2 questions about '92 injectors: error codes 34 and 51

[kdkrone]

My car ('92Q with 120,000--injectors replaced about 25K ago--maintained by Jerry Tucker--two months ago, yearly inspection up to specs including injectors) woke up after work today with the check engine light on and running rough. I immediately opened the hood and played with the MAF connector but no luck. When I got home, I pulled the ECU and it beeped 34 and 51. I reset it, started the engine, and the light came on again after about 30 seconds. This time it was an intermittent, mostly on, engine maintainance light. The bottom line is that it seems like it must be an injector.

Four questions:

1, how damaging is it to the engine to run it on 7 cylinders? I need to make a 300 mile round trip this weekend. Is the vibration very destructive?

2. I think the injector connector is on the driver's side with a gray plug and connector with 4 red and 4 blue wires. It has a funny safety latch on it. How is it removed so that I can check the resistance?

3. now comes the embarrassing part--I don't own an ohm meter (sorry, Q45 tech) but I am willing to purchase one. Does anyone have any recommendations?

4. Assuming that I do, indeed, have a bad injector, is there any chance that it is just dirty and could be cleaned with some kind of gas additive or is that just wishful thinking? Am I looking at having to do major surgery to get at the injector or pay big bucks to someone to have it done? It is very discouraging, as I replaced the injectors about 25K ago and, if I remember correctly, it cost about 2K or more...

ThanksKen K

[maxnix]

1.) Not a good thing to do for even a short trip. How could you tolerate it?

2.) Check Ohm resistance through the harness connector.

3.) Fluke 179 or similar.

4.) BG44K might work, but usually a dirty injector won't completely kill it. CA gas is crap gas, unfortuantely.

[goody90q45]

Ken- Code 34 is knock sensors, code 51 is injector analysis. Don't worry about the KS for now, its a non-issue. The problem seems to be with the injectors. A $100- $150 Fluke multimeter is great if you're a professional mechanic or test rocket motors for a living (I do) but save your money. You can get a digital voltmeter for less than $15 from Radio Shack, Sears, or any auto parts store that will be 99.99% accurate instead of the 99.999% accurate Fluke (may be an exageration).

Ohming the injectors is simple. You've found the 8 prong plug on the PS of the engine. Follow the instructions in the pic and let us know the readings.

Does the Q run any better at freeway speed or is it missing badly at all speeds?

[kdkrone]

Hi, Mike

It is fine at highway speed. It is worst accelerating from zero; one can feel the missing. It idles a little rough, but not as bad as when I needed to have my MAF contacts cleaned!

I will pick up an ohm meter tomorrow and post the results. Thanks for the photo showing which is which.

I finally figured out how to detach the connectors from one another, but one of each pair of connectors has two flanges that attach it to some flat metal brackets and I did manage to snap off about 1/2 of each of the flanges of the knock sensor connector. It still is held on, though. I will have to figure out a way to release the injector connector from that bracket so that I can look at each pin instead of using a mirror...

(Tried calling but no answer or voicemail...you probably received my email as you posted here.)

Ken

[goody90q45]

We played phone tag tonight. Sorry.

Just steady pull and wiggle the connector and it will pull off the metal bracket. Be careful that you don't pull back more than a couple of inches when it breaks loose. From there just depress the clip on the connnector and wiggle the male and female halves apart. When your fingers go numb from pressing that clip use a small flathead screwdriver to depress it (easier on the fingers). They'll feel like they're bonded together until they finally start breaking loose.

From your description of the problem and the fact that the engine smoothes out at highway speed it sounds like injectors. I'm going to get flamed here but if you have only 1 or 2 bad injectors I'd drive her home. It will be interesting to hear your ohm readings. Make sure to do it on a cold engine.

I'm off work tomorrow. Up early and home until about 11:30am. Give me a call if you get a chance.

[kdkrone]

I checked my records. The first problem was at 86,000 miles and the mechanic installed a Bosch injector at that time (injector #4) along with new plugs (Nippondenso something or others. I remember he told me he had done that after the fact and I questioned him because of what I had heard on the forum about being sure to use OEM. I was also not pleased about the Bosch injector.)

About 2,000 later with a rough idle again I went to the dealership and then installed 6 new injectors and 6 OEM plugs (not sure why they only put in the 6 plugs instead of 8.... ). Unfortunately there is no indication of which injectors were replaced, as by my count, there is one original injector still installed. If there is some way to tell the original one, and if it is the one acting up, then that would make some sense of things.

Anyone know if Infiniti has changed the injectors from the original? Perhaps some external marking? (actually, I wouldn't know an injector if it hit me in the face, I must admit...)

ThanksKen

[goody90q45]

They're under the plenum and tough to see. You can follow the wires from the 8 pin connector to any of the injectors on the right side of the engine.

From what I've seen the originals are a light tan top and replacements are a light purple top or some other color if not OEM (red?). Hard to see it unless you pull the electrical connection off. At this point you need to get the ohm readings and go from there. With luck only #1, #2, #8 or any combination of those three is (are) the bad one(s). Easy to get to with minimal labor.

[kdkrone]

First progress note:

I talked with goody94q45 on my way back to Fresno. He suggested using Chevron injector cleaner, so I filled up and drove the last 70 miles with the cleaner. No change. Steady and/or flickering Check Engine light for the duration of the trip. Minimal, if any, vibration except under load.

I arrived at an appointment after the 140 mile drive and came back to the car 1 hour later. Purring like the kitten I love... and no Check Engine light...!!!!!!!

Coincidence? Does the Chevron chemical really work that fast? I don't know, but I ordered two injectors from Joe just in case. ..! I will still ohm the injectors and KS tomorrow and post.

Fingers crossed,Ken

BTW, does anyone know if the BG 44k injector cleaner is similar to that made by Chevron? Would it be silly or harmful to throw some of it in the remaining 16 gallons in my tank?

[kdkrone]

Preliminary results (engine hot and I will repeat it)

All injectors have a reading between 12.8 and 13.4 except #5, which is 19.8.

Well, if that holds, we know it is not the Bosch injector (that was #4); it is possible that it is the remaining original injector. Anyway, I will repeat with the engine cold.

I can't get a reading on the KSs (I had the meter common on the battery + and the red + probe on the KS prong) Not sure what is wrong, although 550K may exceed my meter (anyone have a manual for a Radio Shack Micronta 22-188??

Ken


Modified by kdkrone at 6:28 PM 6/9/2007

[Q45tech]

The KS is grounded thru engine........................the +12 battery terminal would no be a safe place to connect VOM .....................use -12 negative terminal.

[goody90q45]

I can't get a reading on the KSs (I had the meter common on the battery + and the red + probe on the KS prong) Not sure what is wrong.....

Negative probe of voltmeter to negative probe of battery.Positive probe of voltmeter to each of the two pins of the KS harness.

Hot or cold, it does look like #5 FI is going to be the culprit.

[Q451990]

To back up what has already been said... the OEM injectors on both of my Q's have been kind of a tan or almost army green color. The OEM replacements I purchased in 1998 or 1999 were purple tops.

The active ingredient in Chevron (with Techron) is said to be the same thing as what's in the BG44K, but the BG product is more highly concentrated. I would seriously consider a full pressurized injector flush or at a minimum running a couple of cans of 44k through it...

Good luck!

Heath

[kdkrone]

Here are the ohm results:

Cylinder 1 7 6 4 12.2 12.2 12.1 12.2

8 3 5 2

12.2 12.1 15.3 12.3

(See the repeat reading for #5 below...)

The knock sensors were as follows relative to the photo

345 ( see below) 566

(The 345 started with 295 and was climbing at increments of 1-2 every second. My hand gave out holding the probe at 345...! (I have NO idea what the slow increase in value means. Anyone have any ideas?)

The 15.3 is a little out of whack, but I am told by a mechanic friend that between 10 and 30 is OK.

Anyway, afterwards, I went out to check to see how the car would run; it had been about 20 hours since it had been driven. Light on, rough idle again. THE OHM READING WAS NOW 2.2 of #5!!

I have to think it is the bad one...

I have never had taken the plenum off and wonder if it is a beginner's job...

CheersKen

Modified by kdkrone at 10:42 PM 6/9/2007
Modified by kdkrone at 2:02 AM 6/10/2007

[kdkrone]

I checked at q45.org and I don't think I will tackle the plenum...! At least not while I rely on the car to be reliable and repaired relatively quickly. This one is for someone else who knows more...

Ken

[kdkrone]

Followup:

My wife went to help our daughter move out of her college dorm room near San Diego, so I decided to have Professor Tucker do the job. She was lucky: the injector worked well for the 300 mile trip.

He found that, indeed, #5 had high resistance and it was replaced. He also suggested replacing 2 Bosch injectors which had been placed 40K ago. The KS were both replaced and he replaced the fuel injector wiring harness. The Q is like new again.

Thanks to all for the help,Ken