4.0 swap issues

moosemeadows · May 28, 2016

This swap started awhile ago 3 yrs in fact then the guy lost interest and I picked it up in March. It's an 87 Bronco ll with a 93 or 94 4.0 from an Explorer. I have the truck running now but it's not quite where I would like it to be. I have 3 issues that I need help sorting out. 1) no codes from computer but I did get them once but haven't been able to do for a couple weeks even with a Snap-on scanner or a Ohm meter which worked before Battery has not been disconnected for a couple weeks 2) starts great cold but drive to store and let it sit for a few then starts real hard almost like it's flooded. When it does start idles really high then drops off almost to dying. Idle stays up for 2-3 minutes but then goes back to normal. No gas in vac line from FPR changed ETC changed fuel filter.3) Temp seems real low on guage like L in normaL changed temp sender and put some cardboard in front of rad and temp guage went to M in norMal. Dropped back to L when cardboard removed and stays there. Seems like thermostat is working judging by flow in rad but I know that can be misleading.
I know it must be throwing some codes just by the way it runs but don't get anything from connector.It's got good vac 18 in steady and compression is 155-160 all the way around.
Please share your thoughts, suggestions, and input. Not real sharp electronics wise but when pointed in a direction with what to look for and how to do it I usually am able to get the answers requested.
Thanks again for looking at this and sharing.

RonD · May 28, 2016

It reads like IAC valve is not opening all the way, which it should each time you start a fuel injected engine.
I would pull it and clean it and then while it is still off plug in it's wires and turn key on, it should open all the way then turn key off and it should close all the way, repeat a few times.
You could do this test before cleaning and with engine still warm to see if it is sticking.

And it would act "flooded" since it isn't getting enough air with IAC valve closed.
Turning key off and on a few times "unsticks" it so it starts

On 4.0l always clean MAF sensor at first sign of trouble, even if oil is low clean MAF sensor, lol, well maybe not low oil but you get the idea.

PO may have put in a 160 or 180 thermostat, 192degF is spec for 4.0l
My 4.0l runs just below 1/2 after full warm up, and just above 1/2 after a long grade I need to go up every few days

Codes, especially OBD1 codes, are just for monitoring voltages and wires(connections) engine can run like crap or not run at all and there will not be any codes.
Unplug MAF sensor and start engine, you should see CEL and a code for MAF within a minute or so, that will tell you if computer is working as it should, as far as the monitoring side.

moosemeadows · May 29, 2016

Ron D thank you for your thoughts. I'll go try them here in a bit and get back to you with results and findings. When I worked at a Ford dealership the mechanics used alcohol and a Q-Tip to clean MAF sensor. Is that still the best way to clean it or are the sprays for that ok? I remember that you have to be very careful not to break the wires and not leave any residue on them.How about the IAC motor is carb cleaner the best?

cammeddrz · May 29, 2016

RonD said:
It reads like IAC valve is not opening all the way, which it should each time you start a fuel injected engine

1) most IACs are a step valve that extends all the way at key on (this is actually "closing" it, not "opening" it)

2) the 4.0 isn't even a step valve, it is a stutter style valve. It doesn't have varying degrees of open, just "open", and closed. How fast it stutters determines how much air it gets.

To test if the IAC is an issue in a more simple, and definitive way. Disconnect the electrical connector. And put + and - to the 2 pins (doesn't matter which) the engine should raise the idle up to 2500+ RPM .

The gasket for that IAC is difficult to source at parts stores. I usually buy them from the dealer for this reason. So no reason to needlessly screwing up the paper gasket

RonD said:
And it would act "flooded" since it isn't getting enough air with IAC valve closed.

Wrong again, as per my previous suggestion. The 4.0 ruins just fine with the IAC completely disconnected.

This is because this part of the fuel strategy only changes based on RPM. So the IAC lets air in, which raises idle, and the fueling increases slightly with every RPM it increases.

It won't "act flooded" with the IAC disconnected/stuck closed. At best, a bit of throttle to supplement the air it's missing. Ron-you have a 4.0 right? Go try it.

RonD · May 29, 2016

Good article here for cleaning IAC Valve: http://www.explorerforum.com/forums/showthread.php?t=84220

Not sure I would physically touch the MAF sensor wire.
They make a spray cleaner for MAF sensors, it is basically an electronics cleaner that won't leave a residue.
Rubbing alcohol can be used, put MAF sensor part in alcohol and move it around to clean off any dirt.

moosemeadows · May 29, 2016

RonD I went and cleaned the IAC in a very similar way with the same results. It does open and close with the key and while I was there I checked the OHMs which was 10.1 within specs I see. I then went to the MAF after a trip to Harbor Freight for the correct tool pulled it out and with the CRC chemical for MAF's it was clean and back in. I also check the volts here with the Bronco running and got 14.69 @ A & B and .93 at C & D running as well both within the specs I have. As you then suggested I disconnected the plug with it running to see if CEL came on which I'm sorry to say didn't.
Cammeddrz i will go try your suggestion as well but based on the readings I got my bet is that it will race the motor. I will get back in a bit with my results.
With not having the CEL come on means one or two things. 1) ECM toast or 2) my wiring job is. Now after I took the codes I did tidy up my wiring and could have missed something causing it not to work. Now the 87 has an emissions lite in the message center between the tach and speedo which comes on with the key.
Thanks again for your help and suggestions. I know between all that read and suggest things we'll be able to fix it soon.

moosemeadows · May 29, 2016

Cammeddrz yes it does rev the motor when I put 12v toe the terminals. So that being found the IAC motor is good, huh?
Any other ideas as where to go from here anyone?

RonD · May 29, 2016

Does the CEL come on with the key, it should.

Did engine seem to run normally with no MAF sensor?

And is the computer a 1993 or 1994?
1993 Ranger computer number = F37F-12A650-DB
Look at first 2 digits, F3 is '93, F4 is '94

If you see an E7 it is the original 1987 2.9l computer

There is a diagram here for the computer: http://www.auto-diagnostics.info/ford_eec_iv

Also a picture of what the inside should look like, often when a computer has a problem the circuit board will show signs of that problem

moosemeadows · May 30, 2016

RonD the engine ran normally with the MAF sensor un plugged. The computer is a 93 from what I remember.It came from the original vehicle but it was an auto as my Bronco is a stick. I have a computer from a 93 Navaho 4.0 stick in my hands. I'll go pull the computer open it up and see whats inside would be next, huh? Any other thoughts?

moosemeadows · May 30, 2016

RonD the emissions lite did come on with the key by the way. It's in the area between the speedo and tach in this model. Thanks again for your help.

RonD · May 30, 2016

Emissions light is different from CEL(check engine light), Emissions light was only used on Fords until late 1980's, I think it would come on every 60k miles to remind owner to service emissions system, or it would come on if problem was detected.
It uses a separate module, I think on B2s it is by or behind Glove box, it has a reset button on it, it is an internal button, but there is a hole in the case to push it, if it has never been reset then hole will be covered by a label/sticker.

So does the CEL come on with the key?

moosemeadows · May 30, 2016

RonD no CEL when key on I'll go look now and get back to you. Thank you again.

RonD · May 30, 2016

PO could have pulled or covered CEL bulb or it may just be burned out.

But CEL on with the key means computer is starting up and running self check, so CEL should always come on with the key, then go off after engine starts if there are no codes to keep it on.

Found a picture of emissions module here: http://www.ebay.ca/itm/80794-New-In-Box-Ford-E7TZ-12B514-A-Control-Module-/181998127053
And here: http://btsautoparts.com/products/e79f-12b514-aa-ford-relay-module-nos

moosemeadows · May 30, 2016

RonD found the relay you said to reset and I did but come to find out that relay is for the emissions lite for maintence reminder set to go off at 60k. I remember the mechanics coming in requesting them after I got a look at it. I changed all the bulbs out when I had dash out with a new pack off 194's. My thoughts are that I lost communication from ECM to CEK and test port for pulling codes. From what I see the ECM gets power and then sends it out to the CEK. Am I reding this correct?

moosemeadows · May 30, 2016

RonD I just had a grey hair moment. I don't think that in 87 the Bronco ll's had a working CEK. From all the wiring diagrams I have from Mitchel I don't see anything going to a CEK. I do see something going to the emission lite which was a service reminder as we talked about earlier. There is a spot for it and I put a bulb and socket in there thinking it was removed.So could it be that my wiring from the 87 isn't set up for one and I'm wasting my time trying to get something to work that can't? The other thought I had was to find the emissions lite wiring and hook into that if it's necessary for it to run properly. So back to my original concern should I be getting 12v somewhere in the code reader connector from the ECM that I'm not. In my reading I thought that pin 17 was the one going to the single connector where I should get 12V or something to make the OHM meter do it's thing. My thoughts are either I messed with a wire causing it to lose a connection or I may have shorted a wire blowing a fuse or cooking ECM.

4.0 swap issues

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