So my 2006 Exige was exhibiting the ubiquitous "stop light stalling issue". My previous Exige, a 2007 S, was a staller, as well. As some of you may know, I, along with ChronosWS, recently installed the BOE Rev300tvs system in our cars. His car's (2007 Exige S) stalling issues have all but vanished while mine worsened. A call to Phil asking him why and if maybe it could possibly be the tune yielded this gem:
"Well, your car and [ChronosWS's] car are mechanically the same now and share the same tune. So your cars should behave exactly the same. And there's nothing in the tune that says, 'kill the car'."
True. I guess I never thought about it like that. Must be mechanical then. Phil hypothesized that it might have something to do with the throttle body cutting air off to the engine. Within the TB, the TB blade opens and shuts according to throttle position. There are 2 retaining screws that dictate 2 positions of the blade: (1) at idle/engine off and (2) completely closed. The first stop is what the blade should be at when at idle or when the engine is off. The second stop, the ECU can actually drive the blade closed all the way, so this stop is actually set so that the blade will close completely. Apparently there are situations where this is needed.
Phil guessed that on stalling cars, the first stop was perhaps backed out, causing the blade to close too much. He sent me a photo of a TB he knew was working correctly; the blade in that one looked pretty close to mine but maybe it was open a bit more. I couldn't tell because it's difficult to get a look at the blade with the TB still installed in the car.
Seeing as how I had done basically everything else, to no avail, to fix the issue (cleaned MAF, filter, new plugs, new injectors) I figured I should test his hypothesis. So I yanked the TB and took a closer look at my blade. Upon inspection, it looked very close to the reference pic. But looking at the retaining screw in the ref pic tipped me off. Mine was backed WAY out. Probably a full 3 or 4 turns. I tightened the screw in, 1/2 turn. Went for a drive. Car still stalled but way less. Came back in and tightened it again, this time 1/4 turn. Went out again. Stalled even less! Came back and this time, a full 2 turns. Then went out, doing the same run, simulating stop and go traffic, stop lights, right turns. All in all, I probably did about 50 or so stops.
No. Stalling. Whatsoever.
Ok ok. It did once, dip below idle. When I was coming into a parking lot, off throttle, braking from third gear, clutch in. RPMs dipped below idle, but it recovered. Maybe if I had come to a complete stop just then, it would have died? Not sure.
So, did it completely fix the issue? Maybe not. But it is damned close! So close as to be negligible now. Like I said, after 30min of driving it never stalled. Just stumbled once. Far better than before when it was stalling more than half of the times I stopped. (Sometimes even when I didn't shift gears fast enough, coasting at 25mph, no less). I'd guess maybe another 1/2 or full turn will completely rid the car of the issue.
Ok. So how to do this? I can only speak to drive-by-wire cars:
1. Unclip airbox. There are 2 metal clips on the outboard side, top and bottom.
2. Remove the air intake tube from the TB, leaving it connected to the airbox.
3. Remove any hoses attached to the TB. Remember where these go.
4. Remove the electrical plug to the TB. (On the black plastic housing.)
5. Remove the four 12mm bolts holding the TB onto the intake manifold. Remove TB. There will also be a 10mm bolt holding the wiring harness you just unplugged on to the TB. Remove that as well.
6. Now you'll need to remove the plastic housing. Use a flathead screwdriver to pry off the retaining clips. Slide the housing off and you will see the two stops. The one you'll be adjusting has a glob of epoxy over it. Lotus thought maybe this was going to stop it from backing out? Remove that epoxy.
7. Using a 3mm allen wrench, tighten the retaining screw so that your blade opens up more. You can use the picture provided as reference for the final position of the retaining screw.
8. Put everything back together. (Use some RTV ultra grey to seal the TB to the intake manifold.)
I actually used a bit of blue thread lock on the retaining screw (backing it out first, applying, then tightening again). We'll see if this holds up. It should.
It may take some fiddling and you may have to remove/install the TB several times to find the right adjustment. But it's going to be worth it, IMHO. Hopefully this helps!