I'm finishing up my winter project. I built a 97 1500 EC 4x4 with a 408 out of my rusty 94 Ram, 46RE trans, 241DLD and Dana 44/60 axle combo. The 97 came with a bad 5.2L. I have had it up and running around my shop and starts up every time with the key. I took it for a drive today and it stumbled a little when I got on the throttle. A mile down the road, I let off the throttle to make a right turn and the truck died. It fired right back up, but I don't remember if I pushed on gas pedal or not. I drove back a mile to the shop and it died again when making a turn. I will pull and clean IAC, but wondering if using the stock 5.2L ECM could cause this problem. I'm waiting for an SCT tune, but wanted to get a few easy miles on the truck to check over my work. I have 24# injectors and fuel pump pressure was at 45# when I first got the truck running. Thanks for any input.

 

You need a tune on the ecm for that 408 to run right. The 5.2 tune is going to be running incredibly lean on a 408..... That'll give you some odd performance problems......

Welcome to DF!

 

Thanks. I will wait until my tune shows up.

 

Let us know how it works. And how you like it.

I wanted to do a 408 for my 96, but, that just wasn't in the budget.

 

Would a 5.9 ECM make it driveable until my tune? I have had the 408 in my 94 for several years. I used a piggyback tuner for the OBD l system. I started having some issues with it running and support didn't exist for the piggyback. The 408 was going in this 97, so I drove it a bit with the stock 5.9 ECM and ran fine. I knew that if I wanted to get the most out of the 408 and the 97 had a 5.2, a tune would be required. I'm on Flyin Ryan's list for a tune. The 408 is very responsive off idle and has plenty of torque. I had an issue with a small cam and my piston selection. Hughes engines helped me get it sorted out and I installed their Air Gap manifold. I will keep you posted on my tune.

 

5.9 pcm would prolly be better, same issues, just to a smaller degree. In closed loop, the PCM *should* be able to compensate for more cubes.... but, in open loop, it is still gonna run lean.

 

That's exactly how it runs. Closed loop, it ran good when I drove it a mile down the road and back. Yesterday, the coolant temps got up to normal range on my way home and hesitated, had lean hiccups on acceleration, then died when I let off the throttle when I went to turn a corner. It looks like I will have to be patient until I get my tune. Thanks !!

 

How old are your O2 sensors? Wonder if they are lying.

 

Both o2 sensors are brand new. Previous owner let wires and connector touch the exhaust. I had to do some repair work/replacing on the wiring harness.

 

What brand sensors? Our trucks don't really care overmuch for the bosch fellers.

Cleaned the throttle body?