Hey guys I put this on my other thread but now I don't think its pcm related at all.

It appears as though I had 2 problems- 1 got fixed today. It was the ignition switch.

Now my engine runs for a while and just plain dies. No stuttering or anything. No codes at all either. New battery and plenty of fuel. New crank sensor. New pcm (put the old one in and no change). It also shuts down while driving too.

Why would my engine die like that? Its just weird. You'd think that a code would show.

 

Clean out the IAC port and head of the IAC on the back of the Throttle Body. This causes all sorts of problems at idle and I'd also get the battery tested under load.

The battery can cause all sorts of problems on these rigs.

[You'll see why I called it the IAC head when you pull it out LOL]

 

Would the iac cause the engine to die even under load? I was driving it around to test it and it died.

 

No not at all. If it's dying when you're driving and on the accelerator rule out the IAC. Get the battery tested and check pressures for the fuel pump.

My most likely suspicion is the battery but like I said a dying fuel pump will cause it to die randomly while driving.

 

Make sure your getting a good spark from your coil

 

Doesn't the 4.7 use coil packs instead of a single coil?

Ok. I'll take it to a parts store for a batt and alt load testing. I think the fuel system is ok but I'll look at that too.

 

Are we working with a 4.7 engine? Yes the 4.7 has individual coil packs for each cylinder. As for the fuel system, it's an easy enough check and is worth the 5 minutes it takes just to rule out that factor. As for getting a bad spark like Cody says, typically it won't just die as much as not start at all. I'd check the coil packs however to ensure they're doing their job because they can cause the engine to die.

Come to think of it, another issue that could be messing with your system is the ASD relay. It's an Automatic Shutdown System and controls the fuel pump, computer and ignition system.

I'd swap out that relay/fuse with another one just like it and make sure it's operating correctly.

 

Ok. Got new info. We took the vacuum detector plug off and cleaned it. Also we cleaned the IAC. I think vacuum detector was calling for a shut down in combination with a bad IAC. Now it doesn't turn off by itself. Can't try a new IAC until I get it tomorrow but....

Only occaisionally it'll get real low on rpms. When you let off the throttle, sometimes it'll die. I'm thinking its the IAC, because we cleaned it up a little.

The fault at the vacuum detector only showed once and it may have been because of dirty contacts.

Any opinions?

 

It does sound to me like you need to replace that IAC.

Also, yes I believe that fault got triggered by dirty contacts.

 

Ok thank you. I mean it too. Gotta love these forums.

Getting a new IAC tomorrow. About cleaning the port, is there a link to this process? I'm on a phone now but I can get to a pc and print it out. I'm an old school mechanic, my niche is holley and edelbrock- this newer stuff is Russian to me.