Stumble/hesitation on heavy acceleration

[Brit-Car-Nut]

Yes but mine is not chipped, it just has a stock S2 ECM.

The S2 ECM is a closed loop/CAT unit so that should work. Around 50% of the SE models have the wiring for the O2 sensor but the WIKI will explain what to check to make sure the O2 sensor is actually connected.

Alan offers an Everest chip for the early non closed loop and a different one for the closed loop with CAT. He even has the basic S2/FED program for those that want closed loop without the boost improvements.

[Giniw]

Well I have always assumed that the previous owner who did the conversion checked that the lambda sensor is wired to the ECU ^^'
I may check it one day ...

[Brit-Car-Nut]

If the O2 sensor is not connected you will get lots of faults with the S2 ECM.

Check with SuperChips what program is EWKZ and then if it is a closed loop chip, then test the connections at the O2 sensor. The O2 sensor in the picture doesn't look like a normal Bosch unit so maybe Superchips can help identify what O2 sensor they installed or recommended.

[GeoffSmith]

- the car has been chipped, by Superchips Ltd

The 'Superchip' only inhibits the fuel cutoff safety feature to allow a manual boost control (MBC) to be used. Help on finding the MBC is in the Wiki.

[alan e]

- the car has been chipped, by Superchips Ltd

The 'Superchip' only inhibits the fuel cutoff safety feature to allow a manual boost control (MBC) to be used. Help on finding the MBC is in the Wiki.

Geoff if that's the case the o2 sensor is not doing anything on a SE how is your football team doing

[Brit-Car-Nut]

That is assuming SuperChips didn't use an S2/Fed memcal to start with. If they used a closed loop master and then modified it, then it would be looking for the O2 sensor. Screwing one in the hole and just plugging the connector will only work on the later models that had the extra wiring included. Early SEs will require adding the connections per the WIKI.

[alan e]

Its a 91SE so the easy way to check if its connected to the ECM is to unplug it and see how the engine runs when cold.

[bzguy]

OK, I know something more :

- I checked the spark plugs : gaps were set at 0,8 mm
- I test drove : same thing
- after a couple of km's, I disconnected the O2 sensor, and ... it runs BETTER with the sensor unplugged ! Idle is more stable (where it used to be going up and down a bit between 800-1000 rpm), drive is more linear, no hesitations.

Have only driven it for a short while without O2 sensor, I'll try ElanScan asap.

And I will send an email to Superchips.

[HJ2]

... I thought so...
Time to check the base timing first and persuit from there.

[bzguy]

... I thought so...
Time to check the base timing first and persuit from there.

Euh, how do you do that ?

Honestly, it drives really well without O2 sensor

[Rambo]

... I thought so...
Time to check the base timing first and persuit from there.

Euh, how do you do that ?

Honestly, it drives really well without O2 sensor

Time to check on WikiLEC...

http://wikilec.com/view/Base_Timing

[bzguy]

Thank you, will have a good read

Stupid question : if the car runs fine without O2, how come it does ? And what has it to do with possible timing issues ?

Am I wrong to think that indeed the O2 sensor is faulty because the car runs not as good when it is installed and it does when it's disconnected ?

[bzguy]

I'm awaiting answer from Superchips, but I think I'll thor that chip out anyway ; and I need to check if the O2 sensor is really wired (closed loop thing), then I'll go for an Everest chip, probably the best there is ?!

[GeoffSmith]

Have you found (and removed) the MBC yet?

[bzguy]

With MBC you mean the Manual Boost Control ?

I haven't had a look, I don't even know if there is one. Maybe not, as max turbo pressure is still 0,65 ?

Where should I look ? I know how it looks like, it's on a vacuum line ...

[HJ2]

Post a picture pf the engine bay so we can tell you

[bzguy]

ok, will do when back home

[bzguy]

sorry for late reply, work ... (even during the Easter weekend )

Here a picture of the engine bay :

FullSizeRender 2.jpg

I followed some leads from the turbo, and I found a small electronic device that's connected to the turbo waste gate (vacuum hose ?) :

FullSizeRender 3.jpg

Is this an electronic boost controller ?

I haven't driven the car yet since I disconnected the O2 sensor, I'll try asap ...

I have no news from Superchips

[lotusflasherman]

Is this an electronic boost controller ?

That's the Boost Control Frequency Valve, a standard component on all SE's & S2's.

A Manual Boost Controller is an adjustable air valve that allows a controlled leak in the short feedback hose between turbo & wastegate to delay the opening of the wastegate which is set to operate at 0.65 bar. Neither photo shows where it will be. It's sort of underneath the wastegate. MBC is usually inserted into the hose for 'under bonnet setting', or a T connector can take an additional small bore hose into the car for a dashboard mounted MBC, but you'd probably have noticed that

[bzguy]

hi all, I have some updates, as today I had the chance to take the car for a test drive, attach ElanScan and log some files.

1) the stumble is still there when O2 sensor is disconnected, so my previous assumption was wrong. O2 connected or not, is the SAME hesitation/stumble
2) I ran ElanScan, I attached here the log files (zipped) :
- log file cold-until fans cut in (they cut in exactly at 110 degrees C)
- 2 other log files, short random trips

Can anyone shed some light here ?