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esprit17

Help...so many problems with this engine after rebuild

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Hi All,

98GT 50K (previous cracked piston liner)

I have managed to get OBDII connection working and have the following error codes

P0158 – Oxygen sensor Circuit High Voltage (Bank 2 Sensor 2)

P0106 – MAP/Barometric Pressure Circuit range/preformance

P0154 – Oxygen sensor circuit no activity detected (bank 2 Sensor 1)

I have checked all the connections to the sensors but they seam correct

I have also checked and found that the AIT builds to 45'C and the engine temp of 85'C, the engine then the engine shuts down. I cannot start it again until it cools. AIC temp of 45'C can't be normal?, the car was just started and left to idle, didn't even get to the fan cycle

I have attempted to reset the AIC (TPS 0 - 100% x3 in 20sec) but I cannot hear the AIC resetting. (idles well and drives well but cuts when temp rise to 85'C)

From pressing the accelerator pedal I can only achieve 76% TPS, so looks like it is not set correctly by the dealer

The ECU has been checked over and works fine on an other car ( this was the suggested probable cause of the idle issue by the dealer)

The question is there a quick fix? or inlight of the above should I force the issue with the dealer ( they were unable to address the idle issue (cuts at 85'C)

I just think that there is too many things wrong and feel out of my depth.

Your thoughts would be gratefully received, even just some morale support

thanks LEF

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I am not sure where to start with this collection of problems.

(1) If you've had the dealer work on the car (liners or some of these reported problems) and this is what you got back take it back and have him do the work correctly.

(2) The P0158 error means the the O2 sensor (or circuit) is going open. Bank 2 post cat sensor.

(3) The P0154 error means the bank 2 pre cat sensor is not switching back & forth between rich & lean as required by the Cat.

(4) The P0106 error means the Map sensor or wire is open or failing.

This is too many things to have gone wrong at once! Seems to me some heavy hands have been working on this car. I would start with the MAP sensor the car will never run right until this is correct.

Has the plenum been off? the Idle air controll (IAC) seems to also be screwed up. There are lots of wires under the plenum some go the the IAC.

I have no Idea why the inlet air temperature (IAT) never gets above 45* C, just too many thing wrong!

Wayne

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undo both catalyst on the engine, to have an clear flow of exhaust gasses without any sort of 'backpressure' (Ok, it will be something loud.. :) )

read out the Baro & MAP data wile the cra is not started ..should be both around 100kPa. With engine idling and no boost it is mostly in the 'naturally aspirated' low pressure terms -around 30 to 80kPa .

If you place the IAT-sensor with the nose tip into an bowl of water (avoid contact with the wiring loom & water !) -and you heat up the water, compare the readout on the data monitoring together with an additional placed *home health care* thermometer. If the sensor reads correct (mention that you will see faults on an range above specified temperature grades!) there really is somethin wron in your inlet system... .

O2-faults can mean that you have problems with catalyst internals, or carbon (oil) build ups in the exhaust system, as for wrong engine runnig conditions and so on.. .

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I'm no V8 mechanic on these, but could something be wrong with the bank 2 cat internals? Could the matrix have collapsed?

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if the voltage (as noted above -which swaps between high/low permanently on normal 'medium' range of use [no WOT runs]..) is permanently high -it can mean the mixture is extremely rich. This could coincidentwith irritations in the engine management, or perifery ..as far as I think.

But as said, it's all a rough guess as long as you have not used the simple methods for curing the 918 problems. First step is always inspect and simulate without additional parts. If the engine turns into higher rpm without problems you should inspect the exhaust ystem. If the engine does not run even with the help, the problem is probbably somewere on the engine/ engine control itself...

turn over the o2-sensors from one side to the other, all four sensors are the same. Inspect the sensor cover (the slotted part) for sighns of carbon build ups (for example if the O2-heater function is not active as it should..) it can block the sensor part too.. . So the fault can turn over together with the sensor to the opposite side. You can inspect the exhaust system via the o2-sensor holes, and the connection point between catalyst housing and silencer inlet side

Edited by Günter

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Thanks Guys,

some good things to look at, I've also been discussing this issue with supedavelotus as he had a similar issue a few years back.

Looks like my weekend is planed out like this

Remove the boot to gain better view of the o2 sensors, check for damage, then swap them around to ID whether I have a faulty sensor. If not, trace the cables back to the ECU to confirm cable intergirty. If so, remove the Oz sensor and clean any oily deposits etc. try again, then swap off other car to confirm, then order replacement parts.

Remove the cats and check for damage/ blockage (blank 2 is the left hand side looking from the boot to the engine..right?)

MAP sensor, check that it is reading 30 to 80kPa and receiving the correct volts from the ECU and check connections..anything else can be done to determine whether this is functioning correctely.

I'll chec

Spoke to the dealer about IAT of 45'C he says that it's normal due to air being great at absorbing heat, to me the heat can only really come from when the air goes in to the compressor in the turbo then up to the plenum, which should be warming up at this point. Does any one else have any data on this? switch on from cold and idle until the car water temperature reaches 84'C, what IAT values are you getting above the ambient temp (in my case 20'C). If it is not normal then it looks like I have an leak in the induction system pulling in hot air from the engine area.

AIC need to measure the volts to the AIC up to the point when the cuts, this should tell me that it is either being instructed to close from the ECU or not, this may determine whether it is faulty without removal.

I'll post up dates as I go on

thanks all

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in some cases of engine-bay work the wiring connector for the IAT-sensor was undone and dirt, water or whatever has contaminated the contacts inside ...this can also work as an contact bridge with false read-out and irritations. In opposite terms, if the sensor is really faulty and the ECU recognised this, the temp.value set-up will be on 40°C based on workshop book informations ...and the engine control will be based on other parameters like load, oil-temp. (if the specific engine production year means it does have the sensor in the sump..) and water temperatur.

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