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My 1993 F150 5.0 efi recently began bogging down or stalling as soon as you step on the gas from a stop. It will only restart if you hold the petal to the floor and then it belches out black smoke until while slowly throttling down to idle and begin to run smoothly. Usually starts easy when cold and fast idle for a few minutes before acting up. When warm, first 2 starts it will rev up and stall right out, then finally start, belching smoke and settling down to idle. You can "slowly" rev it up and down but a quick rev it will bog, and begin to sputter bad and take a full minute to either recover or just stall. From a smooth idle as soon as you drop it in gear it will stall out. If you fast idle it, get it in gear and kinda roll off, slowly accelerating it will perform just fine going down the road at high speeds.
WHAT I HAVE DONE:
#1 Put a pressure gauge on the rail and under the wiper and monitor it constantly. KOEO instant to 40-42. KOER @ 36-38. Jumps up to 40 when you hit the throttle for an instant. Never drops below 36 and holds pressure overnight.
2 .. Remove Neg cable and gnd. to frame. Replaced Neg. cable. Started up. Ran thru all sequences (stalling, misfiring, est to smooth idle. shut down and checked codes.
Blinked .. #21 and #85 and last #11
3 .. tested MAP sensor, determined it to be "out of specs" (159Hz) .... Replaced it.
4 .. tested TPS sensor via "analog meter method" and it was smooth and passed several tests.
5 ..tested EGR valve via applying vacuum while idling to stall. Idles fine with line off and even EGR positioning sensor removed. No leaks
6 .. tested EGR solenoid with vacuum gauge under wiper while driving around and observed no movement while accelerating or driving. Replaced EGR solenoid with no change in behavior. Temporary blocked EGR to eliminate it as problem.
7 .. Removed, cleaned and bench tested Idle Air Solenoid and it passed.
8 .. Removed EEC , disassembled it to find it was a recent reman, with the 2 main caps already been replaced. A third of a different value was never changed and appeared to be leaking at the base so I changed that one with another of the same value, reassembled and ran the truck with no change in behavior.
9 .. probably forgot something....
UNTESTED so far:
Oxygen sensor
TAB and TAD
Coolant temp sensor (works on the dash)
Crank position sensor (do I have one ? )
I have NOT tested any electrical components yet.
Could anyone here please throw out some Suggestions , Questions or corrections....Thanks !!
Great job doing some trouble shooting! Black smoke out of the exhaust is a positive sign you're running rich.
Next step is to bring your truck up to running temperature and do an code check with the KOEO and KOER. It's important that it's at running temperature.
I suspect it's going to give you a ECT trouble code. Your dash temp gauge and your ECU temp input uses two different sensors. Both sensors are on the intake manifold, but the dash gauge sensor has 1 wire going to it. The ECU temp sensor has 2 wires to it. You obviously know you way around a multimeter so it shouldn't take you too long to disconnect the ECU temp sensor and get the resistance of it. Here's a handy chart. While you're in there, you should check your IAT sensor too. It's also on the intake manifold, in one of the intake runners, and it uses two wires.
Next step is to bring your truck up to running temperature and do an code check with the KOEO and KOER. It's important that it's at running temperature.
I suspect it's going to give you a ECT trouble code.
. While you're in there, you should check your IAT sensor too. It's also on the intake manifold, in one of the intake runners, and it uses two wires.
I have pulled codes many times hot and cold and its always the same #21 and #85. #11 will only show up if I clear the EEC. Will a faulty ECU temp sensor cause the rich mix ? Where can I find test procedures for this and the IAT sensor ? I would like to do some KOER tests too but don`t know how to proceed there either. Would the #85... purg circuit failure cause any issues ? I see where many remove all that, air pump and all. Mines all there in pretty good shape. Isn`t that controlled by the tab or tad sensors which I haven`t checked yet ?
I'm surprised you have 2 digit trouble codes. I was lead to believe that 2 digit trouble codes were changed to 3 digit trouble codes in ~1991. Are you sure you're counting correctly?
Yes, a malfunctioning ECU engine coolant temp sensor will cause over fueling or under fueling.. Same with the intake charge temp sensor.
Testing them are easy, thou. Just unplug them and touch the multimeter to the terminal inside the sensor. Use the chart I supplied above to correlate the resistance to the temperature If it's more than ~10 degrees off, it should be changed.
Use the chart I supplied above to correlate the resistance to the temperature If it's more than ~10 degrees off, it should be changed.
Tested the ECU sensor today and it is indeed about 12 deg. off so I will replace it. Also tested the IAT sensor and found it to be about right. To me they both appear to be the same sensors ?? I`ll report back the results tomorrow.
Proto... I have fixed my problem and have you to thank for it. When I tested the ECU the engine was hot and what I thought was 12 deg. off was really dead shorted. I checked it again this morning and had very low resistance. After removing it I checked it on the bench by heating the end with my heat gun. It seems to go from low resistance to shorted with little in between, I would have never found that as I did not know there were 2 temp. sensors and even had a code pointing right at it. Runs great now ! You must have been very valuable to our boys flying around !
Glad you guys got it going. The code 85 is for your EVAP Canister Purge Valve. Symptoms are Rough idle, lack of acceleration, and low fuel mileage. At this point I would not worry about it unless any of the symptoms listed show up especially mileage. If the CPV is bad, it allows air all the time to exit emissions. Since it is open flow and the CPV is not blocking air when it is not needed the PCM will adjust with more fuel to compensate for the needed A/F ratio.
Yes, I checked the codes again after a good test drive and it was the only one I had left, except for a NEW one, #64 (IAT) which I can only guess was there because I unplugged it and checked it a few times. ( Don`t know how the EEC would know that??) Any way I cleared it, took another ride and checked again and only the #85 is left. NO check engine light. Perfect ! Help me here again. Do the TAD or TAB sensors have something to do with that (#85) ?? They are the only ones left I haven't looked at.
Proto... I have fixed my problem and have you to thank for it. When I tested the ECU the engine was hot and what I thought was 12 deg. off was really dead shorted. I checked it again this morning and had very low resistance. After removing it I checked it on the bench by heating the end with my heat gun. It seems to go from low resistance to shorted with little in between, I would have never found that as I did not know there were 2 temp. sensors and even had a code pointing right at it. Runs great now ! You must have been very valuable to our boys flying around !
That's great! I love testing out components and finding the smoking gun vs randomly swapping out parts. When you said "12° off", I had my doubts that swapping it would fix it because that shouldn't be enough to cause the severe running problems your experiencing... But a dead short sure would.
You're tab and tad solinoid have nothing to do with your cpv solinoid. Odds are, your cpv solinoid is burnt out. You can check it with an ohm meter. I think it should be about 1k ohms, but don't quote me on that. You can also remove it and test it with a 12 volt battery to see if you can blow air through it when you energize the coil.
"cpv solenoid".... I`m not finding that by googling it.. Haven`t seen any other solenoids, UNLess......... Its that mess behind the engine close to the firewall ?????
Sandymane, .....Yea ! ....Mine looks a LOT different than that. Like 20yrs older than that. Thats nice condition. The cannister , lines, some kinda square boxie thing, are all there in good shape, just never looked too hard. I going to try and make it all work. I`ll look for that solinoid. Seems many remove all that, pump and all.
Sandymane, .....Yea ! ....Mine looks a LOT different than that. Like 20yrs older than that. Thats nice condition. The cannister , lines, some kinda square boxie thing, are all there in good shape, just never looked too hard. I going to try and make it all work. I`ll look for that solinoid. Seems many remove all that, pump and all.
They remove the air pump but not the Canister Purge. My 1991 460 is pure stock. No emissions deleted. Good vac lines and hoses usually prevent many issues that cause some people problems and some don't like anything to do with emissions. If you want to go that route, get it going stock and then play if you want. You are off to a good start.
