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Really need help ford 5.0 idle surge terrible mpg
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seedublu3
New User
Mar 27, 2011, 12:43 PM
Post #1 of 5
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Really need help ford 5.0 idle surge terrible mpg
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1987 Ford E-150 van. 5.0L 148k
Original trouble was coolant leaking from intake gasket and water pump. Both were replaced. While doing that a basic tune-up was done. Plugs/wires/cap/rotor. Air and oil filters, and obviously new oil and coolant. Followed timing procedure with the spout wire and set at 10 deg BTDC.
Current condition: Runs Terrible at idle. (surging badly) runs bad at low speed. (lopes or gallups?) and coughs). runs fine at highway speed. mpg less than 5. Also occasional hesitation when coming off a stop sign but when it goes, it goes like a shot! Exhaust smells bad and is black.
Already tried: Changed fuel regulator, throttle position sensor, map sensor, idle air motor. Pulled and cleaned intake air temp sensor.
Any help would be great, thanks!
(This post was edited by seedublu3 on Mar 28, 2011, 10:57 AM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 28, 2011, 3:27 PM
Post #2 of 5
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Re: Really need help ford 5.0 idle surge terrible mpg
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Ideas+ things to check:
Spray carb clean at EGR and see if it reacts to that and if not try removing it (should be easy) and check the pintle. Clean it and push on it. While off spray inside and pintle should pretty well hold carb cleaner. On wood, press on it, it will depress and let cleaner out - a maybe.
* Vacuum leaks - spray carb clean around and if it changes or stalls that's the area
* Check timing again. Rev engine a bit and watch timing. It will move but fluctuations not too good. Also, take dist cap off with timing at zero and turn crank bolt one way then the other noting how may degrees balancer turns before rotor in distributor turns. 5 degrees is enough. This has a plastic cam gear and they don't like age, never mind miles.
* Gotta check valve timing and take a look at harmonic balancer that it turns true. Rare to me on these engines but they can slip yet be on and look fine.
* If you don't mind setting your timing again, see if it improves by advancing or retarding timing then put back where it should be as info.
* Take a plain vacuum reading of actual manifold vacuum at idle. If not close to 18Hg report that. Give the engine a quick rev and it will go down then up and then stable when you let go. If running rough this is a bit inconclusive but if constantly low an indication of valve timing.
Was whole intake manifold gasket replaced or just the upper one also called a plenum to get at the metal heater hose line under it that is common to rust out.
Jump on this as if you are seeing black out exhaust it will harm the converters if let go too long,
T
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seedublu3
New User
Mar 28, 2011, 9:11 PM
Post #3 of 5
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Re: Really need help ford 5.0 idle surge terrible mpg
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Thanks "T". I will get on all of that asap. And it was upper (plenum) and lower intake gaskets.
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seedublu3
New User
Mar 29, 2011, 9:23 PM
Post #4 of 5
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Re: Really need help ford 5.0 idle surge terrible mpg
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Tom, Thank You!!!! It was the vacuum. Rented a vac pump/gauge and did some troubleshooting, after the EGR and timing proved good. It was way up in the plenum area, on the tree. The one to the MAP was so misaligned that it had no Hg to the sensor. I really appreciate your help!!
P.S. For the record, I did not "Throw parts at it"! My friend had an identical motor that was bad internally. We just used all the parts that I changed as a troubleshooting tool, when the diagnostics pointed in that direction.
Thanks again!
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Mar 31, 2011, 7:36 AM
Post #5 of 5
(4324 views)
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Re: Really need help ford 5.0 idle surge terrible mpg
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Low or no vacuum to MAP would be telling it that engine is under load or at wide open throttle and deliver extra fuel for that. It got fooled and was doing its thing with bad info.
Thanks for coming back with the find and fix. Now go give it a good HWY run to burn off extra fuel in converters. Safely from an on ramp for example when all is clear, near stop and floor it to legal speed limit (I can't suggest speeding) - They'll get hot and probably will self correct unless way overloaded,
T
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