1998 Chimaera 450 Misfire after minor job

[SteveSNZ]

Hi guys,
So I’m hoping for some help with my Chimaera 450 – Manufactured in 2018. The car is New Zealand New and doesn’t have Cats or lambda sensors (original).
I replaced the Timing housing gasket after it failed. The job was straightforward and whilst waiting on some parts I did a little bit of degreasing around the engine but was pretty careful not to get degreaser in any sensitive areas. Since putting the car back together I’ve been plagued with a misfire.
Apologies in advance for the long read. To pre-empt the obvious question of why not take the car to a specialist, the local TVR guy here (yes there basically is only 1 in my region) is not an expert in the ECU and I have had many chats with him. I could trailer the car to a Land Rover specialist but that’s probably my next step. I’m reluctant though, because fiberglass cars are “Different”.
So For I have;
Checked timing – also confirmed TDC and the timing mark was accurate – no change
Tried moving the distributor one notch forward and re timing – no change
Replaced Coil, Leads, and spark plugs. I removed the TVR spark plug shrouds. The new coil is designed to be used with “R” type plugs. I bought new BPR6 plugs and the leads are MSD leads with LAVA covers. – No Change.
Checked the earth wires at the front of the engine. No issues.
Took the car to local auto electrical guys (no experience with Lucas 14CUX) and they said the timing is good and the spark is good. But the car is running very rich and the smell from the exhaust is overpowering. I’m fouling plugs within 10 minutes of cleaning them when ticking over. On the road the car pulls strong but feels like it’s in limp mode and misfiring when you’re not pressing hard.
Looked up the LUCAS14 CUX manual and went through all tests.
Notably these test okay;
Battery Power, Ignition Power, Main Relay power, Engine speed sensor cable and resistor, Fuel Pump, Injectors, both banks, Fuel and water temp sensors, Bypass air valve, TPS.
However I have some test that I’m not certain about.
And I also notice a wire that has melted in the loom – OBD connector. The melted wire is the Black white wire and I have peeled the insulation right back to the blue plastic joiner. No other cables look to be damaged. Its also measuring 0 ohms to earth.
The AFM Signal wire (Blue/Green) is giving 0.09V and this should be between 0.2 and 0.7V.
All wires to the AFM test 0 Ohms end to end.
I’m confused about why I’m seeing 0.18V across the AFM Red/Black wire to earth. I though Red/Black was earth.
Anyway I have tried 3 x ECU’s and three AFM’s, all no change.
I have two wiring diagrams that have come from Pistonheads forums. One is from “Rob” and looks to be an excellent diagram and very detailed. Rob shows the Red/Black wire to the AFM as being “Common Ground” and is also joined to other sensors. This makes sense. However I have seen a couple of other RV8 drawings that suggest the Red/Black is the sensor voltage supply line.
I don’t want to start cutting into the loom without knowing for certain if this wire is earth or signal. And, I’m hoping some of our brains trust here may be able to suggest something that I’ve overlooked or misunderstood.
Thanks in advance. – Steve (in New Zealand)

[SteveSNZ]

Hi and thanks for the link. I've been through the g33 several times and it is indeed a great resource. Yes, the car was running very well with no shunting or misfires or anything like that.

[SteveSNZ]

Belle427 said:

i cant help much as its such a strange one, i would be careful about replacing parts such as the coil though as some aftermarket stuff is complete junk.
i would only retrace my steps at this point checking all wiring is where it should be etc and hasnt been trapped anywhere.
Tvrs dont like being started and sat ticking over from cold which may not be helping the plug fouling situation.
Any ideas what tune resistor it is running?

Hi, first an apology. I did go and look at the g33 page and its changed quite a bit since the last time I looked at it. This link is very helpful as it confirms that the Red/Black wire is Earth.

[SteveSNZ]

Belle427 said:

i cant help much as its such a strange one, i would be careful about replacing parts such as the coil though as some aftermarket stuff is complete junk.
i would only retrace my steps at this point checking all wiring is where it should be etc and hasnt been trapped anywhere.
Tvrs dont like being started and sat ticking over from cold which may not be helping the plug fouling situation.
Any ideas what tune resistor it is running?

I believe its a green tune resistor and will update my answer here if its something other than green

[SteveSNZ]

ITVRI said:

As the car doesn't idle properly , plugs fouling and ok on hard acceleration but not on light throttle IMO it’s a fuel issue. Have you checked that the temperature sender has been reconnected as this enriches the fuel if not reading correctly. Also worth mentioning to try Rover Gauge to see if any fault codes have been tripped and to pull a plug from each bank to see if they are the same colour. One side black the other grey may indicate an injector based problem. Rover Gauge will also confirm the temperature sender is reading correctly. If you don’t have Rover Gauge ask on the NZ TVR Facebook page for a loan of a RG connector and download it. My car is parked up in another part of NZ from where I am currently living so I can’t send you mine. If you can spare to wait a couple of weeks maybe have one sent out from the UK. (Mark- Blitzracing - the g33 site you were looking at used to sell them or maybe on eBay) failing all that the other area to investigate would be the MAF sensor plug itself as a few years ago I used to have intermittent issues with overfueling before repairing the plug.

Thanks, the CUX14 manual described how to test the fuel temperature and the coolant temperature sensors and these both test okay (2,500 Ohms at 20 degrees). From that I'm confident the cables are connected as they should. I was aware that its easy to plug the sensors into the incorrect plugs so never unplugged any two at the same time. All plugs have been disconnected, cleaned with electrical contact cleaner, dried and reconnected, then tested again. I have made up a Roverguage cable using the FTDI board (for my first Chimaera), however I couldn't get it to connect in the time I had. I'm not certain if the laptop was properly configure for the USB so will definitely revisit that. I agree re the MAF plug, I will look at it more closely as its possible one of the connectors has recessed into the plug. Thanks, again.

[SteveSNZ]

DVR V8 said:

Just had a look at my 14CUX main build diagram and there are no black/whites in the engine harness. There are some black/slates . A couple are in the blue header by the main ECU . Cavity 27(ECU) to blue header then to tune resistor. The other is Cavity 33(ECU) to the compressor clutch relay (aircon).

Yes I am concerned about the wire. It is Black/Slate after all, I thought it was just grubby as I'd unraveled the electrical tape and its not easy to get good light in there. The internal copper conductor does look compromised but is reading 0 Ohms to earth. The wire has fused itself to the insulation of other wires but they all checked out okay with no insulation breakdown.

I traced the wire from what is shown on my wiring diagram as the OBD connector (but see that the correct name for the plug is a TTL connector) all the way to the blue header.

Interestingly, the diagram I have also suggest this is connected to the tune resistor and earthed at E2. E2 being engine timing cover! THATS INTERESTING!!

[SteveSNZ]

DVR V8 said:

The connector you mentioned with the melted wire is called a header , just a way of connecting multiple wires together. The blue header is a group of grounds. The 14 CUX ignition system does not have OBD. Regards.

Edited by DVR V8 on Saturday 1st April 20:02

Do you know if the header can be opened up. It would be good to inspect the cables inside and possibly run new earth wires from there to all the sensors etc.

[SteveSNZ]

Thanks everyone for their comments and suggestions so far. It may take me a while to get anymore checks done as I have a few things on the go at the same time, including a trip home to Scotland on the 12th May. I'll 100% feed back with any progress or ask for more help as I go. Hopefully I can get time on the car this weekend coming.
Steve

[SteveSNZ]

Steve_D said:

Rob is the name of my car. Those wiring diagrams are mine (and available to anyone who wants them).

Rovergauge is a must as it can answer many questions like, is the ECU seeing the correct temperatures for both fuel and coolant temperatures i.e. with the engine cold both readings should be about the same and read ambient temp. It will also show if the ECU is using the right fuel map. The map is set by a 'Tune Resistor' so any poor connection could cause the ECU to use the wrong map.

The blue 'Loopback Connector' or header is a way of joining together wires of a like function. There are 4 'functions' passing through this connector being...
Ignition switched 12 volt. mainly white/green wires with 1 black going to the coil.
+12V from the main ECU relay. 4 Brown/orange wires.
Earths. Possibly 6 wires black or Black/Slate.
Sensor earths. Possibly 6 wires all Black/Red. These are sensor earths connecting back to the ECU so should only be tested for resistance with all the sensors and the ECU disconnected otherwise false readings can occur such as Steve has already mentioned.

This connector lives in the footwell so (for a UK car) could be a rather damp environment and I have seen a number of cars with corrosion in this area (and in ECUs).
If corrosion is present then each group of wires should be cut from the connector, stripped back to clean copper and soldered together as a group and finally sealed.

Were all the plugs fouling or just one bank? Have seen a situation where the number 1 injector wire (that connects to the ECU) had chaffed through on the coil mounting bracket and earthed so all the injectors were wide open on that bank.

Steve

Hi Steve-D,
Your diagrams are amazing and have been very useful. I will follow your suggestions when I get a chance to get back to the car, with other commitments it may be some time before I get back to it. Its both banks that are fouling and the car has been kept very dry since new. We have hot summers here and I'm told by previous owners that the car has never been on a wet road (I certainly changed that). I'd be very surprised if this is related to corrosion.
Steve

[SteveSNZ]

Hi Guys, I cant believe my car has been off the road for such a long time. Mostly though I've not been working on the car because on my trip home to the UK in May/June this year. Following that, I lost a dear friend Jim Gamsby who may be well known to many of you as the NZ TVR Guru. Jim lost his fight with Cancer and will be very much missed by the local NZ TVR community.

I started going through everything again with fresh eyes about a week or so ago. Here are my findings.

The ECU Wiring has been checked. I had an old wiring loom (From a Griff) that I used to confirm some things that I couldn't physically check. These are shown here;


Of Note and compared to the wiring provided by Steve_D, I don't think the Black/Red wire that connects the AFM and other sensors is directly connected to earth. Instead they all connect at the loop back connector and I assume earth return is via the ECU. Also, the Orange/Brown wire that provides 12V to the AFM via the main power relay is linked in the relay, so removing the relay from the socket separates the two lines so that they can be tested independently.

The advice to remove each sensor, Injector etc. was fantastic. I have now tested every wire for continuity, shorts against the battery +Ve and -Ve and every other pin on the ECU. There are no issues and this also proved how the lop back connector has grouped the wires.

Unfortunately though, I have still not found the issue. In addition to the wiring checks, I have
Put the old ignition coil back in
Changed the plugs back to the original and installed the spark plug shrouds
Checked all tests listed in the 14CUX manual (actually I haven't checked everything - but have all the ones I think needed to be)
Checked voltage and resistance across everything I can check.

The results generally within spec except the AFM. I have two AFM's that were both okay before I did any work on the car. Both test exactly the same.
Signal (Blue/Green) is reading -0.03V (yes negative)
CO Trim (Red/Blue) is 11.9V
Supply (Orange/Brown) is 11.9V

I also have another modified AFM that I know had a fault. It was originally supplied by the Late Ian Whalley (Surname??) I repaired it as it had soldering issues and used it as a 3rd test.
Signal (Blue/Green) is reading 0V
CO Trim (Red/Blue) is 2.33V
Supply (Orange/Brown) is 12V

In all cases the car wont run. If I clean the plugs it starts, then misfires and coughs to a halt. Interestingly though, I don't have the strong over fueling smell now.

I'm at a complete loss now. I have booked the car to a mechanic who is relatively inexperienced with the 14CUX but is awesome otherwise and is picking up some of the local TVR work now that we have lost Jim.

Here are my notes from testing.




I'd be very grateful for any guidance.
Steve

[SteveSNZ]

I forgot to mention that I also got my Roverguage thing working. It showed up faults 12 and 18. I cleared the faults and they showed up again after a few minutes. Interesting the Ian Whalley AFM has not thrown up these faults but the car still doesn't run. This AFM is probably throwing me off rather than helping.

[SteveSNZ]

Some Roverguage Screenshots
To recap, the car has a green tune resistor and no cats were fitted from new, so no Lambda either.

[SteveSNZ]

Yes your right about going in circles. I have the old loom that I could steal the AFM connector off, but I’m really reluctant to cut wires and join new ones. I’ve tested from both the back of the connector and the pins on the inside. No change.
Thanks

[SteveSNZ]

spitfire4v8 said:

I've not read the whole thread, but you should caption your rovergauge screenshots so we know what you're doing.
eg in the first ones the top row is being used in the map, in the lower ones the bottom row is being used. the throttle position sensor records a change between them, were you blipping the throttle or out on the road or something, because neither situation should really occur unless you are on a trailing throttle downhill 9top row being used) or under full load up hill 9bottom row being used.)

If you were just in the garage with closed throttle, or lightly revving it, then you've found your visual symptom reference, if not the root cause ..

Understood, all the screenshots were taken with the car parked and me attempting to run the engine by keeping the throttle open between just open and half. The engine ran for about 2 minutes then I stopped it as it was progressively getting rougher. So cold start, out of gear and parked, throttle blipping to keep the car running and trying to find a point that it "Might clear".

[SteveSNZ]

Another update..
I had a spare AFM connector plug from another loom. I spliced it to the car loom, close to the ECU plug and now I get different readings but the same problem. Using the repaired AFM
AFM Signal 1.75V and AFM CO trim 3.24V.
On Roverguage, I noticed the MAF CO Trim reads as 2.5V which I believe is the outcome you get when the AFM is faulty.

I then plugged in my original AFM, the voltage readings are the same (1.75V and 3.24V), however in Roverguage the CO Trim is reading as 1.26V. The engine still struggles to start and when it does, it cuts out after a few seconds.

I videoed the attempts and have some screenshots. This is with my original AFM, plugs removed and cleaned, engine cranked to clear an residual gasses, plugs back in. In the garage, not moving, cold start.

Images: Before attempting Start
MAF reading = 0. CO Trim = 1.25V


Engine starts well + 1 second.
MAF reading = moves a bit then looks to stick for a moment at 50%. CO Trim = 1.25V


Half a second later - here the AFM reading moves to about 75%, everything is looking good with the engine been running for the 1st second or so. Then, MAF CO trim changes to 2.5V and the engine cuts out.


Engine now fails to start. The MAF reading is sitting at 40% with the engine stopped.

Now with the engine dead, the MAF reading is still 40% or so and the CO Trim is still 2.5V.

I messed around for a while longer. I did get a MIL light on but no fault codes. No fault codes came up again but the MIL light did flash on and off again, then a laptop restart sorted that.

I then checked I was getting a spark at each plug (timing light and turned the engine over), each one flashed.
Then I gave up and had a beer.

[SteveSNZ]

Log file attached.

[SteveSNZ]

spitfire4v8 said:

What happens if you disconnect the afm, then start the car.
With the afm disconnected before turning ign on the ecu will run throttle angle v revs . is it better. worse. or the same?

The outcome is the same, but I haven't been able to grab logs until yesterday so I cant compare logs. But the voltage and behaviors is the same.

[SteveSNZ]

Belle427 said:

From reading about it the Whalley afm has to be set up on the car its used on?
Does it have adjustment as per the 14cux afm?

It has a couple of basic pots for adjustment but I can't get the car running long enough to change anything.

[SteveSNZ]

Steve_D said:

Rob is the name of my car. Those wiring diagrams are mine (and available to anyone who wants them).

Rovergauge is a must as it can answer many questions like, is the ECU seeing the correct temperatures for both fuel and coolant temperatures i.e. with the engine cold both readings should be about the same and read ambient temp. It will also show if the ECU is using the right fuel map. The map is set by a 'Tune Resistor' so any poor connection could cause the ECU to use the wrong map.

The blue 'Loopback Connector' or header is a way of joining together wires of a like function. There are 4 'functions' passing through this connector being...
Ignition switched 12 volt. mainly white/green wires with 1 black going to the coil.
+12V from the main ECU relay. 4 Brown/orange wires.
Earths. Possibly 6 wires black or Black/Slate.
Sensor earths. Possibly 6 wires all Black/Red. These are sensor earths connecting back to the ECU so should only be tested for resistance with all the sensors and the ECU disconnected otherwise false readings can occur such as Steve has already mentioned.

This connector lives in the footwell so (for a UK car) could be a rather damp environment and I have seen a number of cars with corrosion in this area (and in ECUs).
If corrosion is present then each group of wires should be cut from the connector, stripped back to clean copper and soldered together as a group and finally sealed.

Were all the plugs fouling or just one bank? Have seen a situation where the number 1 injector wire (that connects to the ECU) had chaffed through on the coil mounting bracket and earthed so all the injectors were wide open on that bank.

Steve

I commented above that my wiring is different from your diagrams, but its not. Sorry I misunderstood what one of the connections was smile

[SteveSNZ]

blitzracing said:

Ive not read all the posts but here are the basics on a rich mixture.

Both banks over fuelling- AFM. - voltage output too high - check it with no airflow- should be around .3 to .34 volts . This is important if its higher all the AFM output will be wrong across the whole range. Another point is the CO trim voltage stuck high. Check the CO trim as per the G33 web page- it should be possible to change the engine note winding the voltage up and down as it goes rich or lean just like adjusting a carb idle mixture. Low voltage lean, high rich. The CO trim is a 5 k resistor to ground that pulls the ECU supplied 5v down to the trim voltage. If its open circuit you get 5v at the ECU and highly over fuelling. Trim voltage is normally between 1.4 and 1.8 volts. Also make sure the AFM plug / cable are not damaged.

Temp sensors- you have checked them but you can double check with a cold engine when both fuel rail and water temp should be near the same as the devices are electrically the same.

Fuel pressure too high. Lost vacuum to the regulator or blocked fuel return pipe

Stuck injectors- only happens on one bank at a time if the injector loom shorts to ground and opens the injectors constantly.

Just a note on "common" grounds. The AFM has a dedicated ground wire back to the ECU as does the TPS as small signals going back through the engine ground plane could be altered by stray ground voltages. Sensors must be measured on there own ground wires and not the engine block.

Edited by blitzracing on Tuesday 11th April 17:10

Edited by blitzracing on Tuesday 11th April 17:26

At this point I don't smell as much unburnt fuel in the garage when I'm testing. The plugs aren't as wet but now the car only runs for a couple of seconds then wont start without all the plugs being removed, cleaned and installed again. Its becoming very challenging to have any confidence in what's actually going on.