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Sorry for raising this old topic.



Looks like a decent solution to the sticking throttle body problem. I have the same issue on mine so going to give it a good clean, and if that doesn't work, will probably do this mod, just wondered how you got the measurements for the holes to drill. Was it just guesswork or is one of the hole oversized in order to get the retaining screw in the right place please?



Also, is it possible to get the TB off without getting at it through the wheelarch please?

I don't see why you'd have to take it out through the wheel arch...

I just unclamp the intake, pop off the hoses, remove the connectors and cable, and unbolt it.


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Just wanted to bump this since I'll probably be trying this mod this winter. I am on my second throttle now, and it just started showing the symptoms. This is one of those where the general thought of "it's as reliable as a Toyota" is full of holes. It's mounted differently, tuned differently, cooled differently, lubricated differently, and driven differently. At least it is easy to work on...
 

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Just wanted to bump this since I'll probably be trying this mod this winter. I am on my second throttle now, and it just started showing the symptoms. This is one of those where the general thought of "it's as reliable as a Toyota" is full of holes. It's mounted differently, tuned differently, cooled differently, lubricated differently, and driven differently. At least it is easy to work on...

Someone just needs to come out with a finished kit for this to adapt.
 

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I finally got around to making this since things have been getting really bad with the sticky throttle. I used the aluminum as a spring rather than using the bolt to preload though. I also cleaned the throttle bore out, and that seemed to help a lot, too. Overall though, I am still having some issues. I can watch my AFRs go slightly rich (Lambda of 0.8) and then steadily go all the way 1.4+ and the engine stumbles like crazy. I'm starting to think I have another issue, but what keeps bringing me back to this is that the idle goes perfectly smooth after I blip the gas, just like when I had the high idle.
 

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Did you clean out the Idle Air Control valve at the base of the throttle body while you had it out?
No, but that isn't my issue. I've pretty much ruled out IACV issues - rpms surge when I unplug it, and it idles smoothly whenever I manually unstick the throttle. The idle issues are gradually going away as I drive it, so I think now I am fighting LTFTs. As those update, it seems to improve.
 

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Discussion Starter #29
I finally got around to making this since things have been getting really bad with the sticky throttle. I used the aluminum as a spring rather than using the bolt to preload though. I also cleaned the throttle bore out, and that seemed to help a lot, too. Overall though, I am still having some issues. I can watch my AFRs go slightly rich (Lambda of 0.8) and then steadily go all the way 1.4+ and the engine stumbles like crazy. I'm starting to think I have another issue, but what keeps bringing me back to this is that the idle goes perfectly smooth after I blip the gas, just like when I had the high idle.
The advantage of using the set screw in the original design (relative to an aluminum bracket as a spring) is that you can use the set screw to precisely position the butterfly valve right in the middle of the bore. If the flap is positioned even just a little off to one side or the other, you will still get some stickiness (and letting the throttle snap back to closed will overcome small offsets, although it is better not to have that problem at all). I repeatedly looked through the bore at a light in the background to better see the position of the flap in the bore, and adjusted the screw to make the light leakage around the flap as symmetrical as possible. (Be careful of your eye position relative to the center and edge of the bore when you do so, as that can change the light leakage you see.) After locking the screw in place with the nuts, I then opened and closed the flap multiple times to make sure it was stable.

It has now been over 7 years since I did this modification, and it is still working perfectly.
 

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another case study on this problem:

- i did my own hack-fix similar to what was outlined above (and was quite proud of my clumsy artistry), but in the end it was little different in details and execution - essentially, not as sturdy. it worked initially, but only for two years (it stopped working just before i was due for another smog test, which i then couldn't pass due to high idle code)

- i tried tightening the screw i used as a set screw, which then ended being too much and led to throttle valve not returning and engine speed running away and me having to shut off the engine via the key before the engine over-revs - scarry stuff. - enough to make me give up the hacking and reach for new parts.

- lotus charges like something $2500 for the throttle body - which is crazy - isn't that like half the cost of an engine? i found a toyota dealer that sells the new throttle body for about $550 - https://www.oempartworld.com.

but again, this is just temporary, probably for another 30-40,000 miles, which is how long it took for the problem to appear the first time.

- i was all really happy about that, until i installed it and found that the throttle cable suddenly doesn't reach long enough to be hooked up on the quadrant of the new body, even after all available adjustments are maxed out. i was thinking of all kinds of crazy and involved ideas for fixing that, having to do with the cable, but finally realized that the quandrant on the toyota throttle body is different than the quadrant on the original lotus throttle body. then i decided to use the old quadrant with the new body, and that worked. more details and some pictures here:
https://www.lotustalk.com/forums/f101/throttle-cable-too-short-after-new-throttle-body-467526

but then again, this is just temporary, probably for another 30-40,000 miles that it took for the problem to appear the first time. at least in terms of time that is like 10 years for me.
 

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another case study on this problem:

- i did my own hack-fix similar to what was outlined above (and was quite proud of my clumsy artistry), but in the end it was little different in details and execution - essentially, not as sturdy. it worked initially, but only for two years (it stopped working just before i was due for another smog test, which i then couldn't pass due to high idle code)

- i tried tightening the screw i used as a set screw, which then ended being too much and led to throttle valve not returning and engine speed running away and me having to shut off the engine via the key before the engine over-revs - scarry stuff. - enough to make me give up the hacking and reach for new parts.

- lotus charges like something $2500 for the throttle body - which is crazy - isn't that like half the cost of an engine? i found a toyota dealer that sells the new throttle body for about $550 - https://www.oempartworld.com.

but again, this is just temporary, probably for another 30-40,000 miles, which is how long it took for the problem to appear the first time.

- i was all really happy about that, until i installed it and found that the throttle cable suddenly doesn't reach long enough to be hooked up on the quadrant of the new body, even after all available adjustments are maxed out. i was thinking of all kinds of crazy and involved ideas for fixing that, having to do with the cable, but finally realized that the quandrant on the toyota throttle body is different than the quadrant on the original lotus throttle body. then i decided to use the old quadrant with the new body, and that worked. more details and some pictures here:
https://www.lotustalk.com/forums/f101/throttle-cable-too-short-after-new-throttle-body-467526

but then again, this is just temporary, probably for another 30-40,000 miles that it took for the problem to appear the first time. at least in terms of time that is like 10 years for me.
If I were in the position that I needed to replace my throttle body, I'd be buying the big-bore from Blackwatch.
 

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If I were in the position that I needed to replace my throttle body, I'd be buying the big-bore from Blackwatch.
At the Lotus price, ITBs would be a contender, haha

Each time I see a used manifold come up for sale, I get really tempted...
 

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I'm not familiar with a 2zz manifold with ITBs. Does something exist?
I should've said "I get really tempted to by the stock manifold, hack it up, and made universal ITBs fit". I think some Celica guys have done it, but no Lotus that I am aware of because of space.
 

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re: "If I were in the position that I needed to replace my throttle body, I'd be buying the big-bore from Blackwatch.": yes, i will do that next time, if they still sell them then. didn't realize this was going to get so complicated.
 
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