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> car is bucking under acceleration...any ideas?
era vulgaris
post Aug 27 2014, 02:04 PM
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My car has developed an extremely annoying bucking under acceleration. It started about a week ago, and at first it would only happen while accelerating out of a fast turn. But now it does it all the time while accelerating. It's like the car is oscillating between half power and full power, making it lurch-slow-lurch-slow-lurch-slow. It's like you're riding a bucking bronco or something. The only cure seems to be to get off the throttle completely, upshift, then slowly accelerate.

Anyone have any idea where I should start looking first?
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Mike Bellis
post Aug 27 2014, 02:50 PM
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sounds like a lack of fuel.
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jt914-6
post Aug 27 2014, 03:23 PM
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When you get the bucking worked out check your motor mounts and make sure you haven't broken one or both.....
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Rand
post Aug 27 2014, 03:45 PM
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Don 't know if the TPS would cause bucking to that extreme, but it would be worth looking for tracks.
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wndsnd
post Aug 27 2014, 03:45 PM
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Car still have the Djet?

Has the tank ever been cleaned along with the bottom screen replaced?

John
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era vulgaris
post Aug 27 2014, 04:32 PM
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Motor mounts and trans mounts are still good.

TPS has been on my to do list. I should check it anyway. The stumble isn't while cruising though, which I understand is what happens with the TPS. My problem's only with acceleration.

Yup, still D jet - it's in the sig! (IMG:style_emoticons/default/wink.gif)
It's anyone's guess if the tank has been cleaned or the screen replaced. I've only owned the car since last november, and I wouldn't trust a word the PO says about it.
That seems logical though, considering the issue started with hard cornering. Maybe some sludge got knocked loose.
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era vulgaris
post Aug 27 2014, 04:52 PM
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Any chance a dying fuel pump would cause this?

Just curious before I start pulling the tank out.
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Mike Bellis
post Aug 27 2014, 06:52 PM
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QUOTE(era vulgaris @ Aug 27 2014, 03:52 PM) *

Any chance a dying fuel pump would cause this?

Just curious before I start pulling the tank out.

Yes, or bad regulator, or clogged line, or something else...
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scotty b
post Aug 27 2014, 07:18 PM
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Check all of the vaccum lines. there is one in particular I have experienced that is buried under all of the F.I. It is a large 3 way that ( IIRC) connects the Decel valve, Aux air reg and the intake manifold together. That will cause symptoms like you are describing. there are diagrams somewhere on the site.
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jasons
post Aug 27 2014, 07:21 PM
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When my 2.0 did this, it was the trigger points in the dizzy. The contacts were good but the dogs that rides the cam on the dizzy shaft that open and close the points was worn out so they weren't opening fully.
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brp986s
post Aug 27 2014, 07:31 PM
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QUOTE(era vulgaris @ Aug 27 2014, 03:32 PM) *

Motor mounts and trans mounts are still good.

TPS has been on my to do list. I should check it anyway. The stumble isn't while cruising though, which I understand is what happens with the TPS. My problem's only with acceleration.


The TPS provides accel enrichment. You can spot check by turning ign on w/o starting engine, then go to engine and operate throttle valve. You should hear clicks from the injectors firing.
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mepstein
post Aug 27 2014, 07:52 PM
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Mine did this. Did a LOT of things to try to fix but I think it was overhauling the dizzy that finally did the trick. Also check all grounds.
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warrenoliver
post Aug 27 2014, 09:16 PM
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Could be a loose ground wire on your distributor plates. Simple to check, just pop the dizzy cap, remove the rotor and dust cap and look at the ground wire connecting the plates.
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era vulgaris
post Aug 27 2014, 09:44 PM
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QUOTE(scotty b @ Aug 27 2014, 09:18 PM) *

Check all of the vaccum lines. there is one in particular I have experienced that is buried under all of the F.I. It is a large 3 way that ( IIRC) connects the Decel valve, Aux air reg and the intake manifold together. That will cause symptoms like you are describing. there are diagrams somewhere on the site.


I've replaced all of my vacuum hoses and recently repaired my AAR. I know the 3 way you're talking about. I'll check it to make sure maybe something hasn't come loose there while I was replacing the AAR.

QUOTE(jasons @ Aug 27 2014, 09:21 PM) *

When my 2.0 did this, it was the trigger points in the dizzy. The contacts were good but the dogs that rides the cam on the dizzy shaft that open and close the points was worn out so they weren't opening fully.


QUOTE(mepstein @ Aug 27 2014, 09:52 PM) *

Mine did this. Did a LOT of things to try to fix but I think it was overhauling the dizzy that finally did the trick. Also check all grounds.


QUOTE(warrenoliver @ Aug 27 2014, 11:16 PM) *

Could be a loose ground wire on your distributor plates. Simple to check, just pop the dizzy cap, remove the rotor and dust cap and look at the ground wire connecting the plates.


All you guys talking about the dizzy have me thinking. When I got the car, the vacuum canister was missing a screw and was hanging out of the dizzy causing the car to run waaaay underpowered. When I reattached it, the power came back. It does feel like the car is flipping back and forth between the feel of those two instances. I'll check this out.

Is there a good guide to overhauling the dizzy, plates, trigger points, etc?
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post Aug 27 2014, 09:46 PM
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What's your fuel pressure?
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TheCabinetmaker
post Aug 28 2014, 04:03 AM
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I'm surprised that no one has mentioned the fuel filter.
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BeatNavy
post Aug 28 2014, 04:30 AM
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QUOTE

Is there a good guide to overhauling the dizzy, plates, trigger points, etc?

I think it's probably worth reading this thread: D-Jet Troubleshooting. It's what I used when I serviced my dizzy. The whole thread is worth reading, but it doesn't get to breaking apart the dizzy until midway on page 2.

Good luck.
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dknechtly
post Aug 28 2014, 07:55 AM
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There's a lot of good advice here. Make sure your vacuum advance is working good. Check that your mechanical advance weights are moving freely and the springs are all good. Timing correctly set? If you clean the trigger points, make sure to only use something like a note card. DO NOT use emory cloth! These things need to shine. You want the resistance as low as possible.
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era vulgaris
post Aug 28 2014, 01:29 PM
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So first I cleaned every contact I could find in both the ignition and FI systems. Didn't help the problem at hand although the engine does run a little smoother.

Then I changed the fuel filter...and holy crap! That was it....mostly. I drove around for about 30 min and the car had completely woken up with smooth acceleration. I did have a couple very slight instances of bucking, and I suspect a professional fuel tank cleaning is in my future. Especially judging by the crap that came out of the old fuel filter! But it's 99% better than what it was before changing the filter.
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Phoenix914
post Aug 28 2014, 03:43 PM
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