I installed a set of lucas/delphi 42lb injectors recently, I had been running the stock 24lb injectors. I switched to these because I was at 355rwhp with my old setup then did some porting/polishing of my heads and installed better valves/springs while the motor was apart over the winter. I estimated I could pick up another 25hp and thought it might be too much for the stock injectors to handle. After I got the motor back together I ran it on the stockers for a bit and it drove fine. I then installed these 42's and had PCMforless reprogram the pcm for them, I made no other changes. Now the car feels week starting, and stumbles a bit before settling down to an even idle. It then stumbles when i try to pull out, and is barely driveable. I spoke to pcmforless and he told me to check my long term fuel trims, I checked them with my Autoxray and they were at zero. I told him this and he said that is what he shoots for when programming.

I'm wondering, are 42's just too much for my setup and are they harder to program for a small cam like the hotcam? I got these because I plan on going to a larger cam down the road and just figured I would be covered with these for any future changes. Wondering if I should just go with a set of 30-32lb for now and get bigger ones later if needed. Any ideas?

 

as long as the pcm is tuned for it, you will be okay.

 

...that doesn't mean they are right for the engine.

 

In some cases going too larger an injector can cause issues because you can't get the pulsewidth small enough for the car to run right at idle and low speed.

You only have a hotcam/boltons and you were putting down 355 with stock heads? With a good set of ported heads you should be doing pretty good with your setup and I don't see 42's being too big, although they are on the large side.

 

I figured out my problem. I checked my fuel pressure, it was a bit low with the key on (39-40) but after I started it it was going up 3-4lbs, not down like it should. Took off the fuel rail and noticed the fp regulator had something in the vacum line opening. A few weeks ago when I was installing these injectors I had put a bit off tune up grease on the vacuum line cause it seemed a bit dry, didnt realize I got it in the line. So I cleaned out the requlator and line with some carb cleaner, put it back together and now its running great.

Yes, it was at 355 on the stock heads, the hotcam and boltons.
I'm anxious to find out what its at now. Thanks for everyones feedback.

 

Congrats on the fix, well done!