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Author Topic: 2.5 Efi swap issue  (Read 1188 times)

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Offline 2.3stangii

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2.5 Efi swap issue
« on: April 22, 2018, 11:37:24 AM »
Been a while since I needed help on something, or even got to work on any projects but this one has me pulling out what's left of my hair.


I have swaped what was supposed to be a 96 2.3 from a Mazda b2300 that turned out to be a 98 2.5, no hole for distributor, 25l casting on the side of the block as well as casting number f87E etc in a 1980 Pinto. Little bit of customizing to get a front sump pan and get it in the car.
Anyway its in there and running good, but only for a short time then it starts acting like its running out of gas, hitting the throttle at that point will kill it, it will idle while its doing that for a minute or two then die. Wait a little while and it'll start up fine, get moving and it'll go for a minute and sputter out again.


Things that might may hint at the problem are, loss of fuel pressure when I turn the engine off, 02 sensors have not been installed yet but have them connected, then disconnected to the harness and no change there. Got fuel but only about a 1/4 tank so don't know how bad fuel starvation is with these conversions. Showing a p113 code for intake air temp sensor, no clue where that is cause I don't see anything but MAF and IAC sensors. Fuel pump is an inline pump from an 80's f150 mounted just above the tank, added a low pressure pusher pump, again with no change.
alternator doesn't charge. Bout all I can think of that could possibly cause this. I know very little about efi stuff so any ideas are appreciated.
78 Pinto wagon
74 Mustang II
78 Cobra II

Offline Wittsend

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Re: 2.5 Efi swap issue
« Reply #1 on: April 22, 2018, 04:18:22 PM »
With so many things NOT funtional it is hard to even guess.  At least on the LA-3 ECU the car goes from cold start (Open Loop) into Closed Loop and it is looking to the O2 sensors for data. So, maybe on initial start up it is in Open Loop using "tables" stored in the ECU, but shortly afterwards it goes to Closed Loop, can't find the input data and dies???

Where is the pusher pump in regard to the inline F-150 pump?  I just run the F-150 pump without a pusher without issue.   Maybe it is a limiting obstacle??? Most of these systems run with about 40+ PSI on the fuel rail (and it should hold for a period of time after turned off). If the fuel regulator is bad (jammed open) you may be getting just enough fuel to idle and that is it.

I'd check the fuel pressure and fix it if the pressure is low of won't hold pressure when off. I'd get the alternator functional and the O2 sensors I assume plural because you must be OBDII with a 98.

Basically you need to get things "normal" before you can trouble shoot because with ECU control it can be a lot of things.

Offline 65ShelbyClone

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Re: 2.5 Efi swap issue
« Reply #2 on: May 01, 2018, 12:50:18 PM »
You have a multitude of problems, but it sounds like this one is partly from not having a fuel pressure regulator. The '98-00 B2500 and 2.5 Rangers have a returnless fuel system with the pressure regulator integrated into the pump pickup in the tank. Your pump is both dead-headed and running at max pressure and it is probably getting hot enough to make the pressure slump and cause bad running.

I'm pretty sure those trucks also ran about 65psi of baseline pressure.
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'68 Mustang - Built roller 302, Toploader, 9", etc.

Offline 2.3stangii

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Re: 2.5 Efi swap issue
« Reply #3 on: May 05, 2018, 11:08:31 PM »
Update, installed the 02 sensors into the exhaust, fixed the alternator, found the missing air temp sensor and tried another pcm from the junkyard.
I THINK its fixed it cause it now only has a low rpm hesitation and rough idle but seems to do fine higher up in revs when I took it out today. New pcm throws the usual egr codes cause the valve has been bypassed due to the height in the engine bay and p0352 p0351 ignition codes that the other one threw after posting this thread.
I'm guessing it was either the missing air temp sensor, not enough charge to run everything or overheating cause I noticed the coolant was low and may not have been enough to reach the sensors or the old pcm was malfunctioning .

The fuel pressure regulator or pump is still a suspect the more I think about it (or the coil due the the codes) but it does have the same regulator the 2.3 does on the fuel rail as well as a return system. Its basically the same engine aside from the changes in the oil pan, oil pump and block where the distributor hole used to be. Only thing that alerted me to it being a 2.5 was the big 25L and F87E casting number on the block behind the header.
Forgot to add the truck the engine came from had been rolled so there is oil residue in the intake, IAC valve (now clean) and probably plugs so that's next on the list but so far so good.
78 Pinto wagon
74 Mustang II
78 Cobra II

Offline Wittsend

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Re: 2.5 Efi swap issue
« Reply #4 on: May 07, 2018, 04:32:29 PM »
For all of us who remove things like EGR etc. I'm left to wonder at what point the PCM puts the car into the "Lip home mode?"  Just a thought. I have a LA-3 from a '88 Turbo Coupe and there are about 5+ codes that come up simply because the Pinto doesn't have ride control, power steering or A/C (amoung other things like EGR ... etc.)

Offline 65ShelbyClone

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Re: 2.5 Efi swap issue
« Reply #5 on: May 10, 2018, 08:51:16 PM »
but it does have the same regulator the 2.3 does on the fuel rail as well as a return system.

I need to see a picture then.
'72 Runabout - 2.3T, T5, MegaSquirt-II, 8", 5-lugs, big brakes.
'68 Mustang - Built roller 302, Toploader, 9", etc.

Offline 2.3stangii

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Re: 2.5 Efi swap issue
« Reply #6 on: May 12, 2018, 10:57:41 PM »
2.3 intake maybe?
Just when I get everything going smooth, once it heats up to normal operating temp the thing wants to cut out, first at WOT and high rpms then lower and lower till all I can do is idle. Ugh..
Had a lot of air in my fuel rail after it died, efi vapor lock?? Very suspect of the fuel pump now.
78 Pinto wagon
74 Mustang II
78 Cobra II