SaiyanFury said:

OK I had a big problem with knocking in my engine. But Andy told me what the most likely problem was, and he was right! The Crank Pulley! To all people here, remember to replace the crank pulley whenever you do a timing belt!

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Tensioner too?

Did Andy explain why (I'm having some knock problems and am curious)? Is there a way to inspect the pulley to see if whatever Andy was talking about is happening to me (granted, I have a 2g)? I had my belt replaced 2 years ago (15k miles on it), but that was before I knew anything about my car (nothing about BS elimination, etc.), so I just had them do the belt. I still need to check my knock sensor, but I'm interested in all knock problems/solutions right now.

Knock can be caused by any excessive noise/vibration. A failing crank pulley can cause vibration and noise in the belt area, which the sensor could pick up as knock.

Other false knocks-exhaust leaks, lifter tap

Inspecting the crank pulley-it has rubber in it for dampening, and you will see it peeling away or cracking, then the pulley starts to separate, putting a hell of a strain on the belts. If you haven't changed the crank pulley in 60-70k miles, it's probably about time. I think mine made it around 60. It's a good "to-do" when you are doing the timing belt (just like the water pump).

weith1111 said:

Knock can be caused by any excessive noise/vibration. A failing crank pulley can cause vibration and noise in the belt area, which the sensor could pick up as knock.

Other false knocks-exhaust leaks, lifter tap

Inspecting the crank pulley-it has rubber in it for dampening, and you will see it peeling away or cracking, then the pulley starts to separate, putting a hell of a strain on the belts. If you haven't changed the crank pulley in 60-70k miles, it's probably about time. I think mine made it around 60. It's a good "to-do" when you are doing the timing belt (just like the water pump).

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Couldn't have said it better myself. Thanks for saving me the time!

Andy

weith1111 said:

Knock can be caused by any excessive noise/vibration. A failing crank pulley can cause vibration and noise in the belt area, which the sensor could pick up as knock.

Other false knocks-exhaust leaks, lifter tap

Inspecting the crank pulley-it has rubber in it for dampening, and you will see it peeling away or cracking, then the pulley starts to separate, putting a hell of a strain on the belts. If you haven't changed the crank pulley in 60-70k miles, it's probably about time. I think mine made it around 60. It's a good "to-do" when you are doing the timing belt (just like the water pump).

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Good info!

So these are all PK? Do any of these show up repeatably (I get timing dips at certain RPM repeatably at several boost levels - including as low as 9psi). I'm going to do the seafoam treatment in case it's hotspots and check for goo coming out of the knock sensor. Stupid question - Isn't the crank pulley internal? I just remember that when I dropped the oil pan (to fetch a zip tie I dropped into the head ), you had to be careful to use the short bolts on the driver's side end so you didn't tear up the timing belt - which tells me I can't visually inspect it. Sorry, but I don't have my manual at work.

kenamond said:

Did Andy explain why (I'm having some knock problems and am curious)? Is there a way to inspect the pulley to see if whatever Andy was talking about is happening to me (granted, I have a 2g)? I had my belt replaced 2 years ago (15k miles on it), but that was before I knew anything about my car (nothing about BS elimination, etc.), so I just had them do the belt. I still need to check my knock sensor, but I'm interested in all knock problems/solutions right now.

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Are you having mechanical knock (audible knocking sounds) or are you referring to your logger picking up knock (which isn't audible unless it's an extreme case)? Which one you have will define the strategy to find and cure it.

Let me know,

Andy

andymoraitis said:

Couldn't have said it better myself. Thanks for saving me the time!

Andy

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hehe. my name's andy too. i was just filling in for ya!

kenamond said:

Good info!

So these are all PK? Do any of these show up repeatably (I get timing dips at certain RPM repeatably at several boost levels - including as low as 9psi). I'm going to do the seafoam treatment in case it's hotspots and check for goo coming out of the knock sensor. Stupid question - Isn't the crank pulley internal? I just remember that when I dropped the oil pan (to fetch a zip tie I dropped into the head ), you had to be careful to use the short bolts on the driver's side end so you didn't tear up the timing belt - which tells me I can't visually inspect it. Sorry, but I don't have my manual at work.

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The crank pulley is the central pulley, it's exposed. It looks just like the PS, AC, alternator pulleys, but it's on the end of the crank, and has two pulleys. Think about how the pulleys get turned. They have to start somewhere, and the crank is the one that's moving everything else.

The crank pulley is not on the timing belt, it is on the accessory belts, to clarify.
http://www.plymouthlaser.com/timin.htm 4th pic down is a great one.

If you are sure your knock isn't real (low rpms, low throttle positions, off boost) and you are getting enough fuel, it's probably due to some engine noise/vibration. The most common reasons are the lifters or an old knock sensor. That guy should be replaced every so often. A brown goo will start coming out when it's had enough. And it will start picking up crazy knock (or worse not picking up any, even if it's real). Replace it if it's the original one.

Good luck.

for more info search "brown goo" (no joke) and "phantom knock"

weith1111 said:

hehe. my name's andy too. i was just filling in for ya!

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Oh great now there's two of us. This is going to be tough to sort out!

Thanks for filling in...

andymoraitis said:

Are you having mechanical knock (audible knocking sounds) or are you referring to your logger picking up knock (which isn't audible unless it's an extreme case)? Which one you have will define the strategy to find and cure it.

Let me know,

Andy

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I'm inferring knock from pulled timing in logs. The saga can be found here. It's up to 3 pages long, so I understand if you pass. You could just scan through and look at the logs I posted. Anyway, thanks a bunch for the offer!

Skimmed it a bit:

1. did you rewire the pump yet. if not, go do it.

2. did you try the part throttle thing to see if it's PK. i have a 1g so i could see the knock counts, but literally i'd have 43 counts of knock while at WOT, i'd let off to 50% throttle and then get back on it and the knock would be gone. you should be able to tell the timing is getting pulled just from the exhaust tone.

weith1111 said:

The crank pulley is the central pulley, it's exposed. It looks just like the PS, AC, alternator pulleys, but it's on the end of the crank, and has two pulleys. Think about how the pulleys get turned. They have to start somewhere, and the crank is the one that's moving everything else.

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Gotcha, I was thinking you were talking about a pulley on the crank for the timing belt (what's it called, by the way?).

weith1111 said:

If you are sure your knock isn't real (low rpms, low throttle positions, off boost) and you are getting enough fuel, it's probably due to some engine noise/vibration. The most common reasons are the lifters or an old knock sensor. That guy should be replaced every so often. A brown goo will start coming out when it's had enough. And it will start picking up crazy knock (or worse not picking up any, even if it's real). Replace it if it's the original one.

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I'm not sure of anything at this point. It seems to knock at a couple rpm values. The first is when boost hits (after the initial dip) at around 4k, and the 2nd happens in the 5k+ range. Since I can't log knock count, is there a method for testing for PK (uphill, half-throttle pull from 2k rpm or something like that?) I have lifter tick, but it goes away *usually* when the oil pressure comes up. I also thought about adding some octane booster (I can only get 91 here) to see if the timing dips are affected.

Thanks!

I gave it a quick scan and there's no way that a T28 should be outstripping the fuel system at 11 psi. I ran my old Big 16G at 15psi with zero knock on stock injectors and a stock pump.

I would follow Andy's recommendations as noted above, but I'd also like for you to try a couple of different things:

1. Run a hot compression test. Unusually high numbers can indicate serious carbon buildup from running on the stock A/F (9.5:1) and in many cases since these deposits are literally taking up space on the piston crown, they can cause cylinder temps to rise thereby triggering knock.

2. If you come up with fairly high numbers (please post them for us) I'd recommend a couple of Seafoam treatments to get rid of the buildup.

There's another great way to see if your knock is real. Throw some octane at it and if it goes away, it was real knock. If it doesn't then it's phantom, but judging by the timing curves in your logs and how much timing advance you're seeing, I don't think that's the case.

I would also strongly encourage you to feel the back of the knock sensor and make sure there's no goo coming out. A knock sensor is nothing more than a microphone and even if it's not failing, over tightening one can make it overtly sensitive.

Keep us posted on what you find out and just be systematic in your approach to rule things out before proceeding to the next variable.

Andy

weith1111 said:

Skimmed it a bit:

1. did you rewire the pump yet. if not, go do it.

2. did you try the part throttle thing to see if it's PK. i have a 1g so i could see the knock counts, but literally i'd have 43 counts of knock while at WOT, i'd let off to 50% throttle and then get back on it and the knock would be gone. you should be able to tell the timing is getting pulled just from the exhaust tone.

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1) Not yet. I tend to ponder new tasks for a while before I feel comfortable doing them. Looks easy enough, though, assuming I can get the relay at the local Radio Shack.

2) Not yet (see a trend?). I'll do one, but I might come back saying, "Okay, what do I look for in the log?" I'll see if I notice any changes in the exhaust tone.

kenamond said:

I also thought about adding some octane booster (I can only get 91 here) to see if the timing dips are affected.

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Bingo, now you're thinking like a troubleshooter! Try that and also check on the other items we mentioned. Even on low boost, 21 degrees of advance is enough to trigger knock on an 8.5:1 motor, especially if you have carbon buildup aggravating the condition.

For octane booster, I recommend the NOS Offroad formula. It will give you the equivalent of 96-97 octane when mixed with 8-10 gallons of 91. Don't try leaded gas if you have a cat.

kenamond said:

"Okay, what do I look for in the log?" I'll see if I notice any changes in the exhaust tone.

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I betcha it's NOT PK. Phantom knock would show massive timing pulls. Yours are a degree or two which equates to 10-13 counts of knock on the 2G ECU. For reference, here's how that works. At 7 counts, the ECU holds timing advance and for every 3 counts of knock after 7, it pulls one degree of timing (i.e. 10, 13, 16, 19, etc). By using a simple formula, you can tell exactly how much knock you're getting simply by looking at how much timing is being subtracted.

If we haven't mentioned it already, it might be a fuel volume issue as well. Changing the fuel filter if it hasn't been done recently is a good idea. So let's re-cap:

1. Add octane and see if knock goes away.
2. If knock goes away with octane added, it's real and NOT the knock sensor
3. If knock doesn't go away with octane added, it very likely is the knock sensor.
4. Run a compression test and look for unusually high numbers (over 180)
5. If compression is high, run a Seafoam treatment and re-test.
6. If compression is not overly high, replace the fuel filter if not done recently.
7. Re-wire fuel pump or add a 190 if funds allow.

Looks like you've got a few things to try.

Keep us posted,

Andy

andymoraitis said:

I gave it a quick scan and there's no way that a T28 should be outstripping the fuel system at 11 psi. I ran my old Big 16G at 15psi with zero knock on stock injectors and a stock pump.

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The pull that leaned out was at 15psi. I did a 2nd pull and it didn't lean out. That was (still is) confusing. I was planning on doing all of the other things (compression test, octane, check knock sensor, seafoam), so it's good to get confirmation. I can get 92 octane if I drive an hour round trip (Honey, can I drive to Santa Fe to fill up my tank?), so I'm wondering what your opinions are on octane booster instead.

EDIT: Read your post - Okay, octane booster it is.

So I'll feel for goo, warm up the motor, do a hot boost leak test (just in case), do compression test, then go from there.

Thanks Andys!!

One octane point isn't enough to help you rule out real knock. I would stop by your local AutoZone and pick up some NOS. Give it a little time to mix in or run the tank low and throw some gas in over the top of it to make it mix better. Better yet, put some in a 5 gallon can, mix it up with 5 gallons of gas and dump that in your tank. Either way, I'd do that over using 92.

Just thinking out loud here, but I'd also like for you to "read" your plugs and let us know what they look like when you pull them for a compression test. Pictures would be great if you can swing that as plug reading seems to be an overlooked method of tuning. No matter what, they always tell the whole story.

Hang in there. I'm sure we can get you through this.

A.

I'd agree too that you are not looking at PK. Phantom knock doesn't lower your timing, it KILLS it. This is probably a good thing, for your sake.

I'm a big believer in the FP rewire. I wouldn't overlook it, but the octane boost and knock sensor goo check should tell you if you need more/better fuel, or a new/not so sensitive knock sensor. I bet you'll find it's one, if not both of those.

Good luck again!

andymoraitis said:

Bingo, now you're thinking like a troubleshooter! Try that and also check on the other items we mentioned. Even on low boost, 21 degrees of advance is enough to trigger knock on an 8.5:1 motor, especially if you have carbon buildup aggravating the condition.

For octane booster, I recommend the NOS Offroad formula. It will give you the equivalent of 96-97 octane when mixed with 8-10 gallons of 91. Don't try leaded gas if you have a cat.

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I picked up Sea Foam over lunch break, but I was unsure about the NOS octane booster. They only had one type, and it said it contained NOX which puzzled me. It was some race formula, not the offroad formula you mention. My buddies from work were waiting in the car, so I didn't take too much time staring at all the different octane boosters on the shelf (couldn't find octane point info on any of them except the NOS). I'll head back there after work and take my time reading labels.

Any of the NOS boosters with Nitromethane will work fine. You just want to be able to crank up the octane by a few whole number values to see if that squelches knock. 3-4 octane numbers would even be enough to get a good idea.

I'm combining this thread with my original one in Tuning and Engine Mgmt (before it gets moved for me). That way both crowds can help through one thread. Two new pulls posted there, but I still have timing pulled in both.