Misfire help 2.9

[alwaysFlOoReD]

O² sensors are a consumable. ~100,000 mile lifespan.
Kill power to the injectors and try to start engine. Then look at sparkplugs for a wet plug. If you find one then you know which one is leaking.

 

[Terrys87]

I have cleaned and tested injectors using a 9 volt battery, a big syringe and a hose that goes over the end of the injector. I used some fuel injector cleaner in the syringe. I think I found it on YouTube. If you are suspecting an injector just open all the time, you really would not need a battery to test the opening of the injector. When doing this test/cleaning, you can actually put the hose on the end that the fuel sprays out and reverse flow it. I have it noted in another forum and would take a day or so for me to find it if you can't find it on YouTube.

 

[SenorNoob]

I bought one of the cheap Amazon kits when I changed the engine. Made cleaning plugs pretty easy. It had the benefit of working with a can of carb cleaner.

 

[I support common sense]

Ok, it is definitely burning something it should not in those 2 cylinders, if it’s getting less compression, it probably burns oil, but if the compression is fine then it is burning too much gasoline, those are the only 2 reasons I can think of, so either it is running rich or burning oil. Similar to what @alwaysFlOoReD said, try cutting fuel to one of your injectors and physically leaning it out.

 

[1990HossEdishun]

Update. Well based on you alls feedback I'll be buying a new o2 sensor next paycheck and in the meantime pulling the upper intake again to double check those new injectors. I suspect maybe some crud must have still been left in the fuel rail or got into the injectors when I replaced them last month. This is based on the compression being good again today. Will post another update when I get those injectors cleaned out again.

 

[gaz]

@1990HossEdishun
After reading the entire thread, you state that the issue started when you changed the spark plugs. No great expense, maybe just get another set of Autolite or Motorcraft plugs and see if it was the replacement plugs.

 

[I support common sense]

@1990HossEdishun
After reading the entire thread, you state that the issue started when you changed the spark plugs. No great expense, maybe just get another set of Autolite or Motorcraft plugs and see if it was the replacement plugs.

It does sound as though it happened after the op changed the plugs, however, plugs don’t foul themselves, then again I’ve never used super cheap spark plugs.

As for the crud in the fuel rail I don’t think that will cause it to foul a plug either, it sounds as though it’s allowing too much fuel into the cylinder and it’s running really rich choking it on extra fuel.

 

[rusty ol ranger]

Being the 2.9 is batch fire (meaning the ecm fires all 3 injectors on one bank at once) if it is indeed only fouling 2 plugs either you have weak ignition on those plugs (wires most likely) or those 2 injectors are stuck open.

If it was a sensor, FPR, or anything else making it rich you would be fouling all 6.

 

[I support common sense]

Being the 2.9 is batch fire (meaning the ecm fires all 3 injectors on one bank at once)

You learn something new everyday!

 

[89longbed]

I thought you had tested the fuel rail/manifold pressure but I guess that was a different thread. If you have injectors not closing completely the fuel manifold will lose pressure much quicker than if they’re all closing. Do you have access to a pressure tester? I have not been able to get the OEM brand that the parts stores rent to work with the Schrader valve test port. You could improvise but you need to take precautions so you don’t spray gas in your face.
Here’s a cheep and easy test you can do to decide if dirty injectors seems likely. Run the pump several times (KOEO) to fully pressurize the system. Check the pressure. Repressurize to full pressure, especially if you squirted fuel out the Schrader valve. Come back a few hours later and check the pressure. If it has noticeably dropped you likely have injectors that aren’t closing, but I suppose a faulty pressure regulator could also be leaking fuel back to the tank.

 

[1990HossEdishun]

Final update. When I repulled the fuel rail this two injectors were stuck open again. So I cleaned them out and reinstalled everything with another new gasket because it tore. Also reinstalled a brand new 02 sensor and just replaced the plugs one more time since I was giving O'Reilly's my money. Have driven every day since and gone up the the lake a few times and no loss of power, stutters, or fouled plugs! Weird the new injectors had plugged up again so soon but I think I got it licked finally. Thanks all for the help! On the other side it now holds fuel pressure much better. Before it would have to crank a while in the morning to start now. It fires right up as no fuel has leaked out. Even holds it for a couple days on end when I drive the wife's car one day. So I'm pretty confident those injectors being stuck open was the problem. Thanks again all.