 3800 rpm bucking, ok below, ok above - all gears |
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| Axel |
 May 20 2013, 05:14 PM
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#1
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Newbie  Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest  |
1976 FI 2.0 all stock.
Put it away for the winter, now it stutters like crazy under a load at 3,800 to 4,000 rpm. It stutters and bucks so much that it won't pull itself out of the trouble range. Tachometer stays steady. If I shift to a lower or higher rpm gear, it runs great. Checked compression, dwell, timing, valve adjustment, spark at plugs, coil resistance...All within range. Distributor cap, rotor, condensor, and points all look good and have less than 400 miles on them from last year. I can't seem to find any vacuum leaks, but will be replacing all vacuum lines later this week. New plugs last year also...They are still gapped properly, but the 1 through 3 plugs have some dry carbon buildup that is not present on cylinder #4 plug. Haven't yet checked fuel pressure...Can't seem to find a tap point on the rails. Haven't changed the fuel filter yet since the last one seems to have trapped itself under the tank...Not an issue, I'll be replacing the lines with stainless from Tangerine when they arrive. Not sure how it can be fuel related since the car runs great outside of this rpm range. Seems to me that it is more likely to be electrical. Anybody ever run into this issue? Any suggestions would be appreciated. Axel (IMG:style_emoticons/default/wacko.gif) |
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Replies(1 - 19)
| TheCabinetmaker |
May 20 2013, 05:55 PM
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#2
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I drive my car everyday Group: Members Posts: 8,377 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
Your tps board has probably worn or it needs to be adjusted.
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| Axel |
May 20 2013, 06:06 PM
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#3
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
QUOTE(The Cabinetmaker @ May 20 2013, 06:55 PM)  Your tps board has probably worn or it needs to be adjusted. Thanks for the response. I thought about the TPS board, but if I run wide open, it runs great up to the 3,800 rpm point, then starts bucking. Since the throttle position doesn't change during this test, I wouldn't expect the TPS board to be the issue. Maybe I am misunderstanding how the board works? |
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| TheCabinetmaker |
May 20 2013, 06:24 PM
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#4
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I drive my car everyday Group: Members Posts: 8,377 Joined: 8-May 03 From: Tulsa, Ok. Member No.: 666 |
The traces get worn where they sit at one spot. Like at cruise.
Unplug it. If the stumble goes away, you need a new board. |
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| Axel |
May 20 2013, 06:30 PM
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#5
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
QUOTE(The Cabinetmaker @ May 20 2013, 07:24 PM) The traces get worn where they sit at one spot. Like at cruise. Unplug it. If the stumble goes away, you need a new board. Actually, that was the first thing I did when I encountered the stuttering last week. Unplugging the TPS didn't make any noticeable difference. |
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| motorvated |
May 20 2013, 06:47 PM
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#6
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Member Group: Members Posts: 282 Joined: 13-February 13 From: Colorado Member No.: 15,519 Region Association: Rocky Mountains |
QUOTE(Axel @ May 20 2013, 06:30 PM) QUOTE(The Cabinetmaker @ May 20 2013, 07:24 PM) The traces get worn where they sit at one spot. Like at cruise. Unplug it. If the stumble goes away, you need a new board. Actually, that was the first thing I did when I encountered the stuttering last week. Unplugging the TPS didn't make any noticeable difference. Could it be a sticky mechanical advance on the distributor? Although my old Volvo stumbled like that when the TPS got oxidized. I wiped it clean with rubbing alcohol, and it would be good for a while. |
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| mepstein |
May 20 2013, 06:59 PM
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#7
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914-6 GT in waiting Group: Members Posts: 20,750 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region 
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I had the same problem. Tried everything. fuel lines, vaccuum lines, gaskets, dizzy, points, injectors, plugs, wires, tps, fuses, checked mps, ect. Seemed to go away with a different (used) coil. Mine was origional to the car.
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| Axel |
May 20 2013, 07:00 PM
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#8
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
QUOTE(motorvated @ May 20 2013, 07:47 PM) QUOTE(Axel @ May 20 2013, 06:30 PM) QUOTE(The Cabinetmaker @ May 20 2013, 07:24 PM) The traces get worn where they sit at one spot. Like at cruise. Unplug it. If the stumble goes away, you need a new board. Actually, that was the first thing I did when I encountered the stuttering last week. Unplugging the TPS didn't make any noticeable difference. Could it be a sticky mechanical advance on the distributor? Although my old Volvo stumbled like that when the TPS got oxidized. I wiped it clean with rubbing alcohol, and it would be good for a while. I thought about the centrifugal advance on the distributor also. I was really hoping somebody had an easier answer. I've never taken apart the distributor to clean it. Anybody ever cleaned the weights in the distributor? How difficult is it to get to? |
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| Axel |
May 20 2013, 07:17 PM
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#9
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
QUOTE(mepstein @ May 20 2013, 07:59 PM) I had the same problem. Tried everything. fuel lines, vaccuum lines, gaskets, dizzy, points, injectors, plugs, wires, tps, fuses, checked mps, ect. Seemed to go away with a different (used) coil. Mine was origional to the car. Mine was replaced approximately 4 years ago. Tested fine, but I fortunately have a spare that I can try tomorrow. Thanks for the suggestion. |
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| gunny |
May 20 2013, 07:20 PM
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#10
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Member Group: Members Posts: 205 Joined: 17-October 12 From: Madison Al Member No.: 15,051 Region Association: South East States |
I have the same thing on my 76 2.0 Djet. I have tried everything. When it stumbles at 3800 rpms if you pump the gas peddle does it go past the bucking and run great above 4000 rpms? Mine seems to be a something with the firing of the fuel injectors
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| Axel |
May 20 2013, 07:55 PM
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#11
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
QUOTE(gunny @ May 20 2013, 08:20 PM) I have the same thing on my 76 2.0 Djet. I have tried everything. When it stumbles at 3800 rpms if you pump the gas peddle does it go past the bucking and run great above 4000 rpms? Mine seems to be a something with the firing of the fuel injectors Pumping the pedal doesn't do anything, but if I downshift it runs great over the 4,000 rpm point. |
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| mepstein |
May 20 2013, 08:43 PM
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#12
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914-6 GT in waiting Group: Members Posts: 20,750 Joined: 19-September 09 From: Landenberg, PA/Wilmington, DE Member No.: 10,825 Region Association: MidAtlantic Region
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Same symptoms as mine except some days it would be fine. I cleaned and replaced everything from the tank to the injectors but it wasn't a fuel issue. I'm 99% sure it was a spark issue. Old coil just wasn't putting out enough juice. Rebuilding the dizzy didn't help. I still plan to buy a new coil but switching out the old one made the car run much better. Good luck guys!
All origional '71 d-jet |
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| solex |
May 20 2013, 08:52 PM
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#13
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Senior Member Group: Members Posts: 789 Joined: 12-January 05 From: Long Island, NY Member No.: 3,439 Region Association: North East States |
How do the points look. I had the same problem with my 75. New point, condenser and timing did the trick for me.
Also make sure the distributor is buttoned down |
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| Axel |
May 20 2013, 08:59 PM
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#14
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
Points look clean, dwell is at 50 degrees.
Distributor cap, rotor, points, plugs, coil, and condenser were all replaced approximately 400 miles ago. I have another full tune-up set including new wires, so I'll start replacing part by part to see if it makes any difference. |
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| solex |
May 20 2013, 09:06 PM
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#15
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Senior Member Group: Members Posts: 789 Joined: 12-January 05 From: Long Island, NY Member No.: 3,439 Region Association: North East States |
QUOTE(Axel @ May 20 2013, 10:59 PM) Points look clean, dwell is at 50 degrees. Distributor cap, rotor, points, plugs, coil, and condenser were all replaced approximately 400 miles ago. I have another full tune-up set including new wires, so I'll start replacing part by part to see if it makes any difference. When you throttle the engine what does your tachometer do. Mine use to be very bouncy and had the same problem of bucking at that RPM, until I tuned it, try backing down a little on the dwell the range is 44 to 50 degrees. |
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| Axel |
May 20 2013, 09:19 PM
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#16
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
QUOTE(solex @ May 20 2013, 10:06 PM) QUOTE(Axel @ May 20 2013, 10:59 PM) Points look clean, dwell is at 50 degrees. Distributor cap, rotor, points, plugs, coil, and condenser were all replaced approximately 400 miles ago. I have another full tune-up set including new wires, so I'll start replacing part by part to see if it makes any difference. When you throttle the engine what does your tachometer do. Mine use to be very bouncy and had the same problem of bucking at that RPM, until I tuned it, try backing down a little on the dwell the range is 44 to 50 degrees. Tach is very steady...No bouncing at all. |
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| crash914 |
May 21 2013, 02:56 AM
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#17
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its a mystery to me Group: Members Posts: 1,830 Joined: 17-March 03 From: Marriottsville, MD Member No.: 434 Region Association: MidAtlantic Region |
do you have another set of trigger points? I have had a similar miss at somewhere around 32-3500 rpm...new trigger points fixed it...
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| Axel |
May 22 2013, 04:03 PM
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#18
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
Took apart and cleaned distributor. Replaced coil, condensor, trigger points, ignition points, cap, and rotor. Replaced all vacuum hoses. Adjusted dwell and timing. No change to the stuttering/bucking. Any other thoughts?
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| mburkhart |
May 22 2013, 06:41 PM
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#19
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Member Group: Members Posts: 113 Joined: 3-July 05 From: Chester, MD Member No.: 4,364 Region Association: MidAtlantic Region |
I had this exact same issue in my 74 2.0 for 10 years. Numerous mechanics looked at it and were unable to figure out what was going on. I finally took it down to Brad Mayeur and he tried unplugging Temp Sensor #2. For some reason that completely resolved the bucking at 4k rpm. It's worth noting that I have a Petronix installed, so it definitely wasn't the points/condenser.
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| Axel |
May 22 2013, 06:52 PM
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#20
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Newbie Group: Members Posts: 17 Joined: 15-May 13 From: Lenexa, Kansas Member No.: 15,875 Region Association: Upper MidWest |
QUOTE(mburkhart @ May 22 2013, 07:41 PM) I had this exact same issue in my 74 2.0 for 10 years. Numerous mechanics looked at it and were unable to figure out what was going on. I finally took it down to Brad Mayeur and he tried unplugging Temp Sensor #2. For some reason that completely resolved the bucking at 4k rpm. It's worth noting that I have a Petronix installed, so it definitely wasn't the points/condenser. Thanks, I'll give it a shot. |
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