Multiple misfire and no spark on two cylinders (2003 5.7)

[Knuckles]

I have found a lot of dead end looking for info on my problem and might have it figured out. I need some verification and help making sure I didn't miss anything.

My truck is a 2003 5.7l 4wd. with just under 150k miles

The problem started out as a PO357 while driving on the highway but still running fine. I bought some new NGK copper plugs and a set of denso wires. Gapped them and put them in. Plugs were very worn and electrodes were rounded off.

I cleaned up the connections on the coils where the spring is inside the boot and put some dielectric gel on them. I then swapped no. 7 and no. 1 coils incase 7 was bad since it is a lot easier to get to if this didn't solve my problem.

This made things worse. I then had codes PO300, PO351 and PO237.

I bought 2 new delphi coils because it was cheap and easy. I cleaned all grounds and replace positive and negative battery cables. Put them in with no change.

I am getting odd readings on the coil from pin to pin. I think I need a new meter but will "barrow" my fluke from work tomorrow to verify. The are inside coming up to temp. (in the 30s and snowing today)

Then I started looking for info on the problem.

I inspected connectors at coils and pcm and they all look fine. I have continuity on from coil connector to pcm connector (wire not broken) and nothing from coil connector to ground (not shorted).

I unplugged the 2 problem coils and put a spark tester on no.1 and nothing. I then put a noid light on the plug for no1. Turned the key and it started up but ran better then it did with the coils plugged in. I forgot to pull the fuel pump relay. The light lit up solid.

I think my old no.1 coil and the two new ones are still good.

To me it seems like the no.7 coil went bad and fried the pcm driver. When I swapped that coil to no.1 it then fried that driver.

Does anyone have any thought / comments or other things to test before I start looking for a pcm. I don't have a scanner to program it and was at my local scrapyard yesterday and check 15 different trucks and all had the pcms taken out already.

 

[kevkev]

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Definitely scan it and see if the driver is fried. Happened to me on my number 7 coil. Actually melted the coil.

 

[Sherman Bird]

I have found a lot of dead end looking for info on my problem and might have it figured out. I need some verification and help making sure I didn't miss anything.

My truck is a 2003 5.7l 4wd. with just under 150k miles

The problem started out as a PO357 while driving on the highway but still running fine. I bought some new NGK copper plugs and a set of denso wires. Gapped them and put them in. Plugs were very worn and electrodes were rounded off.

I cleaned up the connections on the coils where the spring is inside the boot and put some dielectric gel on them. I then swapped no. 7 and no. 1 coils incase 7 was bad since it is a lot easier to get to if this didn't solve my problem.

This made things worse. I then had codes PO300, PO351 and PO237.

I bought 2 new delphi coils because it was cheap and easy. I cleaned all grounds and replace positive and negative battery cables. Put them in with no change.

I am getting odd readings on the coil from pin to pin. I think I need a new meter but will "barrow" my fluke from work tomorrow to verify. The are inside coming up to temp. (in the 30s and snowing today)

Then I started looking for info on the problem.

I inspected connectors at coils and pcm and they all look fine. I have continuity on from coil connector to pcm connector (wire not broken) and nothing from coil connector to ground (not shorted).

I unplugged the 2 problem coils and put a spark tester on no.1 and nothing. I then put a noid light on the plug for no1. Turned the key and it started up but ran better then it did with the coils plugged in. I forgot to pull the fuel pump relay. The light lit up solid.

I think my old no.1 coil and the two new ones are still good.

To me it seems like the no.7 coil went bad and fried the pcm driver. When I swapped that coil to no.1 it then fried that driver.

Does anyone have any thought / comments or other things to test before I start looking for a pcm. I don't have a scanner to program it and was at my local scrapyard yesterday and check 15 different trucks and all had the pcms taken out already.

P0351 is a primary ignition control circuit code for #1. Changing plugs/coils for this code is done after testing diag tree says to. Make sure that your cylinders which misfire have good voltage at the coil for that cylinder.

 

[Knuckles]

Thanks for the replies. I changed plugs and wires because they were past due. I swapped the coils because they were dead. I have good voltage to the coils that are not firing but it is not pulsing. I ordered a pcm from flashmasters and a set of new coils. The number 7 coil must have failed and burned the coil driver. They were all original and rust was causing the laminated core to swell up.