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Discussion Starter #1
Ive got a 1989 F-150 2wd, 302, AOD, 3.55 gears, 31" tires, has 197k miles on it now. Factory engine and transmission still.

My problem started this week. Driving around town everything is as normal as it ever has been for the truck, acceptable power, easily keeps up with traffic. My problem is that anything much over 60 MPH it begins to loose power to the point that it has to downshift to go up slight inclines that wouldnt have phazed it a week ago. It is not only in OD where the power loss occurs, it is not nearly as responsive in 3rd as it was either. There is no noticable missing or jerking, its still running smoothly, just gutless. Before this issue, driving 75-80 wasnt even a second thought. Now I can barely keep up with traffic at 70.

I dont think it would be a transmission related issue, I have a temp gauge and it doesnt overheat at all, as a matter of fact, it rarely gets over 120 degrees since fall.

In the last year, I have replaced...

in tank fuel pump and sender.
fuel filter.
fuel pressure regulator.
air temp sensor in the intake.
throttle position sensor.
Entire 6 liter tuneup with autolite plugs, MSD cap/rotor and coil with Ford racing plug wires. I forget where the timing is set now. I think its at ten degrees BTDC.
air filter was replaced this summer.
fan clutch.
Radiator.
190 degree thermostat.

I will be replacing the coolant temp sensor this weekend also,

I have an Auto Meter vacuum gauge and while driving in town it reads like normal, but on the highway it reads about 5-6 in Hg at best over 65 MPH and sometimes going as low as 3 in Hg.

There is no CE light, and all gauges read normal, however I havent checked codes yet. I will check codes and do a compression test this weekend.

Ive searched and didnt find anything similar to this on here, and Im looking for any ideas you guys have on a place to start as this is kinda stumping me.

Thanks, Andrew
 

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I scrape on both sides
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sounds like MAP
 

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I scrape on both sides
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not necessarily, mine never did, could just be a vauum leak too
 

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Discussion Starter #5
A vac leak would make sense, but I dont have any issues driving around town 45MPH or less, and theres no high or eratic idle syptoms.

Could it be something EGR related, as the problem is at highway speed when EGR would be being used?

Ive been doing ALOT of reading on this ford fuel injection for a long time, and its still hard to wrap my head around alot of it.
 

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I have an Auto Meter vacuum gauge and while driving in town it reads like normal, but on the highway it reads about 5-6 in Hg at best over 65 MPH and sometimes going as low as 3 in Hg.

There is no CE light, and all gauges read normal, however I havent checked codes yet. I will check codes and do a compression test this weekend.
What is "normal" vacuum while driving around town? Is your tach steady or jumpy, especially at idle? Why are you changing your ECT? How is your initial start-up?

I would be interested in memory codes...
 

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Discussion Starter #7
I keep it out of OD in town, but cruising at 40mph or so in D its about 13-15 in Hg. Can get as low as 5in Hg if I get on it. The needle on the vac gauge is always steady, no vibrations or bouncing around.

I am replacing the ECT because I had starting problems a few years ago, where it would not start when it was warm. I put a used motorcraft ECT in and the problem seemed to be corrected, but lately I've been having it idle poorly, (rough and occasionally stalls) intermitantly at start up when at operating temp.

Initial cold start up, it starts just fine. Has been about 10-20 degrees all week here and never a problem starting or idling when cold. High idle, I think is a little high, but I dont have a tach, and after a minute it idles down to normal.

I have no codes yet. I will be getting those tomorrow, then posting here with what I find.
 

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Discussion Starter #8
I just got back from the parts store, I used their scan tool and only got a koer code 13 for low idle.

No memory codes were stored, and KOEO test didnt show any codes.

I checked for vac leaks and no luck there. Maybe its time for a reman longblock, but the compression test will determine more about that.
 

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OMF
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Do a leak down test while you are doing the compression test...
 
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