Vacuum or trans issue?
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6th Gear
Joined: Aug 2019
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Vacuum or trans issue?
My 1988 E350 fuel injected 7.5L with a C6 automatic started upshifting/downshifting right around the "shift point". Not long later the engine began racing at idle in park or neutral.
With the weather breaking I will be able to start looking into this so just wondering where to start. Vacuum issue? Trans modulator?
The TPS was changed a few years ago so it doesn't have many miles on it.
Wondering if anyone else has had this issue.
With the weather breaking I will be able to start looking into this so just wondering where to start. Vacuum issue? Trans modulator?
The TPS was changed a few years ago so it doesn't have many miles on it.
Wondering if anyone else has had this issue.
Hotshot
Joined: Jul 2020
Posts: 10,359
Likes: 2,594
From: Near Salt Lake City
Check the adjustment of the kickdown linkage
Do check the modulator for oil coming out the vacuum port, but that will not be the cause IMO
The modulator simply cushions the shift
Your trans is completely manual in shifting and relies on the governor to shift, so the TP sensor should have nothing to do with it except for idle speed and throttle response
Good luck
Do check the modulator for oil coming out the vacuum port, but that will not be the cause IMO
The modulator simply cushions the shift
Your trans is completely manual in shifting and relies on the governor to shift, so the TP sensor should have nothing to do with it except for idle speed and throttle response
Good luck
Hotshot
Joined: Jul 2020
Posts: 10,359
Likes: 2,594
From: Near Salt Lake City
If your kickdown is not stuck or the return spring broken
Research sticking C6 governor.
You can get them out and play with them on the bench with the trans still in the car in most cases
If yours sticks, or is sticky in the slightest get another one
When that governor spins fast enough, it shifts, if it is working correctly
Research sticking C6 governor.
You can get them out and play with them on the bench with the trans still in the car in most cases
If yours sticks, or is sticky in the slightest get another one
When that governor spins fast enough, it shifts, if it is working correctly
Thread Starter
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6th Gear
Joined: Aug 2019
Posts: 6
Likes: 0
So turned out the modulator was shot sending fluid into the vac lines which I'm guessing caused a cap on the vacuum tree at the back of the intake to come off obviously causing the high idle issue. New modulator and vac cap and she's back to shifting normal.
Thanks for the help!
Thanks for the help!
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