marc_w Posted January 20, 2004 Report Share Posted January 20, 2004 It sounds like I'm getting some knock at high rpms, just before or 'right as' my truck shifts from 1st to 2nd. The knock I'm hearing just sounds like a quick spell of underhood clatter. Anyone else hearing this noise, or logging any knock here? Link to comment Share on other sites More sharing options...
n2opwr Posted January 20, 2004 Report Share Posted January 20, 2004 Sounds like spark knock. Are you running premium or did it occur while hauling something? You may have just got some bad gas. Link to comment Share on other sites More sharing options...
marc_w Posted January 20, 2004 Author Report Share Posted January 20, 2004 I run 93 all the time... Not hauling anything... Temps have been really low lately, and it's still happening. The knock I'm hearing has been happening for about as long as I can recall. I don't normally drive hard enough to get a high rpm 1st to 2nd shift, and I'm just starting to pick up on it. I think I posted something a few weeks back about how I thought we have some crappy gas here in MA. It seemed like every 1 out of 4 tanks of gas, the truck would run noticeably stronger, smoother, or cleaner, than usual. I was thinking along the lines that the 93 gas doesn't move as quick as the cheap stuff, and it sits around longer getting stagnant. (Gas prices are a little high here at ~1.80, so a lot of people buy the cheap stuff.) I can't track this down to any particular stations. What I cn say, is that every station up here runs MTBE in the gas from November to April or so. I hear this stuff is bad when it comes to performance and fuel mileage. I bought the truck November 1st, so I don't know the difference... Link to comment Share on other sites More sharing options...
Krambo Posted January 20, 2004 Report Share Posted January 20, 2004 What I cn say, is that every station up here runs MTBE in the gas from November to April or so. I hear this stuff is bad when it comes to performance and fuel mileage A noticeable difference when running the oxygenated fuel as far as "tapping" is concerned. Wait till May or fill up at a station in another state that doesn't run that crap. Link to comment Share on other sites More sharing options...
BenKey Posted January 20, 2004 Report Share Posted January 20, 2004 I get the same sometimes, but I don't record any KR at the same time. I know it's just clatter in my valvetrain. I only hear it when I'm in 4th gear and start to increase just slightly. Link to comment Share on other sites More sharing options...
Plwtwo Posted January 20, 2004 Report Share Posted January 20, 2004 Try this: Buy some Octane Boost and keep in your truck the next time you hear it, stop put in the Booster, then drive a few minutes so it can mix. Then get on the gas to see if it goes away....if so, or it gets better....bad gas...if not see BenKey above. Link to comment Share on other sites More sharing options...
deezel Posted January 20, 2004 Report Share Posted January 20, 2004 Yeah, I hear the occasional valvetrain chattering under load, but, like Ben said I don't record any KR with that noise. The KR I do see is often around a shift (like a 2-1 downshift from a 20mph roll), but I never hear any pinging or chattering noises with the recorded KR. (Overly sensitive knock sensors???) My KR is seemingly random - I can do 3 passes with no KR, then get one with - or just the opposite, some days I get KR on 3 out of 4 runs. My point... maybe your suspicions about bad gas are the same thing I am seeing - just the occasional random KR killing your timing. If you are running the stock progamming, the timing is pretty low... I doubt it is spark knock unless your gas is really really bad. Link to comment Share on other sites More sharing options...
Indianarandy Posted January 21, 2004 Report Share Posted January 21, 2004 I was going to start a topic about this. I have also noticed what I would say a clicking noise starting at around 4,000 rpm.It has been cold here also and I have bought my gas(at least 92 octane) at several different places lately because of the crazy gas prices.To me the sound does not sound like pinging as I used to recognize from older vehicles with just mechanical fixed timing.But I wonder if the sound I am hearing is the knock sensor adjusting(i am assuming our trucks have a knock sensor?).Today I bought my gas at my normal place and added a bottle of gas treatment for removing water.I think the noise has almost ended, but I need to drive more to know if this solved the problem. Great topic, anyone else having this problem? Randy Link to comment Share on other sites More sharing options...
marc_w Posted January 21, 2004 Author Report Share Posted January 21, 2004 Thanks guys. I was thinking of trying a bottle of octane boost stuff, but I wasn't sure if it was just snake oil or not. I may take a trip down to CT or RI (not too far away) and see what they got for gas down there. I hear NY is running the corn-based (ether something?) gas now, which is supposed to be better than the MTBE crap. What I'm hearing is just a quick short burst of clatter, right _at_ the shift. I thought it may have been just before, but it's on it. It's only on that 1-2 upshift at WOT. I don't think it's tranny lines or anything. They seemed to stay out of each others way pretty good when I got under there and interogated them. The engine could be torqing a bit at the shift, and the lines might be contacting each other. I suppose it could be valvetrain noise too... Maybe I'll go through the trouble to upgrade the spings before I toss in a cam this spring. Link to comment Share on other sites More sharing options...
deezel Posted January 21, 2004 Report Share Posted January 21, 2004 Another thought on this topic... I have been working up a calculated VE table to use in Edit based on my EFILive logs. My calculated VE table is quite a bit different from the stock one - and I don't have any significant mods (except tuning). Since the VE table directly affects fueling, this might explain a "lean spot" at high load. I will start a new thread on this... EDIT: I will post in the PCM programming thread zippy just started... Link to comment Share on other sites More sharing options...
SilveradoSS04 Posted January 21, 2004 Report Share Posted January 21, 2004 It does sound like spark knock, but do you think it could be that stupid Torque Management? GM has the pcm's pull timing big time right before all shifts-especially the 1-2 WOT shift. I don't think it's KR, due to you being stock-if you were supercharged, then maybe but not stock. You could go to Home Depot and by some xylene and try adding that. Or you could just go get your pcm custom tuned, that would probably fix it. Otherwise, I dunno what else to say. PM Zippy, he is pretty good. Link to comment Share on other sites More sharing options...
marc_w Posted January 22, 2004 Author Report Share Posted January 22, 2004 Thanks SilvSS04... I'm kind of just looking for a sanity check for myself, and maybe a point in the a RPM range to look at when I finally get around to getting some software and tuning. Link to comment Share on other sites More sharing options...
SilveradoSS04 Posted January 22, 2004 Report Share Posted January 22, 2004 There is also somthing called "false knock" where it looks and sounds and even feels like KR, but it's not. Alot of people with grand prix gtp's (that have the same engine as my Impala) experience this. Let us know what you find out Link to comment Share on other sites More sharing options...
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