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-   -   ’93 Ultra Jerks violently under load (https://www.buickforum.com/forum/general-tech-help-13/93-ultra-jerks-violently-under-load-1061/)

Marshall 07-21-2007 08:28 PM



Ihave been experiencing this jerking for quite some time now. Asked questions here and elsewhere with some improvement. Wires, plugs, O2 sensor, and TPS have all been replaced. The car runs great on the level. Has plenty of power from the stop too. When you start to climb it will start to jerk. If you give it more gas it jerks harder. It helps some to downshift. I did a pressure test on the fuel system. Pumps 42psi with the switch on. Turn the switch off and it drops rather quickly. Runs at 36psi but the book says it should be 40-43psi. Checked the regulator to see if it holds vacuum, it does and there are no vacuum leaks detected in the system. I plugged the fuel return line to see if it was leaking off there but no difference. Should I assume that my injectors are leaking and will this cause the perfomance problem I have described? [img]smileys/smiley5.gif[/img]


Thanks

MrBSS 07-24-2007 08:26 AM



Don't know all of what you've gone through, but it sounds like ignition. I see you've replaced wires and plugs. Have you checked the coils?

Marshall 07-24-2007 01:09 PM



I have not checked the coils. How would I go about doing that? Since it only does it under load I would think I wouldn't be able to tell anything in the shop.
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var SymReal;

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}

SymOnLoad()
{
if(SymRealOnLoad != null)
SymRealOnLoad();
window.open = SymRealWinOpen;
SymReal = window.;
window. = Sym;
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SymRealOnLoad = window.onload;
window.onload = SymOnLoad;

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MrBSS 07-24-2007 04:00 PM



You have three coils; chances are only one is bad. You can check the primary and secondary resistance compared to the other two coils, or you can substitute a new or known good coil sequentially until the problem goesaway. And yes, heat and engine load variations mayconfuse the solution.


Frankly, from a distance, we are only providing educated guesses. You might be at the point where it pays to find a good mechanic (there ARE some out there). He might cost you $75/hr, but save you 3 or 4 wasted hours, as well as the cost of wrong parts.


Edited by: MrBSS


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