Even lambda fault code

[Alexc1984]

I am getting the even lambda fault code coming up on rover gauge with my '97 400, but only when stuck in traffic and the car heats up a bit. Temperatures are normal though just at the point where the fans are about to kick in. I think it runs a little rich but the local garage got it through the MOT with a spark plug change. I replaced the lambda probe with no success, as it doesn't seem to be cycling like the other. It drives and idles well but I notice the idle bypass is at 100% a lot despite a a new clean stepper, throttle butterfly is clean and a new AFM. Pre cats are out and I've changed coolant temp sensor. I did see the throttle pot error come up as well today but not seen that before and it was after the usual lambda error. I'm running magnocors and plug extenders which could be an issue but can't keep going along this change everything until it's fixed path. It doesn't really bother me too much for what I use the car for as I'm rarely stuck in traffic, but when it does happen the car goes a bit lumpy when it is usually smooth as anything with good idle and no shunting what so ever.
I don't have a specialist or decent garage near that I know of so I was wondering if these symptoms are ringing alarm bells for a particular fault you've seen before. Any advice will be greatly appreciated.

[Steve_D]

I would try checking/cleaning the connectors.
You know the one close to the sensor but there is another hiding under/with the injector loom or maybe further forward under/behind the alternator.

Steve

[Alexc1984]

Thanks, I didn't think about those connectors. Had a look and they look fine, cleaned a few other connectors, changed the Bosch fuel relays by the ECU as i had spares and this morning I seem to have made it worse. It felt like it was misfiring and was stinking of sulphur and I had AFM, throttle pot and fuel temp errors coming up so I turned round and took my boring car. I did notice that when tinkering I knocked the No.8 lead and it went from smooth to lumpy in a second so I'm now thinking if a misfire from a weak spark is causing the sensor faults, or if moving the loom about above the engine, or moving stuff around the ECU has made a delicate wire or loose connection worse. Does this sound like I'm on the right track? The car has never been quite right since I had a new chassis fitted which makes me think wiring could be the issue.

[Belle427]

It may be worth checking the connections at the engine earthing points etc, maybe they were not tightened correctly or left off.
Im not suggesting your plug leads are at fault but ive not heard one good report about magnecor leads, they would be the first thing id get rid of.
If you still run extenders its worth temporarily removing them for test purposes, your existing leads should reach straight to plug.
A standard set of bosch leads is cheap enough to buy to eliminate lead issues and always handy to keep in the boot as spares if you deceide to buy a fancy set.
Ive heard nothing but good reports about this company for plug leads.
http://www.formulapower.com/

Edited by Belle427 on Tuesday 17th October 10:59

[Steve_D]

Are you sure you have replaced the relays with the correct type?
These relays are not a common type.
Look at the pin numbers marked on the relay. You need a relay that has 2 pins marked 87. If it has pins marked 87a or 87b it is the wrong type.


Steve

[blitzracing]

Whats the fuel trim showing on the failed side? If its adding 100% fuel then the voltage is missing from the Lambda probe, so it could be a broken lambda cable or missing lambda heater supply.

[Alexc1984]

I will check the relays, thanks for the info.
I tried removing the plug extenders which all went well until the no.1 lead and in pulling it off it snapped the connector bit so that says a lot about the quality of magnecor given they've probably done less than 2000 miles. Will be ordering some Bosch ones I think.
Blitz, I think you might be onto something as the even lambda does sit at 100.

[blitzracing]

If you have a dead probe or missing voltage, the short term trim wont cycle at all, and the long term will slowly move (adding fuel) until it trips a lambda fault- but this takes quite a while. It wont trip a fault code if the lambda trim cycles at any point. Check the red wire in the lambda connection for 12 volts, as it uses this voltage to generate a lambda output. No lambda output will cause the failed side to run rich. The other thing is a misfire on one bank reads as a lean mixture to a lambda probe, so the ECU adds fuel, that wont fix the misfire, that can lead to very high trim levels. As for Magnecores- throw them away and fit decent leads. You may have the stepper wise open, as its only running on say 7 cylinders so down on power. Check the exhaust headers are all getting hot- you can do this by melting a cable tie on each one, as a non firing cylinder wont melt as easily if at all.

Edited by blitzracing on Wednesday 18th October 13:09

Edited by blitzracing on Wednesday 18th October 13:22

[Alexc1984]

I've replaced the HT leads with standard ones and ditched the extenders, using socks instead. Thought it was going much better as the idle bypass looked decent, though the even lambda short term was still at 100 with the long term not nudging. Checked the manifolds with a temp gun and they're all hot around 300ish. Then after idling for a while AFM and throttle pot error codes come up and the lambdas drop out (limp mode?). Does this point to anything? I did notice that where the king lead attaches to the dizzy the nozzle looked damaged/ a bit melted.

[Alexc1984]

[blitzracing]

Alexc1984 said:

I've replaced the HT leads with standard ones and ditched the extenders, using socks instead. Thought it was going much better as the idle bypass looked decent, though the even lambda short term was still at 100 with the long term not nudging. Checked the manifolds with a temp gun and they're all hot around 300ish. Then after idling for a while AFM and throttle pot error codes come up and the lambdas drop out (limp mode?). Does this point to anything? I did notice that where the king lead attaches to the dizzy the nozzle looked damaged/ a bit melted.

One step at a time. Is the Lambda trim adding or removing fuel? Assuming its stuck at adding 100% then you have no voltage from the probe- so it could be a broken heater wire, or no connection to the probe, so its worth getting your test meter out. This fault should cause the long term trim to keep moving until it reaches 100% and then it trips a fault code BUT the engine needs to be hot (above 90'c) for this to happen and takes some minutes. If the trim is not moving, then the engine is not hot enough, or the car is not in idle mode as far as the ECU is concerned- this may be tied in with the TPS fault. That is simply a mismatch between the TPS output and AFM output, as you cant have a high AFM output if the throttle is shut. The most likely cause is an open circuit track on the TPS.

Have a read:

http://www.g33.co.uk/img/fuel/14cux_fault_finding....

[Alexc1984]

Thanks, this is all great material and I'm slowly learning loads through this frustration. Anyway, first time I've used my multimeter since it's sat in the garage for years. I'm getting battery voltage at the red wire on the lambda, and the car runs worse with the lambda disconnected to the point it cut out. I did an ecu reset to check the connections which looked fine. Connected the lambda and the car runs ok/ a little rich maybe but the lambdas both read zero until a couple minutes and then the odd starts cycling around -50 to -75 and the even just climbs straight to 100 on the short term and long term sits at zero. It eventually throws up an error code. Possible revelation is that when I shook the part of the loom with the fuel relays the car stuttered and threw up the error codes straight away. I'm thinking a wire somewhere is past its best bit haven't a clue where to start looking. Does this sound plausible?

[Steve_D]

Sounds like you need to do some more controlled experiments now that you know shaking the loom makes a difference.
Get as much of the loom as you can stretched out in the footwell then start bending and twisting the loom to see if you can localise the issue.
If you can then strip off the loom tape in that area so you can spread the wiring and start bending/twisting/pulling individual wires.

My guess is it will be near the ECU.

Steve

[blitzracing]

So the ECU is not seeing the voltage from the probe. Get your test meter out again and measure between the black and white wires from the probe. If the probe is working you will get something over 1 volt once hot, or if its 0 then the probe may be dead. If you have a voltage, but no short term trim cycle, then there is a break in the loom. You can swap probes between the banks if you can get them out to see if the fault moves.

[Alexc1984]

Think I may be getting somewhere, either that or I'm now heading down a completely different fault finding route. Got the car on axle stands and removed both lambda probes. The odd one that was cycling negative was pretty heavily coked and the new one that was just going to 100 had a light layer of soot. Cleaned them both and put the new one in the odd side and the old one in the even side. Fired it up and both lambdas now cycling quite negative until the engine warms up and then fairly close to zero on the negative side which is a big improvement. The long term on both then goes all the way to -100 at hot idle so not sure what this means. Only fault I'm logging now is fuel temperature which seems a bit erratic and did go to -17 but jumped back to around +18 eventually without clearing the error. Stepper is going to 100% despite trying to adjust the idle screw it doesn't move. It seems to be flipping between this wide open but sometimes when I start it it's around 30% so suspecting the new one might be duff or it's all part of this running issue. Could a slightly old battery or tired terminals cause these issues? Or should I just stop worrying and see how it drives as it seems to idle well and didn't go lumpy when the water temp hit 100C in the garage.

[blitzracing]

This is where we need to be careful with terminology- trim by its nature is removing something, so if you have +ve fuel trim you are removing fuel and -ve fuel trim you are adding fuel- but because this can be confusing, RoverGauge marks it as adding or removing fuel to make it clear- The fact the long term has reached 100% simply means its hit the limit, but that may be enough to allow the short term to cycle, even if something is a way out of tolerance. So once you are happy with adding or removing fuel think along these possible lines:

Adding fuel: misfire (this is where you start for 100% adding fuel ) , low fuel pressure, faulty temp sender, low AFM output
Removing fuel:. High fuel pressure (missing vacuum take off to regulator?) or AFM output too high

As for the stepper- what is the base idle speed with the stepper air feed blocked off? The exact speed you need varies a bit depending on the eprom tune, but as a rule of thumb, if you could get 700 rpm with idle bypass screw only, then the stepper only needs to add a bit more air to bring it up to 850 rpm or so, so say 30% open.