Hello New BII owner here.
It is a 88 w/ 2.9L and auto trans. 4x4, w 3.73 gears. Did have 205/75r15's on it, now has 30x9.5's on it, but even with the small tires, it still lacked power.
I posted earlier about this. I purchased this a few weeks ago. Engine seems to lack power. I checked the codes and only got 22 for MAP sensor. Had it check at Autozone and it passed. I changed the plugs, cap rotor. Still lacks power. I thought maybe clogged cat, since I read that can trigger MAP code.
I just ran a vacuum check, motor pulls 18 vacuum, and when I do a quick throttle response check it seemed ok, drops down to about 0 than rises about 5 inches above idlle vacuum than returns to idle at 18 inches. There is no long delay that would leave me to believe that it is a clogged cat. Not much for top speed, don't know if I would want to drive it on the interstate, seems to slow. Beginning to think that these stock 2.9L are just gutless. I think a 5 speed man. would maybe help, but not sure. Any help or info would be appreciated.
Thanks,
Shiny

 

Is your MAP code a KOEO code or a continuous memory code? KOEO codes are output before the separator pulse during the KOEO test, CM codes come out after the separator pulse.
What did Autozone do to test the MAP? Have you checked the wiring between the computer and the MAP? It can be important to recognize that codes point to circuits, not sensors. The condition of the sensor doesn't matter if the signal wire (or Vref wire) between the computer and the MAP is broken.
One last thought: How do you define "lacks power?" This isn't a real high output engine, but I've never been afraid of the interstate. I've heard it said that the 2.9 puts out more horsepower per cubic inch of dispacement than any other engine in the RBV lineup. If that engine is functioning correctly you shouldn't be afraid to drive on the interstate.

 

The MAP code #22 popped up on the KOEO mode and also on the Runnin mode. Autozone check the MAP Sensor by using a 6 Volt battery and using a vacuum pump with a gauge. And measure the frequency between the ground and signal wires. This was all done per the WELLS test chart that they have. It pasted everything according to the charts.
Shiny

 

Okay, I checked timing today, it was right on 10, also the timing advance woorks, but when checking, I got a code 41 EGO sensor-lean, also got code 77- Operator error, not sure were I messed up at, pushed on the brake pedal and everything. Would a bad oxygen sensor cause loss of power?

 

Okay, now I'm stumped? Check for codes with Enigine running, I get Code 11, Pass? But when I checked codes before hand, with KOEO, I still get Code 22, MAP. Also does a 1988 Bronco II with a 2.9L have an EGR valve, thought if it did I would clean the passage ways, but I can't find one on my motor. There is a cover plate on the upper intake near the throttle body, is this where the EGR would be mounted, If I was suppose to have one.
Thanks,
Shiny

 

'86-'87 2.9's had an EGR system, but '88 and on didn't, so you shouldn't find an EGR system.

I hate to, but I have to ask because it's a common mistake. Did you check the timing with the SPOUT disconnected?

I'm going to harp on the KOEO/CM issue. Basic sequence for the KOEO test:
1) prep and initiate test
2) computer performs the actual KOEO test (actuates solenoids, checks sensor outputs).
3) fast codes are output. usually appear as a single pulse. ignore.
4) KOEO codes are output (these represent faults the computer detected during (2)
5) KOEO codes repeated
6) pause then separator pulse
7) Continuous memory (CM) codes are output. These represent faults the comptuer detected during normal operation and then stored the code.
8) CM codes repeated.
Which portion (KOEO/CM) of the KOEO test did the 22 MAP code come out?

Bad O2 sensor signal could cause a loss of power, but false KOER 41 is easily set by not preheating the sensor/engine immediately prior to performing the KOER test. As for the other KOER codes, I'm assuming you figured out when to press the brake and when to perform the "goose" test.

As I said before, a KOEO 22 MAP code could point to a bad connection/broken wire between the MAP and the comptuer. make sure the wiring is intact. A CM 22 MAP code could indicate an intermittent fault in either the wiring or the MAP. This is why I'm trying to figure out which part of the KOEO test it's from.

Other things to look at: What is the fuel pressure? Out of curiosity (because it will really effect how quickly you get off the line), what gear ratio are your differentials?

 

I had the SPOUT disconnected when I checked the timing, and it was right on 10. The gears are 3.73. The code of 22 popped up before and after the seperator code. I checked the wiring and vacuum line looked ok. I checked all vacuum lines for leaks using carb cleaner, did not find any. I have yet to check the fuel pressure, have to get a gauge. ? Wouldn't a fuel pressure problem trigger a code?
Thanks for you help and input, I'm just getting stumped by this truck. Thought V6 would have more power, than what it does.
Shiny

 

Fuel pressure isn't directly monitored by the EEC-IV computer and may not set a code. If it does, it would usually be an O2 sensor code.

So you're getting the 22 in both KOEO and CM. Because a KOEO code is set with the engine off, it almost has to be electrical. You've had the MAP itself checked (off the vehicle), so it should be good. That means the problem must lie in the wiring beteween the MAP and the computer. When you checked the wiring, did you check it with a multimeter, or did you do a visual inspection? Is the MAP getting +5V reference /excitation voltage?

 

I did a visual inspection of the wiring going to the map sensor at first, but I just went and checked the voltage on the harness with a digital meter. I read 5.1V on 2 of the wires coming in, and 0V on the black/white wire, which according to my Haynes book ties into the egr valve on 2.3L, the nuetral safety switch on a mt, and the ps pres. switch for a 2.3L, of which I have none of these options on my BII, but it does show it being connected to the ACT sensor, or is the black/white wire just a ground wire, man I hate eletrical stuff.
Thanks for your help,
Shiny

 

Electrical gets to be a pain, because you have to diagnose electrical carefully and systematically.

I don't have my wiring diagram in front of me, but as I recall, you should have 5V (all voltages referenced to ground) on one (the common wire to the other sensors). This is called Vref, and is a steady 5V power supply provided by the computer as a reference/excitation voltage to several sensors. The MAP signal back to the computer is actually a frequency signal, and I'm not sure what you should see as far as voltage on the other two leads back to the computer. The main signal should show a frequency of about .16 kHz KOEO, if you have a frequency counter in your DMM.

If/When I get a chance tomorrow (after the twins go down for a nap or something), I'll look at mine and see what I measure on mine for comparison.

 

I went ahead and checked tonight, and I get the same thing you're getting: 5.1 V on the orange wire and the green wire and 0 on the black white wire. The green wire (pin 45 at the PCM) showed the expected 0.16 kHz. Possibly your computer has failed internally and can't read the MAP anymore??

 

Had a 87 Bronco II for over ten years from new. Great on the flat or on dirt roads in the desert or on snow (it was a 5 spd manual 4x4). But hills or passing anything with more than a rubber-band? Forget it. Complete tune-up every year and it would feel new for two weeks or so, and then, back to downshifting when climbing a 2% grade (ok, maybe 3%).
Figure out or find someone to put a 5.0 V8 (or even a 4.0 V6 if possible) in it and you will be much happier. Or just use it as is for off-roading.

 

Do you have black smoke or a dirty tailpipe?

Replace the O2 sensor. Cheap and easy to do unless the threads on the pipe are toast. Put some anti-sieze compound with the new one.

Cheers

Andrew

 

I checked the fuel pressure today. With key on it was 38, and with engine running it was at 32. The Haynes book said at KOEO it should have 40, and when running it should drop 3-10. It looks like it is within specs. Oh, and I have no black smoke or dirty tailpipe, although it could use a new exhaust. I'm beginning to think, it is just a slow, lack of power vehicle, especially with an automatic, just dont see how some people can put a lift kit on these and bigger tires, like 33 and have decent power. I'll just drive it for now until I rebuild my motor and trans in my Flareside, than I will look for a motor/trans swap in the BII.
Thanks for all your help and info guys,
Shiny