A couple interrelated questions about knock sensors, ECU codes, etc.

[dubs96q45]

I have done my best to search for some specific answers to these questions and I have been unsuccessful. I apologize if they are redundant.

I have recently been forced to accept that my 96 q is not a repair-free anomaly. I inherited the car from my dad a little over 2 years ago(at 129,000), and was constantly impressed not only by how much I enjoy driving it, but also how little(none) corrective maintenance my 13 year old, well-powered luxury sedan with 137,000 miles had needed. My dad had owned it since 97 and took great care of it inside and out, and I would imagine that the total lack of problems is a testament to this. Since taking ownership I have had 3 oil changes/inspections w/ good oil......Then it happened.

The issue first reared its head one morning on my way to school, in San Diego mind you so it couldn't have been that cold. I started the car, backed out of my spot, and when I put the car in drive and tried to accel. the engine died. It started right up again and then no problems for a few weeks. Then one day it did the same thing at a stop sign when I had been driving it all day. Around this time the CEL came on and it occasionally began to do what seems to be considered bucking/jerking at random times(on the freeway, under 20 mph, right after start-up, after the engine had been running for a while, etc.). I took it in to my reputable local shop and was told it was throwing both KS and MAF codes. Recommendation was to replace the MAF and wait on the KS's. ECU memory was reset at repair, but CEL came back on a few days later. Since that time the bucking/jerking has become more frequent as well as some acceleration problems and since I think I can afford it right now I want to get it fixed so I can have my old q back.

Sorry for the long explanation, but I was trying to cover all the bases. My questions are:

-In the KS replacement tech article, it says that bad KS's will not throw a CEL. Does this mean that I have more problems than just this?

-I was hoping to find some OEM Nissan KS's online at a good price and I am wondering what if any issues I may run into obtaining them this way.

-In general, do the symptoms described above fit with bad KS's.

-I was thinking of doing the spark plugs at the same time, and while I have seen a few scattered recommendations, I was wondering if there is a list of things I should do while the plenum is off.

-Any other related issues/advise/recommendations that I have not mentioned?

-Lastly, is it possible to check codes on OBDII w/o a code reader? I can't tell whether the "ECU codes" article says it is possible to do the same thing for OBDI with OBDII.

Thanks in advance to any and all assistance. Again I apologize for the long post. I am a engineering major and tend to be a little to detail-oriented sometimes.

[goody90q45]

Take advantage of your San Diego sunshine while you wait for more responses and go out and clean up the MAF connector. Use a toothbrush and a small amount of penetrating fluid, electronic parts cleaner or brake parts cleaner if you have it. Coat the connector pins with dielectric grease and do the same process with the MAF pins. Finally, tighten up the pins on the connector to look like the middle pin in the pic. The connector should fit tightly with little wiggle.

You'll need to measure the KS directly to determine if they're really dead and you're fuel pump and FPCU are probably on their way out at 135K miles. Yes, you can check codes yourself with a $30 code reader or pull them off the ECU manually.

Do the easy (free) stuff first by cleaning up the MAF connector to see if it helps.


Modified by goody94q45 at 5:29 PM 7/21/2009

[Q45tech]

As I constantly point out my first 100,000 miles costs $8,000 including a $1,000 for 100k warranty, The NEXT 100,000 miles costs $19,600, the next 100,000 miles cost $14,400.

Remember things are designed to fail just after 100k to be cost effective for manufacturers. That it lasted this long is a tribute to your dads previous work.

[DrewQ45]

Take advantage of your San Diego sunshine while you wait for more responses and go out and clean up the MAF connector.-

If the problem turns out to be a bad MAF and cleaning doesn't help, I have two for sale. I've sold many and haven't had a bad one yet.

zer...r-g50





...Drew....

[maxnix]

Dear Dub, welcome to NICO!

1.) I have recently been forced to accept that my 96 q is not a repair-free anomaly.

2.) I started the car, backed out of my spot, and when I put the car in drive and tried to accel. the engine died. It started right up again and then no problems for a few weeks. Then one day it did the same thing at a stop sign when I had been driving it all day. Around this time the CEL came on and it occasionally began to do what seems to be considered bucking/jerking at random times(on the freeway, under 20 mph, right after start-up, after the engine had been running for a while, etc.). I took it in to my reputable local shop and was told it was throwing both KS and MAF codes. Recommendation was to replace the MAF and wait on the KS's.

3.) In the KS replacement tech article, it says that bad KS's will not throw a CEL. Does this mean that I have more problems than just this?

4.) I was hoping to find some OEM Nissan KS's online at a good price and I am wondering what if any issues I may run into obtaining them this way.

5.) In general, do the symptoms described above fit with bad KS's.

6.) I was thinking of doing the spark plugs at the same time, and while I have seen a few scattered recommendations, I was wondering if there is a list of things I should do while the plenum is off.

7.) Any other related issues/advise/recommendations that I have not mentioned?

8.) Lastly, is it possible to check codes on OBDII w/o a code reader? I can't tell whether the "ECU codes" article says it is possible to do the same thing for OBDI with OBDII.

1.) It almost is if one practices preventative maintenance. Your dad didn't. As time permits, start from the begining and read all of Q45tech's posts and follow all links. Study the 1996 G50 FSM. As a student of engineering, you will be delighted and learn much quickly.

2.) Bet you didn't take it to http://www.jerrytucker.net . Asking a non-VH45DE specialist about ECU codes is like asking me about the stock market.

3.) I believe in OBD II they will. Study the FSM.

4.) http://www.infinitipartsusa.com for Nissan

http://www.sparkplugs.com for NTK KS

Call both with your VIN.

Anything else is a crapshoot, emphasis on crap.

5.) No. But they do fit with lack of maintenance and cleaning of the intake and fuel path. If you guys knew what they were doing, they would have hooked up a fuel pressure gauge and recorded idle and WOT fuel pressures under load. You never mention changing fuel filters, air filters, norusing BG44K, Redline SI1, of ISO-Heet.

6.) All hoses, PCV and valve covers. Look at the inside of hoses before deciding to replace. KS harness and fuel hoses are a must. VC gaskets highly recommended.

7.) Mechanical ATF fluid exchange, PS fluid exchange, differential fluid replacement, auxiliary ATF cooler, OEM specification battery replacement, coolant replacement, and aforementioned filters, brake fluid, rotors and pads. Then there are the suspension bushings, upper links and shocks and gaiters.

8.) Yes, and you can solve second order differential equations on a abacus. But why would you want to? Get a code reader/resetter.

MAF cleanings are highly over rated because they are simple to perform and it is simple to screw up the hot wire element. Should not be required unless a K&N or other aftermarket filter was used or OEM filter wasn't changed frequently enough.
Modified by maxnix at 8:47 PM 7/21/2009

[dubs96q45]

goody94q45:

Thank you for the suggestion and the nice clear pic. It will make me much more confident that I won't screw it up........... I like free even more than I like cheap.

[dubs96q45]

Q45tech:

I will be selling or scraping this thing before I put $19,000 into it. That's enough for a good size down payment on a pretty nice car with a warranty. Nothing against it, I'm just a bit of a novice mechanic, I live in an apartment, and don't have the time right now to learn. After school maybe but right now I do homework 8-10 hours a day, 5-6 days a week. Not the best time to take on additional learning if you know what I mean.

Looks and sounds like your the expert though. The thought of driving a car with 300,000 plus miles is hard for me to even imagine.

[dubs96q45]

DrewQ45:

I just replaced the MAF with a new OEM. Thanks for the offer though.

[dubs96q45]

1.) It almost is if one practices preventative maintenance. Your dad didn't. As time permits, start from the begining and read all of Q45tech's posts and follow all links. Study the 1996 G50 FSM. As a student of engineering, you will be delighted and learn much quickly.

2.) Bet you didn't take it to http://www.jerrytucker.net . Asking a non-VH45DE specialist about ECU codes is like asking me about the stock market.

3.) I believe in OBD II they will. Study the FSM.

4.) http://www.infinitipartsusa.com for Nissan

http://www.sparkplugs.com for NTK KS

Call both with your VIN.

Anything else is a crapshoot, emphasis on crap.

5.) No. But they do fit with lack of maintenance and cleaning of the intake and fuel path. If you guys knew what they were doing, they would have hooked up a fuel pressure gauge and recorded idle and WOT fuel pressures under load. You never mention changing fuel filters, air filters, norusing BG44K, Redline SI1, of ISO-Heet.

6.) All hoses, PCV and valve covers. Look at the inside of hoses before deciding to replace. KS harness and fuel hoses are a must. VC gaskets highly recommended.

7.) Mechanical ATF fluid exchange, PS fluid exchange, differential fluid replacement, auxiliary ATF cooler, OEM specification battery replacement, coolant replacement, and aforementioned filters, brake fluid, rotors and pads. Then there are the suspension bushings, upper links and shocks and gaiters.

8.) Yes, and you can solve second order differential equations on a abacus. But why would you want to? Get a code reader/resetter.

MAF cleanings are highly over rated because they are simple to perform and it is simple to screw up the hot wire element. Should not be required unless a K&N or other aftermarket filter was used or OEM filter wasn't changed frequently enough.

Modified by maxnix at 8:47 PM 7/21/2009

maxnix:

1) Your right. He took it in for the "every XX,000 miles" type stuff and when it had any they that came up, but he was not one to work on his own car or do any major preventative stuff. I would love to spend some time getting savvy myself, but as I mentioned to Q45tech above, I have a little to much going on right now to really give the attention it deserves. Eventually.

2) You got me on that. The guy I went to is pretty good according to Yelp and from my limited personal experience, as well as being much closer. I know I should probably take it to Jerry Tucker for this kind of issue, though.

4) That's what I was afraid of. Glad I asked first.

5) I believe I had the fuel filter replaced with a "fuel system tune-up", but I'm gonna check all that stuff out.

8) I'm not even sure if I remember how to use an abacus, but I like the analogy just the same. I like technical challenges, but not as much as technical toys. I will be buying a code reader.

Thanks for the welcome and all the other good recommendations, etc. This forum seems to be what all forums should be. I will make sure to post my further experiences with this issue.

[Q451990]

Your '96 Q is the only one of the G50 series Q45 with an OBD II ECU, which means you're dealing with a somewhat different animal than most of us. So the knock sensors may actually throw a CEL in your case... I'm not sure though. Check the FSM (factory service manual) available for download in our library at http://www.nicoforums.com/FSM/

I seem to remember someone else with a '96 Q having bucking issues with bad knock sensors, and replacing them cured the issue.

If your MAF checks out OK, I would suspect the fuel pump. If it hasn't been replaced, I would think it's overdue. In my experience (with better gas than we have available today) the pumps tend to get noisy and pull more current at about 80-90K, although some have seen them last longer. The higher current draw causes failure of the tri-mode controller, which can also cause intermittant issues before completely failing.

As the pump ages, you'll typically hear something that sounds like a "hive of bees" coming from behind your back seat at idle. The noise will become more pronounced as your fuel level drops below 1/2 a tank.

Ditto on the comments about Jerry Tucker. I would definitely skip other shops, and even dealerships who see very few older Q45s at this point, and visit him if you decided to get more professional help.

Heath

[qship96]

defective knock sensors DO NOT illuminate the check engine lamp on the 96Q,and in my experience with defective knock sensors on my 96Q do not cause ANY drivability issues like bucking,stalling or hesitation.....after installing new ones, the only difference I felt was slightly crisper acceleration on light "tip in" throttle application. Read your codes, they will lead you directly to the subsystem that needs attention, one of the big benefits of the OBD2 system-a simple $50 Actron pocket scan code reader is a fantastic small investment for any owner of a car made in 1996 or after.

[maxnix]

defective knock sensors DO NOT illuminate the check engine lamp on the 96Q,and in my experience with defective knock sensors on my 96Q do not cause ANY drivability issues like bucking,stalling or hesitation.....

But a code is stored. CEL is basically a notice you are proceeding at your own risk. In ODB I, it is really saying you have already proceeded too far.