My 88 EFI 460 starts cold and idles at about 900rpm if I don't touch anything. If I tap the throttle the idle drops to 500 or so. It revs slightly as I put it in Drive but if I drop it back into neutral the idle drops to 500 or 600 and nearly dies. If I put it back in gear the idle picks up again. Is there an adjustment for the cold idle speed in P or N? I'm not familiar with the single point EFI. On a carb I could figure it out. Any help out there?

 

The 460 EFI has a closed loop idle control system. The computer sets the idle speeds. One for neutral/park and one for drive. It changes the idle air valve to set the engine at a specific RPM. If the engine is almost killing at the slower idle, I would look for a intake vacuum leak. Vacuum leaks are fairly common and would explain why there is barely enough power to keep the engine spinning.

BTW There is no user idle speed adjustment on these motors.

john

 

Thanks f350bronco. This only occurs when the engine is cold. I have a vacuum guage on the truck and it holds about 19 inhg when it's at 600 rpm. I think this is pretty good but I need other peoples experience. What should I expect from an engine with 107k on it? Is this a condition that needs an engine analyzer scope to correct? There's a 60 Minute Tuneup joint locally. Do I need to have the thing scoped?

 

[font size="1" color="#FF0000"]LAST EDITED ON 20-Sep-01 AT 03:37 AM (EST)[/font][p]Try cleaning the throttle body first. Get a can of throttle body cleaner not carburetor cleaner and clean your throttle body out good. I have seen many EFI Fords do exactly as you decribe with a dirty throttle body. It may not be the problem but then again it may.

Well I am saying this but I don't know if the 460 is port fuel injected like the small blocks or uses the throttle body injection like early GM fuel injection systems. Anyway this works on the port fuel injection throttle body.

Superdave

94 Ford Aerostar XL 3.0L
82 Ford F250 4x4 XLT,400 CID,C-6 A/T,8700lb GVWR. Black & Silver

 

Thanks superdave. This early EFI is a throttle body injector system. I'm not sure what there is that I can get to but I'll try your idea. Are you implying cleaning inside the airhorns (or whatever they're called)? I'll pick up a can of throttle body cleaner today and pull the intake ram tubes and douche it out in there. Is there anything I need to be careful of? I had a riceburner efi with a fine wire air speed sensor in the tube that was pretty delicate. I've attached a shot of the exterior of the system if that will help.
https://www.ford-trucks.com/dcforum/User_files/farmpaw/injector.jpg

 

All EFI Ford truck engines have been multi-point fuel injection from the git-go and the 460 is no exception. The throttle body (which is present on any fuel injected engine whether it is throttle body fuel injected or multi-point) is the aluminum casting with the butterfly valves in it. If I remember correctly though my shop manual for my '97 460 said NOT to clean the throttle body.

 

Thanks busdriver1. You're right! The individual injectors are clearly visible and I just "dumbed" over them. Gittin' old, I guess. There's actually nothing to clean on the throttle body but the linkage. I did pull the rubber hose intake tubes and there was some dried deposit laying on the bottom of the aluminum inlet tubes that I was able to wipe off with a rag soaked in throttle body cleaner. I checked the timing with the "spout" jumper removed and it was right on 10 degrees at hot idle which is what it's supposed to be.
My original question was related to fast idle on a cold angine. My only EFI point of reference is my '91 4L Ranger that stays on fast idle even if I shift from N to D and back to N. I would expect the '88 460 to act similarly. Any ideas would be appreciated.

 

If the weak idle problem goes away as the engine warms up, I would suspect the Engine Coolant Temperature sensor.

John

 

Thanks, f350brocno! Can you tell me where the Engine Coolant Sensor is? I assume it's not the same as the engine temperature sensor.
Is it possible that the throttle position sensor could be contributing to the cold idle problem? The cruise control hunts enough to make it uncomfortable to use. The throttle position sensor was bad on my Ranger when this happened.

 

[font size="1" color="#FF0000"]LAST EDITED ON 22-Sep-01 AT 04:09 AM (EST)[/font][p]farmpaw, Not to go against what the other posts said, but I have personally cleaned the throttle body in my 94 Aerostar about every couple years since I owned it. And had no resulting problems. It would get where it would not idle. And my old 88 Aerostar before this one. My 88 did this to where it would not idle at all, I limped it to my Ford dealer, a tech listened to it for a second, then came out with a can of cleaner and fixed it there on the lot. So I observed and learned. I had an 88 Big Bronco with a Windsor in it that would not idle either when I bought it. It hunted up and down when cold, almost die when you would drop it in gear. I did not tell the seller but I just suspected it needed a good cleaning, and that was all it needed. A full can of throttle body cleaner and it was smooth as could be. I always start out with the motor off, pull off your intake tubes and manually fully open the butterfies and spray the shaft and plates and tubes behind the throttle plates, not to much though or it won't hardly start. Then with the motor running and warm work the throttle lever or have someone in the vehicle keep it running for you and spray where the butterflies are and romp it while doing so to open the butterflies while continuing to spray. It will want to stall on you so keep it runnig. Use the whole can and keep track of the spray nozzle. The coolant sensor and temp sensor are the same thing.

Superdave

94 Ford Aerostar XL 3.0L
82 Ford F250 4x4 XLT,400 CID,C-6 A/T,8700lb GVWR. Black & Silver

 

superdave! You da MAN!! I took your advice and sprayed out the throttle body and the idle/shift problem went away. Nothin' like experience! FYI the Coolant Temperature Sensor is just behind the distributer on the drivers side and is separate from the engine temperature guage sensor.
I checked the resistance of the throttle position sensor and it is erratic at light throttle positions. Hopefuly replacing it will cure the cruise control hunting problem.
Thanks again for the solid advice!

 

farmpaw, The engine coolant sensor is sometimes refered to as the engine coolant temperature sensor, that's what I thought you were talking about. The temperature gauge sender is usually refered to as the temperature gauge sending unit. Glad to hear you got the idle problem lined out.

Superdave

94 Ford Aerostar XL 3.0L
82 Ford F250 4x4 XLT,400 CID,C-6 A/T,8700lb GVWR. Black & Silver