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Thread: Cutting Out Under Load

  1. #1

    Default Cutting Out Under Load

    First, I want to thank Danny and the rest here for all of the helpful information. This site has helped with a lot of troubleshooting so far. (I've spent many hours here.)

    I have a problem with my Terminator cutting out under load. Mainly when the map is over 60 kPa and under 3500 rpm. I've been through the basic checks & troubleshooting threads. It will idle perfect and has great throttle response off idle.

    The TBI is on a crate Chevy 350HO. The engine has 5000 miles and ran great with a Holley 650 and large cap distributor last season. The cam .435" intake & .460" exhaust. 212° intake & 222° exhaust duration. It's in a 1981 Jeep Scrambler with one ton axles, a fiberglass body, 38" radials, 5:13 gears, and a 700R4.

    I have been on the phone with Holley tech several times and came up with nothing. I'm going to try and keep this short, my typing is not that great.

    When I first installed the system I had a used factory small cap HEI distributor controlling the timing. When this cutting out started it acted like a spark issue so I changed the plugs, wires, cap and rotor. The problem seemed to get better. The next day it came back. Put in a new distributor, no change. Added 10 degrees of timing to the problem area of the spark table, ran good. Drove good the next day to & from work, I could even lock the converter in overdrive and it would pull. The next day, problem came back. Seemed like if I made a change to fuel or spark it would get better for a bit, then come back. Went back to the large cap HEI, new plugs, and changed the setting in the ECU, didn't help. Ran the wizard again, better but ran rich. Ran the wizard again with a leaner table. Learned quickly and ran great. Cruised it for a couple hours and let most of the table get Learned. The next morning tried to go to work, problem came right back. New plugs again, they were sooty but firing. Last night, I leaned out the TAFR Table, ran decent. Same thing when I left for work, stopped leaned the whole TAFR Table to 14.7 except wide open, ran great the last 20 miles to work. On the way home, back to the same old thing, I had to run driving 3200 rpm to get it run smooth.

    Here's some basics:
    Has a GM pump in the tank, factory suction sock, and ACDelco filter after the pump. Runs 43 psi, no vacuum, and 30ish with vacuum.
    IAC count at 3%.
    Timing was synchronized with the first 2 distributors from idle to 4000.
    Timing is now 12° base, 32° total, and about 16° vacuum advance.
    And power is to the battery second posts, except the keyed red/white.
    The coil was changed to a relay off the battery just in case.
    Wideband reads correctly, I installed a AEM wideband next to it to verify.
    The logs looks smooth & right, no noise spikes or unusual stuff.
    (When it starts cutting out, it shows lean and adds fuel, which makes it worse.)
    Learn table is 0 to 4% around idle and goes up to -20% around the 80 kPa area at approximately 2800 rpm.

    Am I missing something? Has anyone had a problem come and go?

    I bought the system to make things simple. The last system I built a custom multi-port intake, with a custom harness, and a GM ECM, and tuned it with HP tuners. At first this was simple...Now this.

    I'm sure I missed info, what else do you need to know? Thanks in advance.

    UPDATE: See post #116 for resolution (dual-plane intake manifold).

  2. #2
    Join Date
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    Default

    Quote Originally Posted by jbeemer View Post
    The logs looks smooth & right, no noise spikes or unusual stuff.
    (When it starts cutting out, it shows lean and adds fuel, which makes it worse.)
    Before I converted to waste-spark DIS, I had a very similar problem with my single coil intermittently failing. When watching the timing light flashes, they were very inconsistent. When I revved the engine, the timing light flashes would "break up" badly around 3000 RPM. At that point, the WBO2 sensors both read dead lean due to no combustion. (Ignition misfires cause a false lean condition, which show up as full lean spikes.) I checked for RPM errors, wiring faults, timing synchronization, rev limiter, etc. The datalog was fine, aside from indicating the ignition misfiring.

    When the engine is tuned & running well, you should decrease the Closed Loop and Learned Compensation Limits % to lock in the tune.
    I decreased my Learned Compensation Limits to 2% around the idle area, and 10% everywhere else. I left my Closed Loop Compensation Limits at 50%.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

    Default

    The plan is to put the electronic distributor back in as soon as I figure out the problem, so I can control timing. The coil was replaced, along with 2 aftermarket and one GM ignition module, the distributor, wires, plugs. I put the large cap in for troubleshooting as it was a known good ignition system. The timing light flashes are smooth, but I can't watch it in the high map area where the problem is. Looking at the plugs the are all firing, but are sooty and getting too much fuel at times.

    I understand that when it misfires I get the lean spikes, and they show up. But after 3 ignition systems, separate power, and the last being a known good. I started looking for other possibilities.

    I haven't decreased the Learn limits yet. I was trying to get the whole table Learned first, and it hasn't ran good long enough yet.

  4. #4
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    Quote Originally Posted by jbeemer View Post
    Looking at the plugs the are all firing, but are sooty and getting too much fuel at times.
    It seems the Base Fuel Table is too rich. Is the EFI system Learning (self-tuning)? If so, I'd first "Transfer Learning To Base", lean the Base Fuel Table and smooth the Fuel Graph. Try letting the EFI system add the necessary fuel instead of subtracting it.

    Manually adjusting the Base Fuel Table in any area.
    Left click & drag to select a group of cells, then use the CTRL & Arrow keys (▲►▼◄) to change the highlighted cell values.
    The ▲ & ▼ arrow keys adjust the Base Fuel Table slowly (one tenth at a time). The ◄ & ► arrow keys adjust it rapidly.
    Or you can left click & drag a group of highlighted cells, and right click "Offset Selected" to adjust the entire cell group.

    Also, ensure the Base Fuel Table is smooth by viewing & blending the Fuel Graph. It's very important to have a smooth Fuel Graph.
    One aspect of viewing the Fuel Graph: It's better to zoom in, by highlighting segments of the Base Fuel Table (left click & drag), and click "Graph".
    This method offers much greater detail. Looking at the entire "Fuel Graph" will almost always look smooth, because it's not as magnified.
    TIP: When the Fuel Graph is smooth, click "Conversion" (VE% Conversion mode) and continue smoothing the general contour of the VE Fuel Graph.

    I understand that when it misfires I get the lean spikes, and they show up. But after 3 ignition systems, separate power, and the last being a known good. I started looking for other possibilities.
    I agree.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #5

    Default

    The first tune I had I transferred, smoothed, and it looked good. Then this problem came back. It had a little flat spot at first, I figured I tuned it out.

    I loaded a new tune though the wizard, seemed way too rich.

    Loaded a leaned tune and it ran decent, for a couple warm ups & cool downs. Then started cutting out worse.

    It seems if I make a change to the tune to correct the problem when it's warm, the problem will go away for one or two warm ups & drive sessions. Only once or twice it seemed like it was gone completely.

    I had one day last week after adding 10 degrees to the timing table, it ran like a factory engine, even in lockup. 28 miles to work. About 40 miles going home running around. The next day it would barely go.

  6. #6
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    Quote Originally Posted by jbeemer View Post
    The first tune I had I transferred, smoothed, and it looked good. Then this problem came back.
    But did you significantly decrease the Closed Loop and Learned Compensation Limits % to lock in the tune? It seems this might be what's changing your tune. Or maybe your WBO2 sensor is failing. More info under "Wideband O2 Sensor Notes":
    http://forums.holley.com/showthread....ension-Harness (WBO2 Sensor Information)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  7. #7

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    I didn't turn the Learn % down. It only had run good for a day. When it first acted up at that point, I cleared the Learn Table and no change.

    As far as the wideband, I have my AEM next to it in the pipe, right after the "ram horn" manifold (which is sealed and new 2 1/2" all the way back). Both widebands read with in .1 of each other.

    As I stated in the first post about the Learn numbers. Does it make sense that in the current tune the idle numbers are 0 to 4%, and in the higher map kPa they are in the -20s? Should they be more even in a stock motor, or could this be a signal?

  8. #8
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    Quote Originally Posted by jbeemer View Post
    Does it make sense that in the current tune the idle numbers are 0 to 4%, and in the higher map kPa they are in the -20s?
    Yes, that's fine. That's the Learn Table self-tuning a base calibration that's not specifically for your engine.
    http://forums.holley.com/showthread....el-Learn-Table (Additional Information)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  9. #9

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    I thought about a sticky injector, but it doesn't affect idle.
    Maybe a MAP sensor, or voltage to or from the MAP sensor causing a false reading in higher kPa?

  10. #10
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    Quote Originally Posted by jbeemer View Post
    I had one day last week after adding 10 degrees to the timing table, it ran like a factory engine, even in lockup. 28 miles to work. About 40 miles going home running around. The next day it would barely go.
    Next time it runs great, save that "known to be good" Global Folder. When it runs bad again, upload the good Global Folder into the ECU. If it immediately starts running great, you've determined it's in the tune. Then significantly decrease the Closed Loop and Learned Compensation Limits % to lock in the tune.
    http://forums.holley.com/showthread....5760#post45760 (Scroll down to "Creating, Naming & Saving a Global Folder" - 10th framed quote.)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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