I'm trying to diagnose a miss after my truck warms up. Truck runs fine until I get off the freeway. Then at stop lights when I'm taking off it fills like I'm running on 3 cylinders. If I give it some gas, floor it, it goes away after I hit about 30mph.

I have a 91 f150 rebuilt 302. Replaced all the filters, sensors, and switches. The temp gauge read never makes it to the N and I think what's happening it that the computer is stuck in a chock loop. No codes on the EEC.

Thanks for any help!!!!

Jim

 

So I did some research and found that the motor needs to reach a temp of 195. What happens if it doesn't get that hot?

 

What temp is the thermostat you are running?? I have a '90 302 and the thermostat is 190 degrees. Depending on the T-stat temp, if the engine didn't get to the correct temp the T-stat would not open. I honestly don't know what running at too low a temp would effect, but the PCM (computer) might try to compensate somehow for the cold engine?? I am sure some of the engine Guru's on here can tell us what running too cold would do.

guzzler96

 

Well I pulled the themostate out and it was 195. I replaced with anyway since it was apart. made no difference. I'm still getting a miss once it's warmed up. I done just about everything to this POS except sell it. Still no codes KOEO and KOER. I've tried with the AC on, in 4X4, everything. Anyone want a cheap truck????

 

If your temp sensor will not go past N then the computer 'sees' a cold motor and stays in 'cold engine' mode which causes it to run rich and load up. A new temp sensor will correct this. Also too rich of a fuel mixture can be caused by to much fuel pressure, do a pressure test on the Schrader valve in the fuel rail, fuel pressure reg. could be bad or the vacuum hose to it could be shot. You may also have some bad injectors.
The deal on running a hot enough thermo is to allow the computer to 'see' a warmed up engine and set the fuel\air ratio right.

 

I've had this problem ever since I put the rebuilt motor in it. I put all new sensors and switch on the motor. 68torino, which temp sensor are referring to. There is a temp sensor on the right side of the manafold and one on the heater hose tree? I'll try anything. I like the truck, but if it's going to keep this up, well it's out of here.

Jim

 

I doubt it's your gauge. The only real way to see if the motor is running hot or not is to put a real temp gauge on it.

It sounds to me either like a fuel pressure problem, or possibly ignition related. Do you have two tanks? Does it behave exactly the same on both tanks? Have you changed the fuel filter? Check the fuel lines for kinks? Get a pressure gauge and test it. It would be nice to be able to know what the pressure is when it happens, that would at least narrow it down quite a bit.

You can also get the ignition coil tested at a parts store. They should be able to tell you if it's good or not.

 

ECT Engine Coolant Temp sensor is located in the water jacket near the thermo housing.
Have you pulled any codes? I can help with that.

 

I'm getting 38psi on the fuel rail. Bleed down takes a long time so I don't think it has anything to do with fuel pressure. I repalced the fuel filter last week and the problem is on both tank. When I rebuilt the motor, the day after I bought the truck, I replaced all the switches and sensors along with, the EGR, TPS, EGR soleniod, EVP, knock sensor, distribrator, waterpump, powersteering pump, IAC, oil pressure switch and I thought I replaced the engine temp switch, parts where flying when I rebuilt the engine so I might have reused the engine temp switch.
Are you starting to see why this is getting so frustrating! KOER and KOEO tests code 11. Last week the MAP went out and I thought that was the problem with the rough idle. Got a code 41 and 81. After I replaced the Map I get code 11.

What voltages are on the temp switch? I'll check that tomorrow. Then I'm going to buy a for sell sign.

By the way, did I tell you I took it the "Timberline Ford" and They charged $275 to tell me it's not the coil. They had the truck for a week and couldn't find a the problem.

Jim

 

Code 41 would be the EGO sensor output voltage was low.
Code 81 relates to the failure of ECA pin 11 or ECA pin 51.
I'm reading out of How to tune and modify Ford fuel injection.
Voltage for the temp sensor is 5 volts. Volts at around 70* will be 3v and will drop to about .5 v when the motor is warmed up.
Also they recommend doing a tug test on the MAP wires to check for a fault.
Symptoms are stumbling, hesitation or stalling.

 

68torino,

Is the ECA the same as the ECC? Is code 41 related to a rich reading from the Oxy sensor? I'll check the voltage on the temp sensor today ans I'll check the MAP sensor wires while I'm at it. What is a failure on pins 11 and 51, no voltage????

Jim

 

Duane, were did you find those codes i was told to look at www.foedfuelinjection.com for codes definations, i'm not an expert in this feild?
KOEO MEMERY KOER

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</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 26.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=35>X

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 509.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=545>HEGO sensor circuit indicates system lean (right side)

</TD></TR><TR style="mso-yfti-irow: 34"><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 40.25pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=50>

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</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 26.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=35>

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 509.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=545>No HEGO switching detected always lean (right side)

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<TABLE class=MsoNormalTable style="WIDTH: 652.5pt; BORDER-TOP-STYLE: none; BORDER-RIGHT-STYLE: none; BORDER-LEFT-STYLE: none; BORDER-COLLAPSE: collapse; BORDER-BOTTOM-STYLE: none; mso-border-alt: solid windowtext .5pt; mso-padding-alt: 0in 5.4pt 0in 5.4pt" cellSpacing=0 cellPadding=0 width=808 border=1><TBODY><TR style="mso-yfti-irow: 88"><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: windowtext 1pt solid; WIDTH: 35.65pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" vAlign=top width=41 rowSpan=2>81

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 40.25pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=50>X

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 39.7pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=50>

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 26.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=35>

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 509.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=545>Air management 2 circuit failure (AM2/TAD)

</TD></TR><TR style="mso-yfti-irow: 89"><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 40.25pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=50>

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 39.7pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=50>X

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 26.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=35>

</TD><TD style="BORDER-RIGHT: windowtext 1pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0in; BORDER-LEFT: medium none; WIDTH: 509.95pt; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 1pt solid; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" vAlign=top width=545>MAP sensor vacuum was not greater than 2 in-Hg (7 kPa) during normal vehicle operation.

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A better list of codes would be nice to see,
thanks, later mike

 

This might all be caused by your faulty temp sensor (specifically code 41). The engine computer needs to see that the engine is in proper operating tempterature. Put the stock T-stat back in, fix your temp sensor so the reading is correct. I don't believe you should be so hard on the truck. I know it's fustrating, I've had my fair share of pesky problems but have a little patience...it's not the truck's fault (not saying it's your fault either). I see no reason to jump to a conclusion of selling the truck over this....but to each his own.

On to the technical info....

If the code 41 is recieved during the memory codes, it indicates the oxygen sensor output voltage was stuck low for an extended time during the last 40 operations of the engine. If the code 41 is recieved during the KOER test, it means the sensor's voltage remained low throughout the KOER test. This could be caused by your engine's computer thinking the engine is still cold, and adjusting your A/F ratios which screws up your oxygen sensor readings. Fix this problem soon, your engine might be running lean on some if not all cylinders.

If you fix the coolant sensor and it's still the same (i doubt it...but I'm giving info anyway)...begin troubleshooting the code by connecting a high-impedance voltmeter in parallel to the oxygen sensor. Leave the sensor connected. Start the engine, and run it at 2,000 rpm for two minutes. At the end of the two minutes, observe the volt meter. The voltage should be switching from below .45 volt to above .45 volt several times during each five second interval. If the voltage remains low, disconnect the hoses between the air cleaner and the throttle body assembly. Place the end of an unlit propane torch in the intake and open the propane control valve. If the voltage does not increase to above the .45 volt threshold, check the following:

Distributor Cap/rotor/wires/coil/plugs
EGR system
fuel pressure - should be between 30-45 psi at idle on Schraeder valve.
Intake or vacuum leaks

If you don't find any problems with these, replace the oxygen sensor.


The code 81 relates to the failure of computer Pin 11 or Pin 51 to drop low when the engine is not running. Pins 11 and 51 are the control circuits for the AM control circuit. Trace the vacuum hoses from the air pump control valves to locate the AM solenoids (I believe they're next to the coil). Each of the solenoids should have 12 volts on one terminal only. If neither terminal has 12 volts, repair the open circuit between the AM solenoids and pins 37 and 57 of the computer. If both terminals have 12 volts, repair the open circuit between the AM solenoids and ECA pin 11 or ECA pin 51.

A code 11 means that the computer has detected no problems during the section of the test where the code was delivered.

 

I'm thinking that you are paying to much attention to the temp gauge reading and that you should focus more on the fact that the problem only happens when hot. I know it can be easy to get on a train of thought with blinders on (been guilty many times) so here's some fresh insight; I think you should be taking a look at your ignition system. With heat comes resistance this can affect ignition wires (particularly old ones), spark plugs, distributors, modules, etc, and most and sometimes all of these won't set a code. You may want to pay for a scope check at your local garage if you are not in a position to check these things yourself. Good luck

P.S just because it's new doesn't mean it's working properly ie: spark plugs, been caught with that one.

 

Definitely a good point.....but regardless of if the coolant temp fixes his overall issue.....it still needs to be reading correctly for the engine to work correctly. If the computer thinks the engine is cold...it puts the appropriate A/F ratio for a cold engine. When the engine heats up, it requires a different A/F ratio. If the engine is putting in a cold a/f ratio...it'll work fine when it's cold. If it is still putting a cold a/f ratio when the engine is actually hot, it won't work right. This COULD be why his engine runs weird when hot. It sounds like the computer is confused. There is a reason why the instructions I gave tells you to run it at 2000 rpm for 2 minutes. It is essentially warming the engine and the oxygen sensor. The oxygen sensor needs to be warm in order for it to read correctly (hego = heated exhaust gas oxygen). The computer disregards (or partially disregards) oxygen sensor levels when the sensor is cold (ie closed or open loop modes). The only way it knows the sensor is cold, is by the coolant temp sensor. If i am correct, which i am pretty sure I am, the computer is thinking the oxygen sensor is cold, and parially or fully disregarding it's reading. It doesn't know what to make of the situation, so it's trying it's best but not working out perfectly. It thinks the engine is cold and is not fully acknowledging that oxygen sensor reading. Therefore, it's not putting in the correct a/f ratio. This is why I mentioned to check the o2 sensor reading with a voltmeter, to find out if you're sensor is reading lean or rich (and if it's reading correctly/working correctly). If you follow my directions you will solve the problem at some point (depends on what the actual problem is, that I am unsure of, but i am giving suggestions for checking). Fix the coolant temp issue.....and hopefully it fixes your problem...if you're still having troubles after the temp fix....(don't forget to clear your computer by removing the battery for a 1/2 hr) come back and let us know what has changed/not changed...etc etc...and we can diagnose from there.