92 q45 shaking while idling

[mesallem]

hey guys i just bought a 1992 q45 with 143000 miles on it, my question is, when im idling the whole car will shake, the idle is steady but the car still shakes, my concern is the motor mounts but i friend of mine said it could be a dead cylinder, what are the symptoms of a dead cylinder? i would think the check engine light would be on, right? unless the light is burned out lol...thanks in advance for the help,

[Q45tech]

Obviously shaking at idle is from an imbalance, one or more cylinders not firing.

However the motor mounts are also probably worn out from old age and miles.

Every 1992 sold needs lots and lots and lots of work [parts replaced] after 15 years of abuse.

[goody90q45]

For starters, you probably have at least a couple of bad injectors. They're very easy to check (ohms resistance) with a digital voltmeter. Here's the link from the tech help section of Q45.org and a pic to go with it. Let us know what readings you get and we can help you from there. Good luck.

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

[Q45tech]

MTBE used to be the main culprit in injector failure,, this has been replaced by ETHANOL which appears to be even more aggressive in attacking injectors.

The units were not designed to function much beyond warranty [70-100k] with unconventional fuels.

[mesallem]

so could one of the cylinders be bad, as in not working anymore and never will, or would it just be a bad injector?

[Q45tech]

Unless the engine has jumped time and bent valves in a cylinder then it is probably an injector or it's harness especially since car is from CA.

If you are not trained to do diagnosis and repairs find someone who is expert on Q.

Many times shade tree mechanics* do more harm than good, causing additional expensive problems.

* Q is unique for early Nissan [V8], and complicated under plenum. I'm sure that there are a few dozen technicans in CA qualified to repair and thousands that will cause problems.Why didn't previous owner repair the shake because he found out it would/could cost thousands.

We work on more 92Q than many Infiniti dealerships in US and usually have a dozen [90-93] junkers out back in our 3 locations for parts to help our poorer owners. We probably work on more old Q than all the 5 Infiniti dealers in Atlanta combined.There is not a single day when a broken Q doesn't show up.

6 of our techs drive personal Q they purchased for $500 or < and brought back to life as daily drivers.

[mesallem]

so you think the shaking is from one or more bad injectors? could it be anything else? the person i bought it from is a close friend and sold it to me for only 1200 with a subwoofer system a nice deck and an alarm with a remote start. What do you suggest i do to bring the car back up to par.

[Q45tech]

Take it to a qualified technican for diagnosis.

I would pay a dealership a few hours [$200] to find and provide a written list of all that needs repair to return to as new performance, then post the list and we will help you rank priorities.

Normally you can get a reply here within a few hours or minutes.

I scares me that you didn't have a qualified PAID INDEPENDENT inspection done prior to purchase [even from a friend].

[elwesso]

Take it to a qualified technican for diagnosis.

I would pay a dealership a few hours [$200] to find and provide a written list of all that needs repair to return to as new performance, then post the list and we will help you rank priorities.

Normally you can get a reply here within a few hours or minutes.

I scares me that you didn't have a qualified PAID INDEPENDENT inspection done prior to purchase [even from a friend].

I mirror Tech's advice. My opinion is you either need to be handy with a wrench or have a lot of money to get a Q working perfect, either that or you find someone who works on cars for nothing (like myself, but geography wins again)... You can fix a Q by doing your own labor on a honda civic budget and being smart about parts...

Most likely you have a bad injector. I would suggest taking the plenum off, doing all the hoses under there, and sending the injectors out to have them cleaned and the bad ones replaced.

[Jesda]

I paid $1300 for my Q because, as well, it had a bad injector. It fixed itself though and continued to drive perfectly for a year, when two of them finally gave out.

If the hoses are still decent, you can get away with lifting the plenum out of the way to get access to the injectors.

[Q451990]

Maybe you'll get lucky... you can access injectors 1 & 2 without pulling the plenum. Also #8 I think.

I would use the ohm method mentioned earlier first. Then consider buying a Consult Adaptor and Nissan Scan Tech software (see other threads in this forum... maybe back a page or two). You can perform a power balance test that way - which will also narrow down the bad cylinder.

Of course, Tech's advice on finding someone qualified to do the work and give you a write-up of what needs to be done is excellent as well. You probably need to make a decision as to how far you want to go with this car.... $5000+ to restore to as-new conditon - or a few hundred at a time with just enough to get by until something major happens. Standards vary greatly as far as what is acceptable, and at this point for these cars there are pretty good arguments either way depending on your goals.

Heath

[mesallem]

ok i ohmed the injectors and i think i did it wrong because most of them are out of range. i had injectors 1 and 2 only in range. injectors 7 and 3 were above 14 but below 15.5, and the rest were in the 20s. i hope i did it wrong because thats a lot of injectors to replace, how do i know when i can get the them cleaned and when they need to be replaced?

[Q45tech]

Not unusal for injector exposed to ethanol in gasoline to show out of range resistance especially when over a decade old.

Brand new injectors should last a while assuming the blend is water free.

The ethanol swells the plastic part of injector housing causing the internal connections to stretch thus higher resistance.

As the resistance increases the force of the solenoid weakens and the fuel takes longer to flow making the cylinder leaner until it finally quits combusting.

Cleaning high resitance injectors is a waste of money and most ethical companies recommend replacement.

If you buy used injectors KNOW which state and area they came from as currently some states don't have ethanol in gasoline.

"About 30 percent of all U.S. gasoline now contains 10 percent ethanol. Californians consumed about 900 million gallons of ethanol in 2004 and 2005, up from 750 million gallons in 2003."

[mesallem]

is it ok to run the car like that, or could i damage it even more, the reason i ask this is because my budget doesnt allow me to replace injectors right now, would i be able to do them myself? is it a very complicated job. also when im in drive it vibrates a lot, but say im at a stoplight, if i through it in neutral, the shaking almost completly disappears, is that still injectors?

[goody90q45]

.....would i be able to do them myself? is it a very complicated job. also when im in drive it vibrates a lot, but say im at a stoplight, if i throw it in neutral, the shaking almost completly disappears, is that still injectors?

It's injectors. You've got 4 bad ones, 2 marginals, and 2 good ones. Your Q is not going to run worth a darn until you replace the 4 bad ones and while you've got the plenum up you might as well do the other 2.

You can get refurbed ones for about $35/ea. Do a search in Infiniti Parts For Sale Forum for member PopPop. I'm pretty sure he's got them. The job's not hard but you better do a lot of reading here and understand what you're doing before pulling the plenum.

Don't feel bad. My 94Q parts car, which is leaving for the junkyard today, had all 8 injectors ohming at 22+. The engine ran like cr*p. Good luck.

[mesallem]

i kno its running like crap but can i damage something by still using the car right now? can i still run it without any furthur problems arising from it

[goody90q45]

I hate to be the one to break the news to you, but you picked the wrong car to own if you don't have cash in your pockets at all times.

You're putting a lot of stress on the 2-4 cylinders that are firing properly. I wouldn't drive it until I got it fixed. The 90-93 engines are fragile enough with the chain guide issues. You might be pushing the limit.

Check out Craigslist Sacramento and Craigslist SF Bay area. Right now there's 2 Q's for less than $500 each if you've got a place to store a parts car for a month. Grab the injectors, get them refurbished, keep whatever else you need and part out the rest. You'll be money ahead in the end. Good luck.

[mesallem]

shoot...anybody want to buy a 1992 q45 lol. im thinking of replacing the injectors myself, i have worked on a couple of cars before, so i think i should be ok

[mesallem]

would it stillbe the injectors if the shaking reduces in neutral

[Q451990]

Very possible... the bounce at idle is the most noticeable side effect of a dead cylinder, but you'll feel it differently depending on the load. Cruising down an hill with you foot off the gas may make it almost undetectable.

Heath