Vibration at idle and 10 mph acceleration??

[Libraman2k1]

I am having a problem also with my car vibrating at idle and at 10 mph--It feels like a bad motor mount but Infiniti says that it does not seem like that--After looking at my engine, I have found that the plastic cooling fan is warped--I dont know if this is causing that problem but I am thinking of changing it--I even received some info that it may be a couple of bad injectors which causes this--the CV joints also have been checked--any suggestions??:help

[maxnix]

CV joints won't contribute to vibration at idle.

Does it disappear as you accerlerate, then reappear when you hit 10 mph?

Does your engine rock more than an inch when you blip the throttle?

Warped fan should be replaced before it disintegrates and takes out your radiator. Is it also cracked?

If the dealer suspected bad injectors, I am surprised they didn't hook it up to a Consult.

Wait a minute, you're the guy with the bad fuel pump? All bets are off until that is replaced.

And exactly which Infiniti is it you drive?

[Libraman2k1]

ok Brian--lol--all bets off huh!!--yeah, u r right!! I'll wait until I replace that fuel pump--the vibration does not really disappear after 10 mph--it is just very pronounced at that speed--and only upon acceleration--If I am decelerating, I dont feel it--I thought that it was the drive shaft so the dealer agreed with me and replaced it--NO RESOLVE!!-just 800 bucks to their credit--good thing I had an extended warranty--will let u guys know how things work out--Reg

[Mayhem_J30]

According to his profile he drives a 92 Q45. If it's not a pump going bad I would agree with maxnix that it's a mount of some sort, maybe transmission mount

[Libraman2k1]

ok--I hope that the fuel pump solves all of my problems because I have this vibration and I am getting terrible gas mileage now--I once got about 350 miles per tank full--now I am getting 250--sucks!!my engine is still powerful yet I can still feel that it lacks performance and power--will inform u guys soon--thanks

[Q451990]

Does it seem like the car is "bouncing" at idle? A bad injector will do this - and you'll feel rough acceleration that smooths out when it's not under a load.

Heath

[JEC]

I find this thread very interesting as well. I'm the guy with the '90Q that has a bit of vibration at idle and a wicked vibration (through the steering wheel) at 40-55mph, particulary bad at 45mph. transmission shop said it felt like a misfiring cylinder, but it just passed our city inspection with flying colors on the emissions test (0.00% carbon monoxide). Figure that if it's dumping raw gas out the pipe, that would be reflected in the test, right? I'm also thinking new drive shaft; but want that to be a last resort and really don't want to replace it just for the heck of it.

Other than that, she runs great and I LOVE THIS CAR!

[Libraman2k1]

that is EXACTLY what it is doing heath--but I will try the fuel pump 1st before I start replacing injectors--thanks

[Libraman2k1]

I agree with Heath JEC---I already replaced my drive shaft--NOT the problem and they are expensive--most likely fuel injector/fuel pump malfunction or motor mount---have your mounts checked 1st--then suspect a bad injector or insufficient fuel supply to the injectors

[Q451990]

Libraman,

You need to diagnose which injector is the problem... I had two failures shortly after 100K on my 90 - rare for SC and Atlanta gas, but I doubt it got many (any?) injector flushes.

There are a few ways to go in the diagnosis...

1- Use an IR thermometer and compare the temperatures of the exhaust manifold tubes as they leave the heads. They'll vary somewhat, but one will be substantially cooler than the others.

2- Get a power balance test with Consult. The one with 0 RPM change is the problem.

3- Pull spark plugs... one will probably be covered in black soot. The corresponding injector is your culprit.

4- Ohm test the injectors... using the instructions on these links.1 2 3 4

If you're going to do this DIY, Remember to clean or replace the spark plug on the cylinder with the bad injector. In both cases the new injector didn't fix the problem without cleaning the plug because it was covered in black soot and didn't fire correctly! Also, use new o-rings and lubricate them with vasoline or dielectric grease to prevent pinching. A pinched upper o-ring will leak out into the engine bay. A pinched lower o-ring will leak into the cylinder causing flooding and potentially hydrolocking the engine. Also, Avoid Remanufactured Injectors... especially Python injecton. This is a sure way to do the job twice unless you like injectors that leak down and flood the engine.

If your fuel pump is very old (80-90K) I'd replace it as preventative maintenence, but I think you're going to end up replaceing an injector when it's all said and done...

Good luck!

Heath

[Libraman2k1]

I have done the resisitance test on the injectors from the harness and ALL of my injectors show a resistance of 13- 14 ohms which by standard, would make ALL of them bad--I dont think that ALL of them are bad-I just think that I am getting insufficient fuel supply to them---I cant imagine ALL of the injectors being bad--Also, I replaced all of the spark plugs and I replaced the 4 coils on the Left bank because of some "arcing" problems--go figure!!--coils hardly EVER go bad--I think that was another money making scheme set up by Infiniti of Lafayette Louisiana-My butt is sore because I feel I was screwed royally--I havent tested the injectors directly but if this fuel pump does not help the problem, i am going to--thanks

[PalmerWMD]

Great write-up Heath!

Fred..:thumbup

[Q45tech]

Or your ohmeter needs a new battery -when and what did you use to calibrate it...........12-14 ohms is fine. 15-30 is bad [shorted turns in coil]

We never say that ALL dealer techs are competent! Usually they have at least one out of 8-10.............don't assume the service manager is the best he/she is more a manager.

[JEC]

Wow, this thread has done wonders for my stress-levels! At 117K miles and zero maintenance records, I want to replace my plugs and have the injectors looked at ASAP. If this clears up my vibe problems, YaHoooo! This is much more palatable to me than the drive shaft.

Thanks for the info, Heath. And I'm rooting for you that it's just the fuel pump, Libra.

[Q451990]

Libraman...

Good news on the ohm tests! I'd have a rail flush done immediately after the fuel pump replacement. If the pintile is gummed up but still opens enough to get something through, a pressurized flush at 50PSI may get it broken loose...

Heath

[Libraman2k1]

Ok, gonna take the advice and get my injector rail flushed and I will update on the progress after I get my fuel pump--My car ran well over 150 mph when I 1st got it--I love that performance--Thinking about trying to find a supercharger for this car at about 6 - 9 lbs of thrust with an injector upgrade and an ECU upgrade, but 1st, I wanna get this thing running smoothly--

[awrightaz]

My 92 Q45 also has a vibration thru the wheel, particularly at 45 mph. Looks like JEC and I have the same issue. Injector maint and plugs now on my list. This is great.