Need help diagnosing my 2.9

[Broncou15]

Hey everyone I just bought a 1990 Bronco II 4x4 with a 2.9. I’m having trouble getting it to run properly it seems to be running rich and brakes up between 1500 and 2000 rpm under load. The check engine light is on, I tried using an analog voltmeter to reed the codes but the needle on the meter just stays pegged all the time. I also tried jumping the pins under the hood to get the light to flash but got nothing. I’ve tried both the “key on engine running” and “key on engine off” tests from the Bronco II Chilton’s book but nothing is happening. I’m thinking that maybe with it being a last year truck some of the things in the book may be different I know the wiring and some of the sensors shown in the book are not the same. This is my first obd1 truck I’ve built a carbureted 1969 bronco and an obd2 1999 ranger but never done anything with obd1. If anyone has come across this problem or has any ideas on what could be wrong or how to figure it out please let me know.

 

[adsm08]

Try investing in a decent EEC-IV code reader. They aren't expensive, and are worth it.

Now for the easy stuff, if it is running rich the fuel pressure regulator and oxygen sensor are good first suspects, followed by the intake temp sensor.

 

[Broncou15]

The previous owner replaced just about every sensor on the truck but don’t think he did the intake temp sensor I’ll look into it. Any recommendations on what reader to get? I know it has to be one for a ford but other than that anything I should look for in a reader.

Thanks

 

[adsm08]

I have not had good luck with the Actron EEC-IV readers.

If you can find a Blue Point MicroScan II Pro or an old Solus that are my favorites. They work well, are easy to use, and can usually be found cheap.

 

[rusty ol ranger]

I bought one of these...

30 bucks at o reileys, 19.99 on crapazon. Makes reading codes a breeze.

 

[Broncou15]

Ok today I bought an innova obd1 code reader for a ford. I hooked it up but I’m not getting anything it just stays on the home screen of 000 even when you hit the test button. I talked with the company that makes the reader and there saying that it’s not connecting to the truck. Not sure where to go from here not sure if something is wrong with the wiring, ecc, or what could be wrong anyone have any idea where I should go from here?

 

[Paulos]

If you have both the small connector (single terminal) and large connector (multi-terminal) connected to the reader, and have followed the instructions correctly (just checking ), I would say the problem is either the code reader, the wiring to the ECM, or the ECM. The single connector should have a white/red wire (self-test input) which goes to pin 48 on the ECM. The big multi-terminal connector should have a tan/red wire (self-test output) that goes to pin 17 on the ECM. If you check the continuity between the self-test connectors and the ECM connector, I would disconnect the battery and the ECM from the connector to be safe.

But before you do a continuity test on wires/pins 17 and 48, see if you can get the system to dump the codes through the check engine light.

 

[Mike Tonon]

I built one, using an LED, wires, small Tupperware container and I don’t remember what else. Unfortunately I no longer have it or my repair manual that had the schematic for it.

 

[Kuper]

Yeah I used a paper clip in a pinch for a jumper. Hopefully you figure out what’s going on good luck buddy.

 

[Broncou15]

Ended up figuring it out today. I tried the paper clip and the tester but nothing worked I end up tapping into the wires at the ecc and was able to get it to show me the codes. So it looks like I have some broken wires somewhere in my harness.