5 replies to this topic

[azesprit]

Hello,
I bought a 94 S4 last year and have been working out some of the issues, for the most part she is solid and drives well. The nearest Lotus dealership is over 200km from here and they are not equipped for obd1 so they cannot assist much with driveability issues.
I bought the usb-obd1 aldl cable and have run freescan a few times, the issues are not consistent but I have a few suspicions and was hoping for some insight from the more experienced owners.
The first issue is that the idle has always been very erratic, some days it's 950, 1400, 1700, 1150, etc. Lately when I first start her after sitting even just overnight she's very rough and stalls unless power is added, after she reaches temp she runs fine. Also when I first add throttle she drops rpms and can stall unless I add more throttle so I always need to start with lots of throttle.
The second issue happened just a few times, if I am accelerating to highway speeds I can be in 3rd, 4th, 5th gear, 3.5k-6k rpm I just lose all power. As I come of the throttle a little and back in it comes back.. the more I tried to replicate this it seems that I need to have the throttle to the floor for a couple of seconds for this to happen.

I am also showing a few codes...I think they may be related to this issue and may be corrected once the situation is resolved.

Based on these scenarios I am thinking that I am having issues with fuel/air mix and it could be related to the TPS and IAC, I am attaching 2 logs, one shows the idle from start, the other shows the power drop off at highway speed

Thank You in advance!

-Chris

Attached Files

•  hwy_issues.csv   683.14K   21 downloads
•  lotus_1_1_idle.csv   302.97K   12 downloads

[fjmuurling]

What error codes come up ??

[philip600]

Hi, I had similar problems last year with my S4s, please find link to my post I copied on a recent thread.

http://www.thelotusf...-idle-problems/

Hope this is of some help.
Phil.

[azesprit]

Phil, I have been looking through the thread, looks like a lot of good info!

fjmuurling, I am coming up with codes: 13, 24, 34, 26B

Thanks for the great feedback so far!

[Sparky]

I don't like what your O2 sensor's doing...

[Vulcan Grey]

Christophe-Michel,

In your idle data, your O2 sensor is not working, so that data is useless.

In your Highway data, your Idle valve (IAC) looks good. Your wastegate is not opening at all, so there is a problem there. Your battery volts dip a bit low a few times. Your coolant temps suddenly dip down below normal (stuck thermostat or possible an ECU problem (which makes sense with the O2 and Wastegate issue). In this data you O2 actually looks normal. Your boost is going to max, and you should definitely see the wastegate opening, but it isn't at all. And your ECU thinks you are going rich (BLM vs BLM Cell is trending below 128).

Your codes indicate a possible ECU problem, a short in the wiring, or possibly the ECU having an issue with the Low voltage from the battery/alternator. I would reset those codes, and see if they return.

I would also look for shorts in the wiring or bad grounds. have your battery and alternator tested.