C20NE Loom Rebuild

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Cabletwitch
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C20NE Loom Rebuild

Post by Cabletwitch »

So... I'm running out of ideas for the poor running of the 1.8 and the 2.0, and barring mechanical failure in the engine itself (a horrifying thought...), my attention turns to the wiring. I do recall checking the continuity of the CTS circuit and finding that checked ok, but the resistance on it was a little worrying (around 2K ohm or so, iirc). So I was wondering about the feasibility of making up a new loom from scratch.

I figure I'd need the plugs, which is something I'm not sure you can get, or if you can, what to look for exactly. If I can get hold of them, I'm capable of banging it all together and making that good, no worries. The current plugs all seem to be molded rubber encapsulated ones, which is a bastard to work with. Anyone know of any good aftermarket ones?
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

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Re: C20NE Loom Rebuild

Post by Cavalier342 »

Hey mate, not sure if it's already been checked but what about the distributor cap on the cam housing? From experience cheaper aftermarket ones tend to wear out pretty quick, the contacts inside them just shred themselves and they cause poor running. Also check for blue powder deposits inside each HT lead and where the leads fit onto the distributor cap.
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Re: C20NE Loom Rebuild

Post by Robsey »

Firstly - 2000 ohms = an engine temperature of approx 25 degrees C

So that may be not too far out if it is immediately upon a summer cold start.

Degrees C versus Ohms =
25 = 2063 ohms
40 = 1200 ohms
60 = 612 ohms
80 = 329 ohms
90 = 246 ohms
100 = 186 ohms
110 = 142 ohms
120 = 110 ohms

I hope that helps.
Regarding connectors - I will see what I can find out.
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Re: C20NE Loom Rebuild

Post by Robsey »

Personally I would look at the HT and LT coil wires for verdigris as Andrei suggests.

Secondly look at the injector wires for continuity. They get very hot and can break down over time.

Thirdly check all your ground wires.
(Brown insulation)
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

Ahh, I should have mentioned... that was just the wires themselves (shorted the connector with a small jumper, and checked the resistance of the wiring after detaching the plug from the ECU). If the wiring resistance is remaining high, it may cause the engine to remain in it's initial choke condition no matter how hot the engine gets. I'll see about running a pair or wires to the ECU independently and seeing if that bring about any change.
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

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Re: C20NE Loom Rebuild

Post by Robsey »

Ah okay.

So to clarify,

You disconnected the ECU and the sensor from the loom.

With a jumper across the pins of the temperature sensor,
You then put a test meter across pins 26 and 45 of the C20NE ECU connector.

Indeed that does sound like a dodgy wire or a corroded connector pin.
Two good wires should return a resistance of less than 3 or 4 ohms

Here is what my notes say about the sensor wires of the C20NE.

Row 2 -
Pin 26 - Brown / green - wire to Engine Coolant Temperature Sensor P12 pin 1
Note this wire also goes to -
Air Flow Meter - P11 Pin 4
Octane Coding plug X15 - pin B
Throttle Valve Potentiometer P34 pin 1

Row 3 -
Pin 45 - Brown / blue - wire to Engine Coolant Temperature Sensor P12 pin 2Note

If none of the other sensors are affected, then it must be the brown / blue wire on pin 45 at fault.
Or the section of the brown / green wire between the main loom and the sensor.
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Re: C20NE Loom Rebuild

Post by Robsey »

As for connectors,
The majority of Vauxhall connectors are Tyco parts, including AMP parts.

Here is a link -
http://www.mouser.co.uk/Mobile/TE-Conne ... s6ig&No=70

Warning - there are hundreds of parts, so make sure you have a cuppa and some biscuits with you before browsing the pages.

So you are looking for -
Tyco
TE components
AMP connectors
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

Ok, so with the looming MoT coming up, and the embuggerance of having to try and run more wires through sealed bulkhead grommets, I'm going with the shortcut idea of placing a 330 ohm resistor between the associated pins (after disconnecting the CTS), and fool the engine into thinking it's at around 80 degrees once the ECU decides to wake up properly. Not the most elegant solution, but if it works, it'll be one of the best things to happen with this car, AND I'll know exactly how to fix the 1.8 also (I'll get a couple of them and give the other car a try too... if it works, happy days!)

I did ponder a variable resistor, but I'm not sure I can be arsed trying to find a suitable place to fix it all in, run wires to the dash etc. when I'm planning on a more permanent fix in the long run anyway.
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

So... progress!

After pondering the idea of bypassing the CTS and rigging up a resistor to emulate an engine already up to temp, I decided to first check the wiring diagrams to see if it was as straightforward as I hoped.

Hmm, odd? The octane plug is in series with the CTS? How does this work then? Little did I know, I'd managed to misread the diagram, and assumed that was how things were wired up. Completely wrong, but it DID lead me to checking the state of said plug, after some research into what the resistances should be. 4.7K ohm in this case, for a 95 RON engine.

My multimeter told me 'Open Line'.

Ok, so let me try the other one, the 91 side... 'Open Line'.

This, I assume, isn't good. Could this be the actual cause of the whole mess, that the engine has no idea what kind of fuel I'm now running and how to go about using it properly? I can bung a 4.7K resistor in the socket at some point to emulate the correct setup, that's easy. My question is, is this anything to do with the horrendous charade that is every sodding petrol engine in both Cavs I've had so far?

If anyone can shed light on this, let me know. She's in for MoT tomorrow, and the engineer knows about the issues... and has 'ways and means' of ensuring she's all fit and ready by the end. I'm not asking, but I do want a fix...
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

Ok, woke up some, now I've had a good look at this particular information, I see I have a yellow plug, which SHOULD have one side at infinite ohms for the 91 RON program (basic program, the 'resistance' is correct), and the other side should be at 2200 ohms for the basic program at 95 RON (this is currently the same value as for 91 RON). The fact that I get open circuit on both makes me wonder if the resistor on the 95 side has decided to fail, leaving me with an ECU trying to run 95+ fuel on a 91 setting. I'll see if my pet mechanic has any spare RON plugs knocking about, but if this is truly the cause, it's one hell of an obscure one. If nothing else, I'll try and get a resistor of the right value and see if I can bodge it into being...

EDIT: If anyone with a C20NE reads this, can you run a test on your RON plugs and tell me if you get the same result, or actual resistances reported on your plug, and what colour it is? Cheers in advance!
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

I'm a twonk. Had the multimeter on too low a setting, so of COURSE it'll read open line when trying to read something magnitudes higher. The good news is that after retesting, it's all fine. The bad news is that I'm still an idiot, and it's not the magic cure I'd hoped. But the OTHER good new is she passed the MoT 100% with no advisories! (I know... I'm scared too...)

I'm wondering if I should request all these posts be collated into a "Cable is a Dumbass" thread...
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Cavalier342 »

congratulations on the test result, that's always good news. I still can't understand all the electronic work that you've mentioned so far, I didn't think these engines needed all that hassle, should just be a case of wrenches and hammers to fix most gremlins.
Previous:
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Kings Blue 1992 Vauxhall Cavalier LSi Auto C18NZ
Smoke Grey 1994 Vauxhall Cavalier V6 C25XE

Am I a light sleeper or a heavy sleeper? Well that depends on how much I've had to drink...
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

I'm slowly working through all the nightmare that is the electrical control system on these things, mainly because the damn thing runs absolutely fine before the ECU kicks in. Something isn't reporting correct values to the ECU, and thus is presumably causing it to stick in cold start. There have been moments where the revs and engine have smoothed out for a few seconds before going back to the low idle RPM state, so I doubt very much it's a mechanical issue.

I think I'm still going to try the resistor trick for the CTS to see if fooling into thinking the engine is warm from the get go gives me any joy. If that works, it's almost certain the wiring from the CTS to the ECU is wonky, and thus the solution would be an easy one. If not, then it's yet another line of inquiry that led nowhere.

I should point out that this guy is having the exact same issues in a Calibra, so it's not a Cav specific problem...
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Cavalier342 »

Idle control valve?
Previous:
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Kings Blue 1992 Vauxhall Cavalier LSi Auto C18NZ
Smoke Grey 1994 Vauxhall Cavalier V6 C25XE

Am I a light sleeper or a heavy sleeper? Well that depends on how much I've had to drink...
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

I've not yet tried a new one, because they're still insanely expensive compared to the 1.8 variant. IF anyone has a spare I could try at the meet, I'm up for it.
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Robsey »

I know my idle control valve gives problems with a slow jittery idle, and occasionally cuts out when warm idling.

To test the idle control valve, simply unplug it whilst the engine idles.

On my car doing this causes the revs to pick up to a smooth tick over.

The down side is that it will put the engine light on.

As soon as you plug the idle control valve connector back in, the car will cut out unless you rev the car whilst connecting up.
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

I have tried this, and yes, the idle RPM jumps up a fair bit and then dies when replugged. I guess (thankfully) it's not an ICV issue then, at least not directly with it. So now we're back to looking at other causes... and the 2K ohms I recorded on the CTS line were from the 1.8, somehow I managed to transpose that into my 2.0 workings. Blah.
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Robsey »

You guess wrong my friend.
(I did say my ICV sometimes gives problems).
It sounds like the ICV could indeed be causing your issues.

Strangely on my C20NE, I have just fitted a yellow octane plug in place of the black one that I have used all along.

This has markedly improved the tickover and so far the car hasn't stalled even when hot.
But there is still a little lumpiness in the idle, so I shall see if a replacement ICV helps further.
If it does, then I shall report back in a day or two (when it arrives).
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

Heh, mine already has the yellow plug. 2200 ohms on the 95 RON side, should be program 4 in the ECU? At least that's assuming the Calibra uses the same ECU.
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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Re: C20NE Loom Rebuild

Post by Robsey »

Yes the C20NE should be more or less the same for Cavalier / Vectra-A and Calibra.

ECM for the cavalier should be alpha code GE.

No idea about the program "number 4" bit.
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Re: C20NE Loom Rebuild

Post by Cabletwitch »

I forgot to post this wonderful little bit of info, as it gives you all the resistances of various plugs, and what programs they trigger in the ECU (assuming the Calibra does indeed have the same unit, which given it's the same engin set, I would reckon so).

Also, my bad, it's program 2, not program 4. 4 and 5 aren't apparently available when running with a cat unit.
Never use another Cav driver as guidance to a destination, unless you REALLY want to explore the country.

"Won't SOMEBODY please think of the scones?"

1.7TD Ethos (Slightly broken)
1.8i (Given up, going for parts)
2.0i (WHY won't it work?!)
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