'91 F150 suddenly popping with no power
08-29-2015, 03:38 PM
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'91 F150 suddenly popping with no power
Hi guys... I work on TVs, computers, ATVs, motorcycles and lawnmowers but vehicles with computers... ummm, no.
This truck, a 1991 F150 with a 302 V8, has been a good running truck. For a while now it's been running a little rich (you could smell it in the exhaust), but other than that no problems. A couple of weeks ago, I took the truck about 150 miles with no problem. On the way back, however, about half way home, I noticed a sudden loss of power. I pulled off to the side of the highway to check things out. After I pulled over, I found that the engine would idle fine, but if I tried to give it gas, it would pop through the intake and try to die out.
I changed the spark plugs right there (always keep an extra set with me) and cleaned a little white buildup off the distributor cap and rotor. That didn't have any effect.
After getting towed back home, I hooked a code reader up and all I get is a 67 (A/C clutch - I disconnected that when I bought the truck), 33 (EGR valve - which that truck has always given) and 29 (low engine speed). I think the Air Bypass Solenoid may be bad (it reads 10 ohms, but it doesn't activate if 12v is applied to it) but that shouldn't affect anything other than idle, I wouldn't think.
Thinking (hoping) maybe water in the gas (I had filled up about 50 miles before this happened) I changed the fuel filter and pumped all of the gas out of the tank. With the exception of a little debris and a couple of drops of water, I didn't see anything that should have caused this and it didn't have any effect anyway.
I tested the throttle position sensor - it's fine. I put a homemade spark gap inline with the ignition coil and the distributor cap and I do not see any difference in the spark with the truck idling or missing. I checked timing and it read about 17 or 18 with the SPOUT disconnected, so I dropped that back down to 10 and, other than lowering the already low RPM, there was no affect on the trouble at hand.
I have been told that it could possibly be a fuel pump (which I just replaced when I bought the truck 6 or 7 years ago) or fuel injectors. I need to get a fuel pressure gauge to test the pump. The injectors cost about $500 for a set or $70-80 each. The engine, while it does/did run good, I know it has problems... it leaks oil, it was using water after the water pump went out until I put some $30 head gasket leak seal in it... Putting another $500+ in it just doesn't make sense.
I am sorry to be so long winded, but as a technician/mechanic I know that the more details provided, the better...
Having said that... HELP!!!! If there is anything that I have overlooked, I would be ever so grateful for any and all advise! Thank you in advance...
This truck, a 1991 F150 with a 302 V8, has been a good running truck. For a while now it's been running a little rich (you could smell it in the exhaust), but other than that no problems. A couple of weeks ago, I took the truck about 150 miles with no problem. On the way back, however, about half way home, I noticed a sudden loss of power. I pulled off to the side of the highway to check things out. After I pulled over, I found that the engine would idle fine, but if I tried to give it gas, it would pop through the intake and try to die out.
I changed the spark plugs right there (always keep an extra set with me) and cleaned a little white buildup off the distributor cap and rotor. That didn't have any effect.
After getting towed back home, I hooked a code reader up and all I get is a 67 (A/C clutch - I disconnected that when I bought the truck), 33 (EGR valve - which that truck has always given) and 29 (low engine speed). I think the Air Bypass Solenoid may be bad (it reads 10 ohms, but it doesn't activate if 12v is applied to it) but that shouldn't affect anything other than idle, I wouldn't think.
Thinking (hoping) maybe water in the gas (I had filled up about 50 miles before this happened) I changed the fuel filter and pumped all of the gas out of the tank. With the exception of a little debris and a couple of drops of water, I didn't see anything that should have caused this and it didn't have any effect anyway.
I tested the throttle position sensor - it's fine. I put a homemade spark gap inline with the ignition coil and the distributor cap and I do not see any difference in the spark with the truck idling or missing. I checked timing and it read about 17 or 18 with the SPOUT disconnected, so I dropped that back down to 10 and, other than lowering the already low RPM, there was no affect on the trouble at hand.
I have been told that it could possibly be a fuel pump (which I just replaced when I bought the truck 6 or 7 years ago) or fuel injectors. I need to get a fuel pressure gauge to test the pump. The injectors cost about $500 for a set or $70-80 each. The engine, while it does/did run good, I know it has problems... it leaks oil, it was using water after the water pump went out until I put some $30 head gasket leak seal in it... Putting another $500+ in it just doesn't make sense.
I am sorry to be so long winded, but as a technician/mechanic I know that the more details provided, the better...
Having said that... HELP!!!! If there is anything that I have overlooked, I would be ever so grateful for any and all advise! Thank you in advance...
