missing and stalling

[swoop]

Hello all, I ve ahd a ongoing problem. My suburban has been miss firing and running badly. I changed the fuel filter added some heat to the tank to make sure the fuel didn't have any moisture in it. Also I added a bottle of fule injector cleaner to the tank as well. The hard start problem is taken care off as well as all the back firing sputtering and hesitation. The newest issue I have is after the engine starts and comes back down to idle it will stall out as soon as I put it gear. There is a miss that occurs every 10 seconds or so that I notice if Im not moving. While driving it on the highway I can hear it pinging horribly when I push on the gas. The check engine light came on for a couple of seconds and went back off with the issue still occurring. The code is a 43. I have a 89 sub. 5.7. The code chart says that it is the electronic spark control circuit. Would a loose timing chain make this happen? Or the control module at the base of my distibutor? Or what? Any advice would be greatly appreciated. Brian

[2000CAYukon]

A code 43 indicates that no knock signal was detected at Wide Open Throttle above 194 degree or there was a knock signal for more than 5 seconds during normal operations. You should verify that the knock sensor is working properly.

In Nov, I replaced the timing chain on my 90 K1500 5.7 because the timing would jump around while I was timing it. The chain was very worn! Put a timing light on it and watch the mark. If the chain is noisy, it could cause a code 43.

//2000CAYukon

[2000CAYukon]

I forgot to mention that I also had a miss but it remained even after the timing chain was replaced. It turned out that the stock coil was bad and it runs very well now with a new chain and new coil.

Other things to check are a worn out dist shaft and pickup coil.

//2000CAYukon

[swoop]

Originally Posted by 2000CAYukon

I forgot to mention that I also had a miss but it remained even after the timing chain was replaced. It turned out that the stock coil was bad and it runs very well now with a new chain and new coil.

Other things to check are a worn out dist shaft and pickup coil.

//2000CAYukon

Thanks for the info... to verify that the knock sensor is working properly, I would need to check the resistance and volts to the sensor? And how did you figure out that your pickup coil was bad?

[2000CAYukon]

Originally Posted by swoop

Thanks for the info... to verify that the knock sensor is working properly, I would need to check the resistance and volts to the sensor? And how did you figure out that your pickup coil was bad?

If you have access to a scan tool, you can see the knock count to see if it is too high or on all the time. The knock sensor is open (high resistance) when there is no knock and is closed (low resistance) when knock is detected.

In my case, I had a bad ignition coil (not the pickup coil which is inside the dist). After the new chain and gears was on, it still was not running right so I figured it was the ignition coil. Basically, I had a low end miss that would go away with higher rpms.

For the pickup coil, it usually will have a cracked housing and the coil gets rusty. You do need to remove the dist to see it.

Good luck.

//2000CAYukon

[swoop]

Thank you for the help. The scan tool is the tool that will plug into the harnesss under the driver side dash? If so can the vehicle be running to do this? Or is there another tool to check at the sensor. Like a volt meter? As far as the coil goes, I have a seperate coil off of the distributor. I pulled my cap the other day and looked for any bad signs, but the cap was dry and looked brand new. Im going to check my timing as soon as possible. If the timing jumps around alot then it leans towards a loose timing chain? Thanks again..

[2000CAYukon]

Originally Posted by swoop

Thank you for the help. The scan tool is the tool that will plug into the harnesss under the driver side dash? If so can the vehicle be running to do this? Or is there another tool to check at the sensor. Like a volt meter? As far as the coil goes, I have a seperate coil off of the distributor. I pulled my cap the other day and looked for any bad signs, but the cap was dry and looked brand new. Im going to check my timing as soon as possible. If the timing jumps around alot then it leans towards a loose timing chain? Thanks again..

Yes a scan tool plugs into connector under the drivers side dash. It can be used with the engine running and is useful for testing a knock sensor. With the engine running, you can tap the exhaust manifold with a hammer to see if the knock count increases. A volt meter can also be used but it may be hard to see how many times the sensor has reported a knock; however, you should be able to use a volt meter to see if it is stuck closed or never closes.

The separate coil off the dist is the ignition coil and mine was bad.

In my case, the timing jumping around was a bad timing chain. I am the original owner and it had 115K when I did the chain. I took a picture if you are interested to see how much slop was in the chain.

//2000CAYukon