Throttle butterflies stuck shut
Discussion
A little story for community benefit:
Two weeks ago, I last sat in my car making brum brum noises whilst dreaming of the day when I'll be able to say that I have finished rebuilding the thing. Dabbing the throttle impatiently and seeing the quizzical look on my dog's face, that moment seemed quite soon.
A couple of days ago, I bled the clutch and out of habit whilst also being aware that my judgemental dog was locked in the house, prodded the throttle. It didn't move at all.
Cable disconnected. Pedal was happy, cable fine. Couldn't rotate the butterfly shaft, no movement. Linkage disconnected to see if one side was dragging the other: No movement in either. TPS removed from each body: No movement in either.
Swearing, angry looks and comfort food did nothing either.
I called around to discuss it with various people, and a rebuild was required. Joolz remarked that in 24 years, he'd never known them become seized and it's usually the opposite problem, you get too much play. Usual other suspects concurred that it was not heard of, and all recommended soaking them with any and all appropriate sprays first because almost nobody builds them these days.
That night, I also removed the straps holding the fuel rail down as I figured I'd have to get them off anyway and I just happened to have the appropriate bit on a ratchet in my hand.
The following morning I had some movement on the driver's side, and this morning it was pretty much fine. Passenger side is taking a bit longer it seems, but is slowly following suit.
I have however been able to shed some light on this and thought I'd post in case anybody else has a similar issue.
I have the Bosch green injectors for my 4.7, which I think are slightly longer. This may be what made the fuel rail harder to get strapped down than I remembered from times before my rebuild.
I called Dom again to follow up on whether or not he knew anyone who could rebuild the throttle bodies if I turn out to need it.
Apparently, those straps are supposed to have spacers underneath, although my car never did as everything I removed went neatly in to marked food bags. Seems you are supposed to only fit the fuel rail with enough pressure to keep it down. If you're having to push it down to strap it up, you need more washers or bigger spacers.
Dom advised that the tension of the straps if too tight would be enough to bend the throttle bodies. They will take a while to straighten themselves up again because of their material, and that's probably what caused them to appear seized. This also explains why they've gradually improved over a few days of being left alone.
Lessons:
- Straps not too tight.
- Check for spacers
- Joolz was right, they don't seize.
- Kent TVR will still refurb them if needed.
Two weeks ago, I last sat in my car making brum brum noises whilst dreaming of the day when I'll be able to say that I have finished rebuilding the thing. Dabbing the throttle impatiently and seeing the quizzical look on my dog's face, that moment seemed quite soon.
A couple of days ago, I bled the clutch and out of habit whilst also being aware that my judgemental dog was locked in the house, prodded the throttle. It didn't move at all.
Cable disconnected. Pedal was happy, cable fine. Couldn't rotate the butterfly shaft, no movement. Linkage disconnected to see if one side was dragging the other: No movement in either. TPS removed from each body: No movement in either.
Swearing, angry looks and comfort food did nothing either.
I called around to discuss it with various people, and a rebuild was required. Joolz remarked that in 24 years, he'd never known them become seized and it's usually the opposite problem, you get too much play. Usual other suspects concurred that it was not heard of, and all recommended soaking them with any and all appropriate sprays first because almost nobody builds them these days.
That night, I also removed the straps holding the fuel rail down as I figured I'd have to get them off anyway and I just happened to have the appropriate bit on a ratchet in my hand.
The following morning I had some movement on the driver's side, and this morning it was pretty much fine. Passenger side is taking a bit longer it seems, but is slowly following suit.
I have however been able to shed some light on this and thought I'd post in case anybody else has a similar issue.
I have the Bosch green injectors for my 4.7, which I think are slightly longer. This may be what made the fuel rail harder to get strapped down than I remembered from times before my rebuild.
I called Dom again to follow up on whether or not he knew anyone who could rebuild the throttle bodies if I turn out to need it.
Apparently, those straps are supposed to have spacers underneath, although my car never did as everything I removed went neatly in to marked food bags. Seems you are supposed to only fit the fuel rail with enough pressure to keep it down. If you're having to push it down to strap it up, you need more washers or bigger spacers.
Dom advised that the tension of the straps if too tight would be enough to bend the throttle bodies. They will take a while to straighten themselves up again because of their material, and that's probably what caused them to appear seized. This also explains why they've gradually improved over a few days of being left alone.
Lessons:
- Straps not too tight.
- Check for spacers
- Joolz was right, they don't seize.
- Kent TVR will still refurb them if needed.
Joolz, it was me indeed. Email sent back.
Green Giants were purchased at the instruction of a popular engine building place in the Midlands. I needed some new, got these actually very cheaply in a deal from Australia.
Saw some interesting bits of data a while ago about the standard injectors running out of steam and the fact that we see more power from an AJP than those injectors should realistically flow for. Was advised Green Giants would be best by the aforementioned since I was buying new, and had gone 4.7rr.
Green Giants were purchased at the instruction of a popular engine building place in the Midlands. I needed some new, got these actually very cheaply in a deal from Australia.
Saw some interesting bits of data a while ago about the standard injectors running out of steam and the fact that we see more power from an AJP than those injectors should realistically flow for. Was advised Green Giants would be best by the aforementioned since I was buying new, and had gone 4.7rr.
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