92 Q45a shakes at idle. Need help.

[alarsen77]

Hi guys i have a 1992 Q45a that has a shake at idle. It sounds like there is a vacuum leak somewhere but my dad and i have looked for it and can't seem to find it. We haven't tested the injectors yet cause it just doesn't seem like an injector. The car might have a slight shake to it one minute then it will get worse, and then the next day it will be gone. So we aren't too sure what to do now. This is my first Q. I have read that it could be the PCV valve, vacuum leak, bad spark plugs, bad coil packs, bad injectors, and all sorts of stuff like that. So basically i am looking for some advice.

Also where is the closest Q45 mechanic to Mount Bethel PA, 18343.

Thanks.

Alex

[xerexabante]

if you are looking for a vacum leak then spray some WD40 on sections at a time. if you see the idle difference when the WD40 hits an area then you found your leak.

[goody90q45]

Injector failure is so common in the Q and your symptoms sound like it could be one or two going bad. It only takes 5 minutes to do it and then you can positively rule out injector failure. It could be any of the other things you mentioned but start with ohming the injectors. Add MAF, MAF connector, dirty EGR and dirty TB to your list of possible problems. Let us know your injector readings.

[alarsen77]

We sprayed areas with WD40. We didn't experience any change in idle. But it just sounds like there is an vacuum leak in the motor somewhere. Sometimes it sounds worse than other times. But we can't seem to find it.
Modified by alarsen77 at 2:21 PM 7/23/2007

[xerexabante]

try to see if your manifold is cracked. the see if your EGR tubings are OK.

[alarsen77]

I will try ohming the injectors either tomorrow or wednesday. It is raining here today so not a good day to work on the car. I will let you guys know the results. What are they supposed to test between?

[goody90q45]

I will try ohming the injectors either tomorrow or wednesday....... What are they supposed to test between?

Should be 10.0-14.0. If you have more than 1 or 2 out of this range, or even one dead one, your Q will shake at idle but probably run pretty good, except for gas mileage, at speed. Here's a link on ohm testing injectors.

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

[alarsen77]

Well i ohmed my injectors through the harness like your diagram said. Here are my readings1-14.52-12.23-12.74-21.25-34.76-21.57-20.78-14.1

Looks like i have atleast half of my injectors that are bad. So the question is now do i look for a good set of used injectors? or is it best to just buy new ones?

[burijon]

That depends on if you want to keep the car forever. If you plan on keeping it then decide whether you want to spend $170 on EACH injector from Joe at Infiniti Scottsdale.

You could put a wanted to buy add in the classifieds and see if people have any used ones.

It is suggested to move the higher ohming ones to the front so you can replace those without removing the plenum later one when they WILL FAIL. I for one could not remove the injector without destroying it. I had ones to replace anyways so it was a non factor for me.

I haven't read any of your other posts so if you haven't done it call Joe and ask him what is todays price on a FULL plenum kit with all the hoses and knock sensors and fuel pump. I know when I called him he's so nice in not upselling you but I wanted everything and had to call him several times to get all the hoses that you will need. You'll hate doing it but you will be glad it's done when it's finished.

Mine still runs like a top almost 4 months later! Much better gas mileage too! 16.x versus 10 MPGs before rehabilitation.

[Q45denver]

Well i ohmed my injectors through the harness like your diagram said. Here are my readings1-14.52-12.23-12.74-21.25-34.76-21.57-20.78-14.1

Looks like i have atleast half of my injectors that are bad. So the question is now do i look for a good set of used injectors? or is it best to just buy new ones?

Did your state switch to 10% ethanol recently? I have a good set you could buy for $150 shipped.

[sdkhalsa]

[QUOTE=Q45denver]

Did your state switch to 10% ethanol recently? I have a good set you could buy for $150 shipped. [/QUOT

A good strategy is to put new injectors under the plenum and then on #1, #2, #8 put in good injectors that have been tested. Remember to put in new o-rings on all removed injectors. In my experience the injectors last about three years. This situation has to be one of the most frustrating aspects of the car.