Hunting for the misfire gremlin!

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

TruckMeRunnin

Newbie
Joined
Dec 11, 2017
Messages
1
Reaction score
0
Location
Washington
Ok so it's been a long hard road with this 97 GMC Sierra K1500 5.7L . Traded my Honda for it to a guy off Facebook market and got totally hosed on the deal. 5 days after the trade she was knock, knock, knocking on heavens door and that meant time for a new engine I was so happy..(sarcasm) I found a family friend with a 5.7 Vortec out of a Tahoe with 165k on it and picked that up and did the swap. Then the problems continued first it was the famous CMP offset, purchased Bluetooth connector and dash command app then adjusted it to zero and checked that off the list then it was misfires. Started as cylinder 5 only missing at low speeds like 5 or 10mph (I was reading the live data with my scanner) and the 5 miss is it's worst at idle but absolutely no misfire on 5 while driving then one day cylinder 2 started missing heavily at idle and while driving this was intermittent like I would drive to work truck would run like crap missing the whole way then drive just fine on the way home. This weekend I replaced spark plugs, distributor cap, rotor and plug wires #2 miss has disappeared but it has zero effect on the #5 miss at idle and low speed. I've heard some people saying intake manifold gaskets but these were replaced with the engine swap any other thoughts as to what would solve this or how to diagnose the issue with this cylinder?
 
Joined
Jul 6, 2017
Messages
26
Reaction score
0
Location
Mahopac ny
Hook your scanner up and look at the o2 sensor data and at idle on bank 1 see if it reads a little on the rich side with no real fluctuation in reading and then open throttle and see if it starts working normally and switches rich lean rich lean and if it does the injector for cyl5 is leaking
 

tom joyce

Newbie
Joined
Feb 19, 2017
Messages
42
Reaction score
12
Location
Scranton, PA
It's your ignition control module.
They can/do crack inside. Or a failed spark plug wire can mess up the solid state electronics inside the module by zapping the module with high voltage.
Only replace with Ac Delco. I had this exact same problem - replaced with an Autozone module and it lasted 2 days... Ac Delco module has lasted for 115000 miles and counting....
 
Top