brake lights & shaking

[2Q45]

Hay everybody,

I have this problem with my brake lights, the light on the wing light up everytime i step on the break but the two rear lights do not, when i turn on the lights the rear lights do come on, i checked on all the fuses there ok, is there something i'm missing could there be a short or something. Also i'm still having a problem with my Q shaking when the RPM's drop down to about 800 the car shakes, i had the timing done and it ran great for about a month now it's back to doing the same thing, what can i do to fix this. Thanks

[911/Q45]

Tail lights have two elements, one for the lights, one for the brakes. Check the bulbs. Shaking at idle is usually bad injectors.

[2Q45]

I had changed the light bulbs today and they came on for a little while but went right back off again, is there a short? And on the injectors what should I do, should I have all of the injectors and the hoses done or try to find the injector that's bad.

[911/Q45]

I've had mine apart twice to replace individual injectors, so I'm replacing the rest next month. You don't want to pull the plenum more than once, so get all the hoses too. No more ideas on the brake lights, but you can get a lot of good troubleshooting from an auto electrical shop for an hour's labor charge.

[2Q45]

where are the injectors?? are they on the left front side near the back by the fire wall

[C-Kwik]

For the electrical, use a multimeter to determine why the electrical circuit is not beong completed. It's likely a common source for the bulbs or a common ground. You'll probably want some help from someone when you test the positive terminal. If the parking lamp is integrated into the same bulb, there will be two positive leads. The metal shell that encases the terminal end of the bulb is the ground. Turn on the parking light. This should give you a voltage at one of the terminals. This will help you determine which terminal is which. Then, with someone holding the brake pedal down, test the other terminal. Use a ground on the body rather than using the ground on the bulb socket to make sure you are isolating that lead. If there is no voltage, at either brake light, then you'll need to follow the wires to a poit where they receive a common current. The problem will be anywhere from that point forward to the battery.

If you get voltage consistently, then try testing the ground at the bulb socket. Check for resistance between the ground at the socket and a chassis ground. There should be continuity. If not, you'll have to trace the ground wires. However, if you have integrated parking lights and they work fine, the ground is probably not the issue.

[911/Q45]

There is one injector per cylinder and they are located on the intake runners under the plenum on top of the engine. A few can be accessed without removing the plenum, but most are buried. Look for the wiring harness that has tags with numbers 1-8 that runs to each individual injector.

[jbob]

My daughter has a 1990 q45 with the same problem. Did you ever resolve yours? I'm looking at the purple relay that the wiring plugs into inside the rear body panel by the trunk latch.

[Q45tech]

Common for bad bulbs [new or used] to overheat and burn [melt] the contacts on their sockets [replace the assembly] and to melt or destroy the electronic assembly that measures idividual bulb current to drive the warning system...........replace or repair.

[jbob]

I appreciate the response. Bulbs all look OK, remove and replace normally. The small electric box/regulator (?) located inside the rear trunk panel by the latch appears to be the problem based on prior ability to bump/wiggle it and it would temporarily fix the problem. Is this the electronic drive for the warning system you speak of? At $90 I am hesitant to start blindly replacing components. I know you can't guarantee but does that sound like a reasonable shot at repair. My problem is exactly as the original description, where the rear window brake light comes on, but not the tail assembly brake lights. All other lights- running, turn signals- work correctly. Thanks for the response.

[maxnix]

So how about the sockets? And they are OEM bulbs, right? Might try a junk yard controller, but if you go new, go with Joe from http://www.everythinginfiniti.com from the column to the left.

And welcome to NICO!

[Q45tech]

Common problem and sequential destruction.......bad bulbs = bad sockets= bad diagnostic warning module.

Aftermarket bulbs even Sylvania don't meet oem Tohisba specifications........a few of the made in Germany ones come close......the made in Mexcio, China, Malaysia are so so bad.

The Bulbs with the "LL" extension after the model number come closest.

Finding quality bulbs is a serious task for the Q!!!!!!!!!!!!!!

[natsoundup]

inside the trunk box-- whatever it is called..

It cured my problem in the 90Q a couple of years ago... I have been ok with Sylvanias ever since....

[Q45tech]

Replace both rear bulb socket and the sensor driver module simultaneously or you'll just burn out the new module.

Finding a quality bulb is like looking for the Holy Grail because they designed the circuits too sensitive and didn't think about junk US marketed bulbs.......even dealers have trouble with locally sourced bulbs.

[2Q45]

Thanks 4 everything i will get to all of this on saturday.

[Jeff Williams]

If you haven't cleaned the intake throttlebody, it may just be a carbon build-up causing your rough idle. Take the plastic plenm hose off the throttlebody, and open the throttle. Use a screwdriver, to hold it open. Use about a fll oll of paper towels, and a full can of throttlebody cleaner, and clean until the runoff is clear.

This cleared up my rough idle.