94 Jimmy knock sensor torque

[shanes76]

well I got the knock sensor today but cant find out what it is supposed to be torqqued too. Also is the 1 or 2 of these on my Jimmy? it has the 4.3 vortec VIN"W"

[old_master]

There are 2 knock sensors on your engine: One is located in the rear of the right cylinder head, the other is located in the left cylinder head between cylinders 3 & 5. The torque spec is 15 foot pounds. Do not use thread tape; the sensors need to be grounded to the heads and thread tape will insulate the sensors.

[shanes76]

what would the effect of not having one hooked up have? Would it cause a miss at idle? Seemslike a miss when trying to rev up also or does this sound more like a plug, cap, rotor button issue? The only code I'm getting is 43 and I know the knock sensor on the drivers side isnt hooked up cause the wire

[old_master]

I rather doubt it would cause a miss if it's not connected. Knock sensor output is between 4.5 and 5.0 volts. With the sensor disconnected, the PCM receives zero volts. The PCM monitors the signal from the knock sensors. If they detect a knock, the PCM retards ignition timing to all cylinders equally until the knock goes away, up to a maximum of 90 degrees. The greater the amount of retard, the greater the power loss. I suppose it's possible the PCM could go into open loop operation if the sensor is disconnected, but I can't say for sure. The system was designed with 2 sensors, it would be best to connect the new sensor. There are many differences from your 94 to 96 and newer systems. The 96 and newer 4.3's only have one knock sensor. I would assume GM determined only one centrally located sensor was all that was necessary. Your engine has a CMFI system, 96 and newer use CSFI and that most likely has something to do with it too.

Have you checked fuel pressure and leakdown?

[shanes76]

no I havent checked fuel pressure yet, a few days ago after cleaning the EGR and IAC, it ran better but still had a very small hesitation, then maybe a day later sitting in a drive thru it started poping real bad, Idling was terrible, would almost die then get a little better then almost die again, but at the point to where it shifts into 2nd and your giving it gas it smoothes out and runs great at 70 mph or even like 40 mph it runs smooth, so it hesitates at that one spot, I thought that maybe after cleaning the EGR and spraying some throttle body cleaner in the hole under the EGR it might have freed up some chunks or something, but also after cleaning the IAC and it messing up at the drive thru I checked the codes again and got one for the IAC, so I replaced it with one from a JY and it didnt show back up on the codes

[old_master]

Check fuel pressure and leakdown, it tells you a lot of things, takes about 15 minutes, and it's free. If that turns out OK, look at the tune up end of things: plugs, wires, distributor cap, rotor, fuel and air filters, PCV valve, etc. Post your results of the fuel pressure and leakdown tests.

[shanes76]

well Ill have to try and get the guages tommaro, cost 150 to rent them and kinda hard when you dont have the money to really to do that

[old_master]

This is not a professional one, but it does work:

http://www.harborfreight.com/cpi/cta...emnumber=92699

If you own a vehicle with CMFI or CSFI, and you plan on working on it yourself, this should be in your tool box.