Hello everyone. I'm back with another problem. Awhile ago, I posted a problem with a 1995 5.2 engine that quit running well all of a sudden. Turned out to be 3 bad exhaust valves at 300,000 miles. Well, I got rid of that engine and had another 5.2 engine installed that came out of a '94 Ram VAN. One of my mechanics said it would drop right in, but the other mechanic said these two engines are configured different, and several things had to be changed to get it to work in my truck. Long story made short, they did whatever they had to do to get the engines swapped, and I got the truck back and took it for a drive Monday. Seemed to run fine and very smooth around town that first day, and then for about 30 miles on the interstate the next day. But when when I got off the freeway exit, the engine died when I let off the gas. It started back up after a couple minutes, but it wouldn't stay running if I let off the throttle. I limped it back over to the mechanic shop, but every time I had to stop for a red light or stop sign, the engine would die unless I shifted into neutral and kept it above 1000 rpms. Seemed to get worse and worse as I went, and after the last two stop signs, it even felt like it was starting to misfire too.
The mechanic is looking it over right now, but isn't sure what happened.
All of the new ignition parts were taken off my old engine and installed on the new engine (plugs, wires, cap/rotor, crank pos sensor, air filter, etc.) The mech said he used the throttle body off the van engine. Also, the intake manifold was removed to install the van engine, then re-installed once the engine was put in. And another bit of info....the new cranks sensor was damaged during installation of the engine. It was replaced with a new one that was rubbing on the inside of the housing and making a terrible noise. That sensor was then replaced too. Noise went away, and seemed to be working fine.
Where should we be looking? Mech's leaning towards vacuum lines or something electrical that didn't get hooked up when the new engine got installed. He also said he would put my original throttle body from my stock engine back on.
Looking for any suggestions or help. This is my work vehicle, and it has been sitting in the shop since June. I'm about to go insane!

 

Clean the throttle body REALLY well before reinstalling.

Check the crank sensor, and make sure it didn't get damaged during the swap. Make sure no wires got pinched between engine and trans.

Getting any codes?

 

Thanks. I was editing my post when you responded. Crank sensor was damaged upon installation of the engine, then a new one was installed that was rubbing inside the housing. That one was then replaced with a third sensor that seemed to be ok.

Would the throttle bodies be different between the truck and the van engines? If so, would that cause the problem?

I have not checked for codes. I was doing good just to get it limped back to the mechanic's shop without getting killed in traffic! I will check the codes when I get back over there sometime tomorrow.

 

I don't think there are any differences between truck, and van throttle bodies...... (that I am aware of.)

 

Thank you. Good to know. Maybe the one that was on the van engine was just dirtier than my stock one. I will have him swap them and clean it just in case.

What about IAC sensors? What happens when they go bad?

 

PCM can't adjust idle, so, you get interesting stalling or high idle problems. Dirty IAC well acts exactly like a failed IAC.

 

Well I went over to the shop and ran the codes. The only thing that came up was 1 2 55.

 

That would be 12, and 55. So, the battery has been disconnected in the last 50 key cycles, and there aren't any other codes......

So, clean the throttle body REALLY well. Leave the battery disconnected while it's happening. When you have every reassembled, turn the ignition to 'on', count to ten slowly, THEN start. Don't touch anything while you count. This will give the PCM to re-learn the 'zero values' of the various sensors, and make the idle learn process easier.

 

Over the weekend, we cleaned out the throttle body and installed a Mopar crank sensor. Problem solved! Ran it 50 miles yesterday and it ran great. It's like a new truck.
Thank you!