Injector replacement advice

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Injector replacement advice

Postby timatt » Wed Aug 11, 2004 9:34 am

'91Q, 90,000 miles.

I have a rough idle, but car runs well and smooth upon acceleration and at speed. I measured injector resistance at the harness connector using a good Fluke 77 multimeter and got the following results: #1 16.5 ohm; #7 15.6 ohm; #6 14.6 ohm; #4 357 ohm; #8 14.0 ohm; #3 54.0 ohm; #5 15.1 ohm; #2 14.0 ohm. From these numbers it would appear that the culprit for the rough idle is #4, and that #3 looks like it may be on its way out. Obviously, I need to replace some injectors. My question is how many should I replace?

I know that the resistance spec per the manual is 10 to 14 ohm. However, I did measure these at the harness connector, so there may be some resistance contribution from the harness itself.

Shortly I will be replacing all rubber under the plenum, so now is the time to decide. I suppose that I could keep old injectors in # 1, 2 and 8, and buy 5 new for the ones that cannot be reached without removing the plenum.

When I purchase new Nissan injectors, will they be an improvement over the original equipment as far as reliability is concerned? I find the reliability of the Nissan injectors to be disappointing considering the caliber of vehicle. I've got Bosch injectors (both L and LH Jet) on on much less expensive cars that are rock solid even after as much as 25 years and several hundred thousand miles. Seems like the Nissan injectors should be a bit more reliable than they are.


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Postby maxnix » Wed Aug 11, 2004 9:34 am

Injectors on Q45tech's 250K+ mile car are original. CA cars seldom last beyond 100K. Are you in an ethanol fuel area?

Your strategy is sound, but be sure to have KS and harness on hand. You will probably have to replace them soon anyway. You need to decide how soon you want to remove the plenum again.

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Postby Chally » Wed Aug 11, 2004 9:34 am

Normally Nissan improves on their faults, so buying new ones should be a benefit. I had one fail at 130,000Ks for no good reason at all!

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Postby Q45tech » Wed Aug 11, 2004 9:34 am

267,000 miles and still of BG 44k at least every 2 months for 7 years. Quicktrip gasoline [95%] since 1997 [100,000 miles].....nothing but NC, SC, GA, AL, and FLA blends.

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Postby Jesda » Thu Sep 09, 2004 1:15 am

Based on consumer surveys, mid 80s through mid 90s Nissans including the Q45 have higher than average failures for injectors, fuel pumps, or anything else related to fuel delivery.

Yes, they suck.And so does most gasoline in the US.

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Re: Injector troubles can someone help

Postby jonovitch » Thu Mar 12, 2009 3:56 pm

I bought a 94 Q-45 ran great for about 200 miles then all hell broke loose..... the car smells like its burning rich and while driving it hickups and feels like it is not getting enough fuel. At low speeds it will just die but starts up easy. Took it to a dealer and his fix it price is $6,000, he told me 4 injectors are staying open all the time and told me i cant replace only the bad ones i need all 8 and a new fuel pump and control unit. He said he cant tell which injectors are bad. is there any way to check if they are the problem while still in the car? it does not run to rough at idle when its running then it seems to hunt then die. Does this sound correct to anyone? I am a disabled submarine veteran and cant afford to put allot of money in it. If this is true does anyone have extras for sale or trade?

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Re: Injector troubles can someone help (jonovitch)

Postby Infinitiguy19 » Thu Mar 12, 2009 7:12 pm

Do your self a favor and get as far away from the dealer as possible, Because if a dealer says they can't find which INJECTORS are bad then that really puts there knowledge on the G50 Q45 and the VH45DE (Its engine) in question.

If you had a real Consult (Assuming you went to the Infiniti dealership they, should have one too) you can do a power balance test which shuts off the Injector and spark plug for that bank and keeps the AAC valve (AKA IAC valve) locked along with the timing, But then you would see if all the cylinders are with in spec of each other. Because each cylinder creates 12.5% of the engines total power.

But I would check the injectors your self by going here: All you need is a VOM AKA Volt OHM Meter avalble at Radioshack, Walmart....

I would also clean out the MAF sensor just incase the results of the injectors is good:

Good luck and welcome to NICO.

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Re: Injector troubles can someone help (jonovitch)

Postby goody90q45 » Fri Mar 13, 2009 12:20 pm

It really is a crap shoot trying to figure out how may injectors are dead when you know at least 2 or 3 of them are not working properly. It took me 3 tries on my last 90Q to replace 4 bad injectors. The engine was running so bad even a power balance test didn't give any meaningful data. The sure fire fix ifor the stealership is to remove the plenum one time and replace all 8 of them. Unfortunately it's also the most expensive option. For $6000 they must be replacing everything under the plenum.
jonovitch wrote:.....ran great for about 200 miles then all hell broke loose..... the car smells like its burning rich and while driving it hickups and feels like it is not getting enough fuel. At low speeds it will just die but starts up easy......
Ohm your injectors and knock sensors first but from your description you may also be having MAF issues. Is the check engine light (CEL) on? If so your next step would be to pull codes off the ECU. Instructions are in the tech help section at

Back to the MAF....Start by checking the connector and the MAF pins. Are they corrosion free? If not, clean with electrical parts cleaner or penetrant and coat with dielectric grease. Are the connector pins tight? They should look like the middle pin in the pic and can be tightened with something as simple as a small nail. When you reconnect to the MAF it should wiggle up and down very little (1/8").

If the MAF connector is dirty you've got to suspect that other connectors will have the same issue. Clean them all.

As long as you already own a voltmeter you've gotten off pretty cheap so far. Let us know what you find. Welcome to NICO.

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