Help! Knock sensor?

[Mr. Pickles]

This is borrowed from 94Path's post on his recent replacement.

 

Knock sensor post

 

"Sonuva... how long did this take you, and what would you rate it for difficulty on a 1-10. My Pathy started acting up last night. 94 with a 5sp and I just got it out of the shop with a new clutch, so money isn't so great right now. It runs and drives prefect, but won't idle to save its life sometimes. Not always, generally when its warm. I sputters and sometimes dies coming to a stop. Just pulled the codes and I'm getting 34, Knock Sensor. By the way, what does the knock sensor do anyways?"

 

 

So, I cleared the codes and drove around a bit. Same deal, code 34. And it barely lumps along with an idle of just a couple hundred RPM's. What does that senor control, and does it hurt it to drive it like that in the short term? I called Schucks (Checkers) and they quoted me $275! :o Mind you, I just blew $500 on the clutch yesterday and more on fixing our other car last week. Does anyone have a cheaper local source, or know about how much it would cost to have the work done? Its 6:30pm, so the shops I'd call for quotes are closed.

 

I need to get this thing back on the road (if it doesn't destroy the rest of my bank account) ASAP. We're going on a monster camping trip with friends next weekend, and its definately a 4wd required kinda deal to get in to where we're going. Help!

[MatterHorn]

the knock sensor senses any time there is detonation (pinging) in a cylinder (pre-ignition of the air fuel due to high temps) and tells the ECU to add fuel to richen up the mixture, which when you add more fuel, the ionization effect of the fuel actually lowers cylinder temperature, and prevents preignition. 275 dollars doesn't sound right ... have you tried asking the dealer first? maybe they were pulling the wrong part number up there at 'schmucks' (wouldn't be the first time)

 

the only problem is that the sensor is located beneath the intake in the valley of the 'V' for your engine ... which means you'll need not only the sensor, but new intake seals as well and you are looking at prolly a 2-3 hour project if everything goes right ... driving it that way really isn't an option ... you could cause pitting and actual cracking of any pistons or rings because of the detonation, and then you will have a real problem ...

[Mr. Pickles]

Does it sound right that it runs fine at any speed other than idle? Also, I don't hear any detonation but who knows on that front. Ya know what, the extra fuel makes sense. I seems to be pretty dirty earlier today when putting the hammer down. I could see exhaust in the middle of the day. darn darn darn darn darn. Gonna try the stealer and other parts places tomorrow to hopefully score a deal.

[MatterHorn]

well ... if it is giving you an actual code, there is really only two things that could be wrong with it - either the knock sensor is really messing up on you, or the ECU or its wiring some where are messed up ... that's the only real thing I could think or, without actually being there to check it out ...

 

but as always, verify timing, wiggle all the sprak plug wires, check fluids and maybe even pull the cap to see how it is wearing ... that would just eliminate all that ...

[Mr. Pickles]

well ... if it is giving you an actual code, there is really only two things that could be wrong with it - either the knock sensor is really messing up on you, or the ECU or its wiring some where are messed up ... that's the only real thing I could think or, without actually being there to check it out ...

 

but as always, verify timing, wiggle all the sprak plug wires, check fluids and maybe even pull the cap to see how it is wearing ... that would just eliminate all that ...

Well, checking it in daytime, the computer looks like it putting it into limp mode and dumping in gas to fight off (imaginary?) detonation. So yup, I'm going to go through the ignition stuff tomorrow. Cap & rotor are only about 2 months old, as are the plugs, but the wires are old. Is the wiring to the sensor accessible without tearing into the motor? I'm not sure what to look for there. Time to check and double check everything. Also, I just left Napa and then talked to the shop that just did my clutch for super cheap. The sensor is running $169 (better than $275 from Schmucks, but still crazy for such a stupid little part) and he says they would run about $120 in labor for install. That's sounding pretty reasonable to me at this point, if all else fails. I just don't have the time or garage to dive into it, especially with the big trip coming up in a few days.