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Thread: CFI base map, camshaft lift measuring and dropping the gas tank

  1. #1
    Member Arquemann's Avatar
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    Default CFI base map, camshaft lift measuring and dropping the gas tank

    (1985 MGM 302CFI EEC-IV, non-regulator -type EGR)

    In my quest to find out what the everloving fck is wrong with my engine,
    I thought of somehow stopping the ECM from adjusting. There has to be some kind of base map on which basis the ECM adjusts to achieve the stoichiometric ratio and ideal consumption. With variables like the air pump system, EGR and many others, I have a feeling that something might've gone bad in a way that makes the adjust itself in a stupid way and still thinking it's running right. I.E. the damn jerkyness at cruising and low throttle.
    What to do if something resembling a base map can be achieved? BMW's have the AlphaN mode when without MAF(s), of course a CFI doesn't have a MAF and unplugging the SPOUT just stops timing advance.


    I'd also like to check my camshaft to verify that my problem isn't in the engine itself. And I'd rather not yank the cam out, since that's alot of work for possibly nothing. Can I just measure lift with a dial indicator at the rocker arm/ pushrod? These things do have hydraulic lifters, how does that affect the results? Also I don't know if the engine is roller of flat tappet ('85 model), but that shouldn't change anything. What would a collapsed lifter do?
    I bet one of you can link me a sheet of correct lift values and how to check lift at the valvetrain, I'm just wondering about the effect of the hydraulic lifters. And if obvious discrepancy is found, can it be attributed to the lifters, worn cam lobe or even a bent pushrod, in any case the intake has to come off to examine all the previously mentioned components (still less work than removing the cam altogether.
    (I want to check the cam because the jerkyness I've experienced from the beginning has definitely become worse over the summer and it is now present at higher cruising speeds than before and at low-speed-low-acceleration. Every time since the beginning of time, a healthy dose of the right pedal has the car running smooth and seemingly healthy.)
    What about the cam position sensor and what happens when it goes bad?


    I'll also drop the gas tank just to absolutely sure there isn't a damn drop of water in there, since the car always runs better with more throttle.
    I don't recall seeing a drain plug, it's going to weigh a wee bit. What to detach? Level sender wires, pump connector, how are the lines connected to the plate? is it on the side of tank like some Ive seen or just on the top? Line out, return and some sort of vapor vents? Are the lines loose and long enough to have the tank on the ground until I remove them? Two straps seemed to hold it in place, remove it from front to back or vice versa?
    Last edited by Arquemann; 10-13-2019 at 10:27 AM. Reason: Mentioned what car...

  2. #2

    Default CFI base map, camshaft lift measuring and dropping the gas tank

    I know with fox bodies (very similar ecu and setup) if you either delete the egr valve or if one of the egr components isnt working the ecu will disable the egr function from its logic. It may not be the case with these cars but you could test it by unplugging the egr vacuum solenoid, let it get up to operating temp, then take it out for a spin.

    As for checking the cam I think youre wasting your time but you could do it by removing the passenger side valve cover, removing the rocker and measure the pushrod movement. However this will only get you into the ballpark. You would really need to set the cam in a jig with a dial indicator and rotate the cam for accurate results.

    Have you put a vacuum gauge on the engine? Its one of the first things you should do imo. Itll tell you a lot about your motor with a few simple tests.

    Skip dropping the tank. You could pull the fuel level sender and take a peek inside.

    Also these dont have cam position sensors. They use pip sensors, which is like a crank position sensor. However they usually cause either a no start or a random stall when they start going bad.

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    Last edited by 87GrandMarq; 10-13-2019 at 12:34 PM.

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    I post a lot... knucklehead0202's Avatar
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    ^^^What he said. You're likely a flat tappet cam, which leaves the possibility you could have a lobe going flat, or a squashed lifter, but you'd likely have a lot of valvetrain noise if that were the case, and it would be constant. This COULD be an ignition thing but again, usually PIP or TFI issues cause dying or no start, not just weird running sometimes. Does '85 have the duraspark ignition module? My '82 mustang had it and i heard they do funny shit sometimes. Also, CFI is voodoo garbage to me so it could still be something in there. Hope something gets figured out, it's bugging me so i'm sure it's driving you crazy.

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    Member Arquemann's Avatar
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    My idea here is to verify there's nothing wrong internally with the engine, so I can have the peace of mind when I throw out the CFI.
    For the EGR, I've had the vacuum lines and solenoid connectors on and off constantly and I have to say it never changed anything meaningfully. Same with the Thermactor solenoids. From my earlier vacuum tests with the EGR, vacuum was all over the place.

    Mine doesn't have the duraspark, it's got the TFI distributor and a rectangular coil with a 2-pin connector.
    I want to check the coil voltage now that it's got a new alternator, just 12V multimeter from the two pins? I was a little hesitant earlier since the coil isn't at all like the classic barrel coils in all the yt videos.

    From what should I test the engine vacuum from? Manifold trunk or one of many vacuum nipples in the CFI unit? I'll also test the EGR once again,but this time I'll check if the solenoids are leaking.

  5. #5

    Default CFI base map, camshaft lift measuring and dropping the gas tank

    I think youve ruled out egr and thermactor then. If youre testing engine vacuum pull the egr line and test from that port.


    https://www.freeasestudyguides.com/e...cuum-test.html

    Also just for fun, while idling give the tps and map sensor some technical taps and see if your idle changes. Do you have an analog volt meter? You can use that to test the tps for dead spots.

    If all else fails you can pull the o2 sensor plug and see how it runs with it unplugged. Itll run in a sort of failsafe mode. If your problems go away Id assume the issue is fuel in nature.


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    Last edited by 87GrandMarq; 10-13-2019 at 02:00 PM.

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    Member Arquemann's Avatar
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    Quote Originally Posted by 87GrandMarq View Post
    pull the o2 sensor plug and see how it runs with it unplugged. Itll run in a sort of failsafe mode.
    This is what I was kind of looking for.

    Also the thing has a new TPS and EGR sensor, both were throwing codes when I got the car. After I replaced them with new ones, the car hasn't stalled once, which was the more serious issue originally.
    MAP is probably original though.
    You can find all the crap done here: http://www.grandmarq.net/vb/showthre...or-help-though

    I'll get checking tomorrow, forecast promises a whole lot of rain, but that won't stop me now that I'm armed with new knowledge!

  7. #7

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    Im familiar with your car, I didnt want to suggest something that was already done. Also remember that just because its new doesnt mean its good.

    I had an 85 myself for a little while so I know what youre going through. For me the only real issue I had was a rolling idle which was solved by unplugging the o2 sensor, but I didnt like running it that way.

    My money is on the tps but its anyones guess.


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    Yeah I should check the TPS, I've only really dabbled with newer cars or way older stuff that are rather lacking in the digitals department. New stuff not working hasn't been a concern to me, weirdly enough.
    Thanks for persisting, I find myself a bit naive every now and then. I don't know where I would be without all the helpful people and the library of knowledge this forum holds within.

    "Technical taps", hah

  9. #9

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    Thats what we’re here for! Not gonna lie, I didnt make up the technical taps bit but I like using it lol.

    When testing the tps, use an analog multimeter and open and close the throttle blade slowly. You should get a nice increase/decrease in voltage as its opened and closed. If there are dead spots you’ll know it. Also I highly suggest starting with the vacuum test I linked and do it as soon as possible. Its an old way of diagnosing issues but it works.


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    A few questions, did you replace the EGR valve and the position sensor or just the sensor, Did you use a aftermarket part?

    If you replaced the EGR valve with a aftermarket some of those came with different size washer- orifices each vehicle called for different ones depending on applications. I normally tried to stay with OEM whenever possible when it came to EGR valves.

    A worn TPS is a good guess like mentioned earlier and easy to check.

    If you really wanting to check the basics start with timing, disconnect the spout and check the base timing and note if the timing mark is bouncing around
    if it is that may be a indicator of a stretched and worn timing gear- chain set.

    If you suspect that the chain is worn and or stretched it is easy to confirm and we can help with a simple test to check the exact amount of slack in the chain and let you know if it requires replacement.

    Short of that I would do a vacuum test like mentioned earlier, power balance test then a compression test all of which can help you determine the health of your engine.

    BTW if you just replaced the sensor and not the EGR valve the spring in the EGR valve could be worn allowing it to open before it should which I have seen it in the past cause the EGR valve to flutter causing this problem.

    In cases where we suspected a weak EGR spring for diagnosing purposes we would add a small plastic vacuum T fitting then add a tiny calibrated orifice fitting leading to open air that would allow a small vacuum leak at part throttle but not such a large leak that the valve would no longer operate at higher rpm.

    I have also seen neglected clogged fuel filters cause similar issues.

    So keep checking the basics and I think you will find it is something easily overlooked.

    It is my opinion if the cam lobes are worn enough to cause a problem the rest of the engine will be equally worn and obvious that it needs a rebuild. Signs from noise, smoke, oil consumption, etc would have been obvious by now.

    This being said I have seen crappy running engines with worn rings worn timing chain and fouled plugs not smoke at all until you replaced the plugs and timing chain.
    2007 Ford Crown Victoria LX Sport

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    Only the sensor for the egr was replaced, valve didnt leak, and seemed to respond to vacuum correctly. TPS and egr sensor were Standard Motor Products parts ordered from RA.
    You can read in more detail what has been done, from the thread I linked in post #6.
    Timing set was just changed, new double roller set. Every plug out of this engine has been fine, even though it idled quite rich for a while.
    Timing was checked and set before and after the timing set change.
    Fuel filter is also new among ALOT of other things.

    I ought to do the vacuum test and maybe even the cylinder balance test. I botched a compression test earlier due to poor equipment.

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    I mentioned the egr valve possibly having a weak spring meaning it could slightly open and cause the valve to flutter under lower vacuum than it normally needs to operate.

    I do not remember the specifics someone here may know but for example lets say the valve should stay closed at 1-2 inches of vac yet opens or starts to open under light cruise condition the problem your describing could happen.

    Normally one could just unplug the vac line and plug it then test drive to see if the problem went away.
    2007 Ford Crown Victoria LX Sport

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    I managed the vacuum test:Fluctuates between 21-22 inHg on curb idle in park. In gear, it's a very consistent 18 inHg. The idle in park/neutral feels a little high for me, but in gear it's almost a bit low. When the ac kompressor kicks in, in both cases it lowers about 1 inHg.

    I did this test from the plastic vacuum distribution block on the firewall, I didn't have an adapter large enough for the PCV line.
    The EGR line that you've recommended to check from, doesn't get any vacuum... It definitely did get vacuum when I dabbled with EGR earlier this summer. It's the line that goes from the CFI unit to the EGR solenoids. I don't even... The line is tightly around the nipple on the CFI unit, the nipple doesn't rotate or feel loose. I even reconnected the egr solenoids to be sure. I get absolutely no vacuum from the line coming straight from the CFI unit...

    I feel like this has happened to me almost every time with this car; I go to do a check, test or just try to fix something, and I find a new problem.
    Also: during the warmup drive, it was as jerky as usual, but when it idled while I was doing the vacuum tests, it idled very well, it misfired maybe five times and after that it just idled away smoothly. Usually it idles consistently inconsistent.

    Was going to try it with the O2 sensor removed, but the thing is so damn tight and seems to need three hands and two screwdrivers to get loose, and I can just about manage two hands and a screwdriver.

  14. #14
    I'm an air-conditioned gypsy gadget73's Avatar
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    Ever checked closely on the condition of the fuel pump relay and socket? Those get nasty sometimes can cause the fuel pump to not run steady. Should be the green relay on the driver's side inner fender. Make sure the wiring is actually still wire and not a ball of green fuzz. Might also be worth tapping the relay to see if the engine misfires when you do it. Same on the ECM relay, its the brown socket one over in the same area. The black one should be the AC cutout. It won't make the engine run funny but if you're checking wiring, may as well look at that too.

    don't remove the O2 sensor, you'll have a huge leak in the exhaust. Unplug it if you want to try that. Removing the sensor is a PITA, and if you're doing it you may as well put a new one back in.

    Last time I fooled with a CFI car that used too much fuel and had a misfire it was actually two problems. All the same things you have done to yours had been done to this one, intake gaskets, vac lines, timing set, clean the EGR stuff out. The fuel usage was a bad oxygen sensor. Replacing it did not change the misfire at all, but it stopped sucking as much fuel. The misfire we eventually chased to the plug wires. They were new Belden wires, but for some reason they didn't work well on that car. I actually put used Ford Racing wires from my car on it and the problem completely went away. I think those Belden wires actually went on something else and it ran fine. I bought the same set at the same time for my Mark VII and never had trouble with them. Possible it was the routing, don't honestly know.

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    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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    Yesterday I had the relay off to remove pressure and I opened the fuel line to get a sample of the fuel, which didn't have water in it.
    Fuel relay was dirty and sooty, but wiring seemed fime, even if a little stiff. Upon priming the fuel pump numerous times to get the sample, either one or both of the relays are really loud.
    As with pretty much every connector in this car, they're all slathered with dielectric grease from some decades ago.

    Yes I meant unplugging the O2 sensor, and that was a farce. The O2 sensor is new.
    I'll see what I can get done today.

    This car has been through 3 sets of plug wires and 2 sets of plugs, with most combinations of those.
    What helped the most with the rich condition was actually the new ECM. New injectors helped a bit and o2 sensor apparently did nothing.

  16. #16
    I'm an air-conditioned gypsy gadget73's Avatar
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    Where are you measuring a rich condition? Might be worth putting a voltmeter to the output of the O2 sensor to see what it has to say. If the O2 sensor says its flipping from rich to lean regularly, then the engine management is doing what it should do. if it swings from 0v to 1v back and forth, the ECM sees that as a normal mixture. Hanging at 1v is rich, hanging at 0v is lean.

    some info on how to test a MAP sensor.

    http://es.wellsve.com/sft503/counterp_v1_i1_1997.pdf

    need a meter with frequency reading, or a tachometer to do it. Usually they work or they don't. When the MAP fails, the mix tends to be extremely rich and it runs like complete garbage.

    86 Lincoln Town Car (Galactica).
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    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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    Rich condition was measured by the mechanic at the tailpipe, and after all the parts changed and other stuff at the shop, its supposedly rich at idle.
    I'll be out of country for a week, can't do much now. :shrugs:

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    Im starting to lean towards the map sensor now.


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    I'll check the map sensor when I get home, my dad ought to have a spare tacho somewhere. Instructions seemed relatively straightforward. That's what I thought of testing the TPS, I need to depin the connector first to get the rubber waterproofing out of the way to backprobe it while it's conncected.

    For now, I'll enjoy the weather here in Maspalomas, it's not cold, rainy or dark here. Tbh, I only minded it when trying to work on the cars.

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    Took a while to get to that...

    Tach trick didn't work but multimeter had a Hz setting. Ign on not running I get around 130-150 Hz (0.13-0.15 kHz displayed). While idling, it showed around 80-100 Hz and increased a bit with throttle.
    Seems to be correct. Next ideas and hypotheses will have to wait until spring
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