Rough Idle
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New User
Joined: Sep 2002
Posts: 23
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Rough Idle
I have a '90 F-150 with a 302 EFI. It runs right for a while then it runs real rough at times. Even stalls at times. It doesnt do tis all of thetime. I changed the spark plugs, wires, rotar, cap, cleaned the throttle body, replaced the EGR and PCV valves. I ran my code scanner on it and keep getting error Code # 34 now I get error Code #35. The EGR vales checks out OK. Help!!!!!!!
Tuned
Joined: Nov 2002
Posts: 395
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There is a sensor on top of the EGR that you need to test, EVP (EGR valve position sensor). It has a rod inside that the EGR pushes on. The computer supplies a reference voltage to that sensor and that voltage changes when the rod goes up and down telling the computer the EGR posistion. You can take it off the EGR and check the resistance by connecting an ohm meter and moving the rod with your finger. The Ford Fuel Injection and Electronic Engine Control book tells you how to test all your sensors. There is also an EVR Solenoid above the drivers side valve cover by the coil, it is the one closest to the front of the vehicle. It should hold a vacuum if you test it with a vacuum pump on the bottom port and should be 10-70 ohms across the terminals. Pick up a MityVac vacuum test kit, depending on where you buy one it can range in price 30-50 dollars. After I bought mine for 50 bucks I found the exact same one for 30 bucks that came with the brake bleeding kit!!! Anyway very nice tool to test all your vacuum lines, sensors and bleed brakes. It comes with a pretty good book also to help your testing.
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New User
Joined: Sep 2002
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The EGR position sensor checks out OK. I am kinda confused about the EGR solenoid??? Could it be called something else. There is something located next to the coil near the valve cover. Is that it?? If I need to replace it it is not showing up in part store catalogs.
Elder User
Joined: Mar 2004
Posts: 537
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From: Alabama
The other (2) are the TAB solenoid and the TAD solenoid. The first one is also known as the EGR EVR, EGR vacuum regulator. Haynes publishes a pretty decent Techbook, Emissions Control book # 10210, got mine at Advance Auto for about $16. Chapter 3, section 4, discusses the Air Injection Systems. Describes each of the components and tells you how to check them. TAB, Thermactor Air Bypass Solenoid and TAD, Thermactor Air Diverter Solenoid. TAB vents air to atmosphere by way of the Air Bypass Valve and the Tad diverts air to the catalytic converter instead of the exhaust manifold. You can check these components with a hand vacuum pump and a DVOM ( Digital Volt/Ohm Meter). If yours are designed like mine the wiring comes in from the left side of the solenoids on the side. It was definitely easier to check them by removing them from the brackets. I would probably do this one at a time and pay attention to how the vacuum lines are plugged on. Mine also has hard plastic factory vac. lines and these can be brittle and prone to breaking easily. If you setup your signature in your profile and then put the mouse pointer on it, it shows your truck info. If your interested in doing that.
Last edited by guzzler96; Jun 6, 2004 at 06:52 AM. Reason: left out something
