Code 51 Problem

[a.p.barron]

Hey guys/gals,

I started my car this morning and I noticed that the car was running very rough, and also the check engine light wouldn't turn off. Well, I just checked the ECU, and it threw a 51, which, as I understand, is an open injector circuit. So I have a few questions:

1. Is this an easy fix or am I going to have to pull the plenum?

2. Pulling the plenum for me is not an option, since I don't have the time, tools, or space to work on the car, so if I have to take it somewhere, is it safe to drive the car in this condition or should I tow it?

3. Anyone know any good places in the California Bay Area (the closer to Sunnyvale, the better) that specializes in Zs or would be a great place to take the car?

Thanks,
-Alex-

[BigTDogg (MA)]

Step one, do you have a multimeter? Set it to impedance, in a scale of Ohms, and test each injector. You can do so by poking the backside of the harness. They should be around 11 ohms IIRC if they're good. The one that's well above that is the bad one.

1) No, not an easy fix. You either have to dremel the plenum, or pull it. Dremeling is ghetto, and leaves metal shavings everywhere. Pulling isn't actually that hard once you do it once. Since you have old style injectors, the others aren't far behind. Blame the constant +12VDC from the factory and Ethanol from our idiot government.

2) Yes, because see #3

3) Z-Car Garage is in San Jose, about 15 minutes from you. Take it slow and don't drive it hard at all and you should be fine. Listen for pinging or detonation. If you have AAA or another towing service however, I'd have it towed. They did work on my car before I bought it (I got it from a guy in San Jose) and they are top notch.

[a.p.barron]

As a matter of fact, I do have a multimeter. I'll check it out when I get the chance.

Dang, I was afraid of that. Well, I contacted Z-Car Garage, and this sounds like it's going to be really expensive at their $106/hr rate. :-\

Thanks though. :-)

[BigTDogg (MA)]

CA is expensive for labor. Though not a Z specialty place, my mechanic charges $75/hr mechanical work, $85/hr electrical. Z-Car Garage and Specialty Z can charge a premium because they're some of the best Z shops in the country. Not only that, their overhead is higher, so they HAVE to charge more.

At least you know if you have them do it, it'l be done once and done right!

You may also want to see if a local member would help you with the job. If you have space, it doesn't require any real specialty tools.

[txQ45]

Using a consult or Nistune you could do a balance test .. and find the cylinder/injector that's down..
Suggest looking at the top feed injectors ,, handles ethanol better and cost a lot less than side feed injectors

[a.p.barron]

Ok, so it turned out that injector #3 was bad, so I got that puppy replaced. I also got a 90K service, since the person before me didn't seem to take care of the car. :-\ She's now up and running, and she purrs like a kitten.

One problem, so now, the car makes a noticeably high pitched hum that wasn't there before, which I am told is coming from the differential. The mechanic suggested I replace the gear oil with Mobil 1 75W140. So I have a few questions:

What are the chances that changing the gear oil will get rid of the hum? I believe he used Amsoil 75W-90, but I'm not 100% sure.
I think our Z's are spec'd for 75W90, so will the 75W-140 be too thick?
Is the Mobile 1 gear oil a good choice, or is it worth it to go with Redline or Royal Purple 75W-90 gear oil?

Any help would be greatly appreciated, thanks.

[BigTDogg (MA)]

Amsoil/Royal Purple/Redline 75W-90. /discussion.

[a.p.barron]

Well, since it already has Amsoil in it, should I just leave it alone and change it after 10k?? This hum is really annoying, especially when I'm going 65 - 70 MPH. Any ideas on how to get rid of it?

[Ace2cool]

Might be your driveshaft carrier bearing. Easy to check. Jack the car up, locate the center of the driveshaft where there is a bracket that the DS goes through, and try to move it up/down/left/right. If there's any play in it, it's bad, and most likely the cause of your hum/vibration.

Does it do it when you downshift and engine brake? If so, I'd bet money on that being the cause.

[a.p.barron]

There's no vibration, just a noticeably high-pitched hum. It happens when I'm moving/accelerating, and it gets higher-pitched the faster I go. It wasn't there before and only started happening after I got my 90k service. Since it has Amsoil 75W-90 right now and it's doing it, I'm thinking about going with the 75W-140, but I don't know if that will kill my car. :-\ I might even tryout the Redline/Royal Purple 75W-90. The hum is really annoying. :-(

[robomatic12]

It could be a wheel bearing, as you are driving along weave left to right (within reason of course) and see if it gets louder/quieter on one direction of turn. Leave the 75w90, if you want to put some new 75w90 that is all I would do, I would not try the 75w140.

[a.p.barron]

Great, thanks for the suggestions guys. I'll check everything out tomorrow, since I have the day off. :-)