kishy's 1984 Town Car

[kishy]

I'm going to have to dig up that owner's manual and check if the pedal-push to set fast idle is required in warm weather. I can't see that being the case but maybe it is.

Ride height still TBD.

Changed air filter. Visibly, it needed it. Only 16k km (just shy of 10k miles) change interval though, which doesn't seem terribly long.



VECI references for the future:

[DerekTheGreat]

I decided to "poke the bear" and tinker with the idle adjustment. I had both the fast idle and curb idle set a touch high to provide a more consistently reliable experience, and it's finally gotten to the point where it bugs me enough to do something about it.

Successfully lowered the fast idle from 2590 to 1870, where correct specification is either 1900 or 2100, I forget. The difference in engine noise from 2000-2500 is really significant, so it doesn't sound like it's racing now. A proper cold start will be required to verify this isn't too low, but since I'm not planning to run this car in the winter anymore, that may never be necessary.

Curb idle was a little more troublesome, as I thought it would be. There's this convoluted process you have to go through to put the computer into a learning mode to set the idle, and you don't really have a good indication of whether you succeeded or not. Anyway, brought it down from 700 fully warmed, in gear against chocks and brakes, to 550, where spec is 550. I was unable to restart the engine with it set like this without giving it a tiny bit of throttle, so I bumped it up a bit and arrived at 570 ish. I verified the TPS closed throttle voltage is 1.00V on the nose; given that fast idle is achieved by holding the throttle open on CFI, I am quite reasonably certain that the exact idle voltage is not as picky as people make it out to be for SEFI.

More tinkering to be done. When it fails to start, it will start with a tiny bit of open throttle. What I'm trying to figure out is if this is because it doesn't like the TPS value against the actual amount of throttle opening (sloppy TPS), or if the TPS is fine but it's just not sucking enough air (in which case, why is it not enough air when the throttle blade is set per specs).

The TPS is such an incredible pain to change on these that I hesitate to just swap it to see what happens...

I don't know if that's normal or like you said where TPS voltage is involved. I never got that far with my car but if it wasn't cold enough for the fast idle cam to engage, the F'er would never start without the tiniest bit of throttle input. But I wanted it to idle where the sticker said and with the A/C on, I didn't want that dash-pot to make it a chore to keep it stopped at lights. And before I bumped the idle down, it was indeed a chore. This was also before I learned that the dashpots could be adjusted, although I never tried that. I had my fast idle set to about 1,800 rip'ems IIRC. If you have it set too low, you'll know when it gets cold as the car will surge. "Whoom..whoom..whoom" I don't think the computer compensates fuel trim for temperature, only manifold vacuum. So when it sees manifold vacuum drop, it dumps fuel in "whoom" and then vacuum restored, begins to take fuel away, engine speed drops and repeat until the manifold heats up to a point where fuel is no longer falling out & condensing on the intake runners. Reason I am convinced of that is my old '69 Plymouth didn't have a choke but I could start it on the coldest days and it would run just fine so long as the RPM was held around 2k until it warmed up, just like my CFI equipped Ford. If I tried to go lower, it's engine would start to stumble & drop like I flipped the key off, but if I stabbed the pedal to get the accelerator pump to shoot some go-go juice in the carb, comes right back to life. The two are too similar to ignore, cold start behavior wise.

[gadget73]

Some of the idle speed control is by timing. On a CFI car, that actually may be most of the speed control since it has no way of bumping open the throttle.

[kishy]

Right. The VOTM (dashpot) is only used in specific scenarios, not for overall idle management.

Thing I ran into is, when I last did the curb idle adjustment, the engine "tone" changes when it recognizes the 2000RPM-for-60seconds thing as being complete, much like if you were to pull the SPOUT connector and run at base timing. I can't get the car to do that anymore. As a result I think I've inadvertently set the after-timing-compensation idle speed to 600ish RPM rather than the before-timing-compensation idle speed which is what you're supposed to adjust.

The car currently has an 85 computer, and I last adjusted the curb idle using the 84 computer. I'm not sure if this procedure differs from 84 to 85.

Starting it with a tiny bit of throttle is not awful but it also really shouldn't be necessary. This is an EFI engine management system, at the end of the day.

[gadget73]

well, I've already told you how I would fix this so we'll leave that part alone.

Where are you finding the idle adjust process, in the service manual or is this in the emissions and engine diagnostic manual?

[kishy]

As it happens, I originally learned the process via Googling from some guy on another forum. This, I think: http://vb.foureyedpride.com/showthre...=1#post1575876
Edit: I think I figured out why it worked following that ages ago, and didn't work more recently. These instructions linked above specify bringing it to 2000RPM a second time. That's what I haven't been doing these more recent adjustments. Can't wait to try this tomorrow now...

I also later found it here (direct PDF link, I can't seem to find the page it's referenced on): https://www.ford-trucks.com/forums/a...5&d=1507813043
Jump to "“5.0L V8 CFI Engines” on page F155" in the contents right at the top.

The VECI label (further up in the thread from the other day) provides instructions as well.

Finally, most recently, I cracked open my (literally moldy) 84 Emission Diagnosis manual and it happens to outline it in there.

The amount of variance in the instructions from source to source is interesting. It's like no one individual writing the documentation knew the actual information.


But...that may be a non-issue. Maybe. I did all that again twice tonight, set it right on the nose at 550 thinking surely there is a way to make this work properly. This reintroduced the difficulty warm restarting. I then swapped the TPS, and bench tested the used replacement first using an analog ohmmeter. I then checked the one I took off, and it was...I dunno, scatchy-ish just off idle. No dramatic jumps, but it seemed to have flat spots all in that first tiny bit of rotation right off idle. So, replacement went on.

I went a little off the beaten path and tightened it down at 0.81V, since there's at least one reference on the web (but not the conventional wisdom here on GMN) that tells you throttle closed should be 0.80-0.85. Tried to start it. Started with no pedal action. Temp gauge showed 160 at the time.

Idled it up to operating temp, cut it off, immediately re-started OK. Cut it off, let it sit for a few mins, re-started OK again. There is at least the remote possibility that a TPS-related condition was causing the need for the higher curb idle.

Unfortunately, I have now introduced an issue where a rapid acceleration from a dead stop will give a teeny tiny bit of spark knock right at throttle open, but it goes away immediately.

Also, there is the very unfortunate possibility that there is coolant escaping between the timing cover and the block, but I'm really, really hoping that's not the case for obvious reasons.

[DerekTheGreat]

RIght, the only time I noticed the dashpot working was while cruising or holding the engine at elevated speed (You could see it move, it would never make contact with the throttle linkage. Something about the throttle snapping shut being bad so they put that feature in there) or with the a/c on to bump the idle up. My car bumped the idle up quite a bit with the A/C on and it sucked. Without out, it was awesome to drive.

Perhaps my car could've benefited from a TPS as well. Ah, I need another CFI car in my life...

[gadget73]

The TPS voltage setting is not as critical as people make it out to be. 0.8 - 1.2 is supposed to be the normal closed throttle range. 1.0v is of course right in the middle. The ECM doesn't care as long as its in range. It sets the zero value on each startup anyway, which is handy since its going to drift some with temperature and whatnot anyway.

You can adjust the amount the dashpot kicks too, the end on that thing can be set to control the amount of idle bump. Its either that or the adjustment on the sled that changes, I can't recall which but there is a way to control it.

[DerekTheGreat]

I've heard about the ECM setting zero with each start-up. What would happen if you held the throttle slightly just before flipping the key on, starting the engine and then take your foot off the throttle?

[kishy]

My poorly-informed understanding is actually that it's a continuously updated "ratchet"...the new lowest value at any given time is the new throttle closed value, not necessarily requiring a power cycle to recognize it as such.

We know what the car does if you hold the throttle slightly open - it starts as normal and runs like a happy little puppy in a wide open field.

The computer has no way of knowing whether the throttle is open because fast idle is engaged, or because you manually held the pedal down a bit. The TPS is actuated identically by either mechanism.

If it were true that the throttle closed position is only measured and remembered one time per power cycle, I don't think the car would be able to stay running at all once you released the pedal, if you had held it past the highest possible fast idle position.

Throttle position seems to be "relative"...the throttle is now 10% more closed than it was a second ago. If the computer suddenly thought the throttle was 10% more closed than fully closed, and was not capable of accounting for that with the above-described "ratchet", then I presume the engine would start showing some serious idle quality issues.

Gadget, you know this stuff much better than I, so please poke holes in this where needed.

---

I redid the curb idle thing. No changes.

What I'm trying to do is figure out the brief spark knock described a couple replies ago. Once I brought the curb idle (hot in gear against chocks) down from 700ish to 550ish, I introduced a spark knock condition when kind of mashing the go pedal from a dead stop. However, I also haven't experienced it since swapping the TPS, so...

I think that training/teaching the computer the curb idle speed has more to do with the computer crunching part of its timing calculation, than anything else. But this is inferred, not observed nor read in a book.

And yeah, the VOTM/dashpot has two adjustments: overall position (sets curb idle) using the long screw, and something involving turning part of it to adjust the vacuum "throw", but it seems to have threadlocker on it or is otherwise mechanically prevented from being adjusted. Didn't want to break it. They're unobtainium except used now.

[gadget73]

As long as the initial position is within the OK range, it should update itself. If your high idle or low idle get it too far out though you may have problems. I had a bum TPS on the Mark VII that would drop the idle voltage below spec with the throttle closed. It stumbled every time I let off the gas completely and the CEL came on. It would go out and run normal if I gave it any throttle so it was compensating to some degree. It did store a "TPS intermittently below minimum closed voltage" code though.


Normally you shouldn't have to adjust the throw but if someone screwed with it previously all bets are off. Basically if it ain't broke....

[kishy]

Curb idle developed some weirdness. Kind of a pulsing shake through the car. Decided to re-do some things:

TPS throttle closed value: found it had slipped a little to 0.79. Have not checked for codes but I'll bet there's a "TPS below minimum" waiting for me in there. It's now 0.87ish.

Base timing: this was set at 14-15BTDC. Whoops. That may have accounted for some of its peppiness, as well as some of that knocky-knock I mentioned previously. It's now at a more conservative 10-11. I do not believe the balancer slipped, I believe I put it that way through sloppy wax pencil markings previously.

Curb idle: now at 590, which puts free idle in park/neutral around 800.

The above in combination with each other seem to have more or less eliminated the idle shakes and warm restarts aren't being stupid with the throttle position (but the throttle position sensor swap seemed to cure that specific ailment prior).

Other recent events:
I visited Derek and he, being the cool dude he is, hooked me up with some speakers, on account of the sorry state of my audio system. Just need time and motivation to replace the remaining bad ones.

Back when I pulled the windshield for the wagon, I noticed the same car (90 Grand Marquis) had a near-factory-fresh trunk seal, which I gladly bought. My Lincoln's was barely recognizable as a rubber product anymore. Replaced that, and adjusted the height of the pull-down motor to not crush it into nothingness. Rubbed it all around with a silicone spray. Had to trim it a bit as the Mercury trunk opening seems to be slightly larger than the Lincoln one.

I purchased a heater core from RockAuto, eventually to go into the Lincoln when I get to that point (gotta fix the vent selection doors and suspect HC has a small leak). TYC does not package their stuff worth a crap. Through no fault of RockAuto's, and possibly even from mishandling before it went into its box by the manufacturer, the side was indented mildly, enough for me to question if its integrity might be compromised. Submitted the refund request thing and they gave my money back, no fuss, so that's good. Not sure what to do with this thing now.

[DerekTheGreat]

I think all the discoveries and progress you're making and reporting on for CFI are going to do wonders for anyone with one and the determination to keep it in place. Before me, it seemed the only person with one was RyPow with his '85 TC, but he hardly posts and apparently doesn't have too good a reputation within the buyers & sellers feedback thread... Before that it was "Throw it in the trash." What's more is they're just as powerful as a LoPo. I'd like to compare smoothness between CFI & SEFI, so when I get my heater core blocked off and another pay check in the Townie will get washed & come out to be driven and such.

[kishy]

I think all the discoveries and progress you're making and reporting on for CFI are going to do wonders for anyone with one and the determination to keep it in place. Before me, it seemed the only person with one was RyPow with his '85 TC, but he hardly posts and apparently doesn't have too good a reputation within the buyers & sellers feedback thread... Before that it was "Throw it in the trash." What's more is they're just as powerful as a LoPo. I'd like to compare smoothness between CFI & SEFI, so when I get my heater core blocked off and another pay check in the Townie will get washed & come out to be driven and such.

That's exactly what I post the stuff for. It's a record for myself and others to hopefully find if needed in the future. I'm at least partly inspired to write an EEC-IV CFI Troubleshooting Guide, which at the end of the day is not entirely dissimilar from EEC-IV SEFI, or maybe any other engine management system, but specifically does not say the words "throw it in the trash" at the end of the flowchart.

Anyone who has ever uttered those words on here, despite how helpful and what a positive contributor they may have been over however many years, has done a great disservice to owners of these cars and I wouldn't be surprised if the undeserved stigma the system has attached to it now has resulted in these cars ending up as scrap or derby cars instead of being picked up by the enthusiast crowd, which is already very small, and doesn't need to be downsized any further by fearmongering with no true basis in fact. Almost every defect the CFI system can experience can apply to SEFI and I think as the SEFI cars age out just that extra bit more, more troublesome ones will start appearing out of the woodwork. It's like you said on Sunday when I was over...people already carb swap the SEFI cars because they don't know how to troubleshoot them. We need less of that, not more.

[gadget73]

My lack of interest in it is a combination of two primary faults: its annoying fix, and its gutless. The latter being the bigger problem for me, so both get fixed in one go with an engine upgrade and management system swap.


Pressure test the heater core, that will tell you if its got problems. 15 psi of air into it, cork off the outlet, and stick it in a bucket of water.