free hit
counters
High idle but can blip the throttle and it goes back down - Induction/Turbo/Chargecooler/Manifold/Exhaust - The Lotus Forums Jump to content
Techspy

High idle but can blip the throttle and it goes back down

Recommended Posts

I am having a high idle (about 1900rpm) when I stop at times and can blip the throttle and it goes back to normal. I removed my throttle jack capsule but the problem remains. I checked the throttle cable and connections and did not see anything that would explain this. So is it more likely that it is an ECU issue? Every time I get home and back in the driveway I am hoping it is high so I can connect the laptop and espritmon but it is never an issue when I get home. I guess I will need to keep the laptop with me. Should I just go ahead and reset the IAC?

 

Thanks

Share this post


Link to post
Share on other sites

Upgrade today to remove Google ads and support TLF.

What does the Throttle jack capsule do, as occasionally when I start my car I get very high idle and I can see the throttle moving in and out on its own, and the revs go up and down with the movement, idle is approx 2000rpm, if I turn the car off and restart the problem disappears, could this be linked to my fuel smell under phard acceleration?

Share this post


Link to post
Share on other sites

The capsule works in tandem with the exhaust back pressure valve. The latter slows down the flow of exhaust gasses so as to heat the catalytic converter more quickly, that means the engine would then run at a slower speed so, to overcome slow idling (and so stalling, uneven running etc) the IAC increases the air and fuel flow to increase the engine speed back to the desired rate (just as pressing the throttle would).

Share this post


Link to post
Share on other sites

Yeah there have been some reports of the throttle jack capsule causing an erratic idle, especially if the EBPV is removed. It didn't fix my problem however.

 

Ok, here are the butterflies, any opinions?

post-436-0-58940500-1367068920.jpg

post-436-0-46548900-1367068929.jpg

post-436-0-69585700-1367068965.jpg

post-436-0-96627100-1367069007.jpg

Edited by Techspy

Share this post


Link to post
Share on other sites

Ok so I went ahead and cleaned them and went for a drive. It seems to be better but I got a Freescan log from the ride and am seeing some wired stuff. I will be opening a thread in the Freescan forum.

Share this post


Link to post
Share on other sites

Hi John , I experienced the same problem with my Esprit a couple of years ago. I have Freescan and after looking for abnormal values I changed both the Idle Air control valve and the Throttle Position Sensor. I set up the TPS as to the manual reading the value in Freescan. This solved it for me. What I have noticed you can get a High idle speed on cold start and blipping the accelerator brings it down.

The ECU does raise the idle speed as the car starts to move  , it uses the wheel speed sensor in the rear wheel. I think it's to stop you stalling if your riding the clutch on idle. It also raises it if you turn on the air con

 

 

Mark

Share this post


Link to post
Share on other sites

Thanks for the info Mark. I didn't see your response until now. I just posted new info in another thread. Does it still sound like the issue you had? Please see below.

 

------------------

I am still having the high idle. Here are the details;

- It only starts after driving awhile.

- When it first starts, I can blip the throttle and it goes back down but after a few more minutes, blipping the throttle wont make it go back down and sometimes makes it raise a bit.

I recorded Freescan and found the following;

- Initially it shows a TPS of 0 and I can blip the throttle and it goes back down.

- After blipping doesn't help, I can see that the TPS is showing 1 instead of 0.

- When I got home it was still doing it so I checked and found that the throttle cable was not taught and had enough slack and was not holding the throttle open.

- I pushed on the butterfly lever that the throttle cable is connected to, trying to push it toward the closed position but it didn't change the high idle and the TPS stayed at 1.

- I turned the car off for about 5 seconds and started it again and the idle was perfect and showed a TPS of 0.

- I recently disconnected the battery for a day to reset the ECM tables but it is acting the same was as before.

On other note, since I have set my throttle bleed valve to get the IAS down to where it should be, when I start the car and let it warm up, I get a pretty high idle for about a min then it drops down. It did not do that before adjusting the bleed valve. I am guessing this is the way it should be now.



Also, these are the listed cross reference parts for the TPS and IACV. Does anyone know for sure these are correct?

 

http://www.autozone.com/autozone/parts/_/N-9gsmgZ1z141xg?itemIdentifier=3082_0_0_

 

http://www.autozone.com/autozone/parts/Idle-Air-Control-Valve/Duralast/_/N-9gsofZ1z141xg?filterByKeyWord=17111826&fromString=search&fromType=oem

 

Thanks!

Share this post


Link to post
Share on other sites

Whow, the Lotus TPS is $200 and the IACV is $80. Sure hope someone can say whether or not these cross referenced parts will work.

Share this post


Link to post
Share on other sites

I'm looking at your logs.  Don't buy anything yet.  So far your IAC and TPS look to be working fine.

 

in file 1 I see the instance where the idle was high after a good run at speed, and at that same time you have an increase in injector duty cycle and a decrease in MAP, compared to other times where you were at 0mph road speed.

Of course the MAP decrease is due to the higher idle.

 

It is interesting that you aren't getting a Code 35 since your idle speed is ~400rpm higher than desired idle at times.

 

I see in file 2 that your IAC might be adjusted a bit low.  It's getting down to 20 at idle, which shows that it is trying to lower the idle speed.  You may have in air leak in the manifold.

Share this post


Link to post
Share on other sites

Man I double checked for air leaks when I got home with the car running while at high idle. I used starter fluid on all joint locations and got no idle change. The engine was hot so I didn't spray too much but enough I think. But why would it be perfect again after turning the car off for 5 seconds and then starting it back up?

 

Is there a cleaning or resetting procedure for the IACV or TPS?

Share this post


Link to post
Share on other sites

Is the IAC reset when you do an ECU reset (battery disconnected for a day)?

Share this post


Link to post
Share on other sites

nope.  ECU reset works to clear the BLM, the memory locations where the EC has tried to learn what fuel trim to use for various conditions.

 

Resetting the IAC just forces the stepper motor to move to extents in both direction, so it can figure out what it's range is again, and then it finds the "park" position and sets that to 170 clicks IIRC.  Do not do this while the engine is running, and DO NOT turn the engine off for more than 10 seconds after resetting the IAC, or else it can screw up the learning process.

Share this post


Link to post
Share on other sites

Thanks for the info. To make sure I understand, turn the ignition on but don't have it running. Reset the IACV within Freescan, then start the engine within 10 seconds or do NOT start the engine within 10 seconds? Kinda confused what you mean by "and DO NOT turn the engine off for more than 10 seconds after resetting the IAC". I guess it would be best to reset it, wait xx seconds then turn the ignition off?

 

Thanks for the info.

Share this post


Link to post
Share on other sites

Ignition on, engine off, zero rpm while resetting IAC. Do not turn off the key for at least 10sec after resetting the IAC in Freescan.

Share this post


Link to post
Share on other sites

Ah ok, got it. Thanks.

 

Anything else stick out in my Freescan logs?

Share this post


Link to post
Share on other sites

Data looked fine. 

 

The only other thing I can think of is that the throttle cable is too tight once the engine gets hot, since it grows.

 

I actually worked on an 89 that would idle fine until the engine got warm and then the engine would soar anytime you pushed in the clutch.  Turned out the throttle cable was slack when cold but too tight when warm.  So I re-adjusted the throttle cable stop while the engine was hot (and not running) so that I still got 0-100% in Freescan.  Then after that the hot idle was fine.

  • Like 1

Share this post


Link to post
Share on other sites

I though the same thing about the cable too but checked it while it was idling high and it had some slack. I even pushed on the butterfly mount that the cable connects to and it didn't move and the idle didn't drop. I think the biggest clue is that it was perfect after I turned it off for 5 sec and restarted it.

 

I will post back after resetting the iac.

 

Thanks again.

Share this post


Link to post
Share on other sites

Well I reset the IAC in Freescan (at least I clicked the button with the ignition on but engine not running. Is the IAC value supposed to change on the Engine Data page while it is resetting? It didn't change when I clicked reset).

 

Went for a drive and still doing the same thing. Really frustrating....

 

I logged this drive with Freescan but saw nothing different. I guess I will go ahead and order an IAC and TPS sensor. Does anyone know if the cross reference parts I listed above will work???? Otherwise I guess I will be spending 3 times as much for the Lotus parts.

 

Thanks

Share this post


Link to post
Share on other sites

Chuck Freescan in the bin and get a datalog from Espritmon or TunerPro - you'll get more usable (and accurate!) data. Also, don't get hung up on using Freescan to reset the IAC, the ecu does this itself during running to check it's zero position

Share this post


Link to post
Share on other sites

Thanks for the input but Freescan is just what I am familiar with. I did just go for a drive with Espritmon connected and I didn't get a high idle at all. Before leaving the house I did play with the idle in Espritmon but put it back where it was to start with. Probably just coincidence. BTW, with Espritmon you have to run a command line command to get it to record correct?

Share this post


Link to post
Share on other sites

The no command line interface requirements for Espritmon but there is a text file called "lotus.cfg" that needs editing to swap between monitoring and playback modes.

Share this post


Link to post
Share on other sites

Freescan may not be perfect, but I can easily graph the data and quickly compare 2 data sets.  I can compare a known good running Esprit sample to a problem sample and spot the differences.  I have Excel template files set up to just drag and drop the data, and all the graphs are updated.

 

With Espritmon, I would have to watch a playback of the data and try to spot the moment when something went wrong.  It can take a quite a while to analyze 30min of driving data with Espritmon.

 

I have asked Erik for information to allow me to graph Espritmon .asc files in Excel.

Share this post


Link to post
Share on other sites

Well, Lotus TPS and IACV ordered. Gonna be pretty ticked if this $300 of parts doesn't address the issue but I really don't know what else to try now.

 

Thanks for all the help. I will report back.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


×