4AGZE Hunting idle and Horrid Economy

[kolby]

As you guys were so helpful with the diff/ gearbox trouble i was having in a cpl of my ta22's i thought it might be worth a go posting this one.

The car that will be fixed over the next week that had the diff problem has had an idle problem since i bought it.

Basically it starts first turn, but then the dies very quickly unless i keep the foot on the accelerator. While trying to maintain revs the idle hunts between about 1000 and 2000. While driving the revs are fine until you come to a set of lights etc and the idle hunts between those revs. Im also getting approximately 80km per 15ltrs of petrol at the moment.

Does this engine just need a good tune up or could there be other problems?

The 4agze is in a Ta22 and has a microtech lt10s hooked up to it. It has no Air Flow Meter on it and im guessing it must have had a map put on instead?

I rang a Auto place down here in tassie that deals with aftermarket ecu's and the guy thought it just needed a full tune at about $600. Im not convinced by this though, hence the reason for this post.

cheers

kolby

[wiso]

does the engine still run the factory TPS and is it wired up to the microtech? with a stock ecu the TPS "could" be causing an issue like you describe. mine was hunting when I would touch the throttle. very annoying. and at idle I had to crank the idle speed screw right up so it wouldn't stall. TPS can also cause poor fuel economy.

but this is all for standard ecu, I don't personnaly know for your microtech.

Do you know what your engine setup is as far as idle control valve. are you using the standard?

[TERRA Operative]

The Microtech has an onboard MAP sensor. Double check the vac line is undamaged and secure.

Also, as above, check the TPS and Idle speed control valve (ISCV).
Apart from that, a retune by a reputable tuner sounds like a good idea. You say that you've had the problem since you bought it, my money is on the very real chance that the engine has never been tuned properly (or is running a base tune, or one downloaded from the internet).

I would get you to pull codes, but that only works on a stock ECU.
A new tune is the way to go, it's the single most common problem with aftermarket ECU's. That and dodgy wiring.

[kolby]

Hmm not to sure about the TPS. I am pretty sure it is the original factory one. Might have a play with it. Did adjust the idle up to about 2000rpm and it idled steady but that is no good for the long run. As for the onboard MAP sensor. Where do i find this? Ive had a look under the bonnet and it actually looks like a cpl of sensors might not be connected. Can upload photo's if that will make it easier?

cheers

[TERRA Operative]

The MAP sensor is in the Microtech itself.

The car should idle at about 700-800 RPM.

[Suavemechanic]

im thinking temp sensor , yer motor thinks it has snow on the bonnet and is running rich to compensate ?????

[TERRA Operative]

I'm thinking you need to get the tune checked. You have no idea what's going on there and you'll be chasing your tail until you do.......

[kolby]

Yeh i think your right.
Ive been reading up on this and trying to learn along the way but it might be best to put it in and atleast get them to check over it and make sure there are no probs.

I got told about $500 for a full tune up.

Is that what you would normally expect to pay for this sort of tune up? Or is Tassie just a rip off in this area like everything else down here

cheers

[TERRA Operative]

That sounds about right. I was charged about the same at Mazfix here in brisbane to tune a Microtech on a Starlet.

[RT40Corona4AGTE]

microtech has built in map sensor. There should be a vac line going to the actual microtech for this. When you turn the key to the on position but dont crank it over does the yellow led on the microtech remain lit? And then when you crank it over it should flash. If it is not lit solid before cranking then tps is not set correctly. Dont touch accelerator pedal whilst doing this either. Let us know how you go mate. I am thinking tune is needed if above checks out ok.

[The Count]

im having the same issue in my GZE im running a haltech E6X when i start up jumps idle between 1100-2000 like iv got massive cams lolbut sux performance isnt fantastic and fuel is guzzling

[Hen]

4AGZEs will always struggle to idle nicely, especially on aftermarket computers and especially if you have a front mount intercooler. The problem is the large inlet volume post-throttle.

Firstly check that the idle speed control valve is connected properly, it's an unusual 3 wire setup which the ECU may not drive properly. Then try playing with the idle control settings in the Microtech, try slowing down the idle speed tracking (NFI how/if you can do that on a Microtech).

I'd also suggest getting a proper tune or at least the current one checked. Otherwise you'll just be guessing a diagnosis on the fuel economy problem.
Hen

[Duk]

4AGZEs will always struggle to idle nicely, especially on aftermarket computers and especially if you have a front mount intercooler. The problem is the large inlet volume post-throttle.

No help to the OP's fun, but the latest update for the Adaptronic includes ignition timing to control to help with idle speed control. I was having a chat with Andy (top bloke, loves what he does and it shows in his/their product) and they developed it to run supercharged Lotus Elise's. Pre-SC throttle body, intercooled Lotus Elise's .