Sensor(s) Signal Return path problem???


ms88ranger

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Long time forum reader but haven't needed to post in years. Question is on a 88 Supercab, 2.9L, 5-speed manual and approaching 400K miles. Getting midrange bucking and loss of power. New sensors, cat replaced a year or so ago and exhaust new from cat back. ACT, ECT, TPS check OK with meter and behave as expected with temp or position change. Fuel pressure, vac and base timing good. I've pulled and cleaned all the connections and ground points I've found (several times).

If engine bucks/stumbles on the road at around 2,000-2,500 RPM and I open it up (WOT), we take off. More common and worse once engine has fully warmed. Stumble will repeat after backing rpm back down. If sitting in driveway and jacking idle RPM up to 2000-2500, I can create the same effect. It will some time correct on it's on and rpm's go back up. I'm thinking I'm losing spark advance due to an intermittent connection. Only code I get is 54 (KOEO, continuous, and/or KOER). I've yet to starting piercing wires for resistance/voltage tracing and testing and have a buddy bring me a breakout box and harness for the ECM hopefully this weekend to simplify things.

Reading the info on the 54 code and looking at wiring diagram is making me think there may be a problem at the one or more common joints for the signal return on the ACT, ECT and TPS. A intermittent due to temp and/or vibration there could well throw the EEC-VI out resulting in erratic timing. I've done lots of harness wiggling.

So in prep for further digging and troubleshooting, I'd like to know if someone knows about were in the harnesses some of the common signal return tie points might be? I don't mind opening the harness(es) up, just want to narrow it down if possible.

Thanks in advance - Bruce
 


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rusty ol ranger

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Good luck.

This is eerily similar to the issue ive been chasing for a year.

Id like to help ya out...but im lost to.
 

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There is supposed to be a splice for the ECT, ACT, TPS, and MAP grounds in the wire loom near the ACT. I would do a continuity check between the ACT connector's ground (Black/W) and the negative battery terminal. While it's connected during the continuity check, wiggle test all the wire looms in that area. If it's an intermittent problem, it should happen during the wiggle test. Check the ACT connector also, as it may be the cause of the intermittent problem. Bad injectors will cause stumbling, but they would clearly not affect the ACT.

Cheap chinese replacement parts may not have the same tolerances on the pins/terminals of the new sensors, and a 30+ year old connector wouldn't help. Just a thought.
 

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Hard to say for sure where those points are exactly...

Component location views in a manufacturers publication may or may not have component location/harness routing views that indicate splice position. Even if you find that... probably still a crap shoot if you find a splice where they say it should be.

@PetroleumJunkie412 has probably been through a harness or two by now and may be of more help then myself.
 

ms88ranger

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I've been meaning to give an update so here is where I am on the stumbling problem. I did find the relatively new ACT sensor was bad. Ohms would read/change OK until brass body got hot and then go open circuit. Reinstalled old one and that problem when away but still same stumble.

The problem all along to me seemed to be fuel supply related so did some probing on power and return leads to the two fuel pumps. I measured full battery voltage at positive lead relative to ground. The big "but" was when checking, the ground lead for in-tank pump would be 2-5 volts measured against a good frame ground point so voltage across motor was low and would vary. I cleaned the connector and pump pins and used some conductive grease and that seems to have solve the floating ground problem and engine doing much better and truck is driveable. There is still a slight problem at highway speed but OK on streets. I may add an extra ground point to frame close to in-tank pump given the length of the long stock ground return line to ensure good connection. There are now no codes showing on KOEO or KOER tests.

My hunch is the high pressure pump was being starved with the intermittent in-tank pump problem so the rail pump may be damaged. It could generally keep up at idle and low rpm range but not always. While pressure shows OK (about 30-40 psi) sitting in driveway, it may drop under load or damage to the pump may be reducing volume capacity while pressure remains OK. I'll pickup a new high pressure pump at NAPA when I have a chance. I'll change fuel filter as well when under the truck given the amount of "cleaners" I've put through system!

Only other problem after the work, but not related to original problem, was the IAC was not functioning right and the engine would occasionally die at light or stop sign. New IAC fixed that. It was either sticky or the solenoid getting weak and not responding quick enough to maintain idle.

I'll update again after getting new rail pump in.

Bruce
 

rusty ol ranger

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I had come to the same conclusion as you. I pulled a fuel line off, hit the key and had zero output from the intank pump.

Put in new pump, sender, and tank to no avail. High pressure pump was new.

I just put in 6 new injectors, a shiny clean fuel rail, and a new distributor. Once i get it timed ill post results.

(Remember the distributor also controls injector fireing to my understanding).
 

PetroleumJunkie412

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I've been meaning to give an update so here is where I am on the stumbling problem. I did find the relatively new ACT sensor was bad. Ohms would read/change OK until brass body got hot and then go open circuit. Reinstalled old one and that problem when away but still same stumble.

The problem all along to me seemed to be fuel supply related so did some probing on power and return leads to the two fuel pumps. I measured full battery voltage at positive lead relative to ground. The big "but" was when checking, the ground lead for in-tank pump would be 2-5 volts measured against a good frame ground point so voltage across motor was low and would vary. I cleaned the connector and pump pins and used some conductive grease and that seems to have solve the floating ground problem and engine doing much better and truck is driveable. There is still a slight problem at highway speed but OK on streets. I may add an extra ground point to frame close to in-tank pump given the length of the long stock ground return line to ensure good connection. There are now no codes showing on KOEO or KOER tests.

My hunch is the high pressure pump was being starved with the intermittent in-tank pump problem so the rail pump may be damaged. It could generally keep up at idle and low rpm range but not always. While pressure shows OK (about 30-40 psi) sitting in driveway, it may drop under load or damage to the pump may be reducing volume capacity while pressure remains OK. I'll pickup a new high pressure pump at NAPA when I have a chance. I'll change fuel filter as well when under the truck given the amount of "cleaners" I've put through system!

Only other problem after the work, but not related to original problem, was the IAC was not functioning right and the engine would occasionally die at light or stop sign. New IAC fixed that. It was either sticky or the solenoid getting weak and not responding quick enough to maintain idle.

I'll update again after getting new rail pump in.

Bruce
So, there are options for this.

My 88 was converted to a single in tank pump only. Granted, my 2.9 is highly modified. However, a Kemso 340 LPH pump (eBay) does fit in the plumbing for your in tank pump.

_20190726_000105.JPG


Installing the bigger pump has pros and cons. They are relatively cheap ($35 IIRC), will supply more fuel than a naturally aspirated 2.9 will ever need, and removes a second failure point from your vehicle (two pumps reduced to one). The drawbacks are that they are somewhat loud (I hear mine over my headers/Flowmaster/3"intake, etc), and requires the complete removal of the frame pump. The frame pump is replaced by a standard Ranger fuel filter (direct swap).

The one issue I did have was I was dumb and didn't shield the wiring properly the first time. Make sure to use the plastic conduit the pump comes with to insulate over the hot wire, and to properly terminate wires that used to go to the frame pump.

The other thing that I had to replace was my fuel pressure regulator. My 31 year old fpr died a horrible death from the increased volume and pressure from the new pump.

Since then, though, I've had no fuel supply issues even feeding 24 lb injectors (stock 2.9 injectors are 14 lb)
 

PetroleumJunkie412

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Oh, and if you can source one, the polymer intake air charge temp sensors are far superior to the brass ones. They tend to shed heat quickly and report only air temperature, not the temperature of the intake as the brass ones tend to do.
 

PetroleumJunkie412

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Last note on parts quality:

Idle Air Control valves for the 1980s Ford engines (2.9, 302, etc) have been garbage as of late. I'm on my 5th in 18 months. Two have been dead out of the box.

The only one that has survived so far was the Stand Motor Products AC20. DO NOT PURCHASE the "T" series. They are the budget line. Part quality is pathetic, and of the two I had installed, one was DOA, and the other lasted four days.

I've taken to keeping a tested new one in my center console, should one die on me and I can't make it home. Should that happen to you as well, and it dies "closed," disconnecting an auxiliary vacuum line "may" allow you to limp it home. Worked for me, at least.
 

ms88ranger

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So, there are options for this.

My 88 was converted to a single in tank pump only. Granted, my 2.9 is highly modified. However, a Kemso 340 LPH pump (eBay) does fit in the plumbing for your in tank pump.

View attachment 30651

Installing the bigger pump has pros and cons. They are relatively cheap ($35 IIRC), will supply more fuel than a naturally aspirated 2.9 will ever need, and removes a second failure point from your vehicle (two pumps reduced to one). The drawbacks are that they are somewhat loud (I hear mine over my headers/Flowmaster/3"intake, etc), and requires the complete removal of the frame pump. The frame pump is replaced by a standard Ranger fuel filter (direct swap).

The one issue I did have was I was dumb and didn't shield the wiring properly the first time. Make sure to use the plastic conduit the pump comes with to insulate over the hot wire, and to properly terminate wires that used to go to the frame pump.

The other thing that I had to replace was my fuel pressure regulator. My 31 year old fpr died a horrible death from the increased volume and pressure from the new pump.

Since then, though, I've had no fuel supply issues even feeding 24 lb injectors (stock 2.9 injectors are 14 lb)
Thanks for the hints. Single pump might be in future if I have to drop the tank (or raise bed). OK on polymer ACT - makes sense. I had to replace pressure regulator once years ago so it could well be good preventive investment to go ahead and get it replaced while doing all the other work.
 

Paulos

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So, there are options for this.

My 88 was converted to a single in tank pump only. Granted, my 2.9 is highly modified. However, a Kemso 340 LPH pump (eBay) does fit in the plumbing for your in tank pump.

View attachment 30651

Installing the bigger pump has pros and cons. They are relatively cheap ($35 IIRC), will supply more fuel than a naturally aspirated 2.9 will ever need, and removes a second failure point from your vehicle (two pumps reduced to one). The drawbacks are that they are somewhat loud (I hear mine over my headers/Flowmaster/3"intake, etc), and requires the complete removal of the frame pump. The frame pump is replaced by a standard Ranger fuel filter (direct swap).

The one issue I did have was I was dumb and didn't shield the wiring properly the first time. Make sure to use the plastic conduit the pump comes with to insulate over the hot wire, and to properly terminate wires that used to go to the frame pump.

The other thing that I had to replace was my fuel pressure regulator. My 31 year old fpr died a horrible death from the increased volume and pressure from the new pump.

Since then, though, I've had no fuel supply issues even feeding 24 lb injectors (stock 2.9 injectors are 14 lb)
What about the fuel reservoir? Did you remove it? Without the high pressure pump in front of it I wouldn't think it would be necessary.

Did the 24lb injectors effect your mileage?
 

PetroleumJunkie412

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What about the fuel reservoir? Did you remove it? Without the high pressure pump in front of it I wouldn't think it would be necessary.

Did the 24lb injectors effect your mileage?
Not exactly. Just needed them for the planned supercharger.

Like I said, highly modified 2.9 😂

 


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