97 gm 5.7 Tahoe misfire originally on cylinders 2 and 8
changed spark plugs wire, distributor cap and rotor, then misfire went to cylinders 3 and 5 on scan
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Po300 is a multiple random misfire there several things that cause this GM had an issue with the coil wire arcing to the transmission dipstick tube the new routing is to go over the plugs and remain on the inside of tube (old way was behind) USE a new wire. #2 dirty fuel (water contamination) As for the p1345 code this could be caused by ignition arcing inside Distributor Cap I would suggest replacing cap and rotor Clear codes This code will set once engine has gone over 1000 rpm's it updates every time to get spark advance correct if sets again distributor has moved this can be reset with a gm specific software scanner under camshaft offset specs 0 degrees to +4 max.
Gas or compression. Check the injector circuit on 1 and 3. Are they pulsing, to put gas in the cylinders? Do a compression test to rule out loss of compression as cause for the misfire.
Kind of odd it would be 1 and 3, but that is one right after the other in the firing order of 1-3-4-2...so, you have a single coil? So you have a distributor-examine closely the distributor cap and rotor if those were not changed too, with the plugs and wires. Look for damage, little black tracks that indicate shorting of the spark, maybe damage at the electrode tips on the inside of cap on 1 and 3 plug wire towers. Most people change the cap and rotor when doing the plugs and plug wires.
Just a possibility also, that the injector ground wires for 1 and 3 might share the same ground. That is to say, they might splice together before going to the computer where the computer internally grounds injector circuits to cause pulsing. Well, those are my thoughts, good luck. And let me know what you find, always interested.
change spark plugs & wires & coil packs to cylinders that are firing & if those cylinders start misfiring it is one of the 3 i do them one at a time if you have a distributor change cap &rotor
Cylinder #2 is the the second spark plug counting from the right to left.
EX.Below are spark plug on engine
engine
-------------------------------
' (oil cap) '
' (4) (3) (2) (1) '
'_________________'
Your misfire can be cause by couple of things but the cheapest way that you can try to fix your car is to do a tune up by replacing:
1)all spark plugs
2)do a oil change
3)spark plug wires
3)distributor cap and rotor
note misfire can be cause by:
1.bad gas
2.spark plug and/or wire
3.distributor cap and/or rotor
4.valve adjustment
5.injector
6.off timing
7.ECM
8.bad wiring(power, ground or feed line)
You may have got the spark plug wires out of sequence.
Reseat the coil wire going to the center of the distributor cap
Check the spark plug wires at the distributor against the firing order as follows:
The spark plug firing order is 1 - 4 - 2 - 5 - 3 - 6
The distributor rotor turns CLOCKWISE The engine cylinders / spark plugs are numbered :
firewall 3 - 6 2 - 5 1 - 4 front
Best wishes,
TF
If you already replaced the wires, I would suggest replacing the plugs, distributor cap and rotor. They are also very important parts of the spark. Fuel injector problems can also cause misfires.
Do an injector balance test and a cylinder leakage test. Lets make sure its not fuel related. Most important lets make sure you don't have a vacuum leak.
Sounds like your timing is off when you placed the distributor back in or your spark plug wires are crossed. Start with the simple and check the spark plug wire firing order. 1-8-4-3-6-5-7-2 Cylinder numbers drivers side 1-3-5-7 radiator to firewall. Cylinder numbers passenger side 2-4-6-8 radiator to firewall. Distributor cap #1 is at 5 O'clock and rotates clock wise. Once that is establish to be good then make sure the cylinder 1 is at TDC with the distributor rotor at the #1 position. Good luck and hope it's a crossed firing order.
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