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Jerking on deceleration

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Old 02-10-06, 11:40 AM
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Jerking on deceleration

1987 T II. Dp and FCD the rest of the car is bone stock. The car runs fine but jerks on deceleration when you stop accelerating. Any ideas?

Thanks.
Old 02-10-06, 11:45 AM
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My '86 sport NA does the same thing. Happens specially when I let it rev down from higher rpm's (while in gear of course). I did remove the 3rd set of butterfly valves.. I believe this could be my problem, but not sure about yours. I'd reccomend checking the trottle body to see if its been modified any.
Old 02-10-06, 11:54 AM
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I have this problem too. Kevin Landers told me what's wrong (at least when it pertains to an N/A).

Sounds to me like it's not completely cutting fuel on decel...a throttle or TPS setting may be off.

Last edited by DerangedHermit; 02-10-06 at 11:56 AM.
Old 02-10-06, 01:23 PM
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Decelerating from 8000 rpms, the RPMS should drop smoothly to 1500 rpms and then you get a minor bit of jerking. The service manaual does have a troubleshooting guide for the deceleration system. You can download that from:

www.teamfc3s.org
Old 04-02-06, 02:50 PM
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So jerking under 1500 is "normal" ?
Old 04-02-06, 08:33 PM
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Decel problems are generally caused by the TPS. It's not returning to zero, or misadjusted. It can also manifest itself as a jerking or hesitation when driving in 1st gear.
Old 04-02-06, 08:39 PM
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Originally Posted by Aaron Cake
Decel problems are generally caused by the TPS. It's not returning to zero, or misadjusted. It can also manifest itself as a jerking or hesitation when driving in 1st gear.
+1

Slight popping or back-firing on decel can be another symptom of a misadjusted TPS.
Old 04-02-06, 08:47 PM
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I adjusted my tps and it didn't change any. I'm not sure what is meant by a throttle setting might be off.
Old 04-02-06, 09:00 PM
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Have you checked your TPS for dead spots?

By throttle setting, I assume he is referring to the phasing of the primary vs. secondary throttle plates. If the secondary throttle plates open too early or close to late then these issues happen due to lack of air velocity through the ports (poor fuel atomization).
Old 04-02-06, 09:02 PM
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I did the Ohm testing method and I didn't see any dead spots. Or are those only visible with the voltage test?

I'll check the plates.

Would taking off my emissions affect this at all? Because I don't have any of the emissions equipment.
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