Jon94SE

I did a search and read into it a little bit but I wanted to get everyone's opinion specific to B12 Chemtool. Someone recommended it to me for pinging issues. I think it's a carbon build up issue. I tried Seafoam a while back and it helped smooth out my idle and what not but didn't do much as far as pre-ignition problems go. I was also hesistant on just buying it and putting it in because I read somewhere on here not too long ago that fuel additives can cause injector problems with these motors which brings me to my next question. I have the knock sensor bypass on a switch right now. I always use 92 octane and the car runs great aside from some pinging with the resistors on...but..if I have the resistors off, right when I get around 2000 rpm in second and third gear the motor hesistates and stumbles pretty badly for a few seconds and then goes again. From what I've heard that usually means injector problems, but why would it be affected by ignition timing? Especially LESS timing advance? Different fuel map for the lower timing or something? Anyway I'm wondering if anyone's used Chemtool for pinging and if it helped or not, and if it's going to hurt the injectors. Thanks!

braxsusriely

sorry, never heard of it. But then again i didn't hear of seafoam until someone posted it about a month ago. Far as i know our motors don't take well to much other than octane boost. But do you hear pinging or just the motor coughs? Maybe your fuel filter or pump isn't workin in tip top shape? My wife's 98 jeep does it too. They told her it was something electrical which leaves open alot of possibilites.

LvR

Known presence of ping and funky misfires/stumble/hesitation under acceleration is a sure indication that the KS is doing its thing properly - ie - protecting your engine by severely retarding your timing when knock/ping is detected.

If you already know the motor is pinging, then investigate the timing for a first step I would suggest - what exactly is it set at currently?Injectors doesn't know about ignition timing - not at all .................. they are in effect nothing more than simple/stupid high pressure valves controlled by an electric solenoid.

Alex_V

How did you use the seafoam? All in the gas tank, oil or crank case? You might want to try a full bottle in crankcase and see if that helps.

Oh and Id never put seafoam in the gas, its too errosive to our injectors. Most other cars sure but not maxima's. I always use techron inj cleaner it seems to be ok.

~Alex

hadman

iTrader: (21)

I use 1/3 of Seafoam in the gas, 1/3 through the brake booster, 1/3 directly in the crank. No negative issues at all. I don't believe 1/3 of a bottle mixed in with a full tank of gas is cause to worry about corrosion to the injectors.

Jon94SE

It has nothing to do with the knock sensor. My knock sensor has been inoperative for quite some time now, hence the resistors being there in the first place. I don't know how many degrees the base timing is at right now but it's turned down almost as low as you can get it. I know the injectors don't see ignition timing at all. That's what I'm wondering about. If the injectors ARE in fact going bad, why would they only have a problem when the ignition timing is retarded.

LvR

Your description made me think that with the KS bypassed things are OK except for the ping/knock - no? ......................... and with the resistors removed by flicking the switch (when you engage the KS) things go wonky - no?

If so then, even though the KS may in your opinion be "inoperative", its still "active enough" to trigger timing "retards" when knock/ping occurs (hard acceleration in 2/3 gear) .....................imo its this sudden timing delays that is causing your hesitation/stumble experience and not the injectors.

On my own and any other VG motor with a working KS and known good condition injectors, the exact same thing will happen if you have ignition timing advanced too far for the current combustion chamber conditions. If you want to be methodical about tracing issues and troubleshooting problems that is not an option - you need to know and be able to confidently state what the timing is for a fact. From your description I could easily assume you are running with 5 degrees ATDC timing atm because that is how far it can go .................... in which case your descriptions of your experiences are all completely useless and you will never get to the bottom of it all.Simple - they are not going bad - if they were you would have the same hesitation/stumble with the KS bypassed (if the stumble is indeed even caused by the injectors!)Why is it that you can so confidently make that statement?

Jon94SE

I can confidentaly make this statement because never before have I heard of anyone's working or not working knock sensor cause this kind of problem, also the fact my knock sensor has never allowed for timing increase (in-operative) and didn't do this...let's say four months ago. Furthermore there is no sudden timing change because I am not switching the resistors off while under acceleration. While I understand that this may not be an instantanious change, I'm fairly confident that the timing has been retarded by the time I get on the throttle. The marks go in intervals of five if I remember correctly. With the Cam Position Sensor being where it is I can say with reasonable confidence that it is on or around five degrees. Exact timing confirmation isn't really necessary at this point because it shouldn't be pinging with that kind of advance any way. I did introduce the B12 into the fuel system a few nights ago and have seen some improvment in the pinging issue.

LvR

Must say I am a bit confused now, and need to clear a few things.

1. Do you or do you not have a KS bypass switch? (when bypassed you run on the resistors)

2. Do you or do you not complain/compare the motor's performance between the situations where you have the KS bypassed vi athe switch and on the other hand not? (this because of "I always use 92 octane and the car runs great aside from some pinging with the resistors on...but..if I have the resistors off")

3. The KS cannot increases in timing - I never said such a thing - at best it cannot affect timing at tall (when things on the motor is normal and no ping/knock is present with a working KS), and at worst it will cause major timing "retards" (working KS and real ping/knock detected or a situation where you have a funky KS erroneously telling the ECU that knock/ping is present)

Understood - never said it happens because of that - but what is your answer to #2? 4. You gonna have to explain your reasoning to arrive at that conclusion - for the record - I disagreeThat is exactly my point - you dont know what the timing is and is currently assuming you are running at 5 degrees - if that is a fact I agree with your statement, but I have seen stranger things happen with supposed "known" and not confirmed timing setups.

These are just the logical points to consider before you start delving in more complex things like the mixture quality, EGR operation, air intake temperature, oil blowby in the combustion chamber etc etc.

Guess its up to you how soon you want to get to the bottom of it all ...............

Jon94SE

Let me explain how a Knock Sensor works. The Knock Sensor reports to the ECM with a resistance specification. If this resistance is within a certain range the timing is allowed to increase, from what I've heard about ten give or take a few degrees advance. In the event that the Knock Sensor should fail it will not put out the resistance needed for the timing to be increased there for the timing will remain in the retarded state untill the Knock Sensor is replaced (or in my case resistors are inserted into the Knock Sensor connector to trick the ECM into thinking there is no knock). When I say in-operative I mean just that. In-operative. The knock sensor won't vary timing in any way while defunct other than keeping it retarded. Above you had mentioned that I was experiancing a stumble due to a sudden timing change did you not? How is this possible when the stumbling is happening after I have already switched the resistors off and the timing has already been dropped? If you disagree with my confidence that the timing has already been retarded by the time I get on the throttle, (lets say about thirty seconds to a minute) how so? How long do you think it takes to back it off? I can tell you for sure it has already been backed off because, before this hesistation situation began the engine still had a dramatic loss in performance almost immediatly after switching off the resistors but no hesistation. Most likely due to a drop in timing advance no? Even if my timing isn't five degrees, it definatly not twenty so it doesn't matter. It shouldn't be pinging. I can't quite reason out your confusion. Yes I do have a Knock Sensor bypass. Yes I am complaining about the engine's performance between having the Knock Sensor bypassed and the Knock Sensor non-bypassed. You still haven't answered my question, you're debating what the knock sensor does when it's damaged or in-operative. It does nothing except retard the timing to protect the engine. We all know this. What are you getting at? Perhaps you have a CBL.

LvR

I see your good explanation but unfortunately that is not the way a KS works.

KS is a piece of piezo crystal that generates a voltage when mechanically excited - ie - a sharp vibration created by the engine knocking/pinging. That voltage pulse is used by the ECU to determine how severe the knocking is, and the ECU will take appropriate action by, insteps, reduce ignition timing. Resistance has no bearing on the operation of the KS at all - the only reason why the KS bypass needs a resistor replacement iso the KS is to prevent an open circuit situation on the KS input in the ECU experiencing sporadic rouge pulses.No - in fact, with a known working KS, the ECU will, in steps, progressively retard timing from its nominal value you have dialed in under engine idle conditions until knock is no longer detected - that retarded value is usually retained and operated on till the ignition is switched off at which stage the timing is once again exactly equal to the nominal value you have set it to (until the KS via the ECU triggers a retard situation)Wrong -it can and will - you are describing a single failure mode of the KS - there are many.

The rest of your post is irrelevant until you realize what the actual mode of operation and purpose is - any answer I give to your questions there does not answer a question based in reality - your questions are based on your incorrect understanding of the KS and its purpose.Well you see the problem? - if you don't know what it is you don't know what it is and speculation on your part is not adding facts to the environment you experience your problem in - in other word you are not describing the problem to which you seek a solution - you are describing wishful thinking.

Jon94SE

The Knock Sensor is the same as a microphone or speaker. If you've ever put an multimeter on a speaker and selected resistance you'd see that the resistance is the same untill you move it. Same theory behind the Knock Sensor. It is moved out of place during knock, changing the resistance being shown to the ECM. Therefore the ECM decides it's time to protect the engine...timing is backed off. How can a speaker produce voltage? Needless to say there's no means of induction. The Maxima's ECM isn't a super computer. It runs the timing up or brings it down. Once you've done more research we can continue.

LvR

My friend - we have been fairly civil till now, but when you are ready to start pulling your head out of your **** I will respond again - till then, enjoy your ignorance.

Jon94SE

Hold your response, and in the future please just don't even post in my threads. You've never actually helped me or anyone with anything you usually just try to argue with me about events that took place which has nothing to do with what I'm asking. If anyone else has anything constructive to add, be my guest.