High Knock at Low Loads

For the past month or so my LGT seems to feel a little jerky and not as responsive as it usually does. I assumed it was warm humid weather, but recently I found that the IAM was .875, so I knew something was up (tune setup to drop the IAM when there is small amount of knock present).

 

I did some logs and discovered that my car was having large amounts of knock under light loads without boost. Normally I would assume that this was just noise, but the amount of knock events and the fact that I can sometime feel it has me concerned. The issue is worst during light acceleration (.6 to .8 load), but also occurs even cruising on flats roads with cruise control .

 

Even when the feedback knock control maxes out at -11, the knock still occurs. Given that the knock is still occurring with low ignition timing I am thinking that I might have a problem with my motor. Any ideas or suggestions on what to try?

 

I posted a couple of logs just cruising along which shows the large amount of knock events.

 

 

Thanks!

4th gear cruise.csv

4th gear cruise 2.csv

accerating in 2nd gear.csv

First of all, stop doing pulls until this gets figured out. With the maxed FB knock correction you are effectively running 2 degrees of timing at WOT. That looks like false knock, so something is banging or rattling in the engine area. Check for loose heat shields, exhaust pieces, etc. A cracked ringland can supposedly make that kind of noise too, so any other odd symptoms with the car such as oil loss, smoke from tailpipe on startup, smoke from oil filler tube with the cap removed?

 

The jerkiness can probably be explained alone by that much timing being pulled

No more WOT pulls, as mentioned. Could be bad gas that takes a few tanks to get through before all is well again. contact your tuner and have him look at your map to make sure there are not any weird parameters set to change with changing IAT numbers. I would start with that. You can also log each cylinder and make sure you're not misfiring as well.

I don't think it is bad gas. Since I first noticed this issue in my logs I have filled up at least three times with 93.

 

I self tuned the car with support from some tuners on this board and RomRaider forums. Car has been running well for a long time. I have lots of logs from all different temps and this issue only started recently. I will take a look to see if anything is loose under the hood.

 

311logan311 - How do you log per cylinder? Is this the roughness monitor or the per cylinder knock sum which is present in the newer ECU's?

 

Infamous1 - I am thinking that a failed ringland might be the issue What's sad is that I hardly ever drove the car hard. My AFR's were rich and I had my knock strategy setup to project the engine.

I don't think it is bad gas. Since I first noticed this issue in my logs I have filled up at least three times with 93.

 

I self tuned the car with support from some tuners on this board and RomRaider forums. Car has been running well for a long time. I have lots of logs from all different temps and this issue only started recently. I will take a look to see if anything is loose under the hood.

 

311logan311 - How do you log per cylinder? Is this the roughness monitor or the per cylinder knock sum which is present in the newer ECU's?

 

Infamous1 - I am thinking that a failed ringland might be the issue What's sad is that I hardly ever drove the car hard. My AFR's were rich and I had my knock strategy setup to project the engine.

 

Yes, that's the parameter. Your learned a/f aren't bad at all. Like Shamar said, sounds like ringland. Log each cylinder roughness and see if one (or more) is misfiring.

 

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Could this also be tight valve clearances and/or burnt exhaust valve(s)?

 

If so, how do you tell the difference without tearing apart the motor? For example, do cracked ringlands also cause a lot of oil consumption, where tight valves do not?

If I recall correctly your turbo heat shield or something in that area was rattling last month when I did your suspension.

burnt exhaust valve will idle rough and show misfiring of that cylinder. log the roughness parameter for all 4 cylinders.

Defintely log cylinder roughness and see if it will isolate it to a cylinder or two.

I went out tonight and did some logging. During startup I had roughness in cylinder 4, but that went away after 2 seconds. For the rest of my cruise around town I had no roughness indicated in any of the cylinders. My knock was still present and I could easily generate a knock count of 20 + by very slowly accelerating up a slight grade.

 

I will take take a look in my engine bay for something rattling.

I went out tonight and did some logging. During startup I had roughness in cylinder 4, but that went away after 2 seconds. For the rest of my cruise around town I had no roughness indicated in any of the cylinders. My knock was still present and I could easily generate a knock count of 20 + by very slowly accelerating up a slight grade.

 

I will take take a look in my engine bay for something rattling.

 

Keep us posted. I am very interested in the outcome.

Make sure the grounds to your heads are attached and secured as well as both of your battery terminals are smug and secure.

Update. I found that one of the bolts holding my heatshield over the turbo was completely gone so it was a little loose. I also found that one of hose clamps holding on a heatblanket over the downpipe's cat had rusted and was just rattling around the DP.

 

I didn't get a new bolt for my heatshield just yet, but I thought that both of these things were the culprit. I went out tonight and the issue remains. Any time you apply a light about of throttle around 2K to 3K RPM the knock counter increases. I will get a new bolt but I don't think that will fix it.

I went out tonight and did some logging. During startup I had roughness in cylinder 4, but that went away after 2 seconds. For the rest of my cruise around town I had no roughness indicated in any of the cylinders. My knock was still present and I could easily generate a knock count of 20 + by very slowly accelerating up a slight grade.

 

I will take take a look in my engine bay for something rattling.

 

After your cruise, did you monitor roughness again at idle?

 

Also, when you said you noticed roughness on #4, how many misfires did it register during these 2 seconds?

Sounds exactly like my issue. Did you check grounds?

I checked the grounds and they all looked good. They were a little corroded which I think is normal for living in the East Coast, but none were loose or broken.

 

I put the missing bolt in my heatshield and double checked the engine bay for loose bolts. Went for a quick drive and the knock remains.

 

Should I get a compression check done? Any other ideas on what the issue could be? I never touched the knock sensor so I doubt it is loose.

Suggest doing both compression and leak down if you do test it. Leak down helps pinpoint things like valves or rings (compression just shows "something" is leaking). Not that I'm any kind of an expert so I'll let other's chime in.

 

Just FYI...I bought a compression gauge and a leak down tester (can get on Amazon (OTC brand) for around $100 for both) and borrowed a friends compressor to do the test myself. If you like doing that sort of thing you can save some $ (if you don't like that kind of thing, don't bother ;-). Taking the sparkplugs out is a bit of a pain though--the whole process will probably take a few hours if you've never done it before (removing sparkplugs, testing, etc.). What's also nice is if you have concerns, you can go back and test again anytime you want and you'll already have the tools. Also, I feel I now understand these tests much more and what they tell you (interesting to apply some light pressure and then run a cylinder through a cycle listening to air coming out exhaust valves (listen to exhaust), then intake valves (listen to intake), and then crankcase (listen through oil fill)).

Today I took the TMIC off to inspect the knock sensor. I was surprised to find a hose clamp sitting on top of the sensor. I thought this was clearly the issue, but after doing some logs the knock still remains:mad:

 

I also noticed that if I rev while in neutral I get around 2 counts of knock each time. The roughness count is 0 across all cylinders.

 

Any ideas where this hose clamp came from? It appears to be the same one used for my BOV.

Going to do get a compression and leakdown done.

 

Any idea on where that hose clamp could have come from?

 

Thanks

it does look like the bpv clamp. maybe at some point it was removed and the clamp fell where it couldn't be found, and stayed there?

it does look like the bpv clamp. Maybe at some point it was removed and the clamp fell where it couldn't be found, and stayed there?

 

+1

I figure that if knock persists after pulling 11 degrees, then it probably wasn't knock in the first place. It's still a bad thing, of course - if nothing else, it means that you can't trust your knock sensor, and it's kind of important to have that working properly.

 

I don't have any bright ideas though. My guess is vibration or rattling (or vibration causing rattling) but that's just a guess.

 

Good luck, though...

That clamp is locked in the open position, could have been there since day 1, someone at the factory dropped it?

 

Did you get the leakdown test done?

Got the leakdown and compression test done today. I was expecting to find one bad cylinder, not two

 

Cylinder 1 - 148psi / 1%

Cylinder 2 - 90psi / 50%

Cylinder 3 - 145psi / 2%

Cylinder 4 - 80psi / 56%

Where are cylinders 2 and 4 leaking from? valves or rings?