i swapped engines in my 86 bronco over Christmas. took out the original, tired 302 with 300k miles on it and swapped in a used, low-mile engine from a 96 explorer. installed a COMP roller cam, GT40 heads, short tube headers, the good stuff. but of course, I'm chasing a couple of issues with having done such a swap. mostly with how its behaving now.

I took the opportunity to install a 180 thermostat, instead of the factory 195. being in the desert, a 180 thermostat works much better in the hot summers. but does the EEC need that 195 temp to run properly? it runs at about 185 with the new setup..

second question, once I got the engine installed and everything hooked up, I test drove it with open headers. (the old exhaust obviously wouldn't fit, and who doesn't like to hear a nice open V8?) I'm wondering if I could've ruined the O2 sensor in doing so. it got new exhaust built today. so I'm driving it around trying to get it tuned properly again. seems like its running rich.....or maybe lean. the exhaust stinks. maybe I just really confused the computer??? I've got the battery unhooked overnight to reset everything.

I'm also questioning the throttle position sensor, and the MAP sensor. the wires on the TPS are in horrible condition, but it seems to work.(the thing drives)
as far as the MAP sensor goes, all I can say is, its hooked up.... i dont know if its working or not, or if it really matters.

i had to replace the TFI module already this evening. the one that came with the new distributor i installed went bad quickly, or was bad out of the box. had a horrible misfire and would stumble and die. new module took care of that. but the idle was/is also wandering. (it was doing this before the swap as well)

 

You brought over and used the newer fuel injection. So you will now have to learn all about it and how to pull the codes and trouble shoot it.

If it were me, I would have swapped on a carbed intake since that is allowed in the earlier trucks. If you had a 1985 or 86 that had fuel injection already, and it worked ok, I think I would have swapped it in place on top of the new engine. Though you still need to bone up on fuel injection with that engine also.

 

No, I maintained all the 1986 bronco stuff. Only swapped the long block. I'm running the truck intake and injectors and all front dress.

 

Did a relearn and KOER eec test this morning. Came up with a couple of codes to help get it running correctly.

But it flashed me a 77, which on my list says operator error during test. What?

 

Don't think the O2 sensor would be hurt by open headers, but there's always a first time. Since you checked codes, are there any codes for the O2 sensor?

One item which caught my eye is your cam change. The SD EFI system is not very cam change friendly. What are the specs of the cam you used? Maybe look up some of Conanski's posts on the subject, he's the guy to ask.

 

Cam I used was one conanski recommended. A comp 35-349-8. Which is spec'd to be computer friendly.

Yes, there was a O2 lean code. So I'm currently working on replacing the sensor. Luckily they're cheap.

 

Did you get the system pass code 11 from the KOEO test before doing the KOER test. You will get that code if you didn’t momentarily floor the gas pedal when prompted.

The computer is looking for the engine temp to be high enough to go into closed(?) loop mode. It will run rich if it doesn’t get up to temp.

I had that cam and heads with 1.7 rockers in the 302. I didn’t like how it ran so I did a mass air conversion. That was before PimpX was available.

 

No code 11. KOEO tests are just bringing up 31, 81, 82 codes. (Because that stuff has been removed)

The thing RUNS fine. It just won't hold a steady idle by itself once it tries to go into closed loop or whatever. It'll start fluctuating and bouncing up & down. If it gets bad enough, it will stall.

I'm beginning to wonder if there's a vacuum leak between the head & intake. I've plugged/ capped off everything else except the FPR and MAP, but both of those also have brand new lines to them so they aren't leaking.

I changed the O2 sensor, no change in behavior.

 

Does it still have open headers? If so that totally messes up the O2 sensor readings and it will never run correctly in closed loop, so you need to get an exhaust system on it. This combo will need tuning as well as the stock injectors are not enough to feed the motor at higher rpm.

 

No, it has a full exhaust on it now. 2-1/4 from the collectors into a single 3" all the way out the back.

What factors is it looking at to control the idle? Does the MAP sensor play a role? That's about the only thing I haven't looked at yet.

 

Ran another KOER test.
Came up with
21-"Engine Coolant Temperature Sensor Out Of Self Test Range. 0.3 to 3.7 volts"
(I replaced this sensor already about 2 years ago, did it possibly go bad again? Or is this because of the 180 thermostat???)

41-"System Indicates Lean -passenger side(R), No o2 Sensor Switching Detected. always lean -passenger side." (This is what prompted me to change the O2 sensor earlier this morning)

31- EGR code
34- EGR code
The EGR and all related things were seized by an anti- government extremist group that came by when I was working on it.

77- operator error. (I don't know what I'm supposed to do other than read the codes lol)

25- it's not knocking. Yay me.

 

You will always get the coolant temp error code if you do not properly warm up the engine before running the test. The engine needs to be between 50F and 250F. Not properly warming the engine up can also cause O2 sensor codes.

You will always get the error 77 if you do not do the goose test. You are running the KOER tests (Key On Engine Running). Once you put the jumper in and then start the engine you will;

1. Get engine ID codes. You should get 4 pulses since you have a v8 setup.

2. Next you will hear some clicking and the idle speed will go up and down. This is the computer checking things out. If you do not have the air pump on it anymore, you might get some O2 codes.

3. After the above, the engine will smooth out and lock the timing at 20 degrees BTDC. Then you will get one pulse from your code reading device. After the one pulse, you have 10 seconds to snap the throttle to wide open. This is called the "goose" test. The engine rpm must go above 2000 rpm. That should get rid of your 77 code and will also probably get rid of your code 25.

4. After the above,you will get a bump in the code reader, these are called "fast codes" and can only be read by a factory scan tool. After that, then you will start getting your regular codes.

 

Yep, I see all that happening.

Engine was at operating temp when I did all this. Which is about 180-185 now.

I'll do the goose test next time I check them.

I hooked up my Vacuum gauge to it just to see what it could tell me. At startup, before it starts into its bull****, it holds nice and steady at 18". Once the two brain cells in the computer start arguing, it's down to about 15-1/2 to 16.

I unplugged the map sensor with it running, it died. Restarted and ran like crap. Plugged it back in and it smoothed out. So I guess it's working.

It starts normally, drives great. I don't understand what's going on with the idle wandering and stalling.....

 

I would have kept the EGR system since it can lower emissions and increase fuel economy.

As I previously stated, the KOER test requires input from you. Depending on vehicle configuration you may need to goose the throttle, turn the steering wheel and step on the brake pedal.

“Knock not sensed during Dynamic Response Test”. You didn’t do the dynamic response test (see code 77) so….

 

Reading about the same issue over on F150online. One guy said his fix was the intake gaskets. I'm really wondering if that isn't my issue as well.