where is this knock coming from?!?

[TType84]

hey guys im having a pretty bad knock problem..

i dont know where it came from, it just slowly started to happen.

but i have been getting pretty bad knock at 15psi now.

the fp is up.. i think its like 45psi static, at idle its around 40psi so you can tell its kind of high.

this problem is erratic. sometimes it doesnt happen. for instance i was trying to show 2 of my friends the problem on a freeway onramp.. the car pulled very hard from 0-100~ with no knock at all, no lights on the caspers gauge.

later that day, without them in the car, i went wot and had to let off as soon as the boost gauge hit 10psi, cause the knock gauge swung over to red as fast as the boost did.

it cant be a too much boost, not enough octane problem, i used to run 17psi in this car without problems, now i run 15.

it cant be a bad tank of gas, because sometimes it'll be fine and 10 mins later it will suck bad.

lately also on the highway i couldnt even accellerate almost, at 60mph+ if i were to go part throttle to even 5psi i would get RED lights on the knock gauge.

so far ive changed the filter, and today i put a fp gauge on the windshield and as the boost swung up the knock gauge hit a few yellows, but the FP was at SIXTY, yes 60psi.

i thought it was the FP reg going bad but im guessing its not if im getting 60psi fuel pressure. if the FP is up there, it couldnt be the reg or the pump or even the sock collapsing could it? the pump is a caspers hotwired 307 put in in 1999.

could this be bad injectors? i KNOW they leak down fast, and they do it so bad my car is a bitch to start with all of that extra gas in there.

there is nothing else it could be almost. any ideas? HELP!

 

[gnturbo]

I had the same exact problem last week,I mean exactly.I changed to a thrasher92 chip and it pretty much went away.I asked around and got little help.kind of a mystery thing I guess

 

[Richard Inglett]

Try Another Knock Sensor

TType84,

Because of the inconsistency of your problem, might be a faulty knock sensor; but, your injectors sound like they are in terrible shape. Just maybe, one or two injectors are getting stuck open and causing the low rpm knock problems your having.

Try the simple knock sensor change first but seriously consider doing something about your injectors.

Good luck,
Richard

 

[cmokem]

If your FP is set at 45 and you run 15lbs of boost the Gage should read around 60 lbs of pressure.....

If the knock happens under hard acceleration check that it is not false knock...downpipe, i/c etc...is your torque strap tight??
What about the ignition system...coil pack and module, oil in the up pipe, maf as was mentioned as well.

Just a few places to start
let us know what you find


Bob

 

[TType84]

ok guys, my friend has a set of 28lb injs lying around.. but they have been sitting for threee years or so.

should i even bother?

i heard injectors dry out and go bad after they sit for awhile..

 

[Joe Tiano]

camshaft and lifters worn???....

 

[snistrgn]

I had the same problem a few weeks back. I changed the coil pack and the problem went away!

 

[cmokem]

Try the easy stuff first..coil pack etc and see if it helps..a systematic approach is best with these cars.
HTH's
Bob

 

[Nocooler]

Nick, unfortunately you've gotta probelm that could be caused by many things or a combination of things.

Do the basics. Change the plugs and fuel Filter - check the coil pack, plug wires, hotwire fuse and verify TPS and alternator voltage.

Make sure its not false knock, add some octane.

Get some scantool data during all of your testing. Is it rich or lean? 45psi static is a little high on a hotair - but every car is different.

Last - check the mechanical stuff. Hows the timing chain, cam & lifters?

 

[TType84]

well, ill take a few causes off the list.

1. new fuel filter.

2. good hotwire voltage, 14.6 v

in any case.. its not fuel related up until the fuel rail

i have 45psi static and 60psi @ 15psi boost.

the fuel system excluding the injectors cant be the culprit

3. its not false knock, i can hear it ping when it happens.

4. timing chain is a year or two old.

5. is not a lifter tick.

6. i dont think a cam lobe went flat, cause if that was the case im sure this problem wouldnt be erratic.

the plugwires are MSD and brand new, TPS is set right.

the only thing it could be is the ignition or the injectors, and i dont think its the ignition, because ive had ignition problems before and they werent like this, they were more popping sputtering and choking, not the car pulling like a bat out of hell then randomly knocking and pulling back timing.

tomorrow im putting on a friends old set of 28lb red stripes..

they ahve been sitting for awhile but maybe they are better than mine.. if that solves it im buying some bluetops asap.

i will let you guys know how it turns out, thanks as always for all of the help!

 

[charlloots]

i could be wrong but i thought red stripes were 40lb injectors.

 

[3.8Illusion]

dude i had the same problem last month. i could run 16 to 17* on pump gas and no problem. i had put a red armstrong xp plus in early 2000 and last month i was getting bad knock. so i went through replacing every thing else because i thought their is no way it could die that fast. so after changing fuel filter, regulator, and had injectors flowed one thing left. i borrowed a fuel gauge that mounted on the hood. rule of thumb is it should go up 1* of f.p. for every 1* of boost if it drops your are going to get knock. I saw sometimes i would get excessive knock at as little as 3*. and saw some times no knock. when i did get knock the f.p. was dropping. all i can say is get a fuel gauge and watch it!!!

 

[Jon01]

I had a very similar problem.
When I first got the car, it could run about 15-16 psi on pump gas with very little knock.
Slowly got to the point that it'd only go to 12 with same knock, and even then it was borderline.
Then it started ticking and missing...flat cam lobe.