Bringing TBI and Multi Port Fuel Injection to a New Level.     EFI Conversions and Tuning! Seattle to Portland! E-mail Tuning Consultant!
Page 3 of 3 FirstFirst 123
Results 31 to 41 of 41

Thread: Getting owned by an 87 TBI

  1. #31
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    49
    Posts
    2,959
    I've got an '87 GMC V2500
    Engine is a L05, NA4
    Here is the calibration information:

    BCC= AFBW3542 Scan id= 4401 Part number= 16073539
    Release date= 11/05/86 Engine size= 5.7 Trans Type= Auto trans
    ECM/PCM: ECM #01227747
    Used in trucks: GMC
    Possibly used in:
    R20,2WD,3/4 TON R2500,2WD,3/4 TON R30,2WD,1 TON
    R3500,2WD,1 TON V20,4WD,3/4 TON V2500,4WD,3/4 TON
    V30,4WD,1 TON V3500,4WD,1 TON

    Options:
    With L05 5.7L GAS 8 CYL (5.7K) V8 TBI
    With M40 AUTO 3 SPD TORQUE CONV VAR 1
    With NA5 FEDERAL REQUIREMENTS
    With NA6 ALTITUDE REQUIREMENTS

  2. #32
    Electronic Ignition!
    Join Date
    Oct 2018
    Posts
    16
    I don't want to jinx myself, but let's say the injectors don't help, so then I take the valve cover off, measure rocker lift and find out I have an aftermarket cam? Do I have any options other than tearing the engine apart? Do I need to become really good friends with someone who can burn proms until we find settings that work?

  3. #33
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    49
    Posts
    2,959
    I think you've described the two options. IMO if you find the cam is not stock it might be cheaper and better to put a stock or very mild "computer compatible" cam back in. But if you happen to make friends with a guy that can burn proms, well, even a stock engine can benefit from tuning.

  4. #34
    Fuel Injected! vilefly's Avatar
    Join Date
    Sep 2017
    Age
    48
    Posts
    130
    Sorry for interjecting, but this one is a classic case of fuel starvation. The injector acid test for us in the field is to disconnect one injector while it is running, and see if it will still struggle on and stay alive or instantly die completely no matter what is done with the throttle. If it dies, the injector is not flowing enough. Ran across this situation alot with cadillacs and gm trucks.

    I skimmed the posts, and did not see any fuel pressure readings while the throttle was gunned. If the 9-15psi fuel pressure does not drop at all, then go for the injectors. If it does drop at all, look to the fuel pump/kinked fuel lines.
    You may want to get an adjustable fuel pressure regulator in case of a cam scenario. The big block 366 engine uses a 23 psi regulator with the same injectors, BTW. Yup, they cheated.

    Oh, just one more thing. Make sure your harmonic balancer reads true TDC. The outer ring has been known to "walk" over time. The other scenario happens when harmonic balancers were swapped from different motors. Doubt it is a timing issue, but it never hurts to check.
    Last edited by vilefly; 4 Weeks Ago at 08:42 AM.

  5. #35
    Electronic Ignition!
    Join Date
    Oct 2018
    Posts
    16
    It had the wrong injectors! Got new 61 lb injectors installed and the top end of the TBI rebuilt. I could immediately see a huge difference in the size of the spray pattern coming out of the new injectors compared to the old ones. It's 40 degrees out today...the first time I fired it up with the new injectors it came right down to idle @ 600rpm after a couple minutes. Timing checked out at about 2 degrees, which is where I wanted it, and holds nice and steady now. Did the IAC relearn, too. Haven't driven it yet, need to run to the store to get a couple things to finish up an oil change.
    Last edited by GetItBilly; 3 Weeks Ago at 05:51 PM.

  6. #36
    Fuel Injected! vilefly's Avatar
    Join Date
    Sep 2017
    Age
    48
    Posts
    130
    Ah. The ole' switcharoo. Sounds like someone thought the 4.3L throttle body will feed a 5.7L. I used to run into this alot with roofers and plumbers working on their own cars. I developed the "unplug test" because of them. They drove me crazy.

    Enjoy having your sanity back. heh.

  7. #37
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    49
    Posts
    2,959
    Congratulations. Good job working this one out.

  8. #38
    Electronic Ignition!
    Join Date
    Oct 2018
    Posts
    16
    Thanks for the help! I knew I'd probably have a few more things to work out after this, though. Now the truck throws code 42 for the EST wiring after idling for 4-5 mins. I'll have to go through that next. And the trans leaks pretty bad, hopefully just needs a gasket. And the steering box leaks. And the rear passenger drum is probably full of brake fluid since there's none left in the reservoir. And it needs all new coolant hoses. I'll worry about it in the Spring!

  9. #39
    Fuel Injected! vilefly's Avatar
    Join Date
    Sep 2017
    Age
    48
    Posts
    130
    If the wiring on the tan/blk and the white wire to ignition module is ok (continuity), then suspect either the ignition module or the ECM. Especially the ecm if it stalls a lot. Only a waveform test on a scope during a stall event can prove if the ECM is faulty. The rest is ecm resistance expectations from the ignition module not being met. Lower quality ignition modules can cause false code 42 when they become thermally fatigued also.
    This is where the "test with known good part" kicks in.

  10. #40
    Electronic Ignition!
    Join Date
    Oct 2018
    Posts
    16
    So I haven't really started troubleshooting the code 42, but now I'm wondering if I should go straight to swapping the "new" reaman'd ECM out for the original. I ask because most recently, while the truck was sitting idling, it threw a code 45 for being rich, which I would think should be impossible to do when there's no o2 sensor hooked up. By the time I hooked up the scanner, ~650mV was consistently being reported on the o2 circuit, so something is definitely not right. I haven't seen it throw a code 42 for a while - I suppose there's a chance that was ECM related, too.

  11. #41
    Fuel Injected! vilefly's Avatar
    Join Date
    Sep 2017
    Age
    48
    Posts
    130
    Before replacing any ECM, always check power leads and ground leads at the ECM. Especially check for any ground wires on back of the cylinder heads and at the good 'ole thermostat housing area. A fault in these can lead to other false codes, like 42 and others where a resistance check or reference voltage is sent out.
    Should be close to 450mV, but this is referenced against the ecm's O2 sensor ground lead, which had better be grounded very well. Add a ground lead to it if you have a doubt. Combining grounds (running thicker wires to both) can help also.
    Last edited by vilefly; 1 Week Ago at 01:01 PM.

Bookmarks

Posting Permissions

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