s54 e36 hot start issue, goes into open loop?

[Masterchoans1]

Not sure if I'm posting this in the right place, but I'm having a little issue with hot starts. For example, ill start my car in the morning and it will have the typical cold start in open loop. Then ill drive to the store, (gets to operating temp) for example and shut it off. When i get back to turn it on, it'll start rough like the car has been left overnight and it almost feels like its in open loop again. It starts right up its just rough, like its cold(but its not) for 20 secs to a minute.

Cliffs: Car will be warm when i go to start it, but goes into open loop thinking its cold.


I'm leaning towards a faulty coolant temp sensor, but its new..... so not sure. anyone have any ideas? thanks.

[gpeterson]

Have you read codes or run any other diagnostics? If you suspect coolant temp/open loop issues a simple OBD2 reader can confirm, but I'd suggest anyone with a swap have INPA on hand.

[Masterchoans1]

Have you read codes or run any other diagnostics? If you suspect coolant temp/open loop issues a simple OBD2 reader can confirm, but I'd suggest anyone with a swap have INPA on hand.

All I have done so far is checked for codes, and it was clear. Don't have INPA.

[gpeterson]

All I have done so far is checked for codes, and it was clear. Don't have INPA.

Using an OBD2 reader? It should tell you coolant temp & closed loop status as well.

[Masterchoans1]

Using an OBD2 reader? It should tell you coolant temp & closed loop status as well.

I have a generic one, doesn't tell me much.

I just swapped in a new oem coolant temp sensor and no change. I'm pissed.

[Masterchoans1]

Okay just did a little more digging. If the car is at operating temp and I shut it off, but turn it right back on .. It starts up great with no symptoms. If I wait like 5 minutes then I'll get the shitty hot start.


Also, i dowlonaded an obd2 app on my phone and temps are reading good when I turn it on or off . They're not jumping or anything .


One thing though, o2 sensor 1 is good, voltage is ranging from .1 to .8 . Sensor 2 is not so good, it's set at .46 and it's not moving at all. I'm either thinking it's bad or I have to check wiring OR the app doesn't read sensor 2 and only reads one of them .

[gpeterson]

One thing though, o2 sensor 1 is good, voltage is ranging from .1 to .8 . Sensor 2 is not so good, it's set at .46 and it's not moving at all. I'm either thinking it's bad or I have to check wiring OR the app doesn't read sensor 2 and only reads one of them .

There are 4 O2 sensors - the pre-cat ones should swing high/low regularly (every second or so) during closed loop. The post-cat ones will fluctuate less.

[Masterchoans1]

There are 4 O2 sensors - the pre-cat ones should swing high/low regularly (every second or so) during closed loop. The post-cat ones will fluctuate less.

Yep I know . I don't have any post cast sensors. Only pre-cat. According to the app, one of the pre cat sensors is not moving at all. Stuck on .46 which is no good. But then again not sure if it's just the app. I'm gonna try to use another obd reader . Any other ideas ? Can't really come up with anything else .

No fault codes, runs perfect otherwise

[gpeterson]

No OBD2 fault codes is not the same as no codes in INPA. I'd recommend finding someone with INPA or something else that reads proprietary manufacturer codes.

Do you have a vagcom cable? They are under $20 and will work fine with INPA on just about any PC for some (but not all) modules on your car.

[Masterchoans1]

How do i even get INPA? Sorry I'm not very familiar with it. I tried searching on goggle and it's taking me to download sites but none seem to work..

What cable would be compatible? I'll buy the correct one if that's what it takes. I don't have the round 20 pin under the hood.

[purduinaM3]

Vagcom works through OBD2. I have a vagcom cable that we can use if you can get the INPA software on your laptop. I'll bring my Snap On Verus Edge home tomorrow and we should be able to figure it out with that, I'll shoot you a text to see when you're around.

That dead O2 isn't helping anything, I would plan on changing that out regardless.

[Masterchoans1]

Vagcom works through OBD2. I have a vagcom cable that we can use if you can get the INPA software on your laptop. I'll bring my Snap On Verus Edge home tomorrow and we should be able to figure it out with that, I'll shoot you a text to see when you're around. That dead O2 isn't helping anything, I would plan on changing that out regardless.

Sounds good Bobby! Just let me know.

Yeah I want to double check about that o2 though, I don't know about this obd2 app.

[=BA=]

It's also easy to just check voltage of the second O2 with just a voltage meter, just measure on the pins under the coil cover.

If the O2 is bad though the rear bank should never go to closed loop. As far as I know they work independent. On my S54 bank 1 will register closed loop before bank 2 registers closed loop in the engine is warming up.

[Masterchoans1]

Me and Bobby hooked it up to his solus. Both O2 sensors check out okay, temp sensor looks like it's reading good too. Only codes were misfires in bank 2, but that's all.. Nothing very specific. Car is still doing it, not sure what else to try, car feels great and pulls nice besides the starting. Anyone have an idea ?

[TH3 Shifty]

ICV getting stuck or not functioning correctly

[Masterchoans1]

Icv was cleaned when engine was out of the car.

The car will start normal if I shut lt off and start it again immediately.. If it's more than a few seconds then it'll do it

[purduinaM3]

I think its the fact that you have no rear O2 sensors. The DME is trying to heat up the cats because it can't read any voltage coming from the rear O2's. I had them turned off in my DME by my tuner, you may need to do the same or maybe look into O2 sims.

[Masterchoans1]

I think its the fact that you have no rear O2 sensors. The DME is trying to heat up the cats because it can't read any voltage coming from the rear O2's. I had them turned off in my DME by my tuner, you may need to do the same or maybe look into O2 sims.

Yeah I was going to mention that, I remember you telling me. I'm gonna try sending my ecu files to gpeterson so he can check what's been turned off and what hasn't.

[Masterchoans1]

Still does it after dyno tune at TTFS. Frank said it could be because of lazy o2 sensors. Problems happens at start up but goes away after o2 sensors start reading. Any other suggestions ?

[M52 POWER!]

You can code tables that determine at what temperature it goes into "cold start mode" and for how long, was this modified?

[Masterchoans1]

Thanks for the reply. Not sure if this was altered or not. It has now been through the hands of 3 different "tuners", and i guess they haven't looking into that. I just baught the o2 sensors, so I'm gonna go ahead and see if that does anything. But you may be onto something here ...

[Masterchoans1]

UPDATE: new bosche pre cat o2s are in but no change. Anyone have anymore suggestions before I just take it to a shop ?

[TH3 Shifty]

Ceck the sensor harness for breaks in the wires

[Masterchoans1]

I feel like that would throw a code though. Car has no CEL, no stored codes at all and runs very strong

[Masterchoans1]

Frank said it could be the vanos, what do you guys think ? Vanos has new solenoid