MAF start up, pulling codes, etc

[plug ugly]

So, I finally started the damn thing up. Its idling rough, and dies if you dont keep just alittle throttle into into, like 900 rpm. If you let off the pedal, it dies.
It didnt have exhaust, or O2 sensors, so i figured that was it. I got some exhaust put on today, with O2 sensors (new bosch 3 wire), and its a little better, but not good and still wont stay running. Bad enough where I can not get out to time it. I don not have the radiator hooked up yet.

I pulled codes originally, and everything was normal with TAB, TAD, and EGR gone, etc. I now have a check engine light on, and when I try and pull codes, the little code reader I have had for years just beeps a solid beep with a solid light. I tried getting codes without out it also per the RJM injection sight, and I can hear the fuel pump relay and pump trigger, but then nothing happens.

So where do I go from here??????

specs are 94 351 with GT heads and intake, explorer throttle body, and the map sensor without the vacuum line to it which I think turns it into a BAP sensor....A mustang 8LD computer, and all new RJM harness

[CityHick]

Re: MAF start up, pulling codes, etc

Running without the O2 sensors definitely wasn't helping matters. You will never get to closed loop that way.

Moving beyond that, running without EGR is no problem, you get a soft code and that's about it. I am going to assume your TAB acronym is actually IAB (idle air bypass). Not sure what TAD is. If you do not have the IAB/IAC valve installed/hooked up, it will be hard to get it to idle right. It will run but if anything that usually drops the idle down to the point of barely running when disconnected. That may explain why you have to stay on the throttle.

I would make sure that you have absolutely everything connected that needs to be. If the EGR connector is not connected to anything you'll see the check engine light on.

You might adjust the throttle body to allow for a faster idle after you check everything else. Fire it up, time it and then back the idle down and see where that gets you.

I did not even try to fire mine up until I had the radiator connected and full, the fan operational, and basically everything else that makes it drivable in place.

[DirtDonk]

Re: MAF start up, pulling codes, etc

Yeah, some water/coolant in the system will let the coolant-temp sensor work properly. Not that this would make it run like yours is, but it's still not "complete" until it can read coolant temps.

1. An Explorer TB on a 5.8 comes to mind as something that might be off.
2. What about the PCV valve? Is the system hooked up completely and sealed?
3. What about additional vacuum ports? Are they all plugged? If so, how long ago did you buy the caps for them? If more than 3 or 4 months old, change them. They're probably leaking and you have vacuum leaks giving the computer fits.
4. A Mustang ECU with a 5.8 and what size injectors? Stock 5.8? Again, I'm thinking that even though they might be mismatched (TB, Injectors, etc) it might not give you the fits you're having. But add a few things together, and watch out!
5. What about the MAF? Which one?

And speaking of mismatching... What trans is that ECU designed for? Is this an RJM harness? Are the jumpers in the right position for the ECU trans type?

Paul

[plug ugly]

Re: MAF start up, pulling codes, etc

manual trans, 19 pound injectors, 8LD computer. I do have the IAB on the the throtle body. I ran this exact set up on the speed density and it ran fine. I messed with the dizzy a little, and got it to idle after it warmed up a bit, and the CEL went off. Later though, it wouldnt idle again. I need to check to check the vac stuff but cant keep it running to do it.

[DirtDonk]

Re: MAF start up, pulling codes, etc

I'm not sure of all the little nuances, but if this is originally a Speed Density computer, it might be expecting to see a MAP signal instead of a BAP signal.
However, if you're running it in MAF mode and it accepts that sort of thing, then I'm not sure what good it would do to check.
But if you're running SD, then I'm pretty sure that you need a vacuum line on your MAP sensor.

Anybody else know what's what on that score?

Paul