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Low idle when warm - MAF and TB cleaned - TPS broken?

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wenguin
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Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Sat May 16, 2015 6:46 pm

Hi guys

New RS200 owner, 99 auto.

When the car warms up, the idle sits on the tachometer at about 500 and the engine is hesitant. From googling, I see this is a fairly common problem.

I've cleaned the MAF and cleaned out the throttle body, but it still exists.

Now, I have an OBD2 scanner hooked up and when warm, the OBD2 signal tells me the tachometer is at 750RPM. The cluster dial on the Altezza however reads about 500RPM.

Could the 'wrong info' being read by the OBD2 (and therefore via the ECU) tell me something? Perhaps the Throttle Position Sensor is broken, and somehow there are two signals involved - one to the ECU and one for the dials (in the same way engine temperature has a Dial reading and an ECU reading)?

I've reset the ECU and it didn't change anything (by way of putting a new battery in, again, nothing changing as a result).

Also, picture of said RS200 with someones GT86 (TRD?) at local dealership.

Image

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Sat May 16, 2015 7:20 pm

Edit: I Used the OBD2 scanner to check the Throttle position and it gave a reading of 13.X - I understand it should be 14.8 +/- 0.8 ? Perhaps someone has messed with the adjuster?

I'm hesitant to rely on the OBD2 data - there is a possibility it is wrong I suppose?

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Tosh21
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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby Tosh21 » Sat May 16, 2015 9:16 pm

http://z4.invisionfree.com/lexusaltezza ... topic=8980

I assume the auto would be the same voltages

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Sat May 16, 2015 9:37 pm

Tosh21 wrote:http://z4.invisionfree.com/lexusaltezzaclub/index.php?showtopic=8980

I assume the auto would be the same voltages

Cheers, I'll give that a go tomorrow. I've read that the factory TPS screws have yellow paint markings so you can tell if they've been adjusted at any point, hopefully I can get some info from there.

Ideally I'm after someone with an OBD2 reader who can verify if it matches the tach reading on the dial.

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Sun May 17, 2015 5:31 pm

Alright, possibly big update.

OBD2 TPS % @ engine off, throttle closed = 15.3%
OBD2 TPS % @ engine off, throttle fully open = 82.4%

OBD2 TPS % @ engine on, warmed up, throttle closed = 13.3% (revs @ 761)

OBD2 'timing advance' @ engine on, warmed up = 19.0

TPS - can anyone tell if it's been adjusted?

Image

this is where the dash tach sits when warm, with OBD2 giving a reading of approx 760rpm

Image

now for @Tosh21's suggestion. TPS measured from ECU using pins 17 (gnd) and 23 (tps signal primary). throttle control motor disconnected, ignition 'on', engine off.

with throttle fully closed, .772:

Image

with throttle full opened, 2.35:

Image

(note, fully opened measured by manually opened the throttle from the engine bay)

Summary:

The OBD2/dash reading of RPM is still a concern.

TPS measurements from ECU are different from those found here (http://z4.invisionfree.com/lexusaltezza ... topic=8980) - am i doing the readings correctly? is my multimeter set correctly?

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Tosh21
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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby Tosh21 » Mon May 18, 2015 8:04 pm

Bear in mind its fly by wire. You have to take the airbox off and push the butterfly by hand to get it to fully open, that's why you get such a low full throttle voltage. If you do adjust it, reset the ecu. I adjusted mine and revs jumped to 4k! had to reset the ecu then give it a couple days driving for it to settle

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Tue May 19, 2015 3:51 am

Tosh21 wrote:Bear in mind its fly by wire. You have to take the airbox off and push the butterfly by hand to get it to fully open, that's why you get such a low full throttle voltage. If you do adjust it, reset the ecu. I adjusted mine and revs jumped to 4k! had to reset the ecu then give it a couple days driving for it to settle

cheers, once i get her on the road i'll reset the ECU again

but as you point out, resetting tends to see the RPM spike high, not low :(

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby RS Tom-Hundred » Tue May 19, 2015 10:23 am

That is true. Like I said in the thread on NZ site, mine revs high at idle when battery is reconnected. But looking at your TPS, there is no yellow paint on it so maybe it has been moved at some point? This might affect what the base idle is before the learning has taken affect after driving. Although Tosh and I both say they idle high afterwards, they are different with his at 4k and mine at 2k so maybe that is something to do with individual setups and maybe yours will idle low before it is driven more.
The only thing that is a bit odd and doesn't support this though is the fact it was driven back when you bought it and seems to be the same still. But need to drive it around a couple of days after you have the docs sorted to rule that out now you have done the MAF cleaning etc :)

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby SilTezza » Wed May 20, 2015 2:44 pm

try calibrating the ecu again.. i use tech stream software to reset mine..

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Wed May 20, 2015 5:55 pm

SilTezza wrote:try calibrating the ecu again.. i use tech stream software to reset mine..

Hi Sil,

I don't have anything for editing the ECU unfortunately, just a peasant-tier OBD2 scanner (and it's stock ECU so not sure how much I could edit electronically?)

As Tom says, perform a reset and drive it for a bit and see what it learns.

I've new plugs/oil/filter to go in and I'd also like to check the integrity of the coilpacks - as mentioned before, the engine does splutter when each of them is removed, but that isn't to say that one of them is duff. Anyone know how?

Also, i thought it was just exhaust, but the car has the acoustic characteristics of a diesel - anyone know what this might be indicative of?

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby RS Tom-Hundred » Thu May 21, 2015 9:54 am

By the way, I found that following the ECU reset procedure on NZ club (pulling the fuses) didn't work on mine and so I generally leave the battery disconnected overnight instead.

I'd also be interested in the coil pack test procedure (just as an extra health check). I know one was replaced in previous ownership as he told me and I have the receipt.

wenguin wrote:Also, i thought it was just exhaust, but the car has the acoustic characteristics of a diesel - anyone know what this might be indicative of?


Has it got the original dual mass flywheel fitted or a lightened one? The OE ones can give shakes but I find that my car (with lightened solid ally flywheel & TRD clutch kit) has the same diesel noise at idle. If you put your foot on clutch/put it in gear does it go away? Mine does and find myself sat at traffic lights with foot on clutch a tiny bit (maybe 5mm-10mm) so its not embarrassing! Think its a characteristic of these engines tbh!

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Thu May 21, 2015 1:41 pm

RS Tom-Hundred wrote:By the way, I found that following the ECU reset procedure on NZ club (pulling the fuses) didn't work on mine and so I generally leave the battery disconnected overnight instead.

I'd also be interested in the coil pack test procedure (just as an extra health check). I know one was replaced in previous ownership as he told me and I have the receipt.

wenguin wrote:Also, i thought it was just exhaust, but the car has the acoustic characteristics of a diesel - anyone know what this might be indicative of?


Has it got the original dual mass flywheel fitted or a lightened one? The OE ones can give shakes but I find that my car (with lightened solid ally flywheel & TRD clutch kit) has the same diesel noise at idle. If you put your foot on clutch/put it in gear does it go away? Mine does and find myself sat at traffic lights with foot on clutch a tiny bit (maybe 5mm-10mm) so its not embarrassing! Think its a characteristic of these engines tbh!

Yea I prefer the battery pull method myself, no messing about with fuses if I can avoid it.

It's an auto and I believe it's standard clutch and flywheel setup. The exhaust is loud as feck (even louder than my loud performance backbox on my mr2 3sge) - I'm think it's been gutted or modified in some way cos it's seriously noisy at high revs! Actually, on the OBD2/tach difference, I got a reading of over 6200 from OBD2 for revs just to see if it would (think it was 6300) as I understand 6200 is the redline for autos. So def something wrong!

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby RS Tom-Hundred » Fri May 22, 2015 10:39 am

Not sure the redline is that low on the auto or not tbh. I know that the power is a bit lower than the manual cos of the differences in the head and that the torque is the same but comes in lower on the auto but think redline is only marginally lower.

This is actually off Wikipedia but this is what it says:
"The MT version that came equipped with the J160 6-speed manual transmission featured larger diameter titanium intake valves measuring 35mm, larger exhaust valves measuring 29.5mm also made from titanium, a larger 33mm bucket and a compression ratio of 11.5:1. It made 210 PS (154 kW; 207 hp) at 7,600 rpm and 22.0 kg·m (216 N·m) at 6,400 rpm.

Compared to the MT version, the 5-speed AT version came equipped with the A650E Tiptronic automatic transmission and had a lower compression ratio of 11.1:1, a less aggressive cam profile, smaller steel-alloy valves and smaller 31mm buckets. This engine made 200 PS (147 kW; 197 hp) at 7,000 rpm and 22.0 kg·m (216 N·m) at a considerably lower 4,800 rpm. Externally, the AT model can be identified by differences in the wiring loom and the lack of an acoustic blanket on the intake plenum."


So max power is at 7k rpm but max torque is at 4.8k rpm on the auto :)

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby wenguin » Fri May 22, 2015 1:50 pm

Odd, as you can see in the photo of my cluster, the redline appears at about 6250 - I assumed you couldn't go into it due to rev limiter?

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Re: Low idle when warm - MAF and TB cleaned - TPS broken?

Postby Soiled » Fri May 22, 2015 7:43 pm

That's an AS200 cluster. Redline, and fuel economy meter give it away. Which would explain the difference in the ECU and the cluster rpms.


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