darn 3k rpm stumble

[ragingfool]

i have the whitaker chip on my 90SE and every 100 to 150 miles i have to disconnect my batery to make it go away! i'm thinking of tracking down the ECU power wire and running it thru a circuit that is turned off with the ignition. has anyone done this? any thoughts?
chris
90SE

[techspy]

I have considered that myself as I am getting tired of the 3k stumble too. I have found that it only comes back if I use the a/c. Instead of disconnecting tha battery, and having to reset my radio etc, I use Freescan to reset the tables. I wouldn't be to comfortable resetting the ecu every time you start the car. That may lead to premature burnout of something. I wish we could find out exactly what causes the stumble. I remember seeing that someone put some bleed holes in one of the vacuum lines for the wastagate and that helped. Being that the a/c makes it come back sooner, there must be a way to electronically, or in the code of the chip, fix this problem. I would even be for a chip that doesn't allow "learning".

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

[karmavore]

I was thinking a Boost Controler might solve this issue and smooth out the power curve. Thoughts..?

[Del-Esprit]

One of the chip suppliers could give more info, but I would suggest that restting the ECU into it's learning mode is not that healthy if done too often.

The default figures although near correct would lean towards a rich mixture and retarded ignition for safties sake until better values are run, this is not initself a problem but may mean you have extra issues to solve at a later date.

I have had the 3k stumble on my car since having it and basically work around it as a quirk of the car. I do have a puk chip to try, just havn't got it installed yet.

Overall I wish it could be cured somehow but not holding my breath for a solution that doesn't cause issues elsewhere.

[dr.hess]

I think John:
www.wcengineering.com/
has a chip that has the "learn" mode turned off.

Dr.Hess

[Paula&Marcus]

Hi All,
Yes the 3k stumble can be quite annoying ... but with Andys chip installed you have the correct conditions to virtually completely get rid of that problem.
I spent a lot of time (during the last 5 years ;o) finding out what exactly causes this. Here are the causes, what I believe do create the infamous 3k-stumble:

- chips code itself -> upgrade to Andys chip or #1
- mechanical wastegate setting too low -> adjust it to 0.65-0.7 bar (NOT less)
- O2-sensor is giving a (slightly) too high output (this causes the car run a bit too lean after the learn procedure) -> install a new sensor
- wastgate-capsule-spring a bit too weak -> install a new capsule and/or readjust to 0.7-0.75 bar mechanical pressure (mor than 0.75 bar is NOT recommended)

One or more of these conditions will create the "infamous" 3k stumble to a lower or higher degree ....

Cheers
Marcus (www.PUKesprit.de)

[techspy]

Thanks for the info Marcus. FYI, I have the high torque chip and that did help, but it didn't completly get rid of it. I will try your other suggestions. Any idea why it comes back sooner when using the a/c?

John
94 S4

[Paula&Marcus]

Hi John,
Ahhhh good point .... when it comes back sooner with the A/C ON you might have the O2-sensor-reading-too-high problem !

Did you also notice a slightly unstable idling and/or a slightly odd pick up ?

JFYI with the A/C on it is putting some additional load on the engine and may cause some more stumble especially during slightly lean running condition ...

Cheers
Marcus (www.PUKesprit.de)

[ragingfool]

thanks Marcus, i will replace the oxygen sensor. how does one adjust the wastegate setting? it looks like a pressure switch activates the solenoid to open the gate. is the switch adjustable?
chris
90SE

[techspy]

Marcus,
Actually, its no more noticable with the a/c on, but it doesn't happen at all until after I have used the a/c. Meaning, I can reset the tables with Freescan and drive it for months without the stumble. But, as soon as I use the a/c, even once, the stumble is back. I mean even days after I use the a/c, the stumble is there. I can reset the tables and it is gone again..until I use the a/c agaain....strange..
Otherwise, the performance, idle etc are perfect.
John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

>> Edited by techspy on Tuesday 12th October 06:40

[paula&marcus]

Chris,
I´m not sure I understand your question correctly ...

The wastegate gets adjusted at the wastegate-capsule-rod. This rod is adjustable in length. You have to adjust the length to achieve exactly 0.65-0.70 bar mechanical boost pressure. You will find a very good discription of the procedure in the Lotus Service Notes Section EB page 39. If you dont have that I can send it to you.

Cheers
Marcus (www.PUKesprit.de)

[ragingfool]

Marcus,
what is the function of the turbo solenoid valve?
the pressure sensing hose runs thru it.
chris
90SE