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  1. #1

    Default 86 5.0 starts and then dies when cold

    Hi, my 86 GT 5.0 (daily driver) recently developed this thing where it cranks up right away, revs up a bit as usual, but then instead of settling in to an idle it just dies. This only happens when cold ( as in sitting over night). And it does it every morning now.

    2nd crank always starts fine and then does NOT die. Idles fine, drives fine. No other issues other than the die after first crank when cold.

    Also, when I crank it cold after sitting over night and I juice the gas pedal just a little it prevents it from dying and then when I let off the gas it goes into idle just fine.

    So it doesn't seem like a big deal, just a little nuisance after it sits over night. I've gotten in the habit of just tap the gas pedal a little bit when i start it to keep it from dying and then all is good.

    My question is whether this is an indication of something else going on or changing that I need to think (or worry) about? It just seems strange to me that it just started doing this "out of the blue" about a month ago and now it does it every single morning, without anything changing in the setup. Never had this issue in the past...and I have owned this car since it was new in 86!

    I was thinking maybe it had something to do with weather shifting from cooler to warmer and perhaps the winter mix gas transitioning to "normal mix", but it didn't do that last year at this time (or all the years before).

    Just wanted to get some input from you guys before I start dicking with the TPS and air mixture ( it has one of those idle air control adjustment plates by the way).

    Thanks for any input.

    By the way, it is basically a full stock set up. Only mods are a CAI and a larger throttle body. I added the IAC adjustment plate after the CAI and throttle bottle so I could dial in a steady idle. Other than those things...stock.

    -Eric

  2. #2

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    carbon on the back of the intake valves. Classic symptom. Carbon absorbs most of the fuel charge during initial start, causing a lean stall. Second start attempt, carbon is already saturated. Remove intake and walnut shell blast the intake valves through the port.
    Jim DeAngelis
    Cornucopia of Useless Knowledge
    Connoisseur of Dearborn Ferrous Oxide
    '83 GT hatch, currently under the knife
    '79 Capri 2.3L n/a, Medium Copper metallic, survivor
    (bought from MRausch82)

  3. #3

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    How old is the fuel filter, and is the fuel pump the original '86-er? The fuel filter (or the fuel pump "sock" filter) might be clogging up, and fuel pump might be gettin' tired, needing two "primes" to get the system adequately pressurized. Your description of progression to worse sounds sneakily suspicious that it could be those things. Test or get the fuel pressure tested. The rest is about running for possible trouble codes, cylinder balance test, TPS voltage at idle, etc...
    Last edited by Walking-Tall; 05-24-2017 at 01:02 PM.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  4. #4

    Default

    thanks, that makes sense.

    Since it just recently started doing this I was thinking to try some CRC intake valve cleaner through the TB first to see if that helps.

    Do folks here have any good ( or bad ) experiences with that approach?

  5. #5

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    Quote Originally Posted by Walking-Tall View Post
    How old is the fuel filter, and is the fuel pump the original '86-er? The fuel filter (or the fuel pump "sock" filter) might be clogging up, and fuel pump might be gettin' tired, needing two "primes" to get the system adequately pressurized. Your description of progression to worse sounds sneakily suspicious that it could be those things. Test or get the fuel pressure tested. The rest is about running for possible trouble codes, cylinder balance test, TPS voltage at idle, etc...
    Less that 3 years ago the entire gas tank was replaced with a new one, including a new fuel pump and new sock. The fuel filter was also replaced at that same time. So that was about 15K miles ago. I wouldn't think that could be the issue, even for a 3 year old fuel filter with 15K miles on it.

    Worth trying to change the filter though. Can't hurt.

    Thanks for the suggestions!
    -Eric

  6. #6

    Default

    Could be a fuel thing too though, dirt etc.. Yeah, if you remove the filter and empty it, and blow through it by mouth and there's any resistance sensed to blowing through it, they're toast.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  7. #7
    FEP Super Member erratic50's Avatar
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    Nebraska
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    Default

    check for carbon and goo on the back of the throttle body.

    with the engine off open the TB wide open and hose it down good. Let it sit.

    go back in an hour or so and start it.

    A lot of ford techs back in the 90's would shoot the remaining cleaner at the throttle body while the engine is running at idle to "clean" the intake valves.

    Optionally use a top end cleaner like marvel mystery oil.

    in my experience, beating the crap out of it occasionally keeps the engine from carboning up.

    My sons 86 could have won a contest for the most carboned up EFI 5.0 ever when he got it. Didn't take us long to fix that. A good heavy TB cleaning and a long drive all the way to Nebraska from Florida cured that.

  8. #8

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    Quote Originally Posted by erratic50 View Post
    check for carbon and goo on the back of the throttle body.

    with the engine off open the TB wide open and hose it down good. Let it sit.

    go back in an hour or so and start it.

    A lot of ford techs back in the 90's would shoot the remaining cleaner at the throttle body while the engine is running at idle to "clean" the intake valves.

    Optionally use a top end cleaner like marvel mystery oil.

    in my experience, beating the crap out of it occasionally keeps the engine from carboning up.

    My sons 86 could have won a contest for the most carboned up EFI 5.0 ever when he got it. Didn't take us long to fix that. A good heavy TB cleaning and a long drive all the way to Nebraska from Florida cured that.
    Me, my father, and my grandfather (who kept the town's fire trucks as blazing (pun intended, lol!) fast as possible) refer/referred to that as blowing the cobwebs out of it, and you're absolutely right.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  9. #9
    FEP Super Member erratic50's Avatar
    Join Date
    Dec 2016
    Location
    Nebraska
    Posts
    4,575

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    We often refer to it as blowing the cobs out of it.

    Back in the early 1900's guys would run their T on paths you couldn't call a road and they're end up with broken up cobs in the oil bath air cleaner from what I've was told by the old timers. Open them up and the cobs get sucked in and blown out.... Not sure I believe it. I guess that's one way to be a "cornhusker" ....

  10. #10

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    Quote Originally Posted by erratic50 View Post
    A lot of ford techs back in the 90's would shoot the remaining cleaner at the throttle body while the engine is running at idle to "clean" the intake valves.
    yup. That's what my recommendation is on, several decades of experience as a Ford tech and training instructor. The throttle body and IAC gum only amplifies the problem. The primary issue is the carbon on the intake valves. You can run through whatever magic juice you choose, but the only way to really clean the valves properly is walnut shell blasting, or removing the valves and wire wheeling them.
    Jim DeAngelis
    Cornucopia of Useless Knowledge
    Connoisseur of Dearborn Ferrous Oxide
    '83 GT hatch, currently under the knife
    '79 Capri 2.3L n/a, Medium Copper metallic, survivor
    (bought from MRausch82)

  11. #11

    Default

    Quote Originally Posted by erratic50 View Post
    check for carbon and goo on the back of the throttle body.

    with the engine off open the TB wide open and hose it down good. Let it sit.

    go back in an hour or so and start it.

    A lot of ford techs back in the 90's would shoot the remaining cleaner at the throttle body while the engine is running at idle to "clean" the intake valves.

    Optionally use a top end cleaner like marvel mystery oil.

    in my experience, beating the crap out of it occasionally keeps the engine from carboning up.

    My sons 86 could have won a contest for the most carboned up EFI 5.0 ever when he got it. Didn't take us long to fix that. A good heavy TB cleaning and a long drive all the way to Nebraska from Florida cured that.
    Thanks, I've been reading a lot of references on the web about "spirited driving" as a good prevention for carbon build-up, and even to help reduce carbon that already built up. Hey, enough said! All I needed was a little encouragement to start driving it more like I used to drive it! Ha! I guess I have been intentionally treating it a little kinder and gentler thinking it would help the car live longer at this point. Maybe that was counter productive.

  12. #12

    Default

    Was kind of hoping somebody would chime in with any experiences using something like CRC Intake Valve cleaner (what I am thinking about trying), or Sea Foam or something similar, through the throttle body or through a vacuum line.

    Anyone tried that on the HO EFI 5.0 engine ?

    Did it work? Any issues?

    Thanks!
    Eric

  13. #13

    Default

    I swore by sea foam when i was a kid. Now i see it more as just a smoke show. You can do a pretty good job cleaning stuff up with just tap water.

    My old 86 has around 350k miles on it a idles perfectly without dying. One day it just wouldn't start. I tried replacing the iac as it was just a bit too high a threw a code, as did the map sensor. It ended up as the map sensor.

    The sd systems are super picky about vacuum leaks. If you pull codes and nothing comes up, id start there.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  14. #14

    Default

    three parts hot water to one part ATF in a milk jug. Shake to mix, keep mixed. Introduce thru vacuum port as close to the throttle body as possible, to get even distribution. Restrict vac port to about 1/16", keep RPM at 2k-3k. Get ready for a smoke show. But, leaves everything very clean.
    Jim DeAngelis
    Cornucopia of Useless Knowledge
    Connoisseur of Dearborn Ferrous Oxide
    '83 GT hatch, currently under the knife
    '79 Capri 2.3L n/a, Medium Copper metallic, survivor
    (bought from MRausch82)

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