Help! Open.Closed Loop, Please comment!

[KRMusher]

Hello All,
I have changed both front (pre-cat) O2 sensors and done a 90 k service. Am about to turn 100k miles on this 96 Disco 1 SD, US version.
I have a scan gauge and read the sensors direct. Here is the issue:

Once the engine is completely warmed up, including the exhaust manifolds, it switches to open loop operation. If I turn the engine off 10 seconds it goes back to closed loop but than switches again to open loop when fully warm again. So far I have done all my own work with friend's help.

LR mechanic says: do a 30 minute reset of the "adaption" with the testbook to get the computer back to original specs. I think this is reprograming the PROMS.

LR service writer says: replace coolant temp sensor since it goes to open loop only when fully warm.

Any opinions welcomed!

Already posted longer version under Open/closed Loop Coolant Temp Sensor but nobody responded! PLEASE ANY ONE WITH COMPUTER OR obdII EXPERIENCE LET ME KNOW IF THESE DEALER SUGGESIONS MAKE ANY SENSE.


I have increased mpg on a Jeep Grand Wagoneer 5.9L V-8 by 90% and want to do the same or better on my Disco, but can't proceed until I have normal operation as a baseline, then can post my progress!!

[roverX]

Originally Posted by KRMusher

Hello All,
I have changed both front (pre-cat) O2 sensors and done a 90 k service. Am about to turn 100k miles on this 96 Disco 1 SD, US version.
I have a scan gauge and read the sensors direct. Here is the issue:

Once the engine is completely warmed up, including the exhaust manifolds, it switches to open loop operation. If I turn the engine off 10 seconds it goes back to closed loop but than switches again to open loop when fully warm again. So far I have done all my own work with friend's help.

LR mechanic says: do a 30 minute reset of the "adaption" with the testbook to get the computer back to original specs. I think this is reprograming the PROMS.

LR service writer says: replace coolant temp sensor since it goes to open loop only when fully warm.

Any opinions welcomed!

Already posted longer version under Open/closed Loop Coolant Temp Sensor but nobody responded! PLEASE ANY ONE WITH COMPUTER OR obdII EXPERIENCE LET ME KNOW IF THESE DEALER SUGGESIONS MAKE ANY SENSE.


I have increased mpg on a Jeep Grand Wagoneer 5.9L V-8 by 90% and want to do the same or better on my Disco, but can't proceed until I have normal operation as a baseline, then can post my progress!!

Post this on www.lrrforums.com. You might get a better response there. It is more of a tech forum.

[Hank]

The coolent temp sensor sounds logical. But, shouldn't the system be in closed loop until the engine reaches 190 degrees?

What thermostat are you running? Is the engine even reaching 190??

[KRMusher]

Originally Posted by Hank

The coolent temp sensor sounds logical. But, shouldn't the system be in closed loop until the engine reaches 190 degrees?

What thermostat are you running? Is the engine even reaching 190??

I am running a 195 deg f thermostat by choice. The engine is reaching this temp.

An OBDII system runs in open loop until the oxygen sensors are hot enough to provide the ECU with the inputs it needs to run closed loop. Open loop is preset rich parameters to make sure it runs when the ECU does not have proper sensor inputs. It results in very poor gas mileage.

Have you heard of LR resetting the "adaption" with their testbook computer? This is new to me. Thank you for your interest.

[Rovin4life]

We can reset adaptions with T4, but it wont reset anything to do with the thermostat,

In order to reset all monitors on a Gems model Disco 1 you need to do the following,

vehicle has to be less then 60 deg Celsicius, Preferably cold.

1. Key on for 30 seconds

2. Let vehicle idle for two minutes

3. two light accelerations from 0- 35mph

4. two medium accelerations from 0-45mph

5. two heavy accelerations from 0-55mph

6. drive without cruise for eight minutes at 60mph

7. drive without cruise for five minutes at 50mph

8. drive without cruise for two minutest at 35 mph

Do not drop below set mph and do not use cruise. Dont let your foot of the gas as well.

9. idle vehicle for three minutes

and hook up to check to see if monitors are ready.

Running a hotter running thermostat can make the engine run rich.

oh and Bosch Systems are different monitor resets.

[KRMusher]

Originally Posted by Rovin4life

We can reset adaptions with T4, but it wont reset anything to do with the thermostat,

In order to reset all monitors on a Gems model Disco 1 you need to do the following,

vehicle has to be less then 60 deg Celsicius, Preferably cold.

1. Key on for 30 seconds

2. Let vehicle idle for two minutes

3. two light accelerations from 0- 35mph

4. two medium accelerations from 0-45mph

5. two heavy accelerations from 0-55mph

6. drive without cruise for eight minutes at 60mph

7. drive without cruise for five minutes at 50mph

8. drive without cruise for two minutest at 35 mph

Do not drop below set mph and do not use cruise. Dont let your foot of the gas as well.

9. idle vehicle for three minutes

and hook up to check to see if monitors are ready.

Running a hotter running thermostat can make the engine run rich.

oh and Bosch Systems are different monitor resets.

Very interesting... can you define adaptions and monitors for me?

When I put in the 195deg f thermostat I was replacing a 192 running in the low 180s.
I also allow hot air to the intake and my mpg went from 8 to 12. If it would stay in closed loop I think I would actually have good mpg.

What do you think is causing it to go open loop?
TU
KRMusher

[KRMusher]

Getting back to this now:Had a chance to get the "adaption" reset for no charge! (this am) (6-20-06)

Results: no CEL or fault codes since, (20 miles?) Still switching to open loop when hot. Previously noticed lack of power at expressway speeds and 90 deg f temps.

Conclusion: hot air intake at these hi temps and speeds is reducing air density to less than the engine requires. (mile high plus elevation)

Action: closed off hot air intake a fair amount, reopened to cold air, noticed no power loss, Less often switching to open loop.

Also had cleaned MAF and throttle plate and doing some sustained high revving under load to decarbon valves, already used BG chemical.

NEXT: will take suggestion re grounds and sensor connections and VOM test of sensors, otherwise I don't have a clear direction to stop it switching to open loop...

Any comments or ideas appreciated!