1988 Toyota MR2 MK1 T-Bar ... Jimi's Odyssey

Cool car

I'm interested in a build thread for this wee red Toyota

Bookmarked, and awaiting updates

2004 - Manual "Choke" Conversion

MK1's are very well known for having cold idle problems, can be higher than 2000rpm this is down to problems with the cold start waxstat valve ( or Auxiliary Air Valve as Mr T calls it ) for those of you who are unaware of its function it keeps the idle high on the engine during starting until the engine has warmed up.
This however raises a few problems and far be it for me to criticise Mr T's design I’m afraid he didn’t quite get it right when it came to the cold start system.
There's a couple of problems with it, one of which is the annoyance that even if you have a fully functioning waxstat valve with no problems at all it seems to take forever (especially during the colder months) for the idle to return to normal after starting. I’ve see it take up to 3 miles of driving before it settles to 900rpm.
There is no need for the waxstat valve to stay open this long and in fact a few hundred yards of driving or 60 seconds of idling sees it capable of doing without the choke. This in turn means that for an extra 2 miles or so the engine is drawing in more air than it needs and in addition is being supplied with the extra fuel to compensate...... not good for our fuel economy!

The waxstat basically allows extra air to be drawn past the throttle to simulate throttle being applied when the engine is cold, the map sensor informs the ECU that this extra air requires fuel and that’s our choke (I know it's not really a choke, but it does the same job so I'll call it that)

The second waxstat problem is that they frequently stick open, that is, even though the engine has reached running temperature there’s still an extra amount of air leaking past the throttle and the ECU allows more fuel for that.
However the ECU is now being told by the throttle position sensor that the throttle is shut, so on the one hand its being told I have the throttle open (the air leak) please give me fuel, and on the other hand the TPS says throttle shut reduce fuel and the end result is a surging idle as the ECU battles in conflict between the sensors. I’m sure at one time or another most if not all MK1 owners will have witnessed this surging idle when the cooling system has become air locked or the waxstat has stuck open.
OK, that’s how the system works and the problems with it, BTW I did enquired about the cost of a new waxstat valve from Toyota .... £140! and they are now unobtanium. At the end of the day a replacement would it still have the inherent problem of staying on for far too long.
It's also possible to strip them and sometimes they are repairable, but given from new they went wrong relatively quickly I'd expect them to fail again, not worth the effort IMO.
MK1 specialist/guru (font of MK1 knowledge and all round good guy) Paul Woods figured this out and did some R&D to come up with a solution involving a bit of retro thinking. Remember the days of old Morris Minors, Minis and even old Fords when it was a joy to turn the choke off as soon as things got going?
So a cheap manual choke conversion was clearly the answer. Not some pull out cable operated affair like in the good old days but a simple dash mounted switch that can be flicked on or off to control the cold start.
After much toying with the throttle body on a MK1, he found that Toyota weren’t such idiots after all and they have conveniently supplied an extra air pipe on the throttle body that he could use for his system. Indeed He found he could leave all of the original Toyota waxstat system in situ and not even remove a single piece of it, (which is good news for any MK1 purists among us)
The system he came up with is merely an “add on” which can be removed from the engine at any time with no side effects.
The standard waxstat is simply disabled by blocking off its auxiliary air supply with a plastic tyre valve cap, indeed many people were aware of this mod as a cheap fix for a waxstat that had given up permanently.

His manual system consists of a 12v switching air solenoid that plumbs directly to the throttle body and feeds from filtered air on the air filter piping, there’s no holes to drill and no modifications need to be made to the standard set up.
Paul sold a kit for this which I bought, but while carrying out the installation (which was extremely straight forward) I decided to make a few modifications.
These consisted of the addition of a time delay relay, moving the solenoid into the boot and a few wiring mods.
The relay is set up to automatically switch off the solenoid after 3 minutes (this can be altered to almost any value) just in case I forgot to switch it off. The 3 minutes was a trial, which has turned out to be spot on for me.

The relay was an old Audi headlamp washer relay that I had lying about in the garage (one of these you know "it" might come in handy one day items) modified to increase the time delay.

I found the original delay on the relay was set by a R-C network, which I modified by changing the resistor and capacitor values to get a much longer switch off delay (was originally only a few seconds)

I decided to install the relay and the solenoid in the rear boot behind the trim panel as I thought it looked tidier and kept them out of the engine compartment (and away from any water)




I used 8mm red silicon tubing to pipe up the solenoid (just to match the existing tubing) and routed it through the grommets in the bulkhead




The wiring was modified to suit the relay (see the dwg below).


The switch is mounted in a switch blank right beside the “coin holder” to the left of the steering wheel.



I found that I was able to install the switch by taking out the stereo and working through the hole (thought this was easier than taking off the dash surround). and I was able pick up a +12v ignition controlled supply from the stereo.

I installed this in July 2004 and for almost 20 years it's worked perfectly, easily paid for itself in fuel savings and has required no maintenance, a truly excellent mod by Paul Woods.

I do revisit this mod a few years later with a further improvement, which I'll document when I get to that year

This is very interesting, Jimi, and quite technical.

I now know that some (timer) things on your car are controlled by RC network.

What is RC network?

Anyway, I've bookmarked this because I am hoping that at some point in your odyssey you will have seen sense and put the amber indicators back on.

2005 - Headlight Control
The MK1 light switch has 4 positions:-
1. Off
2. Side lights & rear lights
3. Headlights rise and come on with Side/Rear lights
4. If you push the switch in and turn to this position it locks the headlights up but off (for maintenance and to prevent the lights being frozen down in winter)

Main/dip/flash functions are built into the indicator stalk (If you flash with the lights off the headlights rise flash then retract)

When the Dim/dip legislation was intraduced to the UK (1986/87) the MR2 headlight operation was modified to comply which meant on position 2 the headlight come up and on dim (basically both dip beams in series) so you couldn't have just sidelights with the headlights retracted as the aerly cars (1a's)

I (and many other MK1 owners) didn't like this and since the Dim/dip requirement was revoked in the early nineties it's no longer required.
After some investigation and in collaboration with another MK1 owner (Murf_mk1) we came up with this modification to allow you have your sidelights on with headlights down. Once you switch to the headlight position (3) the lights will rise. However if you flash your lights while on sidelights or switch from headlights back to sidelights the headlights will remain in the raised position until the switch is moved to off.

The operation is controlled by the Dim/Dip relay which we tracked down to under the bonnet next to the fuse box, its bright green (on some change over cars it's grey) we identified which relay pin the control signal arrives on and by taking the pcb card out of the box and snipping the connection between the connector and the PCB we could disable the oeration. Fitting a switch makes the mod reversible. Paul used a switch he had lying about as in the picture, I used a minature toggle switch (much smaller)





Re assembled and ready to refit





April 2005
After more investigation I worked out how to allow the headlights to retract after flashing your lights while on sidelights or switching from headlights back to sidelights. This involves a modifiction (similar to the previous one) to the Retract Control Relay
The mod involves disconnecting the red wire that goes to pin 6 on the retractor control relay, the only down side is that in the lock position the headlights will not stay up, however by fitting a switch to the side of the relay case it's easy to re-enable the lock function.
The retractor control relay sits next to the windscreen wiper motor, with the relay removed and opened up this is the control pin


I cut the connection and bent 1 leg far enough to allow me to solder wires on the 2 legs and connected the wires to a minature toggle switch



The switch was fiited to the side of the case and the relay re-assembled


Refitted to the car, easy to get to the switch if I need the headlight lock function enabled.

Great read, keep the updates coming.

2005 - The Jimi™ Throttle Bracket

I did all the initial design and prototype work on this in 2005 but rather that write this up from scratch,  I'll reproduce an article I wrote later that was published in

(issue 7 Nov 2007)

The Jimi™ Throttle Bracket Story

A long time ago in a galaxy far, far away.......oops wrong story !
Back in 2004 after an extensive search lasting 6 months, I became the proud owner of a Red 1988 Mr2MK1 T-bar. I bought it in Newcastle from Lee Hall after a 2 hour test drive ! ( we were both enjoying ourselves ) and I had a very enjoyable 150 mile drive back to the sunny Kingdom of Fife with the T-bars off.
I spent the next day crawling all over the car examining all the nooks and crannies. One of the first things that struck me on opening the engine compartment was the ugly monster tripod bracket Toyota had fitted for the throttle cable, it seemed to dominate the engine bay, more or less obscuring the beauty of Mr T’s fine 4AGE twin cam engine.
“Not much I can do about that” I thought, so I whipped it off, gave it a clean up, a coat of paint and refitted it.




7 months passed as I spent time getting various bits and pieces of the car the way I wanted them, but every time I opened the engine bay, there it was squatting there glowering at me.
Then one fine cold January morning, I was pottering about doing a bit of tidying up in the engine bay when I cracked !
“Enough is enough … it’s got to go !” So off it came. “Now what do I do” I wondered as I stared at the scabby cam covers I had uncovered.
Careful examination of the throttle quadrant revealed that it already had a groove for the throttle cable and a location hole for the nipple, Bingo !! Unfortunately my joy was short lived as I realised that fitting the cable that way meant pushing the accelerator was trying to close the throttle.
Ahhhhh … I can turn the quadrant round ……...nope various reasons why that wouldn’t work either, ah well, back to the drawing board.

But it did give me the germ of an idea, if I made a location point at the other side of the quadrant then the cable would wrap round the groove and the direction of operation would be correct. Here’s the quadrant with the new location point for the nipple on the left.




Once I had the inner cable located I could see where the outer would have to sit, the middle of nowhere! So I needed to make a bracket that was strong enough not to bend or flex when the accelerator was pressed and I needed to mount it somewhere.
First thoughts were off the bodywork, not a good idea, since the engine is rubber mounted and rocks fore an aft. Next up, mounted off the gearbox ?…..nope ….. too complicated to fabricate with the limited material and facilities I had available.
“Hmmmm …. there’s 2 bolts securing the return spring bracket to the inlet plenum, so if I used them, I could make the bracket run across the top of the quadrant to where I need the outer cable to be. So I took some measurements, made up a quick sketch on the back of my cigarette pack, (literally) and off I went to look for something to make it out of.
I found a piece of stainless channel I had acquired when building my sons jeep, (another saga, for another time !) a bonus being that it already had a bend in it that I could utilise. After a couple of hours work with an angle grinder, hacksaw, files, drills and various bits and pieces and I had a prototype and was beginning to believe this would actually work !



I test fitted it to the car and with some minor adjustments it fitted fine. What a difference ! Immediately the engine bay looked less cluttered, more open and the bracket looked like it belonged there.




Now for the acid test … would it actually work ? I took the car for a drive and to my surprise found the throttle action was much smoother and the pedal travel had shortened.... what a bonus!!
I left it on the car for a couple of months to make sure there were no problems and then decided to make an improved version incorporating the lessons I’d learnt from the prototype.
This is the 2nd version fitted, as you can see one of the changes is how the outer cable locates on the bracket.




My next improvement was to bead blast the bracket to a satin finish and etch it with MR2 in the Toyota MR2 font.




Now I was happy with it and could spend some time tidying up the engine and engine bay.

After a few months and having attended several MR2OC Scottish meets, word of my bracket had spread among other MK1 owners and I'd had quite a few requests to make brackets for people, which I was quite happy to do.
But since making them was pretty labour intensive and I had a very limited supply of suitable stainless steel, I decided to investigate other options.
After spending some time talking to various companies and getting some very scary quotes, I found a local company, James C Gillespie of Kirkcaldy who were willing to make up the basic bracket for me in stainless steel, leaving the finishing for me to do.
I gave them the 2nd version to use as a template and incorporated a couple of refinements to the design. They made a sample bracket for me to check the fit and when I collected it a few days later I was stunned by the quality.
They had transferred my design into a CAD drawing package and cut the stainless using a computer controlled laser cutter, then machine formed the bends.



It was so impressive that my first thought was "This is going to be way out of my price range." However, to my surprise I learned that I didn’t need to place a huge order to bring the price down to a very reasonable level. All I had to do was put the money up front !
After a bit of thought I decided to go for it and place an order … and so the Jimi™ Throttle Bracket was born.
I've been making them available with 3 finishes which I do myself, so each bracket is hand finished and unique … no two are identical.



I’ve also done quite a few one off designs as special requests. Here are a few of them:-













Making the brackets is basically a non-profit making hobby, enabling me to keep the price down to the bare minimum, just enough to recover my initial outlay and postage costs.I've never advertised or actively pushed the brackets, news of them has spread by word of mouth and this article, leading to people contacting me asking for one.
I don't sell them in bulk because I don't want anyone profiteering on them, that would kind of defeat my intentions with them, which is to make an affordable, effective mod available to the MK1 community.
Over the last 3 years more than 100 Jimi™ Brackets have been successfully fitted to MK1's throughout the UK as well as Holland, Malaysia and the USA .

My thanks to the following people :
Graham Gillespie of James C Gillespie Ltd for a quality job, at a great price.
Barry Fimister ( Fimmo ) for helping with the graphics on the very first “specials"
Max for her patience and support.
Scottsmale for his support and being customer number 1
All the people that have trusted me and my design enough to buy one, fit and use it.

An interesting footnote is about the name “Jimi™ Throttle Bracket"  Credit for that must go to a fellow MK1 owner and friend of mine, Graham King ( Scottsmale ) who first coined the phrase and it's stuck ever since !

Graham also penned this little ditty:



These Photo Albums Link 1 and Link 2 contain pictures of owners cars with my bracket fitted.
Jimi Lawson 2/10/07

2024 Update :
I'm still making the brackets, not as many these days as there are a lot less MK1's around, but still regularly getting contacted from around the world 🙂

Currently I have produced and sold 405 brackets which have gone to 17 Countries around the world:
Scotland
England
Wales
N Ireland
USA
Canada
Bahamas
Norway
Demark
Germany
Netherlands
Slovakia
France
Spain
Malaysia
Australia
New Zealand

For me the ultimate would be to sell one to someone in Japan ! 😎

Those speakers look really neat, should be perfect when you are listening to Classic FM.