1994 Q45 Vibration around 1900 rpm

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tegva
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1994 Q45 Vibration around 1900 rpm

Postby tegva » Sat Feb 09, 2019 1:28 pm

Could use some advice on a problem on my 1994 Q45 with 87k miles. Recently changed injectors, fuel pump, driveshaft and have two continuing issues. The car is sometimes hard to start but maintains fuel pressure and also has a vibration around 1800 rpm. May be two separate causes or one. I have a running parts car so have readily available parts to swap things out to see what the issue is but not sure what to try next.


sandydennis11
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Re: 1994 Q45 Vibration around 1900 rpm

Postby sandydennis11 » Sun Feb 10, 2019 5:01 pm

Did you replace the fuel pump control unit. Same thing with my '96 for hard start.

BTW, do you want to sell the Air Mass Meter Boot from your spare parts car?

Let me know.
Sandy

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goody90q45
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Re: 1994 Q45 Vibration around 1900 rpm

Postby goody90q45 » Mon Feb 11, 2019 6:44 pm

The 3rd engine mount, AKA transmission mount, will put out a vibration in this rpm range when they start wearing out. It's an easy repair but a replacement part may or may not be available.

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Q451990
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Re: 1994 Q45 Vibration around 1900 rpm

Postby Q451990 » Tue Feb 12, 2019 8:40 am

You said the car is "sometimes" hard to start. Can you find a pattern? Years ago, I had a leaky lower o-ring issue with my injectors - or maybe the actual injectors were bleeding down. The car would start fine after sitting over night, or in a few minutes after turning it off - but from sitting about 10 minutes to about 5 hours, it would start hard, and smoke a little.

tegva
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Car: 1994 Q45 87K, 1994 Q45 320K, 1979 MGB, 1993 Range Rover, 1991 Alfa 164, 1966 442

Re: 1994 Q45 Vibration around 1900 rpm

Postby tegva » Fri Feb 15, 2019 4:35 pm

On my last Q45 I did most of the work myself. This one I had someone replace the injectors and transmission mount but you have all confirmed to me what I should be looking at closer and I'll do it myself this time. I checked the control unit. The other question I have is that I know if the Q is started when cold and turned off quickly it will be hard to start and will need to floor it to get it started. Which is almost like what is happening now. Is there a sensor or valve in the air or fuel circuits that I should look at?

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Q451990
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Re: 1994 Q45 Vibration around 1900 rpm

Postby Q451990 » Sat Feb 16, 2019 8:42 am

What you're describing sure sounds like flooding, which is usually a bad/pinched lower injector o-ring. If it's bad enough you can hydrolock the engine. There's a TSB somewhere that Nissan published to test leak down. I'll see if I can find it.

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Re: 1994 Q45 Vibration around 1900 rpm

Postby 3Q Jay » Sun Mar 03, 2019 9:03 pm

I think Goody is on the trail for the 1800 rpm vibration. If you get that in PARK (yes really), then it is the 3rd mount.
BTW, what did you do for a driveshaft? 1-piece aftermarket?

tegva
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Car: 1994 Q45 87K, 1994 Q45 320K, 1979 MGB, 1993 Range Rover, 1991 Alfa 164, 1966 442

Re: 1994 Q45 Vibration around 1900 rpm

Postby tegva » Sun Mar 24, 2019 10:57 am

I bought a 1-piece aftermarket aluminum from Driveshaft Specialist Inc in San Antonio. Fit right in and is much lighter. Looked for the vibration in park and there is something there. Will take a closer look at the transmission mount

3Q Jay
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Re: 1994 Q45 Vibration around 1900 rpm

Postby 3Q Jay » Sun Mar 24, 2019 3:19 pm

Congrats on the 1-piece driveshaft! I have been considering doing this on the BlacQ 95. interested to know if your 40mph vibrations are less (how much).
besides the 3rd mount, there are rubber pucks that hang the exhaust just aft of the 3rd mount. those can contribute as well.
p/n is 20610-60u00, unfortunately, they appear to be obsolete.
p/n for 3rd mount is 11320-60u02.

Drake57
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Re: 1994 Q45 Vibration around 1900 rpm

Postby Drake57 » Mon Mar 25, 2019 6:53 am

goody90q45 wrote:
Mon Feb 11, 2019 6:44 pm
The 3rd engine mount, AKA transmission mount, will put out a vibration in this rpm range when they start wearing out. It's an easy repair but a replacement part may or may not be available.
Words of wisdom - Replace the rear transmission mount - I just did so on my 1992, and it completely eliminated a nasty shudder that happened when engine RPM hit 1900. The shudder itself seem to be 10-15 Hz, some subharmonic. The car is much smoother & more comfortable.

I never suspected the mount, but it eliminates the trembling, this is what I installed: //www.rockauto.com/en/catalog/infiniti,19 ... mount,8616

In my case, the shudder appeared only after putting the car back on the road after a 4 year period of sitting up. The old part appeared to be sagging, and the rubber webbing was partially cracked.

So hats off Mike, it makes a really nice difference.

I have a slight ATF leak, which I suspected was the transmission tail shaft seal, but the shaft and housing are totally dry, though the connector cluster at the tail shaft are dripping, so I think connectors are the source of the leak. Each time I raise the front of the car for service, while leaving rear wheels on the ground, ATF drips from the connector cluster. It's not a major problem, but I hate the smell of burning motor oil. Has anyone fixed this, or know how the connectors seal?

I also found one of the exhaust mounts that bolt to the transmission cross member is sheared, so if I can locate a replacement, that is next. Good week, all!

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Q451990
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Re: 1994 Q45 Vibration around 1900 rpm

Postby Q451990 » Tue Mar 26, 2019 7:21 am

Thanks for the update!


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