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Troubleshooting. Any help?


lxer96

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Ok Here's the scoop. It's an 85 with the AL4D trans. Compression is good. Wires are all routed to the right cylinder. Plugs are good. Carb is freshly overhauled but in unknown state(it was my first one). The truck will start up and run but runs rough. It runs somewhat better now than it did before the carb work. I pulled the codes on it and here's what I came up with.

KOEO
23. TPS out of range
87. Fuel pump primary circuit failure or temp compensated pump solenoid out of range

MEMORY
18 Loss of ignition diagnostics monitor signal to the control module/spark output grounded
41. No exhaust gas switching detected indicating lean
54. ACT or Vane air sensor voltage too high

KOER
13. Cannot control RPM low during self test or idle speed control inoperative
21. Coolant temp out of range. I did the test with the engine cold so that may be why
22. MAP or baro sensor out of range
23. TPS out of range
25. Knock sensor not detected during dynamic response
41. No exhaust gas switching detected indicating lean


Anyone have any ideas? This truck is a project so I can take my time on it.
 


enginepaul

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Clear the current codes and drive it a bit, then pull codes again.
Then: Get a manual and start fixing the code problems starting with the lowest number.

Don't start buying parts until you are sure that you need them.
I have California factory smog and mine runs fine but it took some time and money to get there. The easiest - if you can legally do it - is the DuraSpark.
 

lxer96

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That's the main problem. I can't drive it. It has no power at all. The engine is very sluggish and if I put it into gear it dies unless I give it some gas. I have emissions testing but no inspection.
 
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Eric Kropp

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Check the "spout wire" by the distributor pig tail. It is the yellow wire that needs to be unplugged when timing and sometimes people forget to hook it back up.

Eric
 

enginepaul

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Go to e-bay and look for an "Emission Diagnosis" manual for your year; it shows how to repair all the codes and give tips for trucks like yours.
Be patient - it will work.
 

enginepaul

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lxer96

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I checked the spout wire and it is ok. Actually the insulation looked very good. Ohmmeter says it has good continuity also. I picked up a junkyard carb today just to try out because I got it for very cheap. Can't hurt to have 2! :)
 

CRAZ28

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dura spark it, if you have got the cash.
 

litleblue

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A couple of things to check. At the end of the KOER test (after the codes are sent)put a timing light on the engine and check the advance it should be fixed at about 27 deg. IF this is the case the spout is connected and working and the computer is probably ok.

The engine needs to be full warmed up and the 21 code should clear.

If the vehicle is running rough and you are retrieving a KOER code 41 check for vacuum leaks first (most likely) and the mixture control solenoid on the back of the carb (less likely). most of the time with oxygen sensors, 41 = lean, 42 = rich, 43 = not working.

the code for the knock sensor 25. if the engine doesn't ping while driving it don't worry about it. The sensor is working. I usually test the sensor by unplugging it and going for a little test drive if you do this you will probably hear the results of the sensor not working.

code 13 can be verified by idling the vehicle and observing the throttle kicker or "Idle speed control" ISC. as you gently advance the throttle the the servo will retract, as soon as the throttle is retracted the servo will extend. The calculated curb idle speed should around 850 to 950 RPM (IE controlled by the speed servo and computer. The mechanical idle stop should be set to around 700 to 750 RPM. If you cannot find a new ISC look for a central fuel injection from a late 80's V6 vehicle. That should work and the connector will be the same.

Map sensor code could be related any vacuum leaks. They usually are like the knock sensor and don't break often.

TPS code may be related the the ISC motor not working properly. These sensors are problematic and wear out quickly. Unless you can verify the resistance of sensor is incorrect while slowly exercising the throttle shaft. If the sensor appears to operate properly I would worry about this last.

KOEO test. at the end of this test after the codes are sent the computer enters an output state test. By slightly exercising the throttle all output solenoids will change state. You can measure the voltage to the outputs and listen to the solenoids click. There should be a group of three or four on the passenger side fender well where the ECM connector is. One of those solenoids is the TCP solenoid, I think it should be hooked up with a blue hose.
From what I remember the vacuum hose color coding is as follows;
Red hose=main vacuum for controls
Blue Hose=Temperature compensated Pump
Green hose= EGR
Orange hose = themactor system. Bypass and dump for the air pump and three way cat.

Hopes this helps. I know how frustrating the control system can be and ask more questions.
 

Eric Kropp

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If your engine and and emissions are stock, then I would make your first priority to carefully check all the vacuum lines. There are a bunch of color coded pre-bent vacuum lines running from various solenoids on the right fender to various locations on the the carburetor, EGR, thermactor, etc. There are also the regular vacuum lines like the brake booster, pcv and so on. The regular ones deteriorate with age and the pre-formed ones can break in the harness and not be visible. Hopefully you still have the vacuum schematic on the from cowell to sort this out. Also, make sure some-one has not incorrectly hooked up some of the color coded lines. And I did have a map and a tps sensor go bad, and had the same symtoms.

Eric
 

Eric Kropp

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I made a typing error. What I meant to type was "front cowell", meaning the hunk of metal that the radiator mounts to. There is a diagram glued on showing where all the pre-formed, color coded vacuum lines come and go from.

Eric
 

lxer96

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RE

Thanks Guys. I haven't had time to look at the truck lately due to the christmas madness, so hopefully this week will be productive!
 

lxer96

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re:

I checked things with a voltmeter today and came up with a bad TPS and a bad ACT. I was unable to check the MAP sensor but more than likely I will get a good working one and try it out. The TCP plug was full of water somehow so I cleaned it out. The TFI module is in good working order according to my voltmeter. The brake booster line seems to be a little lose where it connects to the booster itself and some of the other vaccum lines aren't too snug either. All the plastic ones seem ok but that's just judging by me trying to blow on them and not being able too. I'm not used to carbs having all these sensors but will they really effect the way it runs? I always thought a carb was more mechanically controlled than electrically. I guess this setup is like a transitional period between carb and EFI so it's sort of a funny combination.
 

litleblue

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The ACT sensor was Bad? that sensor is just a thermistor. It should ohm out to a resistance vs temperature table. They are pretty much bullet proof but I guess they could go bad.

That doesn't surprise me that the TPS is messed up that is the highest failure part on a Ford vehicle from the early 80's through the mid 90's. Essentially the same sensor is used on all vehicles through that time period. Again I wouldn't worry about the sensor too much since it is really pretty far down the the list of things that the computer looks at. That should be the last part replace once everything else is repaired.

Again vacuum leak are probably the culprit of most of your problems. Between the check valve off of the main vacuum manifold tee and vacuum revisor I would pipe in a vacuum gauge. Start the engine and stabilize the vacuum. Shut the key off and record the amount of time the vacuum diminishes. You should be able to maintain vacuum on the system for several minutes with out any appreciable loss. If the vacuum doesn't hold first inspect the check valve then go looking for leaky fittings hoses and actuators. This is where a Mighty Vac vacuum pump really comes in handy. Most of the actuators and valves can be checked for leaks pretty easily.

The TFI module most likely is a "go" "no go" problem. they pretty much fail and don't allow spark production. One thing that can happen is a grounded spout wire. If the Spout connection is grounded the TFI module will not allow spark. If the Spout connection is open or the calculated timing is messed up in the computer, the timing will only show what the base timing is, usually 10 deg BTDC. Again after the KOER test the timing will usually stabilize at about 27 deg BTDC. If the timing stabilizes around 27 deg I would think that portion of the emission control system is functioning.
 

enginepaul

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I second this:
"This is where a Mighty Vac vacuum pump really comes in handy."
Those hard plastic lines can get brittle and leak.

Your sensors may show as a problem when pulling codes when it is a wiring problem. I had a bad fitting that kept showing up as a bad sensor. The first thing the manual says is "Check the fitting" I did a quick look; spent a ton of time; then actuall inspected the fitting and found a bad contact! Rare, but don't overlook that.
 

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