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1988 Bronco II computer codes


IIBRONCOS

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Hello, I have a 1988 Bronco II. Cold start is surges up and down for a minute or 2 then it will run rich for a minute or 2, then it changes to a non rich condition. It will repeat this a few times before warm up. Then when warm it runs excellent. Engine light will come on but not stay on all of the time it is running. Here are the computer KOEO readings. by the light flash. It has the correct 1988 computer in it. Any ideas what is wrong.
1
1
1
1
1
1
11111111
1111
1
1
11111111
1111
1
 
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RonD

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Welcome to TRS :)

OBD1 codes are not very good, lol

basically 11 or 111 means computer checks out OK

You need to pay attention to the pauses between flash of the light, that will tell you if your system is using 2 digit or 3 digit codes
Info here: http://www.therangerstation.com/tech_library/OBD_I.shtml

Cold start, all fuel injection computers need a way to detect coolant temp, is engine cold or is this a restart(engine warm).
ECT(engine coolant temp) sensor is what the computer uses.

This is different from the ECT SENDER, 1 wire, used for the dash board temp gauge

ECT sensor has 2 wires and only the computer uses it.
These are not too expensive, $6, so I would just change it.
You can test it cold and then warm with volt meter and sewing pin
1 wire will have 5 volts when key is on
Other wire will have about 3volts cold, depends on outside temp
And it will have about .5volt warmed up, under 1 volt
So volts drop as engine warms up
Use sewing pin to pierce the wires to find out which is which and to test voltage that the computer is "seeing"

This voltage tells the computer to run "Choke mode" rich mix, high idle, advanced spark, when engine is cold.
And to lean out the mix and lower idle as engine warms up

If ECT sensor has connector corrosion or is simply failing then its voltage back to computer could be changing(dropping) and then popping back up, this can cause your symptom and check engine light(CEL) to go on and then off as well


You could have 118(ECT sensor fault), 411(idle control fault) or 84(EGR system fault) depending on 2 or 3 digit code being used
 
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IIBRONCOS

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Thanks RonD for the quick and informative reply. This 1988 Bronco II does not have an EGR system so it couldn't be the code 84. I will order an ECT sensor and give it a try. I used one of those old scan tools that beep, so I just counted the beeps.
 

IIBRONCOS

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I got the new ECT sensor installed today. I started it and it still acts the same as with the old sensor only worse. It took longer to warm up and settle down to a normal idle, and it went through more cycles of running rich ( black smoke) to leaning out and running with no black smoke. Back to square 1. Any thoughts ?
I will try probing the connector and checking for the voltage readings.
 

RonD

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There are two fuel lines in the engine bay, one goes to the fuel rail, IN, the other goes to the Fuel Pressure Regulator(FPR), OUT

The FPR will also have a Vacuum hose attached
If the FPR diaphragm leaks, raw fuel will be sucked into the intake thru this vacuum line, causing Rich running
Remove this vacuum line and check it for fuel.
 

IIBRONCOS

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I will check for fuel in the FPR line today. Thanks.
 

JerryC

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IIBRONCOS

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I guess I should of given a little background on the 1988 Bronco II. When I got it it had sat for about 12 years. I contacted the owner who bought it in 1992 and they state the 46,000 mile is accurate actual mileage. It is still wearing tires from 1992 with half tread left. I carefully took the original engine down to remove the heads to check for problems inherent with them. Everything I could see looked to be in very good condition. I chose to buy a brand new pair of heads. I rebuilt and flushed each fuel injector, and replaced all of the fuel delivery parts and filters. It still has the original IAC and Air temp sensor. I replaced all of the rubber vacuum hoses with new ones. When warmed up it idles very smooth at 800 rpm with 20+ inches on the vacuum gauge. I have cleaned any visible ground wires, but I don't know where hidden ones could be. All ignition parts I know of are new. It still has the original computer in it. I have not driven it yet as safe tires need to go on first. I have replaced a long list of other parts.
 

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Did you clean and test the old IAC and ACT sensor?
 

IIBRONCOS

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Here is the update. I previously cleaned the original IAC but I have not cleaned the ACT ( how is that done ) ? I just did another cold start ( about 70 degrees outside ) the engine just did a little of surging up and down and then sat at 1200 rpm smooth idle for about 10 minutes or so before it settled to about a smooth 850 rpm. It did not have any rich running events. The check engine light came on after the engine was idling at 850. The fuel pressure regulator vacuum hose is dry inside.
So far what could have stopped the rich cycles as previous ? even after I replaced the ECT sensor and had 1 rich running event ?
I'll try another cold start tomorrow and see how it reacts. Should I expect the engine to take 10 minutes or so to come down to 850 curb idle ?
 
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RonD

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IAT or ACT sensor shouldn't effect fuel mix that much, its a "trim" sensor.

Length of time it takes for coolant in the engine to reach 190degF(operating temp) is related to the thermostat condition.
Next cold start, feel upper rad hose just after starting, then feel it again after 2 or 3 minutes, if it is warming up with the engine then thermostat is not closing all the way, and needs to be changed.

Radiator circulation is only for EXTRA heat, so not used until engine coolant gets up above 190degF.
So upper hose should stay cold until engine is warmed up then it will heat up fairly fast as thermostat opens and hot coolant starts to flow thru rad.
Your thermostat should be rated 190-195degF.

If outside temp was 70degF then I would expect coolant to get up to operating temp(190degF) with in 5 minutes of idling or less if driving.

ECT sensor detects coolant temp and computer lowers idle based on coolant temp, so if thermostat is stuck open and coolant is circulating thru rad on cold start then it will take a lot longer to get coolant in engine up to 190degF

Point of the thermostat is to get engine coolant and heater up to 190degF as soon as possible, best fuel economy, oil cleaning and lowest emissions happen when coolant is between 195 and 220degF
 
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JerryC

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To clean the ACT I'd try carb cleaner. It was cheap enough that I just replaced mine, it looked like it was dipped in tar.

What Ron said made me think of something, that is unusual but it costs nothing to check. How is your coolant level? Maybe an air pocket around the ECT would give a false reading until the tstat opens up.

My thoughts temp and not surging:
warmer temps can close tolerances a tiny bit, rubber is a little more compliant to make a good seal, electrical connections are better in warm vs cold.
Cold engines like a little more fuel.

Oh one other thing, is the hose from the exhaust manifold to the air cleaner still in place. It probably wouldn't cause surging all by itself but you might be up against a situation where several small things add up.

How about the MAP sensor? I think I remember reading they are difficult to test with typical home equipment.

O2 sensor good/bad???
 

IIBRONCOS

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The entire cooling system is new. Before I bought any cooling system parts I was on this forum and an expert from a few years ago has an article or link on the 2.9 and mentioned to put in a 180 degree high flow thermostat in the 2.9 to eliminate overheating for the heads. So it has that thermostat in it. New water pump, radiator, heater core and the engine block flushed, and all new hoses.
Yes I have the heat stove and hose to the air intake connected.
The MAP sensor is new, although I haven't tested it. The O2 sensor is also new. Sounds like I should get the OE thermostat. I'll start it tomorrow and check the upper hose for warm up.
 

RonD

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Difference between 180degF thermostat and 195degF thermostat is that the MPG will be lower and the oil not as clean with the 180degF

A working thermostat has nothing to do with overheating
The SAE, Society of Automotive Engineers, ran testing and found that 190-200degF coolant temp kept oil hot enough to burn off most contaminants, i.e. fuel, exhaust and moisture, and cleaner oil is better oil/lubrication.
Ford did their own tests and found 190-200degF coolant temp was optimal for best engine power and efficiency(best MPG).

If your engine loses coolant, has clogged ratiator or water pump fails the 15degF difference might give you an extra 5 seconds before overheating, 250+degF, is reached, so not a valid reason for 180degF thermostat

If "running cooler" was better then why not a 160degF thermostat or no thermostat at all?
Reason is, because it is not better, costs you money(MPG) and shortens engine life, dirtier oil.

Yes, test if thermostat is stuck open.

"New" used to mean "tested and working"
"New" now means "You test it and we will warranty it"

So a "new" part just means NO ONE has ever tested it, lol.
This is our own fault, WE want cheaper parts, and labor is expensive, so most manufacturers eliminated Quality Control departments long ago
 

JerryC

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I was just asking if the cooling system was full and without an air bubble.
 

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