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Discussion Starter · #1 ·
Vehicle Type: It is an OBD1 1994 F250 460 with an E4OD auto.

Previous Problems (fixed): Felt like it was running out of fuel then it would have a spark of full power then repeat (capacitors in the PCM burned up).
//Side note\\: Truck never had the current issue until I replaced the ECU. Got it through autozone and a warrantied it out and got another one because whoever remaned the first ECU did a horrible job and left a glob of solder connecting the current from one capacitor to a neighboring resistor. Second remaned unit looks damn near factory (good reman job).

1st Problem I'm Facing: I am experiencing hard starts. When cranking, 25% of the time it'll fire right up as expected. The rest of the time it'll either crank a couple seconds more and you can feel the engine firing a couple cylinders (still relying on the starter) before it fires up and can run on it's own.

1st Problem (Continued): Whenever the capacitors went bad in my PCM I did impulsively replace parts. Jumping the gun and wasting money as some people do at first. Given the problem I had at the time I replaced the FPR (Fuel Pressure Regulator) with one I got when I ventured to the junkyard, along with a spare ICM (Ignition Control Module) from my friend's parts truck that also had a 460. At the time I also replaced the MAP (Manifold Absolute Pressure) and O2 sensors, both new from napa. After seeing no change I took a step back and tested pretty much everything before I found out it was the PCM. Fast forward to now, after changing the 1st remaned unit with a 2nd one the hard start wasn't as bad so I just dealt with it, but now it is getting worse. I was leaving the store and it cranked continually for about 10 seconds with a couple cylinder fires before it cranked to life. That same event happened twice today. Last week I put my factory MAP sensor back in because the NAPA one had too much play in the plug when connected. That helped a lot I will say. 2 days ago after checking the timing with and without spout plug disconnected. I put my original ICM back on and didn't notice much change, and today the hard starts were horrible. The only thing I haven't replaced with my original one yet is the O2 sensor. The napa one is still in there. The truck doesn't throw any KOEO or KOER codes either.

2nd Problem: I've owned the truck coming up on 6 years now. I mainly drive local and it is my tow rig. This problem was slow but progressive starting about a 1.5-2 years ago. The RPMs when in idle while in park or neutral would stay right at the 1,000 mark. When dumped into any other gear it wouldn't move the idle and if if did it would go right back up to 1,000 rpm. The problem that is progressive and not sure if it relates to problem 1 in any way is the idle is lower than it used to be. It used to sit at 1k in or out of any drive gears. Now at idle out of drive gear it is around 850-900 rpm. When I drop it in gear it goes to around 750 and a couple times I found it sitting close to the 500 mark. My old IAC (Idle Air Control) valve went bad and my friend gave me his from the parts truck. When I first start it in the morning and the truck is in open loop it does the usual high idle around 1,200 rpm then falls to 1k. While in open loop I can throw it into whatever gear and the rpms raise slightly, hits gear, and stays at 1k rpm until the O2 sensor warms up (rather quickly) and then while in gear the rpms will slowly fall under 1k and hang around the 850-900 rpm area.
//Side Note\\: Before the capacitors in the PCM failed I did blow my transmission's separator plate gasket which roasted away the torque converter lockup clutch. When I pulled the transmission to replace the separator plate gasket I couldn't get my hands on a factory replacement torque converter so I took the next best option and put in a HD low stall triple disc converter. But keep in mind that this idle problem occurred before I replaced the converter so that converter doesn't lug the engine. Even before the transmission work, I would come up to a stop sign with my lights on, windshield whipers on full go, and defrost on full blast. The rpms would be low, voltage drops a bit, headlights dim, and my AC fan speed slows significantly.

One other thing. Factory spec for ignition timing is at 10° before TDC. When I pull the spout plug it sits at 10° but when the spout plug is connected and the electronic timing advance does it's thing, it sits at 20° before TDC when engine is at operating temperature. Does anyone know if this is normal? Shouldn't the timing advance be closer to base timing when at idle and no throttle input? I know timing needs to retarded in order to start the engine, so out of the sake of curiosity, I'll have to check the timing as the engine is cranked to life.

If anyone has any suggestions to fix my issues please let me know. Sorry for the lengthy description of my problems, I just wanted to be as descriptive about it as I can so everyone gets the idea. Thanks again.
 

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1990 Ford Mustang LX 351M powered!! Project Cherry Bomb!!
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I gots a few suggestions, have you checked for any vacuum leaks? 2 have you tried a new (not used) coil? have you checked the rest of your ignition system? (distributor cap,rotor, plugs, even the wires with a meter) and 3 it sounds like the IAC from the parts truck is bad too, try a new one and see if that fixes the high and low idle issues..I know how it is these days as tight as fundage is we all try to save wherever we can. That being said, sometimes putting used electronic parts on can cause a lot more issues than we are trying to correct . If I'm off base on anything here or someone else wants to chime in here... Jump on in!!
 

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Discussion Starter · #3 ·
I gots a few suggestions, have you checked for any vacuum leaks? 2 have you tried a new (not used) coil? have you checked the rest of your ignition system? (distributor cap,rotor, plugs, even the wires with a meter) and 3 it sounds like the IAC from the parts truck is bad too, try a new one and see if that fixes the high and low idle issues..I know how it is these days as tight as fundage is we all try to save wherever we can. That being said, sometimes putting used electronic parts on can cause a lot more issues than we are trying to correct . If I'm off base on anything here or someone else wants to chime in here... Jump on in!!
Whenever my pcm went bad a while back and caused some issues for me, I was inspecting pretty much everything after my two impulsive purchases didn't prove useful. I had already started doing a basic tune up before I pulled the transmission and did my work to it so the fuel filter only has 2-3k miles on it as well as the spark plugs. When the pcm failed I did the rest of my tune up as the plug wire that goes from the cap to the ignition coil was corroded on the coil side, which took metal off the coil plug. So the tune up is all finished and the current pcm in the truck is the second remaned one and is much cleaner on the circuit board than the first remaned unit. I guess I could back probe the iac valve plug and check the voltage at idle and when the engine is under load and see if that's in spec? By the way, the idle screw has NEVER been tampered with as I know the issues that could cause, especially with an automatic transmission.

I mean, the engine idle is 100% fine when in open loop on a morning start or if the truck has cooled off completely. When I throw it in gear the rpms jump up then down as it hits the gear and sits at 1k rpm. When it goes to closed loop ad the oxygen sensor is heated up, then the pcm uses the O2 sensor to determine the air to fuel ratio instead of the MAP sensor. After it goes into closed loop operation the idle rpm is under 1k and goes lower when in gear and the rpm doesn't jump up when thrown in gear.

I know I have an ultra low stall torque converter better and this can happen until it is broken in, but I backed out of my parking spot, threw it in drive, hit the gas and my friend said something so I let off the throttle. The rpms went from 1,200 to under 700 rpm. As soon as the needle hit 500 rpm it just smoothly shut off like I turned the ignition off. Yes, I stalled an efi truck with an automatic 😂

The last part I replaced was the ignition lock cylinder. Now my XLT has two sets of keys. And no, I didn't buy it impulsively. The lock cylinder clicked back and forth and had about half an inch of travel. Almost left me stranded at a gas station because I couldn't get the ignition to unlock. Thought it would also help my hard start but I was wrong.
 

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What about your ignition module? Have you checked it for corrosion? Check your local auto parts store to see if they can test it to make sure it's working correctly. I'm thinking if it's got a small short in it that shows up when it gets hot under the hood that may be it??
 

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Discussion Starter · #5 ·
What about your ignition module? Have you checked it for corrosion? Check your local auto parts store to see if they can test it to make sure it's working correctly. I'm thinking if it's got a small short in it that shows up when it gets hot under the hood that may be it??
Whenever the PCM went bad I used one of the parts truck and it worked well. Then after fixing the PCM the hard start was only there like 20% of the time, then it became more constant and I put my factory MAP sensor back on and that helped it out a lot, then a week later it only starts normally about 25% of the time and the rest is excessive cranking before starting or just a hard start with a couple extra cranks with periodic cylinders firing. Feels like I am starting my brother's 1978 350 in his squarebody. I put my factory ICM back on and had no change. I wasn't able to get the vacuum hose off the throttle body that goes to the MAP sensor, I was afraid I'd brake it but I'll just man up, take it off and inspect it for any leaks because that could be the issue. I have sprayed starting fluid around the intake manifold and throttle body. Usually if there's a vacuum leak between those it revs higher and runs richer. It doesn't throw any codes from KOEO or KOER.
 

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Discussion Starter · #6 ·
What about your ignition module? Have you checked it for corrosion? Check your local auto parts store to see if they can test it to make sure it's working correctly. I'm thinking if it's got a small short in it that shows up when it gets hot under the hood that may be it??
OBD1 Fords don't have a data server so the computer only does as programed and can't think for itself otherwise. But I'm kind of wondering what the timing advance does when starting it up, so I'll have to check that. Vehicles have to retard timing to start.
 

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When plugging the spout connector in timing will jump up to 20 to 24* btdc.

Have you ever had a PIP code?
Original distributor?








Scotty J. "AKA" The "Mad Porter"
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Ported BBF iron head specialist & Aluminum heads from all sources.
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Discussion Starter · #8 ·
The ignition control module was changed to a used one when my pcm went bad. After pcm was fixed it developed these other issues. I put my original ignition module back on. Neither of them got hot. Keep in mind that the harsh start happens pretty much all the time now, cold start or warm. But usually it cranks longer then fires right up on cold start, and when it warms up and goes to closed loop operation (when warmed up) it can either crank longer and have a couple cylinders fire before it cranks up or cranks the usual amount that it always has but fires cylinders (when they fire it feels and sounds like I'm cold starting a carbed engine) then it fires up and runs smoothly.

All the new parts: fuel filter, ignition coil, cap/rotor, plugs/wires, and O2 sensor.

Used parts that I switched back to my factory parts: MAP sensor, fuel pressure regulator, and ICM.
 

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Discussion Starter · #9 ·
When plugging the spout connector in timing will jump up to 20 to 24* btdc.

Have you ever had a PIP code?
Original distributor?








Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Log into Facebook
Distributor is the original to the truck. And I've wondered if it is going bad but the truck feels fine going down the road with no noticeable symptoms of what a bad PIP would give. Unless these harsh starts and low idle in closed loop is a symptom.

When plugging the spout plug back in it does jump from 10° before TDC to 20-24 before TDC. Thought about advancing it but after seeing that timing advance while at operating temperature and at idle I really don't know how I'd benefit from advancing the base timing. And yes, when revving the engine up (giving it some load) the timing does advance further up.
 

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Check your throttle position sensor. Be sure you have a good 5 volts going to it..A good ground for it and then the wire that goes back to the computer. KOEO with the throttle closed should have about point 9 volts(.9) and full throttle at 4 volts. The transition from idle to FT should be a smooth increase when the voltage to the computer is checked.
On Youtube there is a series of videos of someone with a 460 motorhome. Had all sorts of problems with idle..shifting..It was a bad wire from the TPS to the computer..He threw all sorts of parts at it..Found the wire and everything went back to normal..
 

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Vehicle Type: It is an OBD1 1994 F250 460 with an E4OD auto.

Previous Problems (fixed): Felt like it was running out of fuel then it would have a spark of full power then repeat (capacitors in the PCM burned up).
//Side note\\: Truck never had the current issue until I replaced the ECU. Got it through autozone and a warrantied it out and got another one because whoever remaned the first ECU did a horrible job and left a glob of solder connecting the current from one capacitor to a neighboring resistor. Second remaned unit looks damn near factory (good reman job).

1st Problem I'm Facing: I am experiencing hard starts. When cranking, 25% of the time it'll fire right up as expected. The rest of the time it'll either crank a couple seconds more and you can feel the engine firing a couple cylinders (still relying on the starter) before it fires up and can run on it's own.

1st Problem (Continued): Whenever the capacitors went bad in my PCM I did impulsively replace parts. Jumping the gun and wasting money as some people do at first. Given the problem I had at the time I replaced the FPR (Fuel Pressure Regulator) with one I got when I ventured to the junkyard, along with a spare ICM (Ignition Control Module) from my friend's parts truck that also had a 460. At the time I also replaced the MAP (Manifold Absolute Pressure) and O2 sensors, both new from napa. After seeing no change I took a step back and tested pretty much everything before I found out it was the PCM. Fast forward to now, after changing the 1st remaned unit with a 2nd one the hard start wasn't as bad so I just dealt with it, but now it is getting worse. I was leaving the store and it cranked continually for about 10 seconds with a couple cylinder fires before it cranked to life. That same event happened twice today. Last week I put my factory MAP sensor back in because the NAPA one had too much play in the plug when connected. That helped a lot I will say. 2 days ago after checking the timing with and without spout plug disconnected. I put my original ICM back on and didn't notice much change, and today the hard starts were horrible. The only thing I haven't replaced with my original one yet is the O2 sensor. The napa one is still in there. The truck doesn't throw any KOEO or KOER codes either.

2nd Problem: I've owned the truck coming up on 6 years now. I mainly drive local and it is my tow rig. This problem was slow but progressive starting about a 1.5-2 years ago. The RPMs when in idle while in park or neutral would stay right at the 1,000 mark. When dumped into any other gear it wouldn't move the idle and if if did it would go right back up to 1,000 rpm. The problem that is progressive and not sure if it relates to problem 1 in any way is the idle is lower than it used to be. It used to sit at 1k in or out of any drive gears. Now at idle out of drive gear it is around 850-900 rpm. When I drop it in gear it goes to around 750 and a couple times I found it sitting close to the 500 mark. My old IAC (Idle Air Control) valve went bad and my friend gave me his from the parts truck. When I first start it in the morning and the truck is in open loop it does the usual high idle around 1,200 rpm then falls to 1k. While in open loop I can throw it into whatever gear and the rpms raise slightly, hits gear, and stays at 1k rpm until the O2 sensor warms up (rather quickly) and then while in gear the rpms will slowly fall under 1k and hang around the 850-900 rpm area.
//Side Note\\: Before the capacitors in the PCM failed I did blow my transmission's separator plate gasket which roasted away the torque converter lockup clutch. When I pulled the transmission to replace the separator plate gasket I couldn't get my hands on a factory replacement torque converter so I took the next best option and put in a HD low stall triple disc converter. But keep in mind that this idle problem occurred before I replaced the converter so that converter doesn't lug the engine. Even before the transmission work, I would come up to a stop sign with my lights on, windshield whipers on full go, and defrost on full blast. The rpms would be low, voltage drops a bit, headlights dim, and my AC fan speed slows significantly.

One other thing. Factory spec for ignition timing is at 10° before TDC. When I pull the spout plug it sits at 10° but when the spout plug is connected and the electronic timing advance does it's thing, it sits at 20° before TDC when engine is at operating temperature. Does anyone know if this is normal? Shouldn't the timing advance be closer to base timing when at idle and no throttle input? I know timing needs to retarded in order to start the engine, so out of the sake of curiosity, I'll have to check the timing as the engine is cranked to life.

If anyone has any suggestions to fix my issues please let me know. Sorry for the lengthy description of my problems, I just wanted to be as descriptive about it as I can so everyone gets the idea. Thanks again.
I suggest, if you haven't done it already, you check all of your grounds. Add a couple of extras (engine to firewall, frame to body) if you feel ambitious. It's amazing how much havoc a dirty or bad ground will cause.
 

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Discussion Starter · #12 ·
Check your throttle position sensor. Be sure you have a good 5 volts going to it..A good ground for it and then the wire that goes back to the computer. KOEO with the throttle closed should have about point 9 volts(.9) and full throttle at 4 volts. The transition from idle to FT should be a smooth increase when the voltage to the computer is checked.
On Youtube there is a series of videos of someone with a 460 motorhome. Had all sorts of problems with idle..shifting..It was a bad wire from the TPS to the computer..He threw all sorts of parts at it..Found the wire and everything went back to normal..
A long time ago I was chasing a problem and I replaced the TPS. Didn't solve the problem so I put the factory one back on. When this problem occurred I checked everything. I put the aftermarket TPS back on because I had it laying around. TPS is within spec and consist voltage output from idle position to full throttle position.
 

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Okay that is great that the TPS has the proper voltages. But is the computer actually receiving the voltage..The problem with the guy in the YT videos was the wire from the TPS to the computer was bad. As the engine stalled and shook all over the place, the wire would send a bad signal to the computer. The TPS was fine..the computer wasn't getting the signal of it..
Pull the harness out of the computer. It has that bolt in the center..It is 60 pins. Pin #47 is the return to the computer from the TPS. It is a Gray with a white stripe color. Check the voltage at that pin while the KOEO (Key on engine off) test is conducted again. Jiggle the harness around..Hold the throttle at 1/3 or any where else you want and see what the voltage is at the #47 pin..
You are trying to find an intermittent problem..which is hard to do.
 

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Wait!!
I gave some bad info in the previous post. If you unplug the 60 pin plug from the computer, you will have nothing to test. The 5 volts and the ground come from the computer..If it is unplugged, you will have nothing..Leave the 60 pin plug in..You will need to back probe that #47 pin while the computer is powered up..You just need to see what the voltage is at the computer to be sure the wire isn't bad..
Sorry about the previous post. It is Saturday morning and the caffeine was flowing yet!!
 

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Discussion Starter · #15 ·
I will get around to check it later. Running errands at the moment. But I will say this... I have a feeling my catalytic converter is clogged. The exhaust doesn't smell like sulfer or rotten eggs exactly, it just smells like exhaust fumes. But I think it has been slowly plugging up over the years because the idle in park/neutral has been slowly falling and can't keep around 1k once in closed loop (up to operating temperature). Now with a low stall converter it sometimes bogs the engine down to around 700 rpm in gear and sometimes it doesn't when I come to stop sign it'll hang around 900. Before I came to town to run my errands I took the napa O2 sensor out. The truck wasn't hot but it wasn't cold enough to be in open loop. Started right up and stayed at 1k rpm. I dropped it in gear but I can't remember if it bogged or not. I was focusing on the beauty of the exhaust rumble (being the average gear head with a V8). I put my factory one back in to see if it will change anything. Doesnt start hard but then again I didn't let it sit very long before starting it again. Probably had some fresh gas in a couple cylinders. When I get back home I'm going to pull the O2 sensor again and wrap anything important with foil so nothing burns. When I took it out the first time I didn't let it run long because I didn't want to roast any wires or anything lol.

I'll let you know what I find out. But it makes sense for it to be clogged because it doesn't have as much hill climbing power as it did 5 years ago. And 5 years ago the idle would stay at 1k rpm in or out of gear.
 

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Discussion Starter · #18 ·
Hook a vacuum gauge to a manifold port..Even at 1000rpm it should be fairly high...16-18ish. If it is in the 10 range, unscrew the O2 sensor ..It will improve the vacuum signal if the Cat is plugged..
Well I don't have a vacuum gauge and I'm unsure as to where I would hook it up. But I just took my O2 sensor out again and let it idle and put in gear, just going through the hoops. It'll stay at 1k rpm for a prolonged period of time before it drops under 1k and hangs around 900 or a little more. When I put it in gear the rpms rise up and then go back to where it was when in park/neutral. With the O2 sensor in when I go from drive to neutral the rpms drop from 900 or so down to about 700 then bounce back up. With the sensor out I let it warm up and when I went from reverse to neutral and drive to neutral the rpms didn't fall when it came out if gear. the idle pretty much stayed the same.

So where would I connect a vacuum gauge to the intake?
 

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Discussion Starter · #20 ·
I had a feeling that's where it was. But it I'm being honest, I don't think there's any problems with my tps wiring. Truck shifts great and I can even get the torque converter clutch to lock in second gear with some finesse from 1st to 2nd gear shift. When the pcm thinks you're going WOT in 2nd it'll lock the converter. I don't floor mine but I go from 1/4 to close to 1/2 throttle and it'll lock. That being said, the transmission fully responds to throttle input so I think that is all good.
 
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