For the last few weeks my Evo has been starting on 3 cylinders when sitting overnight. As soon as it starts to warms up you can hear the 4th cylinder kick in. Here are the specifics.

- Same E85 tune for the last year and a half.
- Cruise and WOT trims are as normal as ever.
- AFR is very lean when running on 3 cylinders 16.0-19.5 until the 4th cylinder kicks in and then it hops back to 14.9. Logically this seems to indicate a bad injector or an injector not firing.
- Compression done a year ago was fine.
- Never knocks.
- Replaced plugs last week after issue started. Old plugs were copper NGK with 20k miles. They looked pretty normal with no signs of oil. Just worn.
- Coolant looks normal
- No significant oil consumption.
- No CEL ever (weird)

So I don't think its spark related or a leaky injector because its running lean. It also doesn't seem like a flooded cylinder with coolant either. It just seems like one of the injectors does not want to fire until its warm. Am I on the right track?

What should I do? I only get one shot in the morning each day to diagnose the issue. After that it runs fine. Should I just pull the injectors and inspect them or is there something else I should try first? What is the best and easiest method to figure out what injector is not firing?

 

are you running injector dynamics injectors

 

Ah forgot to post the injectors type. They are FIC 1050's.

 

How cold does it get at night?

 

Sinced tuned the car would always one crank start even in single digit weather. It's been around 20F to 45F in the mornings lately.

 

Sounds like a bad injector to me. the resistance is out of range until the engine warms up which warms up the injector bringing the injector, or even that part of the circuit, within resistance. Ohm out the injectors, you may be able to to tell which one of the four is not like the others. If not lookup when the resistance is for your injectors and see if they are in range.

 

It's "lean" because you have one cylinder pumping unburnt air into the exhaust. If that air has fuel with it and if it's getting spark is the question but the lean indication is likely a symptom and not the cause. If you have the P0300 code disabled, I don't think it checks for misfires at all and wouldn't throw a code for it.

New plugs and inspect the coils and wires is where I would start.

 

hmmm, how about e85 clogging the injectors. Lots of talk and pics on the forum. Pull the rail and have a look to see what you got. good luck.

 

I am not sure how to do this. I do all of my own work outside of clutches but the electrical side of things I don't have much experience with.

 

This is likely the culprit. I have been running E85 for about a year and a half. I would be surprised if there was not at least some buildup. I have another temporary vehicle to DD while I put the Evo down for maintenance. I have brakes, coil-overs (to replace blown struts), and this injector issue to fix in the next few weeks.