Idles high, dp diaphragm not being closed properly

[Bri7man]

Alright so this has been going on since as long as I've had the car.. It's finally bugging me enough to get down to business, I knew it would be finicky, I gave it a go, could not come to a solution, now asking for others thoughts.

Issue: high idle around 900rpm's - settles down to 700rpm on start up once warm but after giving it any amt of gas randomly/rarely/sometimes/or never returns back to 700rpm on any given drive. Bliping the throttle sometimes fixes it until I use the throttle again.
There is no constant.

Issue: seems to take +-3 or more seconds to return to idle(whatever idle decides to be...)

What I've done is followed the TSRM EC8 and checked out the DASH POT system.

Here's what I found: holding throttle valve at 3000rpm, then pinching vac line from DP Diaphragm to VTV, idle drops from 3000 to 1200(bad) letting go then drops down to idle in +-3 seconds to 700rpm(repeated 2 times with same result). I backed out the DP adjusting screw about 2 turns and then dropped from 3000 to 1800(close), idle still taking +-3 seconds to settle at 900rpm. Backed out the screw another turn and still returns to 1800, +-3 secs to 900rpm.

Note: TPS is .2V at .50mm and 4.5V at .90mm
Note: the VTV and filter is NEW from Toyota

Issue as stated above that I would explain and could possibly the cause: Majority of the time once given any amt of throttle the gap between the throttle stop screw(which was not tampered with) and the lever has a gap. Now if close this gap with my finger(takes the force of just more then the weight of my finger) the idle drops to 700 and stays there until I open the lever again. WALA!

SO... is my DP Diaphragm not closing all the way, is it sticky inside? Can this part be replaced?

What do you guys think?

---------- Post added at 04:51 PM ---------- Previous post was at 04:41 PM ----------

AH, it is!! http://www.cygnusx1.net/Supra/Library/EPC/291420/catalog.aspx?F=2211&P=2 If anyone thinks the DP Diaphragm is not the case please lmk.

 

[Bri7man]

bumparoo

 

[Dan_Gyoba]

Only thing that sounds familiar is that if the IDL is not working on the TPS, it won't cut fuel when the throttle returns to idle, so the RPM doesn't drop as fast to the fuel return point. Doesn't explain the high idle though, since that shoud be controlled by the ISC. (That might be sticky though.)

 

[Bri7man]

Funny you say that because I actually checked those both this morning.

IDL - E2 @ .5mm = .14k ohms
IDL - E2 @ .9mm = no reading

ISC resistance between terminals is 23.4 ohm a bit high but within spec(probably from old age), check valve is squeaky clean.

Any ideas?

 

[3p141592654]

I would suspect the throttle valve itself is hanging up. Have you cleaned it and checked its action for any roughness? Same for the throttle linkage.

 

[Bri7man]

I thought it could be that also, but the throttle valve closes perfectly with no gap between the lever and stop screw when the car is off. I then checked out the throttle cable and loosened it a bit to be completely sure it wasn't being hung up on anything. I'm going to look at the check valve in the iscv today and make sure the spring behind the rubber is in good condition.

 

[Bri7man]

I forgot to mention, my engine also dies at high boost after I push in the clutch, it sort of sputters like it's trying to recover but drops below 500rpm and then dies if I do not either give it some gas or shift gears. I'm thinking this is related to the problem at hand.

 

[Devin LeBlanc]

Do you have a blow off valve that is venting and not re circulated?

 

[Dan_Gyoba]

That's exactly the sort of thing that happens with a BOV blowing metered air to atmosphere. It could also be symptomatic of a boost leak.

 

[Turbo Habanero]

I know every one say that that's what happens when you have a Vented BOV.. But mine never stalls or has the problems.. guess im just lucky

 

[Bri7man]

It's not vented it's a stock BOV, but yes, I shall check it!

 

[Bri7man]

I tried blowing through my BOV as hard as I can and I couldn't. There was some oil in the vac line that goes to the BOV, seems to be spraying lightly as there is some residue on the outside of the hose too.

My cps wire resistance was out of spec and intermittent so I replaced the wires from the rubber seal to the connector today and it dropped the resistance just below max spec and with no intermittent connections, although rpm's still dropped to around 400rpm's after high boost (although I didn't get many in) and idle still high and slow returning.

I'm going to look more into my ISCV tomorrow as I didn't get time today. My cps issue today caused my car to die on the highway and I had already called for tow, but by then I got it running again and drove home.

 

[Bri7man]

STILL have not sorted these issues.. I cleaned my iscv valve(wasn't very dirty), I cleaned my bov thoroughly and removed a good amt of cooked oil from prev owner inside. I switched to my other TPS and calibrated by voltage and the problem STILL exists! In fact this other TPS made the issue worse, the idle would not go down to 700rpm even WITH throttle blips now! To make it even worse, I shut off the car and then tried to start back up and would not start, I was filming it while it happened:


I'm wondering if my iscv check valve is okay? Does the spring wrapped around it look normal? It seems to close the rubber against the grill just fine..

 

[Bri7man]

My current setup: dashpot returns faster than than the next clip I will show, although does not extend all the way, I can pull it out another 2mm
[video]http://s373.photobucket.com/albums/oo175/Bri7manx/Idle%20issues/?action=view&current=VID-20110921-00053.mp4[/video]

Random TB I came across: extends further than the first dashpot clip above, although returns much slower.
[video]http://s373.photobucket.com/albums/oo175/Bri7manx/Idle%20issues/?action=view&current=VID-20110921-00052.mp4[/video]

I'm thinking buy a new one from Toyota along with a TPS.. Sick of troubleshooting switching from one bad part to another, I bought 4 used TPS's also each have a different personality after adjusting by voltage, none of them functioning the proper way. Owning a 7M in a 20yr old sports car sure is expensive.. :nono:

 

[3p141592654]

The check valve is only used to prevent boosted charge from being recirculated back to the turbo inlet, it will have no impact on your idle problem.

My car's dashpot no longer offers any resistance, but I have not experienced any idle issues with it in that condition.

The TPS IDLE switch needs to be working properly to initiate idle control. From the postings, it seems you have adjusted this correctly on multiple instances, so I cannot see that being the problem either. From what I see in the ECU code, the throttle position input is not used for idle control at all, and is mostly used for correcting throttle transition events.

To rule out the idle program, warm the car up and get it idling correctly, then unplug the ISCV. The ISCV will now be fixed at the correct airflow for a warm idle. The ECU won't know any better as it has no diagnostics on the ISCV. Go for a drive and see how the idle behaves. Whatever you observe will not be due to the ISCV being adjusted by the ECU.

The hot restart issue may be due to your FPU VSV not being operational, and then would be unrelated to the idle problem.

I would suggest a hard look downstream of the throttle valve for a leak. That could explain the crappy post-boost idle quality, and possibly the elevated idle, although it normally impacts idle quality more than idle speed.

 

[Bri7man]

Hmm but with each TPS the idle is different, one tps makes the car idle at 1400, one at 1100, one at 900, and one at 600 that acts indecisive. This is with only the tps as a variable.

Appreciate it, ill try that out.

 

[JD&Co]

try a different ecu

 

[Bri7man]

O_O

 

[Bri7man]

Okay! Idle Issue solved!

I had previously modified a TB by switching the JDM linkage to a US TB. Keep in mind, one version of the 7mgte TB does not have the mounting for the spring that extends from the TB mounting and helps pull the TB valve shut. (Not sure which it is, too many variables I've changed)

So I took a US TB I acquired, switched my JDM linkage to it and added the spring which was all that was needed to properly let the TB shut on its own completely.

Okay, here's pics of everything I'm talking about so you can see. Apparently there are 3 versions of 7mgte TB for the supra.

The TB I modified that I was having trouble with:

The US TB I acquired:

After cleaning the US TB I acquired and switched the JDM linkage and spring to:

It finally sort of idles correctly!! I think... I'm not sure, I've never really seen it idle this well before. It does take 6:50 to get it to hot idle position though..

Here's a vid, I'll let you be the judge. (I need some input to know for sure)
It takes 6:50 to get hot enough to where the idle drops to where I presume is normal, no need to watch the full vid, you'll get the idea, just jump forward to save some time.
[video=youtube;N41jWLpEhw8]http://www.youtube.com/watch?v=N41jWLpEhw8&feature=player_embedded#![/video]

 

[3p141592654]

That seems normal now. In your post #6 you claimed it was all working properly?