92 f-150 runs but not correctly. Help
11-28-2015, 02:49 PM
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92 f-150 runs but not correctly. Help
I have a 92 150 with a 5.0 in it. It starts but won't continue to idle. It will run at half throttle but doesn't pick up rpm after that and as soon as you let off the gas it dies. It has a new throttle position sensor, distributor, and ignition control module. While cranking if you install an online Spark tester it flashes probably 12 times a second. After it starts it flashes slower and brighter. If anyone has any good ideas of what to check next or any solutions please by all means reply.
01-21-2016, 12:01 PM
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Hi Dave,
It used to be, only 3 things were required for an engine to run: spark, fuel, and compression. But now with engine management computers, there are so many places for something to go wrong. You may need to get your hands on the Emissions Testing Manual which still step through a logical sequence of tests to rule out various things. If your estimate of 12 firings a second during cranking is accurate, that's 720 a minute, or double-firing for cranking. Crank speed is around 250-350 RPM. But something is also affecting higher RPM. Possibly air mass sensor. Could be more than one thing which makes it really tough. Bad idle can be the Air Bypass Valve (what Ford calls it), otherwise known as the Idle Control Solenoid (ICS). Does the Check Engine Light come on? If so, get a readout of the fault codes. Also try disconnecting the battery for a few minutes to reset the computer mapping to default, and see if it acts any different when you first start it up.
I've got a similar problem with no idle, but engine runs fine otherwise. It was NOT the ICS as I thought, so now I'm going to have to be more thorough in my testing to find it. Hope it works out for you.
Milo
It used to be, only 3 things were required for an engine to run: spark, fuel, and compression. But now with engine management computers, there are so many places for something to go wrong. You may need to get your hands on the Emissions Testing Manual which still step through a logical sequence of tests to rule out various things. If your estimate of 12 firings a second during cranking is accurate, that's 720 a minute, or double-firing for cranking. Crank speed is around 250-350 RPM. But something is also affecting higher RPM. Possibly air mass sensor. Could be more than one thing which makes it really tough. Bad idle can be the Air Bypass Valve (what Ford calls it), otherwise known as the Idle Control Solenoid (ICS). Does the Check Engine Light come on? If so, get a readout of the fault codes. Also try disconnecting the battery for a few minutes to reset the computer mapping to default, and see if it acts any different when you first start it up.
I've got a similar problem with no idle, but engine runs fine otherwise. It was NOT the ICS as I thought, so now I'm going to have to be more thorough in my testing to find it. Hope it works out for you.
Milo
01-22-2016, 03:04 PM
#3
Might want to test that TPS - unfortunately new does not mean that it works. The tps is one of the things that most people will recommend "motorcraft only".
Also might want to check the fuel pressure as well to be sure.
It does seem to be related to your throttle position. It's a good starting point anyway.
Also might want to check the fuel pressure as well to be sure.
It does seem to be related to your throttle position. It's a good starting point anyway.
06-08-2016, 12:29 AM
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map sensor makes a lot of sense. i'll be looking at that next. Thank you to everyone that posted information. i appreciate it and i'll let you guys know what happens. thanks again. dla
06-19-2016, 03:04 AM
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sooooooo. i hate to admit this but the new distributor was not phazed correctly. retimed the motor and installed the distributor correctly and changed some plug wires around and its happy.