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2.9L Reality Check: Highway capable?

RonD

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The TFI and distributor are independent, computer is only connected via SPOUT to adjust spark timing based on Load, air/fuel mix

TFI sends computer the timing signal so it can run the injectors based on RPM, but doesn't need the computer to run spark
That's why you can unplug the SPOUT connector and engine still starts and runs

But spark timing does need to be changed based on Load so your lack of power "under load" could be a computer issue

You could leave SPOUT unplugged and go for a drive, should be sluggish when accelerating but OK cruising, and a lack of power
If thats what you have with SPOUT connected then I would say computer is the issue
 


eightynine4x4

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The TFI and distributor are independent, computer is only connected via SPOUT to adjust spark timing based on Load, air/fuel mix

TFI sends computer the timing signal so it can run the injectors based on RPM, but doesn't need the computer to run spark
That's why you can unplug the SPOUT connector and engine still starts and runs

But spark timing does need to be changed based on Load so your lack of power "under load" could be a computer issue

You could leave SPOUT unplugged and go for a drive, should be sluggish when accelerating but OK cruising, and a lack of power
If thats what you have with SPOUT connected then I would say computer is the issue
Yes, that’s a pretty good way of describing it. Power is fine in lower RPMs. Gets weaker the higher you go.

So, if I replace just the TFI module but not the distributor, and then run the truck and have the same issues, are we now narrowed down to just being the computer?

Or is it possible that the stator in distributor could cause issue in communications?
 

RonD

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No, the hall effect sensor failure would cause running issue all the time, usually no start
 

eightynine4x4

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All right.
So the problem was the TFI. New generic one from down the street works great. I’ll keep the story short but I had made 2 stupid mistakes installing it, so it didn’t work of course.
I’ll cancel the order for the new whole distributor/TFI assembly and keep the OEM old distributor and just stay on top of the TFI sensitivity. Will at some point relocate it as per the popular mod.
Once I had the TFI installed right, the engine turned over and idled immediately smooth which has never happened before. It sounded like a different engine. It also sounded like maybe I wasn’t even getting all cylinders before. It’s all running now. I gave it a few revs and could tell it was very different. Watching the HG was a different experience too.
So I reset base timing and was quickly on a test ride. It climbed small town hills just lightly holding the throttle. So I went on down to the highway for a short 1/2 mile stretch. Cruised up a long on ramp and merged at 65. Slight down hill after that so got up to 70 and took the quick exit. Ran an errand, got back on return highway trip, again with a long uphill on ramp but this time the highway stretch was against the wind and a little bit uphill. Accelerated steadily to around 65 before hitting the exit.
None of that was WOT. Just giving a very healthy dose of throttle. The truck wants to accelerate the higher the revs go. Before it was the opposite.
The truck wasn’t even in this realm before. It’s almost like a new truck.
To recap, I’m on 31”x10.5x15, have a 4.10 rear limited slip, have a 2.5” suspension lift, crappy old brake pads which give some resistance on their own and which I still haven’t changed, is automatic 4x4, and I’m rolling without fenders and grill so I’m a huge wind sail.
I have to conclude that this is a highway capable vehicle. I figured as much, and was in denial that I had the proper performance. I’m glad I didn’t settle. I think the previous owners gave up at this step since i eventually discovered last year that the distributor bolt clamp was loose and it was all moving around as I drove.
It will only continue to improve from here. There is still ticking but it sounds light weight instead of kinda banging.
 

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What were the two simple mistakes?
 

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eightynine4x4

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What were the two simple mistakes?
Stupid mistakes, not simple haha.
Firstly, I tried removing/installing the TFI while still on the distributor. That was silly. The 3 contacts are invisible from all angles so it’s by feel only, and those 3 slots turn out to be quite weird and misleading. Very easy to think you’ve made the electrical connection but actually have not at all. Fired up the truck and sure enough didn’t turn over. Assumed new TFI didn’t work.
Then I decided to just take the whole dist out and double check the TFI connections while off the truck. That’s when I discovered and corrected the above. Those 3 slots are kind of poorly designed with flimsy plastic around them and you can easily get a metal pin up in just a plastic hole without making a contact electrically but be in the sorts same spot. Was excited to hook it all back up. When i put the dist cap back on, somehow I didn’t notice that it was backwards 180 and started bolting it down with the small screws. Amazingly, and of course because why not, when you put the dist on backwards and lower it, it’s not centered but rather there is an offset to the circle/bolts overall, and in this position inside wall of cap pushes down perfectly on the very edge of the metal T-shape piece of the rotor. When I was bolting it down, I heard a snap. It sounded just like the sound of the cap settling into place, like the rim had been slightly off and finally snapped in. So I ignored it. But unbeknownst to me, that whole metal piece mounted in rotor had broken into a few pieces and had silently fallen down into the distributor well. But not knowing that happened, as soon I realized it was just all backwards, took it off and spun it around and remounted it and tried starting the truck again. But, there was absolutely nothing metal in the rotor now and I didn’t know that. So of course it’s not going to distribute much. But all I knew if is the truck didn’t start, for the second time, so this time I fully concluded the TFI was faulty since I knew for sure it was mounted properly to the distributor.
Somehow I found the conviction to open it all up and check again today. A third check. I was going to focus on TDC and the rotor direction, and that’s when I noticed that the rotor had no metal piece in top. It took me a while to notice it. So I realized what had happened but then panicked that it had fallen down into cam in engine. Would have been a nightmare. Fortunately I found the pieces were down in the distributor and was able to fish them out with a light and some tweezers. I also took the whole dist out and made sure there were no more remnants, dumping and shaking it upside down. Then I reinstalled the dist with its properly mounted TFI, and bought a new rotor and put that in. Then it was a new day.
 

eightynine4x4

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There's been a development about the TFI:
Up until now it's been running seemingly like a good TFI, timing in higher rpm's seems good and the truck can reach higher speeds. But i finally took it on a long trip and sure enough after maybe 90 minutes or so the timing collapsed and i was hitting max 40 MPH downhill, maybe 25 MPH uphill. It was worse than I'd ever experienced.
I'm not sure if it happened all at once or if it slowly morphed into a faulty state, because i was driving on low speed roads while it changed. Once i got on to a 55 MPH road again, i was forced to finish the last hour of the trip constantly pulling over to let people pass. Not a fun thing!
I also seemed to burn through fuel way faster for that leg which makes sense. But i'm not positive about that since my fuel gauge has developed a personality as of late.
Anyways i got to the destination and stayed the night and the next morning i expected to just have a useless TFI, thinking it totally burned out. But alas, the truck ran fine when i took it on a short 10 minute trip on a 55 MPH road and back.
It was surprising to me that a circuit board or component inside the TFI could recover from a temp overload issue and perform well after cooling down. One logical answer is that it is in fact an IC but it has a temperature overload function that shuts itself down and turns itself back on when cooled off. That's a pretty normal function. Maybe different manufacturers of this TFI use different IC qualities and some cheaper ones auto-shut down at lower temp thresholds than more expensive ones. If this is in fact the answer, it's a shame that nobody advertises the fact that theirs has stronger specs and will remain active during higher temps. I'd just buy that one and not do the relocation mod.
But alas, these TFI's seem to have some grey area of health... they can be fully dead as mine was (i think), and they can also be only dead/off at high temps. So i guess the fully dead ones are just old and zapped from use. Maybe new TFI's that shut down are not actually getting zapped they're just turning themselves off temporarily.
I'll post an update with the mod or solution when i move forward with it.
 

lil_Blue_Ford

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Yeah, TFI modules react weird to heat. Autozone and some other parts stores used to be able to test them and I was always told to run the tests until the module got warm to the touch, which was usually 3-4 times. I also learned to test new ones. Some would work fine the first 2-3 tests then fail miserably. Let it cool and it works fine again. I believe the only one of my trucks that still has one on the distributor is my 88 Bronco II and I’ll probably remote mount it when I get that truck back together.
 

eightynine4x4

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31 x 10.5 x 15
Yeah, TFI modules react weird to heat. Autozone and some other parts stores used to be able to test them and I was always told to run the tests until the module got warm to the touch, which was usually 3-4 times. I also learned to test new ones. Some would work fine the first 2-3 tests then fail miserably. Let it cool and it works fine again. I believe the only one of my trucks that still has one on the distributor is my 88 Bronco II and I’ll probably remote mount it when I get that truck back together.
Gotcha, yeah it’s been pretty bizarro so far. It seems like it’s half good now, still operating ok when cold but not as well as it did when it was brand new a few weeks ago and cruised up to 65/70 without much effort. So I think I’ll use my cheap new one as the connector and get yet another new TFI for where it goes.
The only thing that’s annoying about the mod is finding a used TFI heat sink from the list of compatible vehicles in that page. Kinda weird that a heat sink of that magnitude is required even when the TFI is no longer on the distributor, so I guess that means it carries a ton of current in the circuit so the heat sink is required even with TFI mounted way far from engine.
 

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