Hello everyone,

I have replaced headgastket seals, O rings, ignition coil seals, 8 ignition coils, spark plugs recently. Everything was okay but after few days while driving at 100 kms a strange vibration started and I can see my rpm drops sometimes in between. Check with computer that I m having a misfiring in cylinder 4, I changed the coil again but the misfiring isn’t going away. Strange thing is that the error isn’t showing now in computer.

need assistance

thanks

 

I hate to say it, but since you've already replaced the plugs and coils in that cylinder, the next step would be a compression and leakdown test.

 

try swapping the spark plug too, also take off the intake and look in the manifold to see for any obvious blockage or coolant, my manifold leaks coolant internally however i dont know why this would cause misfiring. check your fuel system as well as that could be the culprit, the new gaskets may have been slightly incorrectly installed so as the other guy said a compression test will probably be best as well

 

I tried everything, swapped coils, checked leakage, cleaned one spark which turned black due to less electricity supply in one cylinder, it worked for a few miles but the misfiring started again.

one thing is bothering me when I bought new ignition coils from showroom, they showed me two different part numbers, one was the stock one and second was mentioned as SUBS, I went for the SUBS one because they didn’t had the stock ones.

so what I m doubting that, can this be an issue?

 

Swap the spark plug from cyl 4 to cyl 2 to see if it changes which cylinder is misfiring. However if cleaning cyl 4 spark fixed it for a few miles but it acted up again it sounds like theres something thats gumming up the spark plug and not letting it fire. a cylinder compression test sounds like it may be necessary here, see where you can rent one from nearby, if your compression is bad you may need new piston rings or a gasket somewhere, in which case a leakdown test may be necessary to see if it is the piston rings or a gasket. if you have another car to drive for the meantime it may be a fun project to rebuild your engine, otherwise you can get a used one for relatively cheap online.

edit: i am by no means an expert and I am just trying to help, you might want a mechanic to look at it first before you make any big decisions

 

If # 4 plug is getting fouled causing misfire it also might be worth using a borescope to see how the # 4 cylinder walls are holding up. Is your car burning oil? Blue smoke?

 

No blue smoke, fuel consumption is same, no engine oil leak.

 

Clean the injectors off the motor

 

Check the connector for #4. Sounds like the 17-23 year old wiring has broken, probably when you swapped out the coils.

 

If you swapped coils and the misfiring stayed on #4, problem is likely your wiring and/or harness connector (even though substiture coils are probably poor quality aftermarkets) or the fuel injector on #4. You have to be VERY gentle on these old brittle wires. Someone probably cracked a wire, so when the engine runs, it vibrates the wire and causes intermittent connection.

You can buy a ignition coil tester like this https://www.partsource.ca/products/4...n-spark-tester then plug your coil into it and then you can visually observe spark firing pattern (or lack of) while wiggling the harness/wiring.

If your spark plug is fouled, that will also cause incomplete spark and misfiring, so you'll need to clean your plug or install a new one after you verify your coil and coil wiring is good.

If coil, coil wiring, and plug all check out (and problem stays on #4 when you swap coil and plug with another cylinder), then it's almost definitely something with the fuel injector, either wiring or injector itself.