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1988 Ranger runs rough


Leonard55

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Joined
Jul 5, 2018
Messages
2
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Vehicle Year
1988
Make / Model
Ford
Transmission
Automatic
I acquired a 1988 Ranger XLT that has been sitting for almost 10 years. I have replaced both fuel pumps, cleaned tank out to where it is spotless, replaced fuel filter, injectors, fuel rail (mine got tweeked during removal), fuel pressure regulator, spark plugs, cap and rotor. It will only start when slightly mashing the pedal. And then it will rev really god for 2 or three times like that and suddenly will not go above 1500 rpm
I am at my wits end. Almost ready to push it outside and set it on fire.
The motor sound great when it is running as far as the bottom ends goes anyway. But it is like it only runs on 5 when it does rev and maybe on 2 or 3 cylinders when it won't rev up.
Any help would be greatly appreciated

Also I have done fuel pressure test. It has 40 psi for about 15 seconds then slowly drops to around 25. What causes it to not hold pressure? That is with it running about 1000 rpm

Please email me with any possibilities
Thank you
Leonard55
 


RonD

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Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
Welcome to TRS :)

Vacuum from the intake manifold will lower fuel pressure, via the Fuel Pressure Regulator(FPR), once engine is started, that is normal.
25psi is OK for lower limit.
You can remove the Vacuum hose from FPR, and plug the hose, then test fuel pressure, it should remain higher with engine running, but thats not your issue, if pressure only goes down to 25psi

Double check firing order, then have a friend check it, lol, I would swear it was right and it was WRONG, so just a heads up on that, very much an overlooked problem that will have you chasing your tail.

Distributor shaft bushings, sitting a long time could have caused an issue here, distributor shaft now has a wobble so as RPMs increase so does the wobble.
Pull the cap and check how firm the shaft feels, crank the engine while you watch the shaft rotate, some times you can see the wobble.

TFI Module, these are known failure points when older.
If you are not sure of the age then I would just replace it and save the old one for back up, unless problem goes away then throw out the old one :)

TFI Module controls spark advance for RPMs, engine computer controls "vacuum advance", i.e. throttle position spark advance, via SPOUT connector.

Google: 1987 2.9l SPOUT connector

It should be near distributor on the TFI wiring harness, make sure it is plugged in, plastic insert, and try unplugging it to see how engine runs.
You may need to set base spark timing to 10-12deg BTDC, so have timing light handy
 
Last edited:

Leonard55

New Member
Joined
Jul 5, 2018
Messages
2
Reaction score
0
Points
0
Vehicle Year
1988
Make / Model
Ford
Transmission
Automatic
I checked all above and no difference, so I am putting it for sale. It will have to be hauled out but it is pretty good shape for one that has set since 2007.
Thanks for your help anyway. I just can't sink any more money in to it.
 

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