2 new writeups a la elwesso

[elwesso]

As promised I have the 2 new writeups as promised...... Enjoy (currently hosted on Q45.org)!!

Checking Ignition timing

Ohm testing injectors

Article manager: These are OK to put into infiniti articles section

[hal90000]

Many thanks, the article was printed and filed in the Q file for future reference.

[par2za]

ok question on timing adjustment. don't you have to disconnect anything to put the engine in base timing since the computer is still adjusting timing,by you just hooking a light on and turning the cas, the computer doesn't know your making the adjustment. so if im to adjust timing i need to unplug or do something to let the ecu know im making this adjustment. please let me know if there's anything else to do prior to making this adjustment.

[DAEDALUS]

Nothing to disconnect--the timing at idle is the base timing. But yes, the ECU does not know what the timing really is. Thus if you advance it 2* you will always be 2* advanced.

There are some caveats to method B that should be addressed regarding the effective waste spark. The timing light does not blink 1x every 2 revolutions like it should. More importantly, this means that any dial-back functionality on timing lights will not work with this procedure, at least not without a large range of dial and a bit of math.

[par2za]

not to keep questioning you but are you sure the timing is at base because if the knock sensors pick up a knock the timing is retarded thus telling me computer has control at all times. which means you need to disconnect something to put the ecu into base timing. as far as i know all vehicles obdI and II you need to unplug/jump somthing to put it into base timing.

[DAEDALUS]

Bad knock sensors do add another variable, but I don't think there is any reaction at idle; timing is altered under throttle only (advanced less). Temp is another factor, but only if you're idling at 195* or higher.The ECU has control over spark timing, but relative to what? We say degrees before top dead center of #1 piston, but the ECU only knows what the CAS tells it. The ECU wouldn't know if the crankshaft is twisted, or if the timing chain was stretched or jumped a tooth, or if the CAS isn't in the right spot. If there was complete feedback to the ECU for all this you wouldn't need to set the timing with a light, and the CAS wouldn't have been made adjustable.

[elwesso]

Nothing to disconnect--the timing at idle is the base timing. But yes, the ECU does not know what the timing really is. Thus if you advance it 2* you will always be 2* advanced.

There are some caveats to method B that should be addressed regarding the effective waste spark. The timing light does not blink 1x every 2 revolutions like it should. More importantly, this means that any dial-back functionality on timing lights will not work with this procedure, at least not without a large range of dial and a bit of math.

So are you saying that my METHOD B isnt as accurate???

[DAEDALUS]

It's as accurate as any of the other methods. Advancing 2* using a couple of marks 5* apart on the balancer is a good enough method I think. It's an inductive pick-up--the gun will flash when it detects a spark pulse, which is why you may have noticed the gun flashing *really* fast at idle.The problem is with using any of the simpler dial-back timing guns that aren't made to compensate for the "waste spark". This isn't unique to the Q, just something you need to be aware of if you own one of these tools.

[elwesso]

So basically what your saying is only buy inductive timing lights, right?

[DAEDALUS]

LOL I'm not familiar with any other kind.

Actually, I'm sure they exist, I've just never seen one. As you've demonstrated, these newer ignition systems are making inductive lights harder to use. There are much fancier lights out there, but I sure won't need one for at least a whlie.

[elwesso]

Pretty sure they'll make it so you have to pull the plenum or something to check the timing.. Make all the easy stuff hard and hard stuff easy...

[IvoryJ30t]

so the Q45 uses a waste spark ignition setup?

with the direct ignition and descrete triggering, i would have thought it did not.

[DAEDALUS]

Well, that's why it called it "effective waste spark" cause I didn't know what else to call it. There's no wasted spark in the plugs, but the results are the same when you try to measure the timing with a light. Because you're picking up the signal at the bank transistor unit, you have to compensate when using a dial-back light, assuming it allows you to dial back that far.

[DAEDALUS]

Pretty sure they'll make it so you have to pull the plenum or something to check the timing.. Make all the easy stuff hard and hard stuff easy...

Surely that's not the driving force behind automotive engineering. The technology just gets better and better. The fact that our tools get left behind is just a side effect of progress. We could all drive 20-year-old chevys and find all our tools for a buck each at garage sales.

[IvoryJ30t]

oh, ok. its just an anomoly when using the wire loop.

when you said waste spark, i was wondering why they would go through the trouble of setting the ignition up with descrete channels if the coils fire every revolution.

[par2za]

the system in question is not a waste spark its called a cop....coil on plug.its a sequential fuel injection and by being that the ignition system fires the plugs in the firing order. a waste spark system would be a system that uses a coil system that has one ignition coil firing 2 spark plugs at the same time one on compression while the other one in exhuast thus the term waste spark. the vehicle is equipped with a crank and cam sensors and yes the ecu can control timing at idle too. the variables are rpm, knock ,temp and throttle. so the system allways controls timing dont forget also on this system timing is used to control small variations of idle speed if it cant the iac(ide air control) will then be used to make the changes. that means if your going to make any timing adjustments you need to unplug or jump somthing to let the ecu know not to control timing. i will be back at work on tues and will look it up to see what the prucedure is to adjusting timing not saying that wes is wrong but i think theres a step thats missing. hell i can be wrong but ive been working with imports for many years (never really worked on Q45) and all of them always had a step to put the system into base timing before making the adjustment thats all im trying to say.dont mean to beat a dead horse but if theres a step to put it in base timing and you dont, you will over advance the system and possably damage the engine.

[elwesso]

Par.. Not to sound snobby, but I have LITERALLY memorized the section on checking timing, and there really isnt anything you unplug...

HOWEVER, this is very important... It lists at the beginning to make sure that basically everything is running right before you start playing with the timing.. Meaning knock sensors, injectors, coolant temp, idle is normal, so on and so forth... Basically you arent supposed to play with the timing UNTIL THE CAR IS running pretty much perfect...

[qship96]

wes,according to my 96q service manual,it says to disconnect the throttle position sensor when checking the base timing!

[elwesso]

It doesnt say that for the OBDI Q.....

[DAEDALUS]

the variables are rpm, knock ,temp and throttle. so the system allways controls timing dont forget also on this system timing is used to control small variations of idle speed if it cant the iac(ide air control) will then be used to make the changes. that means if you're going to make any timing adjustments you need to unplug or jump somthing to let the ecu know not to control timing. i will be back at work on tues and will look it up to see what the prucedure is to adjusting timing

Timing is also affected by signals from the CAS, MAF, speed sensor, throttle valve switch, gear switch, AC switch, power steering oil switch and battery voltage. *RPMs are not an input to timing*. Timing is not used to control small variations of idle. I have hard copy FSMs from 3 different model years, including for your '95, that all say the same thing. If the resource at work says otherwise, it's wrong and you might want to make a correction in it. While I can really appreciate your wide knowledge base as a tech, realize that this car is the only car that I, as well as others here, are truly passionate about.

[HeavyDuty]

Great writeup Wes, not to muddy the waters, but I too think there's one more step involved.

I saw a post here from Tech about forcing the timing change via disconnecting the TPS, I believe.

91> SR20's involve a warm start, shutdown, TPS disconnect, and 3 revs past 3000(?) rpm before returning to idle before a change will be accepted. Idle speed at setting makes a huge difference, too. Even if the cooling fan turns on it will change the idle.

JWT NOS ECU's on 91-95 SR20's, at least, have to be forced to accept a change by jumping two wires on the MAF harness.

[par2za]

wes your right i just installed my repair manuals in my computer and found nothing that says disconnect anything so your procedure is right. And no your not snotty. this is the first time i heard and saw a system that required you to do nothing to adjust timing. thanks wes for a great write-up too buddy you put in a lot of work in these forums keep it up. and sorry if i offended anyone here with my write-ups