Quick update. I am waiting for my new plugs to come in today. I pulled all plugs on the driver side and also changed out coil wire. I did test it with a voltmeter and it was bad. It was also routed from the coil on TOP! of the thermostat housing. I rerouted the new coil wire the correct way and also put that wire conduit protector on it to help protect it.

Wish me luck. I hope that after I change the plugs and after changing the coil wire that the misfire P0303 goes away and I can proceed to the steering column fix.

 

Well changed plugs and wires and still get the misfire p0303 code.
After going through the DTC P0300 Engine Misfire Detected steps in the FSM I need to go to the Fuel Injector Coil Test. Since I am 99% Certain it is a clogged injector I am going to change the fuel filter and order FIC LT4 injectors from the Vendor on this list. I just don't see the benefit of changing one and also going through the whole process of taking off the fuel rail change cylinder 3 injector and then the others OEM Multi Tec injectors go bad. Here are some pics.

I had to drill out one of the t15 Trox screws. It looks like someone was in there in the distant past since it was stripped and one was missing. I want to disconnect the fuel lines before I change out the fuel filter to relive pressure at the fuel disconnects on the fuel rail.

Here are some pics. I also found a wasp nest at the top of the fuel neck!

 

Is the spark on #3 still an "orange yellow" color? If so, you're probably dealing with an opti cap issue (assuming the other plugs are sparking blue).

 

RUU, thanks for the tip. I am going to test this tonight before pulling the trigger on the Injectors.

 

Did the Spark Test on Cylinder 3 and 7 and they looked the same. Light Orange/White Spark. Looked like a strong spark to me, so I am going to rule out Opti. I am going to order Injectors from Jon at FIC. I am going to pull fuel pump out for sock inspection and also change fuel filter before hand. I am also going to inspect tank and gas. Oh well .. the saga continues!

 

In that case, can you swap the #3 injector to another cylinder and see if the misfire follows it?

 

I was pretty sure there is a way to remove the basket strainer inside of an injector and clean it?

 

I was thinking about that. Just don't like doing things twice. I might try and do it tomorrow.

 

I am going to pull it tomorrow and see if I can pull the strainer out and then hopefully find out if the parts store sells the basket strainer.

 

Did not look that bad to me. I will change the gasket and the Fuel Strainer then filter and then change out or clean injectors! Wish me luck .

 

Keep a eye out FIC likes to put sales around holidays. Inspect your plug wire and look for sparks in the dark.

 

Thanks AF. New plugs and wires no northern lights as of today. I am going to start wrenching soon. I hope to have an update late today! Wish me luck.

 

No luck needed you have the love. Just know when to walk away for a bit. and do not twist the injectors you can nick the orings and have a barbeque.

 

Cleaned the injectors up and swapped injector one and 3. Cleared codes now need to run it a little to see if code comes back wish me luck. Oh yeah found a heater hose near the water pump had a pin hole leak so Off to the Auto Parts store for a new one. Happy Corvette Saturday!

 

well its clean for sure!

do lt4 injectors get "ohm tested" the same as l98 and if so what r the results? guessing they ohm test fine which is why u expect clogged?


have u seen the carb cleaner method of cleaning injectors on the bench?

 

VikingTradr I did not do the ohm test but I think they test the same as LT1's . I did not Ohm test because I heard just because they ohm right does not mean they work. I did the Long Screw Drive to the ear test on each injector and I heard the same ticks on each so I assumed they all worked. I took out the injectors and did a quick de-greaser then brake cleaner Blow out. Dielectric lube on the o rings and popped them back in. i did switch out 1 and 3 injectors. So far after two quick neighborhood trips no codes. But I want to make sure by driving it some more. I did the quick and dirty clean because in the near future I hope to buy some FIC Bosch III injectors!

 

Hopefully this was the issue!

 

For future reference, if they ohm bad, they are f'd. so if u know your 3 is where u get the miss, ohm it. if its different from the kther u r greenlight to replace.

as aklim says a couple times a day though, just because they ohm right, doesnt mean they are ok. in your case u suspect clogging it sounds like.

you could do the bench carb clean method. ive done it and it works.

i

 

Just coincidence, but I ran into code P0303 and P0300 on my LT4 this last week too. The car has been running fine (smooth) with the only symptom being a very slight surge under moderate acceleration when cold.

The first time I got code P0303 about a 1/4 mile after starting the car. The light was flashing. After about 1/2 mile the light stayed on steady without flashing.

I cleared the code and the next trip I got code P0300 about a 1/4 mile after starting the car. The light was flashing. After about 1/2 mile the light stayed on steady without flashing.

I cleared the code and got code P0300 the next several trips in the same situation as stated above.

I found that the crankcase ventilation system leaks can cause these codes because it can make for a bad mixture. It also has the PCV vacuum port in the manifold near the #3, so sometimes it is a P0303 and other times it is P0300. Also when there is a opening in the system (even the right side) it can act like a vacuum leak through the PCV system that enters the manifold on the left.

On my car I found that the hose from the passenger side of the throttle body was loose at both the throttle body and where it enters the side of the passenger side valve cover. There was even some resistance to seating it in the valve cover, the hose seemed "springy" and tried to pull out of the valve cover and then the wrong angle for entry into the throttle body hose.

I worked with it a while and got both ends seated. I was getting the codes every trip before and then after reseating the hose I have not had any codes for the last dozen or so trips.

I hope mine is as simple as this and the codes don't reappear, but so far so good.

Since you are getting the same two codes it might be worth looking again at the vacuum hoses for the crankcase ventilation system.

Probably just coincidence, but it might be worth checking.

Good luck.

 

Thanks QCV! This morning the code came back at P0303 so I was going to pull the Valve Cover off to look at the rocker but since I think it is running too smooth to be a mechanical problem I am going to look at all my PCV/Vacuum hoses etc like you suggested.

The more this vette fights back the more I will stay calm.