Misfires etc

Misfires etc

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Discussion

Paulprior

Original Poster:

864 posts

104 months

Wednesday 20th September 2017
quotequote all
If i drive the car with the ECU just laying on the floor in front of the battery it always drives perfectly, but as soon as i try to tidy it away, i have tried beside the battery, on top of the battery, above the glove pocket and tied to the heater pipes then i get an assorted mix of intermittent misfires, coughs and cutting out, i have managed a couple of times to pull over quickly and lift the bonnet, the left hand manifold feels colder that the right one, this is just by hand.
i have pulled back the cable coverings to check the cables, they all look good externally.
Any ideas?

bobfather

11,171 posts

254 months

Wednesday 20th September 2017
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Something very similar happened to me. I checked the ECU loom and socket and found that one of the socket connectors wasn't latched into the socket housing properly. That caused it to push inside the socket housing when it was connected to the ECU. It was still making contact but any twisting of the loom caused intermittent open circuits.

Belle427

8,864 posts

232 months

Thursday 21st September 2017
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If laying it down flat helps it could be a poor connection or dry solder joint inside.
Have you opened it up and had a look inside for moisture ingress?

mk1fan

10,507 posts

224 months

Thursday 21st September 2017
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14CUX ecu?

Could well be dry joints within. Also could be the plug.

I think Python Racing provide a ecu inspection and repair service.

If it is the plug then you'll need to check it on the car unless you want to whip out the loom.

A simple fix could be to use a temporary strap - you can get a large reuseable zip tie type thing from Toolstation or it might be TLC - to keep the plug in place.

Loubaruch

1,164 posts

197 months

Thursday 21st September 2017
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As said above the ECU plug/socket is the probable culprit. Not too difficult to peel back the plug/socket covers and inspect the pins.

The mess in the foot well was not one of TVRs brightest moments. The reason I decided to move the fuse panel, ECU and loose relays.
No problems since and checking fuses and or relays now a doddle. The loose relays and ECU are now bolted to the bulkhead so no strain on the cables entering the ECU plug/socket.

As Chimeras do not have a glove box several other owners have moved them elsewhere.

http://www.bertram-hill.com/moving-the-fuse-panel....

Edited by Loubaruch on Thursday 21st September 11:22

ianwayne

6,244 posts

267 months

Thursday 21st September 2017
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Assuming your floor in that area isn't too wet (a lot are!), it could be a loose connection as described. On my last Chimaera, I wedged the ECU between the carpet and the battery box with some thick cardboard. A bit 'heath robinson' I admit, but it held it slightly above the floor and it didn't then get banged about.

Paulprior

Original Poster:

864 posts

104 months

Thursday 21st September 2017
quotequote all
My floor is dry, but wasnt when i bought the car last year, the ECU certainly has external signs of corrosion,
I have opened up the plug and all cables and pins look very good, the plug holds in place very well.
I have thought about trying another ECU but the price for a TVR one is very high, but i see a Land Rover one is much less, my chip is removable and i am happy to swap it over, is there anything i need to check if i buy a Land Rover one?, i see there are some other numbers apart from 14 CUX.
The other option is a break inside a cable, not so easy to find.

mk1fan

10,507 posts

224 months

Thursday 21st September 2017
quotequote all
mk1fan said:
I think Python Racing provide a ecu inspection and repair service.
I am lucky enough that a friend did mine but they don't do it 'commercially'.

QBee

20,905 posts

143 months

Thursday 21st September 2017
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All Chimaera/Griff ECUs are identical apart from the main central chip.
Anyone who upgrades to an aftermarket ECU will have the 14CUX spare.
Put out an appeal to borrow one for a test.
Just swap your chip in.
In the mean time open it and check there is no water inside or obviously loose bits.
You could have borrowed mine, as I upgraded, but I have already given it to a friend.

But if you know another Chim owner locally, ask if you can try their ECU in your car.

To be honest, it sounds to me like you have a break in the loom connected to the ECU.

Steve_D

13,737 posts

257 months

Thursday 21st September 2017
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The changes related to moving the ECU would suggest it is in the wiring or connector. It could be a dry joint where the connector is soldered to the circuit board.

If one bank is running cold I would suspect the injectors for that bank.
Cyl. 1, 3, 5, 7 wire colour Yellow/Blue ECU pin 13.
Cyl. 2, 4, 6, 8 wire colour yellow/White ECU pin 11.

Steve

Paulprior

Original Poster:

864 posts

104 months

Thursday 21st September 2017
quotequote all
When I first started testing this I put the ECU away I then covered it all in with the carpet section in front of the battery, the car ran really badly, but intermittently all day, I removed the front cover thinking it was overheating, it seemed a bit better, but still not perfect until I laid it on the floor
Others following me mentioned that they could smell petrol while it was misfiring, so I don't know if the injectors are switching off or on too much.
So any ideas of how to actually narrow the possibilities down would be grateful, I don't have access to another ECU unless I buy one

QBee

20,905 posts

143 months

Thursday 21st September 2017
quotequote all
The fuel smell is the injectors not firing.
Steve D has got it right. The question is, where is the fault?
If it's in the ECU, then a different ECU will work fine.
If it's in the wiring, then you need to find the fault.

Just start a thread asking for anyone local to allow you to try their ECU. That will answer the ECU question. Alternatively, take it off the car, undo the four screws and see what you can see inside? Corrosion? Water?

Paulprior

Original Poster:

864 posts

104 months

Thursday 21st September 2017
quotequote all
I had the ECU open last year QBee, you loaned me your ECU which I was going to try until I found 2 pins out of position on my chip, I know that the internals look ok.
How does the lack of signal to the injectors give the smell of fuel?, but yes loosing a signal makes more sense than firing too much, I guess I can hook up an LED to the output of both, or would voltage displays show more?

Steve_D

13,737 posts

257 months

Friday 22nd September 2017
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I'm still thinking injectors but from the extra info that there was a strong fuel smell this would indicate the injectors are firing but perhaps during the misfire they are on continuous indicating a short to earth somewhere.

Another possibility is a Lambda fault.

It's not been mentioned but running RoverGauge may show something.

Steve

Paulprior

Original Poster:

864 posts

104 months

Friday 22nd September 2017
quotequote all
If we assume that a break in the cable is more likely than a short, then what would be the reaction to a loss of signal from the Lambda sensor?
I do have Rovergauge if someone could advise on what to look for, the fault can appear very quickly after starting, less than 1/2 mile sometimes

mk1fan

10,507 posts

224 months

Friday 22nd September 2017
quotequote all
My fuel smell and poor running was down to a faulty CTS (coolant temperature sensor) but that was on a 4CU car not a 14CUX. Don't know if the 14CUX has a similar signal input or whether it relies on the lambda sensors (is it a precat car?).

I'll say it a third time - send the ECU to Python Racing for testing. Other companies do similar service but I can't recall their names.

Whilst it is off, carry out some continuity tests on the wiring.

Finally then start testing the [various] sensors

I am assuming you've done the obvious checks - HT leads. Rotor arm. Dizzy cap. Spark plugs (inc gap). Coil. Ignition amplifier. Wiring to these.

If the car is over fuelling then it could cause bore wash, melt the cats, and coke up the lambdas. All of which will have their own associated knock on effects and repair costs.

Steve_D

13,737 posts

257 months

Friday 22nd September 2017
quotequote all
mk1fan said:
....I am assuming you've done the obvious checks - HT leads. Rotor arm. Dizzy cap. Spark plugs (inc gap). Coil. Ignition amplifier. Wiring to these..........
None of the ignition system goes near the ECU so if the fault is related to positioning/movement of the ECU then the ignition can be ruled out.

OP
Run RoverGauge and look for anything out of place.
Start with the engine off, ignition on, and check the temperatures. If the engine is cold then both coolant and fuel temp should read about the same and close to ambient.
Start and watch for anything out of place...readings at the wrong end of scale etc. or readings that are not logical.

Steve

FoxTVR430

452 posts

110 months

Friday 22nd September 2017
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Another idea might be that there is a loose or bad connection further up the loom.
I found this on mine some time ago. Follow the wiring loom up from the ECU connector (you might need to remove the black tape) you should see a collection of black cables soldered together. Check that these are secure with no signs of a dry joint. smile

Paulprior

Original Poster:

864 posts

104 months

Friday 22nd September 2017
quotequote all
I think having the ecu tested will not necessarily show anything as most of the time, at least 95% everything works perfectly, i have stripped the connector cover off and checked all the pins are fixed correctly, i have removed all the cable wrapping as far back as i could and everything looks to be in good condition along with the various joints.
originally i thought it was heat, but now its tucked up on the roof of the footwell without any covering and still it sometimes plays up within a mile or 2, so dodgy cable / connector does look likely, i guess its going to need continuity testing while i bend all the cables around.
Does anyone have a reliable circuit for a 1995 500?

Steve_D

13,737 posts

257 months

Sunday 24th September 2017
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If you have Microsoft Visio I can send you my circuit (97 400) you can then amend it for your car as you learn more.

Or I can do it as a pdf.

Steve