88 NA2T No power under load

  • #1

    88 NA2T No power under load

    Hi Guys,
    Recently just completed a NA2T on my '88 5-speed. All parts for the swap came from a running '86 automatic.
    So the car idles and revs up awesome in neutral, no smoke, no hesitation, rebuilt turbo spools great. However, try and drive it and it bogs down and misses under slight load.
    For lack of a better description if sounds like it hits a rev limiter at about 2500-3000 rpm.
    Current specs:
    - 20 degree timing at 700rpm
    - New BCPR6E-11 plugs gapped to .040"
    - New cap, rotor, and wires
    - New timing belt, tensioner and water pump
    - Idle up solenoid deleted
    Played around with timing, backing it off to 15 degrees BTDC, but to no avail. Pulled the plugs and they all show even tan colouring, no fouling or overheating. ECU also shows no trouble codes.
    I'm really at a loss as to where to go from here. Any suggestions would be greatly appreciated
    Last edited by 88ZYaL8er; 08-06-2016, 12:38 PM.
  • #2
    Will it clear up after the engine warms up a bit? Mine will do that, kinda hit a dead spot when its cold under load, but this goes away as soon as coolant temps come up. I think it has something to do with the cold start injection strategy. It started doing it as soon as I deleted my idle controls. My wideband shows it as a "lean" spot, I would suspect yours is also running lean. Do you have a way to check the AFRs?
    Butter (credit where credit is due): "You have this "gift" where you can make cooking a Hot Pocket seem like you need a certain wavelength microwave and involve brown mustard."
  • #3
    Unfortunately I'm not that fortunate for it to just be a cold start issue. It is consistent whether cold or hot. After going over the ignition system so many times I am starting to think it may be a fueling issue. Clogged injectors or lack of fuel pressure. I also have a spare FPR that I may try swapping in to see if that helps although the existing one seems to check out fine. I dont currently have an AFR gauge but that may be in the plans if this keeps up
  • #4
    It's leaning out under load. Probably a vac leak somewhere
    Cha iro

    enjoy building it yourself.
    if it fails, fuck it.
    at least you gave it a whirl.
  • #5
    Do a compression test.
  • #6
    UPDATE:
    Checked all vacuum connections and ran a vacuum gauge, 22 in/hg and no leaks.
    Compression test was performed before and all cylinders were within 3psi of each other.
    Also rechecked all intake joints for leaks. Drove the car around the block this morning and noticed if I baby it up to 4k rpm then it smooths out and pulls good. It just seems to be that window between 2-4k rpm that its super rough and no power.
  • #7
    Trust me on checking the compression again. If it's fine, awesome, but I developed the exact same symptoms after turning up the boost a little and it turned out that I had gone from all cylinders within 165-170 to one cylinder at 90 and two at 120 within like 2K miles. Carbon may have been providing your ring seal
  • #8
    SOLVED!
    Fuel pump is on its way out. Stuck a pressure tester on, fuel pressure would not climb past 30 even with the FPR disabled (FPR is a known good unit). Also drove the car with the gauge hooked up and it would not climb past 30 for more than a split second then drop down to 26-28 psi.

    I'm looking into either the Walbro 255 or the Z32 TT pump.
    My question is, what Walbro 255 are you guys using? I see they have 3 different offerings.
    Or do you recommend another pump?
  • #9
    Quantum 340lph, I have one in my 87 and another to go in the 88. Better flow, less noisey.
    Last edited by Augustus Maximus; 08-14-2016, 07:11 PM.
    Cha iro

    enjoy building it yourself.
    if it fails, fuck it.
    at least you gave it a whirl.
  • #10
    Thanks Augustus, I couldn't find a Quantum locally, so I went with the AEM 340lph that I had sitting on the shelf at my work. Looks identical, nice and quite as well. Had to rewire it as it draws 15amps and the stock circuit is only rated for 10. Car runs as it should now.