. They suggested to pull one out and look.but time dies not cause them to oxidize or anything like that.
Also please elaborate on why 1990 is more sought after than 91 or 94 or 95

[BCC93QT]

If the plugs are original you should probably get some new ones in there. The 1990 is the first year of production in the US. Supposedly the faster and best handling of the G50 Q45 series. BTW, have you confirmed the timing chain guides have been replaced?

[Q451990owner]

I calles infinity, My VIN Number was de archived per my request and. There is no records. They only found a record that the Rabby who sold it to me (1st owner) took it in and they quoted him to fix the ABS , the steering pump and a leaking shock . He declined the work and did it privately.
Nothing about the timing belt that I can find out if they changed the attic rails....
Is there. An easy way to find out?
Re plugs, I will check them, however, if it is recomended to fix after 60,000 miles it was probably done , as I bought it with 85,000 and it now has 87,000 original miles . The car looks like new inside. All intact .
I bought the wood grain shifter panel from a 1995 hoping to add some looks to the interior , but it does not fit. The wood panel is bigger than the plastic one. Too bad. I will have to return it.

[BCC93QT]

So between injectors, plenum work, hoses, plugs, etc. AND the timing chain guides, you need atleast 5k worth of parts let alone labor.

Read this article for the timing CHAIN issue
thinking-about-buying-a-q-check-this-out-t213450.html

[qship96]

Too much $$$$ to put into a 24 year old old,out moded gas guzzler.....

[Q451990owner]

I don't know where you guys do your repairs. I have spent $2000 so far and the enum is a $500 Job for me Including injectors and labor .
My car has only 87,000 miles I'm not going to worry about the timing rails.

[qship96]

I don't know where you guys do your repairs. I have spent $2000 so far and the enum is a $500 Job for me Including injectors and labor .
My car has only 87,000 miles I'm not going to worry about the timing rails.

Plenum job,if done correctly,requires $1000 worth of the correct hoses and knock sensors.....plus labor.Injectors are about 100 each////////////////chain guides are a ticking time bomb

[Q451990owner]

I have access to a guy who would do it almost for nothing and. Will put $40 injectors (6) that i have not changed yet.it Will cost me $240 + 90 For spark uva And $150 labor .

[BCC93QT]

$40 injectors? What are they, used off ebay? You will have the plenum back off within a month. Most if not all of us have much experience with the car. We are not just pissing out random opinions. Checking on your guides should be number 1. If not, sell it to someone who will do the work the car needs.

[Q451990owner]

How can I find out if the car needs the rails ? Is that something that was replaced by the factory under warranty or a recall ?
Where do I look in the car to see if the rails are plastic or metal ?

The injectors, these are BG remanufactured injectors that I can get wholesale for $42 each and if I return the core I get &15 back. That would be $27 each. Retail on these is like $100 - $70 each.
This is a 24 year car (made in 89) I'm not trying to make it an antique collectors item, just trying to use it

[Q451990]

They're timing chain guides. I'm not pointing that out to be a beiotch about it, but if you're calling around asking for quotes or parts the terminology is important.

The only way to know if they've been replaced is to pull the timing chain cover. If the front engine cover has a light blue RTV sealing it, chances are pretty good that they have not been replaced. There was no recall... Infiniti fixed the ones that broke under warranty, buried their heads under the sand about the issue, and updated the design for the 1994 model year. Most of the dealership personnel don't know much about the early Q45 and have no clue that there ever was an issue. Failures occurred at a wide range of mileages, so low mileage doesn't mean you're safe.

Heath

[BCC93QT]

Engine could be vibrating due to the timing chain jumping a guide? Tell ya what. If you just want a good running car that will last you will trade you my 1992 for you 1990. It has updated guides, injectors, and the full plenum job. New tires and brakes. It runs like a champ with 315k on it. Title for title. I will take on the issues you '90 has

[Q451990owner]

No thank you. Mine has 87,000 original miles.