Engine light coming on for awhile and then going off for awhile.

[robertbassin5]

I have a 1999 chevy truck with a rebuilt engine 4.3L V6. The engine has about 3000 miles on the rebuilt engine. But I keep getting code p0327 which is the knock sensor. My cuz works for Firestone and he check it out and it was working. The problem that I am having is that the engine light will come on for awhile and then it will turn itself off for awhile. Can't figure out why. Anyone have any ideas?

[MT-2500]

What engine?
The code is for a front knock sensor circuit problem.
It is coming and going.
You need to test it when the light first comes on?
Lot of wiring problems on them and always us dealer oem sensors.
Get a factory repair manual or all data online sub.
http://www.alldata.com/products/diy/index.html


A repair flow chart for that code will take you threw the test for repair.
Good Luck
MT

[Scrapper]

have you tryed resetting your computer? but it could be your thermostat or the sensor in radiator.but i would take it to autozone or some where when check engine lights on.just one little sensor can throw it off on your computer...good luck...

[robertbassin5]

My dad gave me this truck back in Feb 2008 and I had for less then a month when the engine spun a rear main bearing. My dad had the engine replace with a rebuilt one. When my dad had the truck for 8 years he never had the engine light do this.

[robertbassin5]

According to my cuz at Firestone my truck only has one knock sensor.

[ukrkoz]

CEL normally has nothing to do with parts and issues outside the emissions system. i do not think knock sensor is one of them. to me, it souns like you have 2 seperate issues - one for CEL, and one for knock sensor.
i'd start with resetting error codes and replacing fuel tank cap before you start the engine after that.
apperently, you need to replace knock sensor or, at least, check for good contact.
on V6 engines it is located in the transmission mounting flange portion of the engine block below the oil pressure sending unit. looking at the pic, it is across from the large white tag on the firewall, with the transmission disptick to the left of it, with 2 hoses between the dipstick and sensor. it looks like a cylinder with a nipple and lays horizontally.

[robertbassin5]

I have already replaced the fuel cap and had the computer reset 5 times already. And still the same.

[snooks]

I had a 1996 Chevy that did the same thing when I towed my boat (not a big boat, was a fiberglass bass boat). Everytime I towed the boat the service engine light would come on. It finally dawned on me to try 89 octane instead of the 87. Low and behold the problem ceased. I would have bet against that fixing the problem, but I know for a fact it did. Try it and let us know.

[lweford]

I had this very same problem with my 4.3 where the SES light would come on and go off. Everytime I had the cold checked it said knock sensor. After about 3 years I found the problem...bad sparkplug wires. They finally started breaking down badly under load. Replaced with a set of good wires and the problem was fixed. The "missing" under load and the SES light. I'd try it if I were you. It makes sense to have a knock sensor code if your "spark" isn't as hot as it needs to be. Let us know.

[j cAT]

Originally Posted by robertbassin5

I have a 1999 chevy truck with a rebuilt engine 4.3L V6. The engine has about 3000 miles on the rebuilt engine. But I keep getting code p0327 which is the knock sensor. My cuz works for Firestone and he check it out and it was working. The problem that I am having is that the engine light will come on for awhile and then it will turn itself off for awhile. Can't figure out why. Anyone have any ideas?

it is possible that the engine is making noises under load setting off the engine light...I would inspect plugs measure plug wire resistance,,,,and posssibly the engine is running too lean....could also be carbon in cylinders from engine breaking in...causing preignition..check for vacuum leaks...

[robertbassin5]

When the rebuilt engine was installed it was installed with new spark plugs, wires, distributor cap, and rotor. Checked for any vacuum leaks and there were none. I have already done the things you'll are saying and even carried it back to the shop where the engine was installed an they are stomped. And so am I.

[j cAT]

Originally Posted by robertbassin5

When the rebuilt engine was installed it was installed with new spark plugs, wires, distributor cap, and rotor. Checked for any vacuum leaks and there were none. I have already done the things you'll are saying and even carried it back to the shop where the engine was installed an they are stomped. And so am I.

did they measure resistance of wires??? new don't mean anything...I've found plenty of new wires that were defective...also are you sure the wires have the oem resistance or some other value....???? what type of plugs oem or some other brand????

[robertbassin5]

To be honest I don't know the brand plugs they put in there. I don't know if they are regular plugs or platinum plugs.

[j cAT]

Originally Posted by robertbassin5

To be honest I don't know the brand plugs they put in there. I don't know if they are regular plugs or platinum plugs.

The forum members have had plug problems most recommend ac delco...also the wire resistance is very important must be close to the OEM value....


there is the posibility that the knock sensor connectors are bad....this is common...

[MT-2500]

Several TSB's on the knock sensor check engine light to deal with the problem.

99-06-04-036 sept 99

Later revised 02-06 04-023A June 02.
Get a copy of them and see if they fit your truck and problem.
They deal with reprograming The VCM.
Good luck
MT