I have a 1969 chevelle that I put fuelinjection off of a 1986 camaro. It has a painless wire harness and a holley stealth ram. The computer is a 5.0 computer on a 350 with 19lb injectors at 43 psi. The car runs but three cylinders do not fire properly when carb was on car it ran fine. The cam is a l79 .222 .447. I am not sure where problem is. I have done a comperssion check and heads are fine. Running out of ideas.

 

19 lb injectors at 43psi isnt enough fuel for the 350. 19lb are for the 305. You may be able to get some improvement by increasing fuel pressure but the best fix is to switch to the 22lb injectors intended for the 350. Lb/hr rating is based on 40psi. Increasing fuel pressure increases output linearly. An increase of 20% pressure will increase output 20%. You may also have 3 bad injectors.

 

injectors are new but I think if they were too small they all would starve not three intermiently

 

Okay. Let's step back a bit. You have power loss on 3 cylinders? Are the three cylinders ajacent to one another? Could be a manifold gasket leak. Check with a smoke machine or even aeresol brake cleaner. Watch for the leak to be into the cam valley. This wont show with brake clean but it will show with smoke.

Even new injectors can be defective. Try swapping injectors from the 3 bad cyls to the 3 best cyls. Just to be safe, check ignition KV to these cyls and compare with the best cyls. Verify pulg and wire health. Check the EGR for being stuck open.

 

i have checked injectors and i have checked plugs and run a compression test also but i didnt do a leak down test my main thought is that the cam is out of phase two cylinders are adjacent the other is on the other bank. I did not have this problem with the carb but i am not sure of lobe angle seperation and what not with this tpi setup

 

LSA for TPI shouldn't be less that 112. 110 is about the minimum allowable and will cause some roughness. I doubt the problem is in the engine mechanical if it weren't there with a carb. Cam phasing or LSA would affect all cylinders, not just three. Unmetered air at any point in those three cyls? Is it possible that dirt may have gotten into the fuel rails and found its way into the screens on those three injectors?

 

i have moved injectors to other cylinders and they work. My ******* method of checking cylinders is a squirt bottle on the exhaust they are weak I have not put a temp gun on them to see how much difference there is. I moved plugs also and didnt change either. I have thought of maybe a bad set of lifters. I didnt build this engine and am thinking of just tearing it down and going back through it. I am thinking now that may be it is in the head area.

 

The exhaust temp method is valid. I trust the old cylinder kill method using either spark plug boot pliers to pull wires from plugs or a test light to peirce the boot at the cap. The latter is tough on new wires but if the wires are near the end of their service life, it's not a bad way to go. An engine analyser is the very best way to go. Certainly check your valvetrain, though as I said, it follows logic that the problem isnt engine mechanical since it isn't there with the carb. You may have just had 3 lifters drop on you while the engine sat during the intake swap. This would cure itself in several minutes of running.

 

i honestly dont drive the car now i am still doing suspension work but i want the motor right. I may just run the car for a while to see if the lifters will pump up and i also have a old set of plug wires i may try with the test light. Most times i only run the car for about three minutes

 

Yeah, running the engine longer may smooth things out.

 

ran car today and changed plugs and it helped two cylinders still seem weak checked injector plugs and may move the two injectors to try that

 

Some improvement is good. sounds like you're on the right track. Its got to be either fuel, ignition, compression, or vacuum leak. Keep the EGR in mind if you have one. A leaky EGR valve can cause misfires that are very hard to pinpoint.

 

car is running great now! I have been running a 305 chip for some time now but put in my 350 chip and drove car around a little it has never run this good. When i first put 350 chip in car ran rich but at the time i had a bad maf and didnt know it. I ran the car about an hour today and no problems plugs looked good when i got back from a short road trip. I did the old squirt bottle test on the headers and everything looks good. I need to adj. the lifters on one cylinder has a little tick but other wise all good. Thanks for all the help!

 

Awesome. So it was perhaps a slight lean condition due to the wrong PROM. Glad you got it fixed.