ChuckH

After driving for what seems like forever (over a year) having to use premium fuel to avoid preignition on my X, I finally went out and bought a timing gun, figuring the timing was probably a bit advanced. What really drove me to this was Mosi constantly remeinding me at Moab that my truck sounded like a diesel! Anyway, thanks to OffroadX, I got the instructions to do this procedure myself and I was able to find a timing light on closeout for $16 at a local parts store. So, here's the procedure for anyone who may be experiencing preignition. (Note that I have not driven on regular gas yet to verify that's what was causing my pinging):


What you need:


Inductive timing light (cheapo one is fine).

12mm socket with flexible shaft of some sort.

Phillips screwdriver (short) for adjusting idle (if needed).


Locations of things you may or may not need to touch:


Adjusting nut for distributor is at the base of the distributor to the right if you were looking in from in front of the hood (driver's side).

Idle adjusting screw is at the back of the manifold on the driver's side toward the firewall. It's balck and actually goes into the manifold. It's also kind of hidden behind some hoses and stuff. If you look straight across from the brake master cylinder toward the side of the manifold, you'll find it.

Throttle position sensor is located to the left of the throttle cables if you were looking in from the front bumper area. There are two plugs there and the throttle sensor is the lower one.

Timing pointer just above crankshaft pulley.

Timing notches on crankshaft pulley. Notched at 0, 5, 10, 15, 20 degrees going left to right as you look at it from the front of your truck.

number 1 spark plug wire closest to you as you look into the engine compartment from front. It's labeled, so you can't goof!


Specifications:


Ignition timing: 15 degrees +/- 2 degrees BTDC.

Idle with throttle sensor disconnected: 700 +/- 50 RPM.
Idle with throttle sensor connected: 750 +/- 50 RPM.


What to do:


Warm engine until the temp guage is halfway (normal operating temperature).

Rev engine @ 2000 RPM for 2 minutes.

Reve engine to 2000-3000 RPM 2-3 times with no load and then let it idle.

Turn off engine and disconnect the throttle position sensor wiring harness.

Start engine and rev 2-3 times to 2000-3000 RPM then let idle.

Connect timing sensor to the number 1 spark plug wire.

Hook up the timing light power with the positive battery wire connected to battery and the negative to chassis or similar grounding point. Do not attach to battery negative or near fuel lines!

Aim light toward the pointer above crankshaft, pull trigger, and watch for the notches (or was it nachos?). Remember left to right goes 0,5,10,15, 20, which means you should be hovering around the second one from the right. If not, you are out of spec. (FYI, mine was hovering just shy of the farthest one right or about 19 degrees BTDC, also known as 2-4 degrees too advanced).

If necessary, adjust timing by loosening the distributor nut enough so that you can twist the distributor freely, but with some resistence. Check your progress with the light. Small movements make big changes! If I remember correctly (duh!), counterclockwise advances the timing and clockwise retards it (forgive me for not remembering for sure...you'll find out right away anyway!). Once adjusted, tighten nut.

Remove the power and ground leads of the timing light and then the inductive pickup from the spark wire.

If you're idle speed needs adjusting, you may as well do it now too. Again, I don't remember which way did what, but I think counterclockwise increased the idle. Mine was at 600 RPM when the sensor was disconnected, which is about 100 RPM too low. ALWAYS TURN ENGINE OFF WHEN CONNECTING OR DISCONNECTING THE THROTTLE SENSOR HARNESS!!!


That should be everything. Now go out and put regular gas in your X and save some money!

Sorry I didn't take pictures, but I figured if I could do it without pictures anyone can! If anyone sees any obvious ommissions from thee instructions, please let me know. I'll try and read through it again and think of my steps though. Good luck!

Afterthought note!!!: The wiring connection for the throttle sensor is a bit tricky. When you remove it you push the green piece as indicated by an arrow to release the connection and just pull it off. When you reconnect it you really have to push hard. I actually couldn't do it with my hand and had to get the handle of the screwdriver up against it so I could put more into it. When you push it in enough, it sill click and the green thingy will pop back out.

Also, since you will be doing this procedure while the engine is running, be careful of the radiator fan. Pulling the ratchet the wrong way or not paying attention could result in an accident you would rather not have. You have to lean over the fan too, so no loose clothing...especially ties (as if anyone would!).

__________________
ChuckH

Schludwiller

Yikes! You've been putting in Premium all this time? You probably could have bought a lift with the extra $$$ you've spent.

Nice post, but one question. Nissan wouldn't take care of this for you?

ChuckH

I was only putting premium in during the summer months (or mixing premium and mid grade) because using the A/C results in more load and more pinging. The rest of the time I was putting in the mid grade or regular and putting up with it. Actually, I had kind of forgotten about it until it warmed up and I started driving with the windows down again.

I didn't take it to Nissan because everytime I go in there they just blow me off. Also, they would have tried to sell me the 30K mile service and whatever else they could think of to screw me and would have charged me for checking the timing. I did almost call them today to make an appointment, but then I saw the timing light for $16 and figured what the heck. I don't really trust the dealer anyway and like to do whatever I can myself. If I continue to have problems I will take it to them though, since that would likely mean something I can't fix. Actually, I originally asked my Audi guy if he'd check it, but he wasn't interested in doing a job on something he wasn't familiar with.

A conversation at Nissan would go soemthing like this:

"My Xterra is experiencing premature ignition." :o

"Well Mr. Hedberg, I see that you have dirt in your engine compartment. Have you been driving your Xterra offroad?"

"No sir...I have a gravel and dirt driveway."

"I'm sorry Mr. Hedberg, but this mud up here on top of the manifold and in the fenders indicates otherwise. How do you know the timing is off on your Xterra anyway?"

"Well, it pings badly under load or when the A/C is on."

"Well Mr. Hedberg...that is normal and well within spec. No warranty for you! I see you're at 33K miles. Would you like us to check your suspension and change your oil for $300 and check the timing for another $50?"

"No thanks Mr. Service Nazi...I'll do it myself."

"Mr. Hedberg; not doing your 30K mile suspension check and oil change will void your warranty."

"What warranty?"

__________________
ChuckH

Philosopher

YIKES !!!

I can't believe the crap you guys go through at your dealers ... when I go to the dealer my service advisor always smiles at me and says "Have you gone off-road recently?" Cause he wants to hear my stories and such. And the service tech always says something to the effect of "Man I like this truck, what are we doing to it today?"

I guess I'm just really lucky.

ToeJam

Man, what dealership gave you this shit? I'm guessing it is Bellevue Nissan. My rig is there right now having the horn replaced. I've really been happy with their service and haven't had any problems. Go figure....

I was expecting them to give me hell because of the mud in my engine compartment. My answer to their "Have you been offroading" question was going to be "Yes, I've been running dirt trails just like Nissan does in its commmercials".....

Schludwiller

I wouldn't bother replacing the horn if you're going to continue offroading.

That thing gets clogged up very fast. Mine barely makes a sputter anymore.

Eventually I'll get an air horn back in the engine compartment, but for now I just rely on the old "INTIMIDATION FACTOR" to keep people away from my truck.

The ARB works wonders to keep people clear of your front end, and after I get the KMA on back I'm sure that will end any thoughts of tailgating too.

Synchro

maybe for the pacified northwest. but down here in DC, people still tailgate me and the ARB is more something to gawk at then be intimidated by. course driving here and driving out there are TOTALLY different. when iw as in portland people actually did the speed limit. we haven't had that since the 70s.

ChuckH

Well, they haven't really given me shit, but Bellevue Nissan hasn't exactly been all that helpful the last couple times I've been in there. It seems like if you just need an adjsutment or soemthing, they aren't interested in helping. When I went in because my steering weel could be pulled in and out, they replaced the steering column, but at first they commented that I probably damaged it by using it to pull myself into the truck because I'm a big guy. I thought they were going to make me pay for a new steering column at 10K miles! They did take care of it though and it's been fine for 20+K miles. I had gone in there several times for a rattle. Everytime, they;d go on a drive and write up a report, telling me they'd fix it on my next visit. Well, I'd get there the next time and they wanted to go for a drive again and write another report. Uh, you already did that! I just get the feeling that you actually ahve to have something broken and easy to diagnose or they don't want to take the time. L ike your horn: It was obvious that there was a problem, so they are fixing it. Heaven forbid they should ever have to hook up a diagnostic computer or soemthing! Anyway, unless I have a serious problem, I'd just rather stay away. I bought my truck at Younker in Renton, but they'd probably like to see me dead and cut my brakelines or something. OK, maybe not THAT bad, but I'm quite certain they would mess with my truck.

Schlud: People will still tailgate you with the KMA. Not only that, but you won't be able to see them behind you when they do. Sometimes I'm quite sure when I come to a stop, the car behind me actually stops under my spare! The problem with the ARB is that it's too much of a temptation for me. I can't count the number of times I've thought about using it to push people out of the way, or have thought of not swerving to avoid someone because I would like to see what the ARB would do to someone's door! This self control thing is killing me! :badass:

__________________
ChuckH

ToeJam

I figured that is what happened. I had to replace the damn thing, I was going nuts. I've had more people cut me off or do 20 mph in a 30 zone since the horn went tits up I was about to go postal. The stupid thing sounded like I had a cat strapped to the engine block and was pulling on its tail to honk.

So where are the horns anyway? The dealership said there were two and I can find the one in front of the radiator. Where the fruck is the second one? I'll just wrap a condom over them before I go wheeling again.....:hehehe:

ChuckH

The one up front is the one you use to get people to pay attention. The other one is for you "security" (note the quotes!) system and is located in the rear corner of the engine compartment on the passenger side and up pretty high...on mine anyway. It is still prone to water and dirt though.

Wrapping them may not be a bad idea when offroading, but reaching the front one isn't easy and, uhhhh, I'm not sure condoms come wide enough to fit over the born. Maybe they'll slip on sideways or you can ask for Super Duper Magnum size and really impress the chick at the drugstore counter!

__________________
ChuckH

Schludwiller

The second one is in your engine compartment by the rear passenger side. It's for the alarm.

Which is why my truck still honks ok when I arm it, but has the drowning toad sound when I'm driving.

xterrabull

Just thought I'd chime in on the ignition timing:
I adjusted mine (from 20 to ~16 degrees BTDC) about 8 days ago. The reason I checked to begin with Is that I had a serious MPG drop in mid-November (from 17.5-18.0 MPG to ~14.5 MPG (mostly freeway driving)). I tried everything (tire pressure, changed fuel filter, etc....) that I though might remotely affect it to no avail. I did not notice abnormal engine sounds as ChuckH mentioned he did but they may have indeed been there.
Anyways, before adjusting the timing I tried using 92 octane gas & found I got about 15.5-16.0 MPG with it.
Now after adjusting the ignition timing and burning through 1 1/2 tanks of gas, my gas mileage with 87 octane is...~16 MPG.
I guess it's tolerable, but I'm still mystified about the sudden MPG drop. I remember the good ol' days when the low fuel light went on at 285-290 miles instead of 245-250 miles like it does now.
Any suggestions out there?
Also, here is some food for thought: when I brought my timing back within spec, I too (like ChuckH mentioned in his post) had to adjust my idle RPM back up (from 600 to 700 with the throttle position sensor disconnected). Now, if my timing had been at 15 initially, and it SOMEHOW advanced to 20, wouldn't my idle RPM have gone UP from say 750 (with TPS connected) to 850 just as it went DOWN when I retarded the timing back from 20 to 16???
Did anyone actually read all of this entirely too long post????

ChuckH

Hmmm, my mileage only dropped after putting the A/T's on, so I don't know why you would have a sudden mileage drop. If you don't drive with your windows rolled down much or put a lot of load on your engine, you may not have even heard the pinging or maybe not have experienced it. Unfortunately for me, my ears are quite sensitive to things like that so I tend to hear things many people might not. Funny though, I can't understand people when they talk!

I do not know yet what kind of effect changing my timing will have on my mileage, but I had to actually try to make my truck ping today to get anything from it. I had the A/C on and throttled it at low revs to make it do it. Before it would do it everytime I would accelerate from a light, even with the A/C off.

I believe you are right about the idle speed and think that our trucks actually came out of the factory with the timing wrong. Besides, I can't even see how it could change itself. The bolt on the distributor was super tight and I doubt my timing belt jumped a cog or anything. Nissan did send an extra radiator cap in my skid plate as apparent compensation though. Imagine my surprise when I took the skid plate off the first time and there was a brand new extra radiator cap sitting in it!

BTW, I usually get about 16 to 17 MPG city driving and between 18 and 21 (21 if I stay at 60 MPH) highway with 31" Scorpion A/T's set at 34 lbs. I also drive fairly aggressively a lot of the time and have a manual tranny. Not rubbing it in, just comparing facts!

__________________
ChuckH

ChuckH

Apparently I can't add a photo to my other post, so here's what I came up with today. It's not great, but maybe it will help someone!

Attached Images

timing1a.jpg (63.9 KB, 1175 views)

__________________
ChuckH

KillerX

You didn't go to a larger tire size did you? It's entirely possible that you are just logging less miles due to a larger tire size and think you're getting lower gas mileage. If you haven't changed tires, then forget I said anything.