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[maracus]

Pardon me if I have asked about this before but i have a wideband issue with my cavalier turbo, let me explain...

For a while now, i have had this problem where my wideband gauge reads lean (circa 17's) after the initial "choke time" warm up, until anything between a few minutes after, and a few miles down the road. sometimes it will read lean after exiting roundabouts until a gearchange or two then read normal from then on. once the cars well warmed up it seems to behave as long as i drive the car, until its been off for a half hour or more, then this problem seems to re-apear again.

When the car goes normal, the readout will snap down to 14.7ish and the car will simoultaniously run better. Its very obvious when it does it.

Heres the thing. My wideband feeds into a piggyback ecu and adjusts fuel accordingly. So the wideband tells the ecu to chuck in more fuel. more fuel goes in, it still reads 17's on the display. so yet more fuel goes in.

As a result, my car is, in reality, heavily overfuelling. you can smell it, you can hear it, and it runs charicteristicly as if its overfuelling. But the widebands seeing it too lean. Its to the point where £50 is not gaining more than 150 miles!!

I am certian theres no leaks to the exhaust system, as before i had the map fine tuned, there was three technitions under the car, searhing for a leak, and couldnt find one, as i had expressed concearn there may be one. I have checked the voltage from the battery to the power in for the wideband and seeing 14.3v when running, i also have good continuity at the earths. I also have replaced the sensor with a new one.

Im also sure its not something related to the "factory" engine electrics, as surely, if something else was telling it to underfuel, the wideband would automatically adjust this? (although im not certian) I did wonder about the AFM, so as i had a known good spare and a known bad one, I tried both and the good one showed no change. The car ran rough as hell on the broken one.

What im thinking is that maybe my problem is with the main box that the sensor feeds into that controls it all, but wondered if theres any way of testing this. I feel as if theres some kind of excessive voltage trickle, maybe damp has got inside the unit and causing a short before the condensation evaporates off the circuit boards or something.

I have a wiring diagram for the unit, but im a bit stumped as to how to go about diagnosing my problem and if anyone on here knows a thing or two about these, or experienced similar issues?

thanks... 

[Kevin Wood]

Hmm. A tricky one.

How's the sensor mounted in the exhaust? Is it reasonably close to vertical in the top of the exhaust as is generally the recommendation? Just wondering if some condensing water is getting into it?

Failing that, either the heater control or the balancing circuit for the measuring cell is perhaps going haywire occasionally. As you've changed the sensor, this might be an issue in the controller itself. What type of controller is it? I'd hope it would generate an error, or at least fall back to indicating 14.7:1 in such circumstances but some are less intelligent.

Also.. Has this setup previously worked but has now failed or has it never worked properly?

[maracus]

Its deterioated over the time i've had it. When i first had the car it was fine, but it didnt take long before it started to show occasional issues, but has gradually got worse.

The sensor is at a 2 o'clock position. i wouldn't have thought the sensor itself is getting moisture in there, as when i renewed the sensor, the new one was instantly tested as soon as it went in, I can remember being dissapointed that it still read wrong. Calibration sequence was also followed through.

The sensor used is a Bosch IIRC,the box being an INNOVATIVE LC1 control unit, if thats anything to you haha! I dont know how well reputed these are in the scene. And yes, thats about how I feel with it, the problem is in the control box itself. Although, I cant help but feel it would be somewhat potentially costly to willy-nilly replace the control unit, both financially and the time to replace those wires that dissapear under the seat and reappear somewhere else under the car, if its not that. Are there amy other diagnostics I need to carry out or do you think it would be a pretty sure bet its the unit itself?

[Kevin Wood]

I'm not that familiar with the LC1 but it's a well respected piece of kit. I believe you can connect up a computer and talk to it. That might give you a clue as to why it's misbehaving sometimes? You can at least compare the reading reported in software to that output to the gauge?

Might be worth removing the kit from the car and bench testing it. You can check the sensor response by holding it over the flame from a gas cooker or cigarette lighter.

[maracus]

Ah thats a handy pointer, ill have another look in the manual with that in mind, it might actually stand out knowing its there!! 

I would imagine I can download software for such a task, although I cant picture off the top of my head if theres a plug anywhere thats USB shaped or if I would need to obtain a cable? (maybe theres one in my "box of bits", i'll get looking )

Or, maybe ill get in touch with innovative themselves, and see what they suguest. They might give me somewhere to send it to for testing.

On the other hand, I could just spend £95 ish on a new unit and see, I mean I bet they'd charge me £40 or more just to courier and test the old one?

We'll see what happens after a google search  thanks 

[Kevin Wood]

OK, but if you get stuck give me a shout. I might well know someone who has one if I ask around...

[aaronjb]

Pretty sure I still have my LC-1 around here someplace, and an LM-1 both incl. known good sensors if you want to try swapping bits out one weekend?

[maracus]

Pretty sure I still have my LC-1 around here someplace, and an LM-1 both incl. known good sensors if you want to try swapping bits out one weekend?

Ah that would be excellent to try another unit, cheers 

I'll try and follow up at some point first on what Kevin Wood has said, and if im still none the wiser, when I get a spare afternoon ill try and figure the best way to pull the LC1 out of mine and where the cables routed, then, when im on the ball and know what im doing with it a bit better, or when I find its in my hand not connected to anything ill pm you 

Also, would this be with consideration towards a sale of said unit, or for evaluation purposes on wether I need a new LC-1? just so I know where I stand...   

Out of interest, whats the difference between the LC and LM?

[aaronjb]

I was thinking more of a lend you them so you can see if yours is faulty rather than potential sale I'm hanging on to them in case I do end up going EFI on the Cobra..

The LM is a standalone big square box with a readout and internal logging memory plus the same controller circuitry as the LC, otherwise they're the same (the LM is a bit easier to wire in temporarily as it has a cig lighter plug on it)

[maracus]

I was thinking more of a lend you them so you can see if yours is faulty rather than potential sale I'm hanging on to them in case I do end up going EFI on the Cobra..

The LM is a standalone big square box with a readout and internal logging memory plus the same controller circuitry as the LC, otherwise they're the same (the LM is a bit easier to wire in temporarily as it has a cig lighter plug on it)

ah I see, so a viable option would be to test with the LM as less wires to soilder? Rids the need to connect earth and power feeds as its from the cig socket 

Would you rather I came to you with the car and try it at yours as oppose to posting back and forth? I'll bust out the debit card and get the car taxed again, I was going to try and sort this wideband thing before putting it back on the road, but I dont need much persuation to bring it back out for a play, especially in this nice weather! Then I can try it at your end? 

[maracus]

Just thought I'd give an update...

I ordered yesterday a new LC-1, decided it would be easier and by the time I've put fuel in the car etc I may as well just order a new one. If it is that then great, If not then ill sell my old one on and be safe in the knowledge the unit is brand new and get back the money that I wouldn't have spent by driving to aaronjb to try his unit, so would just overall be easier. I'm fairly sure it IS the problem though so hopefully ill update soon saying its cured it! 

So we'll see how it goes from here...