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Thread: Vacuum at -23 when cruising and running pig rich!

  1. #1
    Mitsu booster
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    Vacuum at -23 when cruising and running pig rich!

    I blew a head gasket a few weeks back on my 87' Shelby Z, not the end of the world so I used it as a way to clean up the engine compartment etc.... I got everything back together and running but now it seems to have lost some low end grunt and midrange, vacuum at -22 / -23 when idling when cruising it's around -16 / -19 my AFR bounces around between 10.1 and 13.4 on my autometer wideband. The car starts and idles fine, I set the timing to 12* BTDC when it was at operating temperature, just smells really gassy, plugs are a darker brown color and when I get on it, it feels strong. I know my mileage is suffering my Traveler says I'm getting about 22-23 mpg just taking it easy. Fuel pressure is a static 55 psi, didn't mess with that setting after I pulled the head off. I had to install a vacuum block since I snapped the factory plastic union off the back of the intake, checked for vacuum leaks numerous times. I've checked the timing 3 times everything looks correct, here is the kicker though, when I start it cold it has the normal -16 / -18 of vacuum my AFR bounces from 14.3 to 15.1 which is normal and then after it heats up a bit usually within 5 minutes of driving the vacuum changes along with AFR, here are a list of mods on the car.

    Also I noticed that my waste gate solenoid is sucking vacuum through the bleed, is that normal? Found that when I was searching for vacuum leaks.

    : Aftermarket blow off valve
    : High flow conical air filter
    : Underdrive pulley
    : Mystery cam (Not sure of grind) on the car when I got it
    : Zener diode
    : MBC
    : Mopar performace computer
    : Water / meth injection - pre throttle body / pre compressor
    : AFPR
    : Ported 2.25 inch swing valve
    : 2.5" to 3" down pipe / exhaust
    : Boost set at 19 psi
    : 160* thermostat

    This car ran extremely strong before with no issues, the only addition was the vacuum block

    Thanks in advance for any help!

  2. #2
    Supporting Member II Turbo Mopar Contributor tryingbe's Avatar
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    Re: Vacuum at -23 when cruising and running pig rich!

    Take the 160F thermostat out and put in a 195F. Colder thermostat is not always better. I made 290whp using a 195F thermostat.
    Double check the cam timing.
    Take the zener diode out and put set the boost to 14psi. (Your MP calibration doesn't add more fuel after 15psi, which means the ECU gives the engine same fuel at 15 psi all the way up to 19psi, which is really bad)
    Put in a stock ECU. Some MP ECU does not use o2 feedback.
    Last edited by tryingbe; 06-09-2016 at 10:21 AM.

  3. #3
    Hybrid booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    I would re-check your cam/crank timing. It will run like you've mentioned when off a tooth.
    Crank at 0 in the flywheel window, cam wheel top center, inline with engine.

  4. #4
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    Quote Originally Posted by tryingbe View Post
    Take the 160F thermostat out and put in a 195F. Colder thermostat is not always better. I made 290whp using a 195F thermostat.
    Double check the cam timing.
    Take the zener diode out and put set the boost to 19psi. (Your MP calibration doesn't add more fuel after 15psi, which means the ECU gives the engine same fuel at 15 psi all the way up to 19psi, which is really bad)
    Put in a stock ECU. Some MP ECU does not use o2 feedback.

    Thanks for the info but it has to be something else, the car ran great on this setup for a year solid until the head gasket blew, I'll check the cam timing again.

  5. #5
    Supporting Member II Turbo Mopar Contributor tryingbe's Avatar
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    Re: Vacuum at -23 when cruising and running pig rich!

    Quote Originally Posted by crow1970 View Post
    Thanks for the info but it has to be something else, the car ran great on this setup for a year solid until the head gasket blew, I'll check the cam timing again.
    Ever considered your head gasket blew might be because of the reasons I listed above?

  6. #6
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    Thanks Joey, I checked it again this morning, put it to tdc, on 0 in the fly wheel window, rotor pointed at #1. I thought it might have been retarded one tooth so I did advance one tooth but when I put the timing belt cover back on with the window popped out of it, the cam gear mark didn't seem centered, too far off the mark and to the right of the window. I didn't even start the car just put it back the way it was. I'll go fiddle with it again to see what happens. Thanks for the advice!

  7. #7
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    It's always possible but the head gasket was 15 years old, I talked to Mike over at Forward Motion, he told me the reason head gaskets primarily fail is due to heating and cooling cycles and the break down of material over time if correctly installed that is, not so much boost pressure.

  8. #8
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Vacuum at -23 when cruising and running pig rich!

    Quote Originally Posted by tryingbe View Post
    Take the 160F thermostat out and put in a 195F. Colder thermostat is not always better. I made 290whp using a 195F thermostat.
    Double check the cam timing.
    Take the zener diode out and put set the boost to 19psi. (Your MP calibration doesn't add more fuel after 15psi, which means the ECU gives the engine same fuel at 15 psi all the way up to 19psi, which is really bad)
    Put in a stock ECU. Some MP ECU does not use o2 feedback.
    I believe the only MP computer which doesn't use O2 feedback is the S60. Great advice though.

    If you're in Elgin, that's not far from the SDAC Chicago crew's monthly meetings. I would check them out and see if someone could help you with some diagnosis. Better yet, bring the car to SDAC and you'll be done by the end of the first afternoon most likely.

    One thing I don't believe I've seen mentioned yet is how much have the block and head have been milled? That can effect the final timing if they've been milled a lot. My money is on cam timing.

  9. #9
    We Todd D dot D Turbo Mopar Staff sdac guy's Avatar
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    Re: Vacuum at -23 when cruising and running pig rich!

    +1 to getting rid of the 160* t-stat. The ECU is looking for above 185* or so before it allows the system to go into closed loop.

    With coolant limited to 160 degrees, the ECU never sees the engine as heated up, and adds fuel just like a choke does on a cold carb car. It doesn't matter if the condition you are now seeing started with the head gasket change. While running a cool t-stat is an old racer trick to get more out of older V-8 engines, it just doesn't work on an ECU controlled motor where engine temp is monitored more closely.

    Run the 195* stat. Your engine will be a lot happier.


    Barry
    86 Shelby Lancer Prototype
    90 Daytona Shelby VNT
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    For your questions about SDAC, please contact BadAssPerformance


  10. #10
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    Update - Advanced the cam, ran worse than before crappy low end felt good in the higher rpm range, retarded it also just for the hell of it, ran better retarded one tooth. Had plenty of power low end seems top end might have suffered some. I ended up putting it back to where it was originally and after it ran good, decent power through the rpm range I just can't figure out why it's pulling so much vacuum and running rich.

  11. #11
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    I advanced and retarded one tooth from my original cam time and both weren't as good as my original setting. I triple checked the timing before I put it together, the cam gear mark was basically centered in the window of the cam cover, the arrows on the cam gear were parallel with the cam cap, used a straight edge from that mark to the crank bolt, intermediate shaft was all good as well. gonna take Barry's advice and start with the thermostat swap to a 195er.

    Thanks for you input!

    -John

  12. #12
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Vacuum at -23 when cruising and running pig rich!

    You have pulled the codes right? Anything there?

  13. #13
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    Nope haven't pulled any codes yet, I'll try and get that done tomorrow, swapped out the stat and the only difference it made as of now was make it run hotter.

  14. #14

    Re: Vacuum at -23 when cruising and running pig rich!

    I would check for the obvious, broken, cut or connectors unplugged, codes and start unplugging things while it's running to see if things change or stay the same. Codes first though. Someone else has a thread going about a rich condition and they are getting a bad O2 code error, 52 or 53, I don't remember. If it runs different after working on it, it may very well be a user error issue and not mechanical. Trust me, I've been down that road.
    [SIZE="3"] [B]Jon Trotter[/B][/SIZE] [B]1985[/B] Dodge Shelby Charger, Currently decommissioned [B]1987[/B] Shelby GLHS, #937 [B]1987[/B] Shelby Lancer, #628 [QUOTE=Reeves;587010]I can be ready. Please send pics of wife. _____DodgeZ add comments here______[/QUOTE]

  15. #15
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    Thanks Jon, I did put a new O2 sensor in maybe it was bad from the get go, thanks for the advice.

  16. #16
    Super Moderator Turbo Mopar Staff contraption22's Avatar
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    Re: Vacuum at -23 when cruising and running pig rich!

    Quote Originally Posted by cordes View Post
    I believe the only MP computer which doesn't use O2 feedback is the S60. Great advice though.
    If I recall correctly, my old MP computer for 1986 T1 also had no 02 feedback.
    Mike Marra
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  17. #17
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    Pulled the codes before the ECU reset and got #17- Engine too cool / #35 Radiator fan relay open / #51 Running too lean
    After reset and thermostat swap to 195* all I got was #12 for a battery disconnect and ECU reset.

  18. #18
    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: Vacuum at -23 when cruising and running pig rich!

    You didn't leave the bolt out of the bottom of the throttle body neck for the brace did you? Did that before, took me a week to figure out what I did wrong lol. That was on a 2-piece intake though.
    Rob M.
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  19. #19
    boostaholic Turbo Mopar Contributor
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    Re: Vacuum at -23 when cruising and running pig rich!

    Quote Originally Posted by Force Fed Mopar View Post
    You didn't leave the bolt out of the bottom of the throttle body neck for the brace did you? Did that before, took me a week to figure out what I did wrong lol. That was on a 2-piece intake though.
    Man I have done that several times.....

  20. #20
    Mitsu booster
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    Re: Vacuum at -23 when cruising and running pig rich!

    I did take the brace off to paint it while out but I put both bolts in, so it's good, I appreciate the suggestion.

    -John

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