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  1. #1

    Default EGR vacuum help on 1986 GT

    Hello, new owner of an 86 GT and am having issues passing CA emission (high HC, everything else passes no problem), I have tested the egr valve (tested good, holds vacuum and passages are clear), I have solid vacuum (15-18 to the solenoid with no leaks) but when I raise the rpm to activate the egr valve, I can see the diaphragm move then quickly go back down, when I measure vacuum from the (new) solenoid as I raise and hold the rpm (1500 rpm range, not WOT) the vacuum jumps to 2 or so then immediately goes back to 0.
    Shouldn't the vacuum hold steady from the solenoid while maintaining part throttle, cruising rpm? The only code I am getting from my scanner is a 31 which point to the EGR position sensor (have a new one on order), would that cause the solenoid to not maintain the vacuum at cruising rpm? Any help or ideas are appreciated.

  2. #2

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    made some progress, I figured out the reserve vacuum canister or its hose was leaking, so got that plugged off at the T going to the TAD solenoid. At least that's working now. Got the replacement EGR position sensor today but it arrived too late to get it installed today, going to tackle that first thing tomorrow and finish installing my front shocks and springs,, got the back shocks and springs installed and finished just as the sun was going down.

    Quick question on quad shocks, should they have any rebound or are they just a dampener, basically when I was dropping the rear to install the springs and disconnected the quads they just expanded and stayed in whatever position you set them in. Not sure if that is the way they are supposed to work or not.

  3. #3
    FEP Power Member Ourobos's Avatar
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    They're an anti-roll type dampener.. If you drive the car like a civilized adult, you'd never know they were there or need them.. You you romp on it, they help prevent some deflection with the semi-flimsy stock control arms. A set of good aftermarket control arms eliminates the needs for the quad shocks even when thoroughly abusive.
    1986 CHP SSP Coupe

  4. #4

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    ok, so they are not supposed to have a rebound type effect? It is just that this car has not been maintained and everything I have replaced so far has been a 31 yr old factory part. I may eventually upgrade the control arms, just wanted to know if these were plain worn out or not.

  5. #5
    FEP Power Member Ourobos's Avatar
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    Right, dampeners.. Not shock absorbers
    1986 CHP SSP Coupe

  6. #6

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    ok thanks, still need help or info on this egr, when part throttle I can see the diaphragm move for just a moment, vacuum gauge confirms movement from 0 to 2 or so then immediately back to zero with throttle still part open or cruising rpm?

    replaced egr position sensor and that took care of code 31 now KOER test is code 11 (no fault codes) cylinder balance is code 90 (pass) just trying to figure out if this egr operation is normal or not.

  7. #7

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    If you are not getting koer egr codes for egr you should be ok. Also the purpose of EGR is to reduce NOX emissions not HC. So if your engine is running well and not using oil. Make sure your air injection is working and look into the cats. Chances are they have lost some efficiency if they are original.
    84 LX Vert. 5.0 5speed canyon red on white
    99 cobra, electric green on medium parchment, vortech s-trim

  8. #8

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    Thanks, replaced the rear cats and working on the thermactor system now, not getting any codes now. One thing i noticed with the car fully warmed up was the temp before and after the rear cats with my electronic thermometer was not significantly hotter. I can get exact readings today but was trying to test the TAD function. If it is blowing air into the cats shouldn't the outlet temps be a lot hotter than inlet?

  9. #9
    FEP Super Member erratic50's Avatar
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    One thing you could try is raising the idle rpm a few hundred then advancing the base timing. That's all I had to do with my 86 to pass with flying colors when I was out in CA back in the late 90's. My car had 200K on it at the time and my numbers were better than any of the new cars they had tested that day. The tech was confused about it.

  10. #10

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    I am at 10 BTDC, the test is done on a rolling dyno 15 mph and 25 mph tests, not sure if that is different than the late 90's.

  11. #11

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    "High" HC = rich... be that from too much fuel injected by EFI (a variety of reasons/causes, not "bad" enough to set trouble codes but "bad" enough to not meet dictatorial emission test ranges... dirty injectors, fuel pressure too high, TPS idle voltage too high, malfunctioning MAP sensor, etc...) or some gassy blowby from the crankcase with oil that could use being changed. Is the oil and filter pretty fresh? How old are the distributor cap and rotor and the spark plug wires and spark plugs?
    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/

  12. #12

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    all fresh, plugs, wires, cap, rotor, ignition coil, map, ect, tps, tfi module, air temp sensor, both o2 sensors, fuel pressure regulator, 2 new rear catalytic converters, egr sensor (egr valve tested fine), new timing chain, cleaned pcv valve and screen =etc. No codes when tested today (code 11), idles fine and pulls 18hg of vacuum at the tree.

    I just got the vehicle last month, going through everything. I am going to change the oil and filter again this week as a precaution.

    I did have the front brakes replaced as well as the rear wheel cylinders and now my brake pedal is very firm, not sure if this would contribute but I have a feeling maybe the brake booster is bad? Could a faulty power brake booster cause a vacuum leak and thus a lean condition without throwing any codes?

  13. #13

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    fuel pressure is 39lb at idle and regulator is new , no fuel leaks when vacuum hose is removed from regulator.
    installed 8 new 19 lb, 4 hole injectors,
    TPS is new and voltage at idle is set at .97, doesn't stick throughout range.
    Car runs good, it doesn't smoke at all and idles at 700 -ish rpm, doesn't surge unless A/C or defrost are on.

    I do hear a very slight tick around #5 cylinder, I may pull the valve cover and check the valve lash.

  14. #14
    FEP Super Member erratic50's Avatar
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    The pre-test shop did it just the same. Actual inspection was not rolling but my numbers were very good.

    With high HC being rich you might have some sticky injectors ruining your fun. I would overdose the car on fuel injector cleaner for two tanks. I'd show up "test" day with a tank full of 93 octane premium and base timing advanced to 13.5 degrees. I would still increase the idle 200 RPM also if its a stick - they are cleaner at tip-in with the TPS set to 0.98V and this arrangement of timing, fuel, etc.

    My thought is give it a puncher's chance of fighting off the rich condition. If it cleans up you're golden.

    My son's 86 was running just about pig rich even with the timing advanced. We added injector cleaner and it was a little better but still didn't want to idle very smoothly. Turns out the ignition pickup in the dizzy was failing - which we found out by having it stall on the side of the road. New distributor, cap, rotor, ignition module. Found the wires were crap by inspecting them when we pulled them off of the old cap -- corrosion city. Solved all that and we were back in business.

    The other day my son played with it a little bit at the throttle body with the air inlet bypass unplugged. He had it idling smoothly as low as 350 RPM which was ridiculous - I've never seen such a thing. Still carried decent oil pressure there warm, not that I would ever tempt fate by leaving it so low.

    On a 5-speed I like my foxes idling no lower than 800 and no higher than 950. Personal preference I guess.

  15. #15

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    Don't know how many miles are on your car, but don't be afraid to run a bit thicker viscosity oil in it. You're on the other coast, and I imagine it's warmer over there. I'm still running some garbage 10w30 "winter" oil in mine. Have a look at your options where you get your oil. Thicker oil can help all of the pistons' rings do their job (and take up some of the extra crankshaft bearing clearances that can be with something with some more miles on it too), but especially the oil control rings for keeping crankcase vapors out of the combustion chambers for this questionable "emissions" situation.

    If you go ahead with some fuel injector cleaner stuff in the gas tank, be prepared to maybe having to change out a few fuel filters afterward. I did that with my '86 5.0L Elan Thunderbird years ago, and after a few hours of running the WOT bucking (WAY lean, like running out of gas lean, lol) would take the hat right offa ur head! I changed out 3 or 4 more fuel filters before they'd stop clogging up with crap from the tank/system.

    Unless the brake booster/hose/connector is leaking some vacuum, I don't think it would contribute to this rich problem. Oddly enough, the computer might be over-compensating with fuel if there is a vacuum leak though, and might be your hard brake pedal issue. A too-firm brake pedal though usually points to some air in the brake hydraulic system, needing to be bled better. I'd suspect that since some brake work was recently done where the system was opened...

    "... doesn't surge unless A/C or defrost are on" ... is a curious statement. Can you explain that some more? Surging is almost always a lean condition... to which EFI might have learned to spritz in a bit too much fuel sometimes...

    I wish "they" hadn't gotten rid of the ability to check and adjust "lash", about 20 years prior to 1986, first with "positive stop" shouldered rocker studs nonsense, and later with the bolt-down rockers nonsense. The shim kits Ford did or does still sell do nothing for this situation of wanting to or being able to actually adjust rocker arms for correct lifter pre-load, but only raising the rocker, only addressing if there's too much lifter pre-load. So if you do have a ticker at #5, unless the rocker pedestal bolt happens to have loosened, there isn't much you can do about it. Again, a bit thicker oil might pump up a lifter there that might not be fully pumping up for operating conditions. I've pondered this situation some, and the only real solution (without having to piss around buying different length push rods for different cylinders... please) to "adjust" if there's clearance (ticking) out of a bolt-down rocker, and provide the bit of lifter pre-load that is a good thing, would be to remove the pedestal and remove some material from it's bottom face that seats against the cylinder head.
    Last edited by Walking-Tall; 01-29-2018 at 01:31 AM.
    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/

  16. #16

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    thanks for all the suggestions, as far as the Surge goes. the idle is steady with defrost or a/c off, when the a/c cycles on and off the idle raises 100 rpm or so.(read that maybe freon could be low since the a/c cycles on and off every 10-15 sec with on defrost setting?)

    I did change the oil and filter yesterday and bumped up to 10w-40 from 10w-30. The 10w-30 had less than 1k miles since change and was pretty dark. I did have some MMO in there to see if that would help with the tick on #5.

    the odometer says 85K but not sure if that is original or has been rolled over. Cylinder balance test (from innova handheld scanner) comes back code 90 so that is good.

    When I got the car last month the brake pedal was going to the floor and barely stopping the vehicle. So I inspected the brakes and found the pads, rotors, drums and shoes to be in serviceable condition. I removed the master cylinder as the brake fluid was dark brown to clean and bench bleed. I then had the entire system bled, had front rotors and pads replaced as they were glazed over which helped but pedal feel is very firm almost like manual brakes.

    on the ticking I was just going to check to make sure the rockers were bolted down to spec and give it a visual inspection since I have not had the covers off this car yet.

    I have checked for vacuum leaks, spraying some carb cleaner around the vacuum tree and hoses as well as throttle body and intake manifold and did find a small leak by egr valve, replaced that gasket and no problem since, vacuum at idle is 18 and steady off the vacuum tree.

  17. #17
    FEP Super Member erratic50's Avatar
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    A lubricant like Slick50 often helps silence ticking in lifters -- sometimes even long term. Mine shut up at 200K and have went over 250K more since.

    i'd go 10W40 + slick50 and run it on that part.

  18. #18

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    Thanks erratic50. May give that a shot, the ticking is very minimal

  19. #19
    FEP Super Member erratic50's Avatar
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    With defrost on the compressor is supposed to kick on and off. It runs at low pressure with the intention of removing humidity from the air to help defog windows.

    Fluctuation at idle AC on vs AC off are likely due to a problem with the air inlet bypass setup that was designed to let more air in when the AC pump is on.

    The best fix I am aware of - provided you've done correct idle adjustment procedures without the AC on is to get an adjustable bypass then work with it while the AC is on to try to get it so the engine load changes but the rpm does not AC on vs off.

    Bear in mind that if you get your base idle perfectly matched to the air bypass vs AC design an adjustable bypass isn't needed.

    Also cars that are turned up with lots of timing advance will tend to get warm and load up if left idling too long. They straighten right back out if you start driving them hard for a little while. Not that a foxbody would ever beg its owner to drive it hard. Lol.

  20. #20

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    Quote Originally Posted by vrm71 View Post
    fuel pressure is 39lb at idle and regulator is new
    There's your problem lady.

    FP should be 39psi KOEO but should be about 31-32 psi ER at idle and increase with increasing throttle opening.
    https://www.google.com/imgres?imgurl...viTHWh6e0hy0_M

    If you have 39 psi at idle you are going to run extremely rich even in closed loop.

    Paul
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  21. #21

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    I will double check that Fuel Pressure, got the top end torn down right now, but thanks for your help. will keep you all posted

  22. #22

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    just a follow up and conclusion to this issue, I ended up tearing the engine down to the shortblock and installing gt40 heads, explorer intake new shorty headers, 65mm throttle body, diverter valve and front 2 catalytic converters (all 4 converters are new now). Passed CA emissions with flying colors and got my 2018 sticker. Last tag on the car was 2009!

    Next up is gears, subframe connnectors, shift kit and torque converter.

    Thanks for the help getting this Car sorted enough to be back on the road, legally!

  23. #23
    FEP Super Member erratic50's Avatar
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    That's great news! Enjoy it!

  24. #24

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    Thanks! This AOD needs some help, got 4.10 gears, shift kit and hi-stall converter on the way. Hope that helps this thing get moving.

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