Page 1 of 10 1 2 3 ... LastLast
Results 1 to 10 of 91

Thread: 3.0L Megasquirt w/ EDIS: Headers running at different temps?

  1. #1
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    596

    My VIN:    767

    3.0L Megasquirt w/ EDIS: Headers running at different temps?

    After an oil delivery issue, I'm back to getting my 3.0L conversion idling. I'm having trouble, though, and I may have tracked down the cause, but I want to ask if anyone has any ideas before I tear the engine apart again.

    First:
    - Ignition timing at idle is currently at ~14 degrees. I confirmed that what TunerStudio shows is the same as what a timing gun shows, so I believe this to be correct.
    - Coil-on-plug via EDIS, spark plugs are all firing
    - Fuel delivery appears to be good
    - Engine cranks and starts, but seeks at idle (500-800 RPM)
    - DPI headers, Magnaflow CARB-compliant cats, Borla Pro XS muffler
    - Fairly sure there aren't any vacuum leaks...

    The first problem I had was that the passenger side exhaust pipe and part of the catalytic converter (on the outlet side of the cat) was glowing once the engine got up to temp. Theorizing that this the silencers were too restrictive, I put in new pipes without silencers. I also replaced the cats with shorter ones that gave me a little more room for mounting, which also rules out the cats. Neither of these had any effect, other than the glowing was limited to the cat now. It's worth noting that ONLY the passenger side cat was glowing in both cases, and that the passenger side headers were reading about twice as hot as the driver's side with an IR thermometer.

    I found out that the throttle wasn't closing all the way (mis-adjusted throttle cable). I fixed that this morning, but I didn't have much time to play with the car, so I only had time to start it once and let it idle. It never quite got up to temperature during that time, and eventually stalled out as I played with the VE table to try to smooth it out.

    Using the IR thermometer, I got a reading in the high 300s (350-375 F) for the driver's side at the point where the header pipes merge to the exhaust pipe before the cat. On the passenger side, however, I was only reading in the low 100s (115 F or so). I individually tested the header pipes from each exhaust port as well. I got in the low 100s for cylinders 1, 2 and 3, in the high 300s for 4 and 5, and a more like the mid 300s for 6. I'm guessing some variance is normal given the inaccuracies of the IR thermometer and ambient heat in the area, but not the amount of variance I'm seeing between the driver's and passenger sides.

    In all of these situations, the AFR reported by TunerStudio via my LC2 O2 sensor was way too high. With the slightly open throttle it was around 22:1, and now it's down to around 19:1, but as I understand it I want 14.7:1. Note that the single O2 sensor is installed in the driver's side header (there's a narrow band sensor plugging the bung in the passenger side header, but it isn't hooked up to anything).

    The question is: Why is the passenger side's temperature so much lower than the driver's?

    My current theory is that I may have incorrectly installed the timing chain to the passenger side camshaft. If it were off by a tooth, that might explain why it's running so lean (I think?). Of course, I need to pull at least the valve covers and I think the timing cover (and thus the muffler to get enough room) to re-time. I'd really prefer not to take all that apart to find out that it's not a timing problem, so I'm wondering if anyone else has any other ideas first. It does seem like it would explain all the issues, though. Really wish I'd though to recheck this when I replaced the main crank bearings...

    I've attached a TunerStudio log from today's test in case anyone can glean anything useful from that. It took three tries to start the engine, and I started playing with the VE table near the end to try to smooth out the idle a bit before it eventually stalled out.

    Thanks!

    -- Joe

    Glowing Cat:
    IMG_1224.jpg

    TunerStudio Log: 2018-07-14_09.08.05.msl

  2. #2
    Not a DeLorean Guru
    Join Date:  May 2011

    Location:  Rochester, NY

    Posts:    2,089

    My VIN:    01049

    Are you getting the same AFR on both banks?

    Have you made 100% certain you don't have vacuum leaks?
    -Mike
    1981 DeLorean, Carb LS4 swap completed
    1999 Corvette, cam/headers/intake manifold, 400 rwhp
    2005 Elise, stock
    2016 Chevy Cruze

  3. #3
    Senior Member Josh's Avatar
    Join Date:  Mar 2013

    Location:  SK, Canada

    Posts:    1,753

    My VIN:    11408

    Club(s):   (TXDMC)

    After you get this sorted you will need to do some tuning. It is running WAY lean. dangerously so.
    Part of the tuning is setting the resting position of the throttle body blade. it may not be all the way closed at idle.

  4. #4
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    596

    My VIN:    767

    Quote Originally Posted by opethmike View Post
    Are you getting the same AFR on both banks?
    I only have the one wide band O2 sensor, so Iíve only been reading the AFR from the driverís side bank. I suppose I could move the sensor to the other bank and see what I get (I think the wire is long enough...). I can test that this morning befor I stat taking off the valve covers.

    Have you made 100% certain you don't have vacuum leaks?
    Not 100%, but pretty close. I did a pro-and test a few weeks ago and couldnít find anything, although holding th e propane at the throttle didnít show anything either, which is odd; Iíd have expected the engine to rev. I can do another test this morning. I think I have a vacuum test kit somewhere that I can try too.

    Thanks

    ó Joe

  5. #5
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    596

    My VIN:    767

    Quote Originally Posted by Josh View Post
    After you get this sorted you will need to do some tuning. It is running WAY lean. dangerously so.

    Part of the tuning is setting the resting position of the throttle body blade. it may not be all the way closed at idle.
    The throttle was very slightly open, (more accurately, it wasnít closing all the way when the throttle was released). But Iíve fixed that so it is completely closed at idle by adjusting the throttle cable. Iím not entirely sure if you mean that the problem my bethat itís not completely closed, or that for some tunes it may have to be adjusted so that it isnít completely closed.

    Back on my 2.8L engine I had a problem with the throttles not closing all the way. It turned out that the bar that the throttles were attached to was slightly bent, so while the spring was all the way returned, the blades never quite closed all the way, and this caused it to run way too lead and for the cats to glow. This took me way too long to figure out, in part because I thought I read somewhere that they were supposed to be slightly open.

    If I can get the AFR down, I think I can finally tune for idle and get this thing on the road. It did run a little smoother with your tune, incidentally, but obviously I have to fix the extreme lean situation before going any further.

    Thanks!

    ó Joe

  6. #6
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    596

    My VIN:    767

    I swapped the wide band O2 to the passenger side and hooked up a vacuum gauge to a T in the vacuum line this morning.

    AFR is reading 22 on the passenger side. Iím honestly not sure if the O2 sensor is working correctly. I did calibrate it in open air just a couple of weeks ago. It reads around 7.5-7.7 when the car is off, but after about 20 seconds it flies up to 22 again and stays there, just like it does when itís running.

    EGO Control in TunerStudio is set to Single Wideband, Local port. I have TunerStudio set to the LC-2 in the Calibrate AFR Table Settings. I donít think thereís anything else to set, is there? Josh, did you change any of the LC-2 settings from the defaults?

    Vacuum varies, since the engine is seeking at idle, but it seems to be between around 17 in/Hg at lower RPMs (below 600) and close to 28 in/Hg when it seeks higher (800s).

    Video of the gauge. You can hear the engine seeking as well. https://youtu.be/EzR6lXzU_wg

    I did a second test and it idled a little better, stying in the high 600s and low 700s. This showed vacuum of closer to the range to 18 to 23 in/Hg. Hereís a video of that. https://youtu.be/UtsHRUjhABc

    To be honest, Iím not sure what Iím looking for here. I seem to have vacuum that holds reasonably well, and varies with engine speed.

    Iím going to hold off on taking off the valve covers until next weekend, I think, just in case anyone has any other ideas for what I should try first.

    Thanks!

    ó Joe

  7. #7
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,016

    My VIN:    03572

    That vacuum seems way to high. Does your engine have deceleration valves on the throttle plates? That high vacuum would make them open. I would guess your throttle plates are completely closed and your just idling with the idle speed hold system.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  8. #8
    Senior Member
    Join Date:  May 2011

    Location:  Norton, MA

    Posts:    596

    My VIN:    767

    I honestly donít know if there are deceleration plates. This is a 1989 Monaco engine with a Mustang throttle (that last part I got off Josh).

    A quick correction to my earlier post: the RPMs were ranging from the 500s to the 1100s when it seeked. Not sure if that puts the vacuum in a better range or not.

    I connected a multimeter to the narrow band O2 sensor. I understand 0.5v is stoichiometric, and I got at most 0.35v, which eventually dropped to about 0.19v before it stalled out. Iím definitely running way too lean ó maybe that wideband is working after all.

    Thereís a noticeably loud whooshing sound from the intake, but thatís just the slot above the throttle blade where the idle air motor sucks in air. I havenít noticed any other vacuum leaks by casual inspection.

    I also tried pointing my open but unlit MAP torch right into the intake and the engine revs didnít change at all, which seems sort of odd. I was under the impression that the gas should make the engine rev up, and thatís how people find vacuum leaks.

    I put my fingers around the obvious connections and couldnít feel any suction. I can do a more thorough check next weekend.

    Thanks.

  9. #9
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

    Posts:    7,016

    My VIN:    03572

    I would try to open the throttle plates a little with curb idle screw to see if you can smooth out the idle.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  10. #10
    '82 T3 Turbo FABombjoy's Avatar
    Join Date:  May 2011

    Location:  Lansing, MI

    Posts:    649

    My VIN:    10270

    Trust the wideband. Add fuel and flatten the VE table in the idle region. Maybe post your msq for multiple second opinions.
    Luke S :: 10270 :: 82 Grey 5-Speed :: Single Watercooled T3 .60/.48 :: Borla Exhaust :: MSD Ignition :: MS3X Fully SFI Odd-fire EFI :: DevilsOwn Methanol Injection

    Console5.com - Game console parts, kits, games and more. [shop] [wiki] [RSS] [f] [t]

Page 1 of 10 1 2 3 ... LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •