I am having problems with getting my swap running well so ican get it to the track. It is a lq4 with milled 243 heads, tick stage 2 cam, fast 90/90, long tube headers, 42lb injectors, holley efi, aeromotive 340 pump. So i got the car fired up and it will run for about 10 to 15 seconds and then it will back fire out of the exhaust. The problem is on the passenger bank. When i pulled plugs (brand new) 2 were very black and wet and 2 were wet with zero signs of firing. The header tubes were cold and the drivers were too hot to touch. I have verified spark at the plugs and its getting fuel. The intake and injectors i bought used so i have removed the injectors to send to be cleaned and flowed. What else could it be? Should i replace crank and cam sensors? I have the latest firmware downloaded in the ecm. I am at a complete loss and i dont want to just start replacing parts. Any direction in where to look next to trouble shoot this would be greatly appreciated thanks.

 

Fuel pressure at the rail??

Rick

 

Im using the vette filter, all parts are new.

 

I'm a Holley EFI dealer/installer, send me a PM. I'll see if i can help you out.

 

I had a similar problem with brand new injectors. One leaked so bad that cylinder wouldn't fire. i pulled the rail and put 58 psi on the rail and found 2 that leaked one real bad. Got a new replacement set and 2 of those leaked which caused hard start when hot. Ended up getting a set of flex fuel oem 50lb injectors and everything is fine now. I bet the 2 that are wet are leaking to much fuel and at idle those cylinder won't fire.

 

I have the injectors out so i can send them in to get cleaned and flowed. I bought them used and have no idea when the last time they were used. I just have to decide where to send them. Also at this point after i get the injectors back i may have someone remote tune it so they can read the data log and give me a clue whats going on.

 

 

The wiring is the wiring harness i got from Holley with the HP efi. As far as the valves hanging open i thought about that but wouldnt both banks have issues instead of just one bank? I will have to read up on how to measure pushrod length. I have an adjustable pushrod to check length. I used the same size pushrod as the person i got the heads from, i know not the most ideal way to do things. This project has been off and on for years and i finally have the time to get this car on the road.

 

Pic of car5

 

The stock passenger side wiring harness has a separate ground for the injector connectors. Not sure if that is the case with the Holley harness. Agree on checking the ground, long shot but easy to rule out. Hit the block and gound connector with some sand paper to make sure grease, grime, paint are not an issue.

What type of rocker do you have? Could be too much preload on the two that don't fire holding the exhaust open? If you have O2 sensors that might be an issue, switch the two upstream sensors and see if the problem moves to the driver side.

 

Dang thats a nice looking 3rd gen!!

 

 

Im confident its not a ground. I have one ground from the harness to each head, and a good ground from the block to the chassis and battery to block. I will have the injectors back next week so i will spend a couple days checking push rod length while i wait on the injectors. I have owned this car for 22 years and havnt drove it in 20. To say im looking forward to drive this car is an understatement.