Looses power when it warms up
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5th Wheeling
Joined: Aug 2003
Posts: 28
Likes: 0
From: Prescott, Az
Looses power when it warms up
Greetings, I have an f-150 that runs great when its cold to luke warm. Once the truck gets to full temperature, its seems to loose power, sometimes it will stall when idling down, when moving slow and turning (Power steering seems to make it stall or loose power and then it won't recover), but only when going slow, giving it gas and then letting it off. I thought it may be the Idle Air Bypass. I cleaned it, and it seems to working but have not changed it yet. It will also get a slight surging or cycling up and down at lower RPM's only when its hot or up to temp. It has new TP, Oxy sensor and Catalytic converter.
Help ! Any ideas to check ???
T
Help ! Any ideas to check ???
T
New User
Joined: Jul 2004
Posts: 4
Likes: 0
From: Alaska
I am having many of the same problems
My truck is making many of the same problems it starts but sometimes I have to firewall it just to make R's. I have replaced many sensors same as you. I have no useful info except check voltages and Ohm's on water temp and plug wires and distributer caps sometimes crap out for no reason.
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5th Wheeling
Joined: Aug 2003
Posts: 28
Likes: 0
From: Prescott, Az
Thanks. It is a 1992, 5.0 EFI, 4 in. Lift, 3 in. Exhuast but otherwise stock. I have a temperature gauge that seems to work fine and registers a perfect temperature. Last year I replaced the radiator, hoses and thermostat. If the temp sensor was bad, wouldn't it register strangly on my gauge ?
Thanks
T
Thanks
T
Temporarily Deactivated
Joined: Aug 2003
Posts: 1,859
Likes: 2
Sounds like you are running rich. Check for codes and check your fuel pressure. Check your air filter.
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5th Wheeling
Joined: Aug 2003
Posts: 28
Likes: 0
From: Prescott, Az
I changed a ECT, Air filter and plugs and it runs the same. When it warms up. How do test fuel pressure ? I have 2 tanks, the truck runs the same on either tank and each tank hs its own fuel pump in the tank. Could it be my regulator ? Wouldn't it run bad when cold also if the regulator wasn't working properly?
Thanks for your help
Thanks for your help
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Post Fiend
Joined: Oct 2003
Posts: 6,214
Likes: 13
From: New Jersey
There are two CTS sensors, as I just went through this myself. Truck ran "fabulous" in open loop (just started) and once it went into closed loop, it ran like a drunken dog.
For my truck, I ended up replacing the CTS sensor for the ECM (not the gauge one), and the O2 sensor. Once both was replaced, it runs consistant warm or cold.
To Xtrem's question about testing fuel pressure, its fairly easy. There should be a schrader valve (almost like a tire valve) on your fuel rail, you hook a pressure gauge to that and turn the truck to the "on" position, but not starting it. You should have 35-38psi of pressure. Start the truck and let it idle for a few seconds, and the gauge should read somewhere in the mid to upper 20's at idle. Rev and it goes up.
If your pressure does not change, or is over 38psi, your regulator is hosed and needs to either be replaced, or maybe the vacuum hose to it is clogged. It uses vacuum to change the pressure in the rail.
Hope that helps.
For my truck, I ended up replacing the CTS sensor for the ECM (not the gauge one), and the O2 sensor. Once both was replaced, it runs consistant warm or cold.
To Xtrem's question about testing fuel pressure, its fairly easy. There should be a schrader valve (almost like a tire valve) on your fuel rail, you hook a pressure gauge to that and turn the truck to the "on" position, but not starting it. You should have 35-38psi of pressure. Start the truck and let it idle for a few seconds, and the gauge should read somewhere in the mid to upper 20's at idle. Rev and it goes up.
If your pressure does not change, or is over 38psi, your regulator is hosed and needs to either be replaced, or maybe the vacuum hose to it is clogged. It uses vacuum to change the pressure in the rail.
Hope that helps.
Thread Starter
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5th Wheeling
Joined: Aug 2003
Posts: 28
Likes: 0
From: Prescott, Az
Frederic, When you use the term CTS sensor, you are refering to Coolant Temp Sensor, ECT is the same thing, correct ? I replaced the ECT connected to the ECM. Its located on the coolant fitting connected to the intake manifold on the 92 5.0 EFI. I hope that was the right sensor to replace, its cost me $49 bucks. I replaced the O2 sensor about 10 - 11 months back when needing a smog. It turned out the Catalytic converter needed replaced instead. It passes smog but is not running optimal in closed loop. The minute it changes to closed loop, the engine weakens noticably. I will check the PSI, but you are correct, the problem starts when the computer takes control. Any other ideas ?