Truck just started thsi new trick. It seems to run fine, other than a bit of a rough idle until the AC is turned on. At which point it will begin to surge and stall out at idle. It doesn't care where we are as long are stopped or stopping. It will just stall. It will usually start right back up without fail. If I turn the ac off no more stalls. Any ideas. I am going to hook up the Sunpro to it, but wanted to give anyone who may have seen this before first dibs.

Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's

 

sounds like a dirty throtle body or iac I pulled mine apart and cleaned it with carb cleaned and a new gasket

Ed

 

Ok results of KOEO and KOER tests. Can anyone explain these to me in layman’s terms?

Continuous Memory Test (KOEO)
Code 173 - O2 Sensor-voltage indicates "rich" (bank #1)
1. O2 Sensor was replaced about 6 mths ago-what is the difference between "bank #1" and "bank #2" which would have been code 177?

KOER Self Test
Code 412 - Cannot control RPM during engine run test - high RPM check
Code 538 - Insufficient RPM change or Invalid Cylinder balance test-throttle position movement or Invalid cylinder balance test-cylinder identification problems
Code 536 - Brake On-Off switch-circuit failure or not activated
Code 632 - Overdrive Cancel Switch-no switch action detected during Engine run self-test

Thanks in advance,
Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's

 

I don't know if this applies here or not but I'm pretty sure you probably have a sensor or switch in your system which steps the idle up when you are running the A.C.. It only functions whne the A.C. is "on". It's purpose is to keep you engine running when, at idle, the A.C. compressor puts a load on the engine. A similar arrangement is used on the power steering pump so that you can turn the wheels while idling without stalling the engine. I hope this may be some help.

 

I do not believe there are any sensors for the ac. None of my manuals show any. It seems to be pulling more power from the alternator than it should as the amp gauge dips way down when I turn the ac on. Could it be my alternator? Nothing else seems to be affecting it at all.

Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's

 

I have tested the voltage at the battery with the truck running and it read 14.6 volts, so it appears that the alternator is good. I do notice that when I turn on the ac the amp gauge dips immediately then comes back up to the normal location. If I turn the slector switch from lo to the next level the amp gauge drops a little, the next level it will drop more, then to hi it dips way low and may or may not cause the truck to stall. Could it be a ground somewhere that is causing this to happen? Why only when I turn on the ac?? If I turn on the heat everything seems fine, no dip on the amp gauge and no fluctuation in idle.

Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's

 

Anyone have any ideas or input?

Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's

 

[updated:LAST EDITED ON 04-Jun-02 AT 01:26 PM (EST)]The computer should sense the ac on, and adjust the idle. If that is not working, the ac compressor may be loading the engine enough to cause it to stall. On the other hand, you may have a problem with your compressor, and it may actually be loading the engine more than it should. I had a Mustang once that the rubber on the clutch pulley melted because the compressor locked up. When it cooled down, it was fine, and the compressor worked well for a long time.

There is also the possibility you mentioned that the alternator may be the problem. It could be that there is a low resistance or short in the compressor clutch, and it is overloading the alternator.
In my experience, when there is a heavy overload of the alternator, it will make a loud whine.

So, there are many possibilities. What I would do is have someone switch on the ac while I watched under the hood. Look for a jump of the belt or a rough start of the compressor. Secondly, you mentioned it had a little rough idle anyway. If there is a vacuum leak, or some other problem, the extra load may be all that it takes to stall it. That would be the first thing to diagnose (the rough idle).



Winford

 

Winfordr,

Thanks for the response. I have, when time permits been tracking a vacuum leak as the ac when set to max will shift to the defrost vents. I think I have found the culprit there, yet have not gotten to fix that line, yet. I think that all vacuum, to include ac/heater controls and intake originate at the tree on top of the Upper Intake. Is that correct? If that is the case then the line I have that connects to the solenoid on top of the Heater unit under the hood, and is dry rotted could be causing the ac air flow problem as well as the rough idle problem. Is that too correct?

Thanks again,

Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's

 

Yes, I believe you may have hit on the problem. I had forgotten about that part of the equation. Good Luck!

Winford

 

I agree with EHUHN. if the vacuum hose replacement does not cure it, cclean the IAC before you do anythung else. I have seen this be the problem quite a few times.

 

yup! Sounds to me like you may have hit upon the source of the prob

 

>KOER Self Test
>Code 412 - Cannot control RPM during engine run test - high
>RPM check
>Code 538 - Insufficient RPM change or Invalid Cylinder
>balance test-throttle position movement or Invalid cylinder
>balance test-cylinder identification problems
>Code 536 - Brake On-Off switch-circuit failure or not
>activated
>Code 632 - Overdrive Cancel Switch-no switch action detected
>during Engine run self-test


Ok here my 2c's.
code 412-that is the problem. can't control idle because idle air control isn't working. Had the same problem with a friends truck. Shut off when the ac kicked on, otherwise ran good.

code 538- You didn't stab the throttle at the appropriate time during the test.

code 536- You didn't touch the brake pedal when needed during test.

code 632- You didn't push the overdrive off button when needed during the test..

Try cleaning the Iac, if that doesn't work replace it. It is the culprit.

Good Luck, Hippie.

 

I will be checking the IAC out tomorrow and will repair the vacuum line that has dry rotted as well. I will post my results then. Thanks to all the replies.

Hippie I have always admired your truck. It is extremely nice and has a few of the engine mods I am considering. If you don't mind I may be shooting you some questions in the future. Have to resolve the issues at hand first.


Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's

 

I cleaned the IAC and the inlets to the throttle body yesterday. I also repaired the dry rotted white vacuum line at the outside recirculate door vacuum motor. Althought it has not stalled at idle yet, it still does shift the air to the defrost vents when I turn the AC to the MAX setting. In the Norm setting it seems to function normally. Guess I have another vacuum leak somewhere. Still searching for it.

Mike

93' F-150 Ext Cab 5.0L E4OD, MSD, K&N, 31x10.50's