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Old 10-17-2014, 09:04 PM   #1
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Default Stangas - 1989 F150 5.0L Efi Issues

Hello all..

First post on this forum. Previously on an Australian forum that has run out of suggestions. So I thought some American input would be useful, since you built these machines.

Prelude...

I have a 1989 F150 4wd with the 5.0L injected V8
It has been a problem from the get go with it never running properly since i bought it.

The problem i have is the engine will idle nicely from cold, and it will accelerate fine when cold.. It is as if when the ecu goes into closed loop mode it stumbles when the accelerator is pressed, almost like a misfire or over fueling. I need to rev the engine and almost dump the clutch to get it moving.. almost spinning the wheels.. Once running it is fine out on the open road, but as soon as i decelerate the engine is burbling in the exhaust and if i come to a stop it will stall.. Restarting the engine will run nicely again for about 30 seconds and then return to the dodgy deceleration.

So what have i done..

1) Smog pump and thermactor system was removed when extractors were put on.. this is how it was purchased. I have checked the back of the heads and the port is definitely blocked with a welsh plug.
2) Replaced all vacuum lines throughout the entire vehicle. The coffee can is in good order. Altho due to thermactor not in service i did not supply the 2 solenoids with vacuum, but did still plug them in. I have carried out a smoke check for vacuum leaks and there is definately NO vacuum leaks.
3) Rebuilt all injectors, placed a new pressure regulator in and now maintaining 30psi with no drop in pressure when the engine is turned off. Is 30psi sufficient??
4) Replaced the MAP sensor after finding codes. Codes went away.
5) Replaced the air inlet temperature, the engine coolant temp sensors.
6) New thermostat and cooling system holding nicely at the N of normal on the gauge with no leaks.
7) New leads, plugs, dizzy cap, rotor button.
8) I have reinstated the EGR (it was not there when purchased), although i am about to hook the exhaust back up to it on Tuesday.. it was electrically and vacuum connected, but not exhaust connected. This will then increase the inlet air temps.. but the tables for the ECU say this will only adjust timing a max of 2 degs which i would not think it makes that much difference.
9) New TPS as was pulling codes.. this ended up being the ECU had pulled a pin out of the plug.. hence step 10
10) Bought an American ECU with the exact same number that is on my original ECU
11) Put a full earth kit in.. thinking maybe poor earths.
12) Compression checks out ok.. but going to do another anyway soon.


My mechanic is saying that it is the ECU, but i rang the bloke i purchased it from and he said it was tested before it left him.. I have to believe him i suppose.

His reasoning was he checked the O2 outlet with a separate piece of equipment and he said that at idle the O2 is very very rich, then at 3000rpm the O2 is very very lean. This is why i overhauled all the injectors and fuel reg. He also stated that my trucks O2 sensor was reading the same results.

Well I am out of ideas... and getting so frustrated that my 465 Holley that is sitting on my work bench is looking pretty damn good right now.

I have just purchased a brand new coil and will be replacing that also.

Everything i have done has made a small difference along the way as it was obviously not looked after before i bought it, but still this stalling is horrible when trying to drive slowly in carparks and the like.

Hope someone out there can help me, and i sure hope it is an easy fix.
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Old 10-17-2014, 10:37 PM   #2
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Measure engine vacuum and let me know what the needle is doing. What codes were there from the beginning. Check and clean all plugs, what color are they and do they all look the same? Having a extra set of plugs is nice when u got sever problems like urs. Once we know what the needle is doing and vac is we can move on to testing and troubleshooting other things.
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Old 10-17-2014, 11:11 PM   #3
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That's a bit like what was happening to mine when I had the wrong O2 sensor. Less problematic when it was unplugged. Got the right one in there and no more problems.
Your fuel pressure though is barely adequate to run the motor at all. You need 30 to 45, with 30 being not at all good. Typically you have about 40 to 42.
I would suspect a plugged filter, a leaking fuel pressure regulator or a failing pump. Without adequate pressure the injectors don't spray, they just kind of dribble. Some fuel injector cleaner in the tank may help a little too.
Personally, I would start by getting the fuel pressure up to normal first before replacing anything else.
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Old 10-17-2014, 11:27 PM   #4
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I missed the 30 lb on the fuel pressure.
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Old 10-18-2014, 04:05 AM   #5
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awesome guys.. i will replace the fuel filter.. the regulator is new and injectors are good... if that doesnt fix it then i will put a new pump in.. can i bypass the filter briefly to see if a difference is made??

Vacuum is reading 21inHg and steady.. when revved the vacuum drops to about 5 and returns to 21. So sounds about right??

I bought a spare O2 sensor also, so something i can check.
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Old 10-18-2014, 10:10 PM   #6
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My vacuum runs about the same.
Filter is cheap - just replace it, can't hurt
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Old 10-19-2014, 08:40 PM   #7
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ok new filter and pump on its way this afternoon...

fingers crossed..

in saying this i will be slightly annoyed if it is, because i sent it to a mechanic ages ago and suggested fuel pressure and he ignored me and went looking elsewhere. This was over 12 months ago and i been struggling with this thing ever since.

Mechanics are not really mechanics these days... more service technicians
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Old 10-20-2014, 09:39 PM   #8
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New fuel pump and filter placed in and no ****ing difference??? Well increased the pressure to 35psi when the engine is off, but dropped to 30psi with it running

Those dodgy looking connectors.. if they are letting air into the system, would that make a difference??

I think i can hear air at the inlet of the pump.. is there a new o-ring or something that can be used? when i put them together it felt too easy.

Thinking about replacing hose connections to hose clamps.. any thoughts?

Last edited by Stangas; 10-20-2014 at 09:42 PM.
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Old 10-20-2014, 09:48 PM   #9
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Can you smell gas when you are by your tank(s)? Did you recheck the fuel pressure after install?

Did 89 have the high pressure pump along the fuel line or was that earlier models?
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Old 10-20-2014, 09:51 PM   #10
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yeah the 89 has the chassis pump and the 2 intank pumps..

I can smell gas because it went bloody everywhere.. LOL

As for while it is running, I cant see any leaks, but i can hear some air?? at the inlet of the pump.

Would the truck run if neither of the tank pumps are not working?? and how would i check if they are working... I would assume the truck would not work at all, and the chassis pump would be sucking only air?
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Old 10-20-2014, 09:51 PM
 
 
 
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