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  #1  
Old 09-20-2004, 12:06 AM
Bakedbricks Bakedbricks is offline
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'88 Ford Bronco II - Power loss after warming up

Hello, I'm new to this Forum, but have found information on these forums quite useful. I have a 1988 bronco II with a 2.9l engine, and am having major power loss problems after it warms up, it's like after the engine hits a specific RPM it won't go any higher, almost like i've down shifted, only worse. I have checked the codes and these numbers are the ones that come up (Koeo) 67, 89, 86. (I've replaced the automatic transmission with a 5-speed so i feel i can disregard these ones) Continuous mem, 114, 96. The fuel pump seems to be alright, as the pressure is correct. I've replaced the O2 sensor, plug wires, and distributor cap to no avail. i've checked my timming corectly with the (spout plug out), and it seems to advance right, after the plug is replaced. I'm at a loss at what to do next, i'd rather not go through and replace every sensor. I wonder if anyone has any suggestions that would be helpful.
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Old 09-20-2004, 11:55 AM
mrshorty mrshorty is offline
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A faulty neutral position switch (obviously yours is completely missing) can cause a few problems. The computer looks to see if the engine is under load or not, and adjusts accordingly. I don't think this would cause your symptoms (especially looking at the CM codes), but, if it were me, I'd want to wire in some "dummy" circuits to eliminate those KOEO codes.
CM 14 (the initial 1 is simply a separator pulse to separate the KOEO from CM codes). indicates an problem in the ignition system.
CM 96 indicates an intermittant fault in the wiring to the fuel pump.
However, usually one likes to check the KEOR codes before working on CM codes.
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Old 09-20-2004, 07:29 PM
Bakedbricks Bakedbricks is offline
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I have checked the KEOR codes and I get a clean pass, and i see that the CM code ,96, is indeed intermittent, because I checked the codes again today twice and once it came up and another time it did not. After i changed the transmission it still ran well, it'snly been recently that the "major power loss" has plagued me, and i fear that it might be getting worse (of course i may be paranoid as well) In any case, i was reading that the O2 sensor worked in conjunction with the ECT sensor, so that if the ECT wasn't working properly, the O2 sensor might be telling the computer to improperly mix the fuel after it warms up, would this be anything?
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Old 09-20-2004, 08:30 PM
nijwnfi nijwnfi is offline
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Are you sure you get KOER codes? Does engine ID flash first? 3 flashes for 6 cyl. I couldn't get KOER codes until I corrected code 67. Hope someone can help with wiring dummy circuits around neutral safety switch. I don't have a clue on that one
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Old 09-20-2004, 09:11 PM
Bakedbricks Bakedbricks is offline
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Yup, I'm sure about the KOER codes, I get the three sweeps for a 6 cyl, then one sweep, and then another. 11 = pass.
Also, I should say, when I've checked the fuel pressure the engine was cold and under no load. Under normal operation when one depresses the gas peddle the preasure remains the same unless it is abruptly depressed, then it goes up but is quickly regulated back down to normal.(correct me if i'm wrong) Well when my Bronco has warmed up and is "acting" up and (again under no load) as I push the peddle down the preasure goes up and does not return until I remove my foot. Now I was all ready to buy a preasure regulator but a number of people told me that it most likely was not at fault, and I've already spent $40 on a O2 sensor that was not needed, so I'd like not to repeat my mistakes and spend another $40. I've not checked the pressure under load conditions because I'm not sure how to safely do that and without kinking the hose.
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Old 09-21-2004, 12:13 PM
mrshorty mrshorty is offline
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So we essentially pass the KOEO test (At least we know why the transmission codes are there), pass the KOER test, next step is to look at the CM codes.
Becaues the CM 14 is more consistent, I would probably start there. CM 14, as mentioned above indicates some problem in the ignition system. I haven't spent any time diagnosing this code before, so I'm not real familiar with it. This code indicates an erratic PIP signal. As I understand it:
1) The crankshaft position sensor picks up crankshaft position and relays it to the ICM.
2) The ICM uses this to determine base timing and sends this information on to the EEC-IV computer.
3) The EEC-IV computer uses this and other engine load parameters to determine timing advance and sends this information back to the ICM
4) The ICM sends spark to the plugs.
As I understand it, this code indicates that the input signal to the EEC-IV computer (steps 1 and 2) was erratic. When this input is missing, then the computer either fires the spark plugs at the wrong time or not at all. This would contribute to poor performance.
If this were me, the first thing I would do is go to the library and get a hold of a good manual and figure out how to diagnose this thing. I expect it would involve inspecting the CKP, the ICM (which you've replaced, but the TFI module is known to have problems, especially when it gets too hot), and all associated wiring.

The CM 96 indicates an intermittent fault in the fuel pump circuit. Note that the EEC-IV computer does not measure the fuel pressure at the rail; it only monitors the fuel pump circuit and can really only determine if the circuit appears intact or not. While measuring the fuel pressure is a good diagnostic step, as you noted, it can be difficult to set something up that allows you to measure the fuel pressure while driving. I would suggest that, rather than measuring the pressure, measure the current flow through the fuel pump circuit. On a normally operating system, pump current is an indicator of pressure. At higher pressures, the fuel pump draws more current to overcome the higher pressure. As the pressure drops off, the pump current goes down because the pump isn't working as hard. If the current drops to 0, that means the pump shut off. Of course, if the fuel pump is cutting out intermittently, that could contribute to a lack of power.

I wish I could help more with the 14, but, like I said, I haven't ever done it, so I'm not familiar with the details. The fuel pump circuit is pretty basic, and you should be able to figure it out from a wiring diagram and some basic electrical tests.
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Old 09-21-2004, 12:18 PM
mrshorty mrshorty is offline
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Quote:
Originally Posted by nijwnfi
Are you sure you get KOER codes? Does engine ID flash first? 3 flashes for 6 cyl. I couldn't get KOER codes until I corrected code 67. Hope someone can help with wiring dummy circuits around neutral safety switch. I don't have a clue on that one
This seems to vary from year to year. I have heard this same thing from earlier EEC-IV systems, where it just plain wouldn't run the KOER test until it passed the KOEO test. Later, they made it so the test would run, but there's a code (98 I think) that is output when the KOER test is performed before getting KOEO pass. Other times, it just goes ahead and runs the KEOR test.
As for wiring in a dummy circuit, it's basically just a switch that is closed when the transmission is in gear and open when in neutral (or the other way around, don't remember). Not sure if you can use the PNP switch on the AT for this purpose. Just get a wiring diagram, and figure out how it should look to the computer and make it look that way.
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Last edited by mrshorty; 09-21-2004 at 12:26 PM.
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Old 09-21-2004, 02:16 PM
Bakedbricks Bakedbricks is offline
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Ok so a friend of mine had a TFI module and gave it to me to replace mine, telling me that it would correct the "14" code, and now it no longer comes up in the codes, but it didn't do anything about the main problem. So I was looking at my timing again, and I'm not sure that it is set right, or i could be confused about what is right, i removed the SPOUT jumper and set the timing mark to the "TC" line, but i've been hearing other people talk about setting it at the 10 line, and after replacing the spout jumper mine goes to 23, and other say it should go to 20. I'm not a real automotive guy, so i'm confused by this, so if you could tell me what the timing is supposed to look like i can move on from there. Again I set enitial timing at the "TC" line and after replacing the spout jumper it goes up to 23.

Thanks for your patience guys
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Old 09-21-2004, 03:32 PM
redlightning redlightning is offline
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Does it have a lot of miles.Have you checked for a clogged cat converter?
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Old 09-21-2004, 05:56 PM
Bakedbricks Bakedbricks is offline
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Quote:
Originally Posted by redlightning
Does it have a lot of miles.Have you checked for a clogged cat converter?
It has 160,400 -ish miles on it. I had the cat off with full intention of smashing the insides out, but it was very clean and air goes right through it so I left it alone.
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Old 09-21-2004, 06:01 PM
mrshorty mrshorty is offline
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The TC mark marks Top dead center (TDC). The 10 mark is 10° Before TDC (BTDC), and so on (20 = 20° BTDC, 30 = 30° BTDC).
With the SPOUT unplugged, base timing should be set to 10° BTDC.
With the SPOUT plugged in, the timing advance test should yield base + 20° BTDC (10+20=30° BTDC). Timing advance test is part of KOER test (see ignition timing tests at www.dalidesign.com/hbook/eectest.html).
What you describe would be retarded timing, which would easily explain your lack of power. Get the timing set right and see what you get.
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Old 09-22-2004, 05:53 PM
Bakedbricks Bakedbricks is offline
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Ok, i've set the inital timing to 10 BTDC and after the advance it goes to a little above 33 BTDC. How does this sound? it's close.

And now i've driven it to work and back, it has more power, but the same problem still exists, just not quite as bad. After it warms up power drops, now i was making some notes and if i had a tach i believe you see that it really bogs down at a specific RPM and won't go any higher unles your going down hill. In first gear the speed-o-meter goes up to 20MPH, and in second i get to 30MPH, and third 45MPH and so on. So i assume it's all at the same RPM. And just to make it clear, when it's acting up, it loses power, but when the engine hits that specific RPM it really cuts down, and does not want to go any faster. I hope this makes sence.
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Old 09-22-2004, 06:23 PM
mrshorty mrshorty is offline
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Now you've got the timing set right.
Did you ever resolve the CM 14 and/or the CM 96? Can you pinpoint under what conditions each one is set? I expect once you find the cause for the 14 (the 96 might also be contributing), you're going to resolve the problem.
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Old 09-22-2004, 11:17 PM
Bakedbricks Bakedbricks is offline
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The CM 14 code no longer comes up, just the 96
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Old 09-23-2004, 05:53 PM
Bakedbricks Bakedbricks is offline
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Alright, i was inspecting some wiring and found a wire that goes to the fuel pump someone had just twisted together, and while on my lunch break, i took a wire nut and secured it. I then cleared the memory, and after i got home i checked the codes again, and the CM code 96 did not show up. However the problem still exsists. I'm out of codes i'm not sure where to look next.
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Old 09-23-2004, 05:53 PM
 
 
 
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