Engine issues...need some help
12-11-2014, 02:51 PM
#1
Engine issues...need some help
Hey, guys. My '92 F150 5.0 is giving me some fits. I've been gone for a month working on the river. When I got home Tuesday, the truck started right up, but was idling erradictly. It would surge up to about 2-4,000 rpm and then drop down and start cutting out. It would do that a few times before finally dying. It acted like it wouldn't take gas, without playing with the pedal.
I pulled codes and had a bunch of them, but mostly just from where it wasn't up to operating temp. The one that stuck out was related to the tps. I had a suspicion that might be the culprit, so I took a closer look. The wires were starting to pull out of the sensor and were exposed. I don't think one was really even making connection. I didn't bother testing it because I knew it needed replaced. The truck has ran pretty good up until now, except for idling a little high sometimes, which I just attributed to the iac needing a good cleaning. I replaced the tps, cleaned the throttle body and iac really well, put everything back together and it ran horribly. Idle was sky high and it was cutting out worse. I tested the tps and sure enough, the new one was bad. Replaced it and idle is now running normal speed, but still cutting out like crazy and won't run very long without dying. I had the battery disconnected while replacing the sensor so the ecu would re-learn everything. Now the koeo test is only showing "111", which I believe means everything is within spec. The koer test, for whatever reason, will not respond. Not sure why, but the truck will idle for a while and then cut out and die. Not driveable at all and very hard to restart.
Other things I tried: Disconnected iac plug while running and there was no change in idle at all. Plug looks good. Valve looked good when I had it apart. Checked the fuel pressure. It stays in the neighborhood of 38-42 psi idling, running, and with/without the vacuum line hooked up to the pressure regulator. Checked for vacuum leaks by spraying carb cleaner around the hoses and connections. Checked out good. I even disconnected one small vacuum line and sprayed in the area just to make sure the engine response was noticeable. It revved pretty good, so I'm fairly certain of no vacuum leaks.
Sorry this is so long, but I thought you guys might want to know what all I've tried to get to this point. Any ideas?
I pulled codes and had a bunch of them, but mostly just from where it wasn't up to operating temp. The one that stuck out was related to the tps. I had a suspicion that might be the culprit, so I took a closer look. The wires were starting to pull out of the sensor and were exposed. I don't think one was really even making connection. I didn't bother testing it because I knew it needed replaced. The truck has ran pretty good up until now, except for idling a little high sometimes, which I just attributed to the iac needing a good cleaning. I replaced the tps, cleaned the throttle body and iac really well, put everything back together and it ran horribly. Idle was sky high and it was cutting out worse. I tested the tps and sure enough, the new one was bad. Replaced it and idle is now running normal speed, but still cutting out like crazy and won't run very long without dying. I had the battery disconnected while replacing the sensor so the ecu would re-learn everything. Now the koeo test is only showing "111", which I believe means everything is within spec. The koer test, for whatever reason, will not respond. Not sure why, but the truck will idle for a while and then cut out and die. Not driveable at all and very hard to restart.
Other things I tried: Disconnected iac plug while running and there was no change in idle at all. Plug looks good. Valve looked good when I had it apart. Checked the fuel pressure. It stays in the neighborhood of 38-42 psi idling, running, and with/without the vacuum line hooked up to the pressure regulator. Checked for vacuum leaks by spraying carb cleaner around the hoses and connections. Checked out good. I even disconnected one small vacuum line and sprayed in the area just to make sure the engine response was noticeable. It revved pretty good, so I'm fairly certain of no vacuum leaks.
Sorry this is so long, but I thought you guys might want to know what all I've tried to get to this point. Any ideas?
12-11-2014, 07:31 PM
#2
I got home this evening and tried to check things out again. Now, it won't start at all. There is no spark whatsoever. And also, another new symptom. When you turn the key to start it, it continues to turn over even after you let off of the key. Sometimes for just a second, sometimes for a few seconds.
This makes me think it has something to do with the ignition switch, although, I don't know how that would relate to the surging idle...unless I have 2 or more separate problems going on. This thing is driving me friggin crazy.
This makes me think it has something to do with the ignition switch, although, I don't know how that would relate to the surging idle...unless I have 2 or more separate problems going on. This thing is driving me friggin crazy.
12-11-2014, 08:07 PM
#3
Patience. Just gotta find the gremlin.
Your fuel pressure is up in range, so that's good. You should notice it rise up to it's max with the regulator vacuum unhooked and drop down 5 to 8 psi with vacuum (that's at idle). Presumably you checked that vacuum line for fuel smell.
Moving on to no spark, that could be coil, distributor pickup (PIP) or ICM, presuming the wires, rotor and cap are ok and the distributor is actually turning.
All that ignition stuff only comes into play IF the coil actually has power to it in the first place (positive side of the coil, closest to the driver's fender). Test light from ground to the coil positive.
It does sound like your ignition switch is acting up which may be why you don't have power to the coil with the key on - if that turns out to be when you test the coil.
If it turns out that you suspect the ignition switch, that is bolted to the bottom of your column about 2/3 of the way down - big (usually) white switch with a lot of wires. There's a rod with a hook on the end that fits into that switch. The key tumbler pushes the rod when you turn the key.
Another thing that can give you ridiculous problems is bad grounds. They'll drive you crazy checking things that don't make sense. Good idea to clean them all up.
Your fuel pressure is up in range, so that's good. You should notice it rise up to it's max with the regulator vacuum unhooked and drop down 5 to 8 psi with vacuum (that's at idle). Presumably you checked that vacuum line for fuel smell.
Moving on to no spark, that could be coil, distributor pickup (PIP) or ICM, presuming the wires, rotor and cap are ok and the distributor is actually turning.
All that ignition stuff only comes into play IF the coil actually has power to it in the first place (positive side of the coil, closest to the driver's fender). Test light from ground to the coil positive.
It does sound like your ignition switch is acting up which may be why you don't have power to the coil with the key on - if that turns out to be when you test the coil.
If it turns out that you suspect the ignition switch, that is bolted to the bottom of your column about 2/3 of the way down - big (usually) white switch with a lot of wires. There's a rod with a hook on the end that fits into that switch. The key tumbler pushes the rod when you turn the key.
Another thing that can give you ridiculous problems is bad grounds. They'll drive you crazy checking things that don't make sense. Good idea to clean them all up.
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broncojunkie (12-11-2014)
12-11-2014, 11:22 PM
#4
Patience. Just gotta find the gremlin.
Your fuel pressure is up in range, so that's good. You should notice it rise up to it's max with the regulator vacuum unhooked and drop down 5 to 8 psi with vacuum (that's at idle). Presumably you checked that vacuum line for fuel smell.
Moving on to no spark, that could be coil, distributor pickup (PIP) or ICM, presuming the wires, rotor and cap are ok and the distributor is actually turning.
All that ignition stuff only comes into play IF the coil actually has power to it in the first place (positive side of the coil, closest to the driver's fender). Test light from ground to the coil positive.
It does sound like your ignition switch is acting up which may be why you don't have power to the coil with the key on - if that turns out to be when you test the coil.
If it turns out that you suspect the ignition switch, that is bolted to the bottom of your column about 2/3 of the way down - big (usually) white switch with a lot of wires. There's a rod with a hook on the end that fits into that switch. The key tumbler pushes the rod when you turn the key.
Another thing that can give you ridiculous problems is bad grounds. They'll drive you crazy checking things that don't make sense. Good idea to clean them all up.
Your fuel pressure is up in range, so that's good. You should notice it rise up to it's max with the regulator vacuum unhooked and drop down 5 to 8 psi with vacuum (that's at idle). Presumably you checked that vacuum line for fuel smell.
Moving on to no spark, that could be coil, distributor pickup (PIP) or ICM, presuming the wires, rotor and cap are ok and the distributor is actually turning.
All that ignition stuff only comes into play IF the coil actually has power to it in the first place (positive side of the coil, closest to the driver's fender). Test light from ground to the coil positive.
It does sound like your ignition switch is acting up which may be why you don't have power to the coil with the key on - if that turns out to be when you test the coil.
If it turns out that you suspect the ignition switch, that is bolted to the bottom of your column about 2/3 of the way down - big (usually) white switch with a lot of wires. There's a rod with a hook on the end that fits into that switch. The key tumbler pushes the rod when you turn the key.
Another thing that can give you ridiculous problems is bad grounds. They'll drive you crazy checking things that don't make sense. Good idea to clean them all up.
I will have to check the power to the coil tomorrow. I was about worn out this evening. If I'm getting power, it will be with ignition in the run position, correct? In other words, if I can turn the key and get power to the distributor, the ignition switch is probably ok?
The grounds all looked good, but I do understand that it can cause some strange issues. I replaced the main battery ground not too long ago, along with the starter. Everything still looks good.
Will check the power going to the distributor tomorrow and go from there. Thanks for the input!
12-12-2014, 08:59 AM
#5
Well, I tested the power going to the distributor this morning and I do appear to be getting power with the ignition on. I also appear to be getting power to the coil. At this point, I'm thinking the coil might be bad...although I'm still confused about why the motor keeps cranking a couple seconds after letting off of the key. Have any of you had to replace the ignition switch? Is it common to go bad?
12-12-2014, 09:34 AM
#6
1994 F150 XLT 5.8L 2wd
You may try pulling the bottom of the steering column and watching the rod to make sure it's returning to resting position when you you move back from start position.
12-12-2014, 10:17 AM
#7
Anyone know if there's a good way to bench test the ignition coil? Can the parts store do it?
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12-12-2014, 11:13 AM
#8
1994 F150 XLT 5.8L 2wd
I was referring more to it sticking on the return stroke. Not unheard of for it to gum up a little bit and return slower than it should causing the starter to stay engaged slightly longer than the key is turned.
Bench testing I'm not sure about, find someone with a similar F150 and try the coil on their truck.
Bench testing I'm not sure about, find someone with a similar F150 and try the coil on their truck.
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broncojunkie (12-12-2014)
12-12-2014, 12:41 PM
#9
Senior Member
It would be easy to test if that was the problem, and also which of the two solenoids it was, if that is in fact the problem. A remote starter switch would come in handy here.
12-12-2014, 04:04 PM
#10
Well I pulled out the ignition switch and the part that slides seemed to not work very smoothly. Wasn't sure if that would cause it, but I went ahead and replaced it, since it was only $20. It didn't cure it. I tried jumping at the solenoid on the firewall and it seemed like it still wanted to stick. Regardless, I still have no spark and no start. I took the ignition coil off and bench tested it. It appears to be fine, according to the ohm specs. I even took it to the parts store to have a second opinion. They looked it up and sure enough, it was within spec. My next step, I think, would be to check the pip in the distributor. Anyone know how to test it?