92 Mustang 5.0HO in 89 Crown Vic

I just recently rebuilt a 92 HO 5.0 out of a 92 Mustang and dropped it in an 89 Ford Crown Vic that had a NON HO 5.0.
This is just the longblock. The lower and upper intake are off the crown vic, as well as injectors,egr spacer,tb, etc.

Obviously I know the HO has a different firing order. So I swapped the spark plug wires to HO firing order. I also pulled the processor connector and swapped the wires for the injectors to put them correct too.

I thought all this would work ok, even though I know the HO has a slightly more aggressive cam and the heads flow better. Well turns out it didn't work so well. The engine starts cold and idles ok, but once it gets warm the idle sucks, surging, shaking etc. Also the car runs like crap while driving, it just has no power, especially at lower rpms. I have replaced the MAP sensor, TP, IAC, and checked for vaccum leaks, set the timing, set the TP, etc. Not helping.

I have pretty much come to the conclusion that the lower vaccum created by the cam in the HO is throwing the MAP off, which in turn is throwing everything else off too. From what I can tell the engine is running real lean. When I pop the vaccum hose off the fuel pressure regulator the idle improves some. Also the idle gets much better if I pull the ECT wire or the IAT wire. I am a ford tech, and am pretty familar with ford EEC. I hooked up an NGS star tester at work, and ran all the normal self test. No codes, also ran it through a cylinder power balance test were it kills each and every cylinder individually and it passed. So I know I got the injector wires right.

My current plan now, since I don't want to tear the engine back down to replace the cam, is to get a 87-88 mustang speed density computer, and harness and try to put it in the car. I am also going to get the 19lb injectors, since the crown vic has 14lbers. I am also thinking about getting a Mustang upper intake and EGR spacer and TB so everything matches. Might just put duel exhaust on this damn thing too.

My questions are.

1. Have I missed anything here?
2. Will the HO upper intake fit with Throttle body facing the driver side, like it does on the crown vic upper? Won't the upper fit either way, I mean the bolts will line up right?

331 cobra said:

I have heard about a variable in the EEC that tells the computer how long to wait before it reads the EGO sensor for each cylinder. Your EEC is set up for the old firing order, so my guess is that it isn't associating each exhaust pulse with the right cylinder.

So, if cylinder A goes rich, the EEC leans out cylinder B, then richens cylinder C, etc.

I think the nuts and bolts solution is to rewire the EEC connector and put in a HO computer. The software solution would be a custom chip.

The Ghetto solution would be to put a resistor where the ECT sensor goes and convince the engine that it is stone cold all the time, and just run around on the open loop cold start calibration.

I would try the Ghetto solution first, that will either confirm or disprove my theory.

Good luck.

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Funny you say that(Ghetto solution), because that is what I was going to do originally. But I kind of decided that.

1. Gas mileage is going to SUCK going that route.
2. I still have a lack of power, probably because of what you are saying, plus decreased timing because of reduce vac to the MAP.

I hate the idea of going to the trouble to rebuild this engine, only for it to be gutless and Ghetto rigged to work.

Basically it makes less power now, than it did with the NON HO 5.0 in it. And it didn't make much power before. I am probably stupid for spending the money and doing the labor of the mustang stuff, but I figure if I am going to drive this car, I would like it to have some get up and go. I am too damn used to driving my 94 Cobra, I can't stand gutless cars.