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MG TF 135 '03
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Discussion Starter #1
Hi all,

I've owned my MG TF 135 (2003) since July last year, it's my first car and I'm absolutely in love with it.

Last Saturday (13th March) I went for a drive and on the return journey pulled over in a lay-by for a quick break, I could hear that the car was running a little rough but got back in and carried on.

As I reached my home town I stopped at a set of traffic lights and the idle dropped to around 200 RPM and she began to misfire. I put my foot on the throttle to keep her above 1000 but she died, I managed to restart her and got her home in which she died and wouldn't restart.

I read the ECU with an OBD tool and it came back with Camshaft Sensor Fail in bank 1.

Ordered a new camshaft sensor and lead which came today, fitted it and now the car cranks but won't fire. I read the car again and the camshaft error had gone but there was no other DTCs.

I got my friend to push the car and she started for a few seconds but sounded like she was only running on two or three cylinders. The engine bay smells of fuel when you try and start her so I know she's getting fuel but there's no ignition.

I plan to check the spark plugs but I don't know how to check the ignition coils and leads.

Does anybody have any thoughts about why she's not firing up? I don't want her to be dead because I've become quite sentimental about her. Please help :(
 

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'10 TF135
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Welcome. Yep I think I'd suspect an ign/coil pack. I don't know how to test other than by substitution, tho'. I think I'd buy a new one/good used one and try swapping it around. (clean/gap/replace the plugs, too...)

18-year-old electrics:confused:...

Cam sensor? They're only weak magnets that get heated up (like the coil packs) and plastered with oil. Recently my 2010 TF started throwing this cam sensor fail code so I fitted a new one and all's well. A new lead would've made it really expensive so I verified continuity with a multi-meter first and cleaned all the contacts with a screwdriver blade and WD40. I gather you need an oscilloscope to check the cam sensor, so I just replaced it when I knew the lead was okay.

In the last 2years I've replaced both coolant temp sensors and the oil temp sensor; I reckon 10years is a good innings for any hot sensor.
 

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MG TF 135 '03
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Discussion Starter #3
Thanks for the reply, I'm thinking about removing the coils/leads and spark plugs and then rotating them round, if a spark plug works on one coil but not on another then I'm guessing the coil is dead, by checking with all four spark plugs I should get a reliable answer.

Do the O2 sensors have any impact on if the car starts? I'm thinking mine might need replacing as she runs a little rich and before you could smell fuel from the exhaust, although that might be the spark plug/ coil breaking down?
 

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'10 TF135
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338 Posts
When you take off that black plastic cover I think you'll find there's two coil packs / 2 leads - which might explain why it died so spectacularly!

Running a little rich and iffy tickover could mean input air control valve (iacv) might need adjusting when you get it going. (There's lots of posts around giving the procedure.)

I'd have thought O2 sensor would be detected by OBD reader?

(I'm hoping someone will pop up with a reliable coil pack test...)
 

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mg_tf
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1,596 Posts
There are two ignition coil packs and two ignition leads. The TF uses the 'lost spark' design where one coil pack serves two cylinders simultaneously, except only one of those two cylinders has a fuel/air charge in it at any one time, so the spark in the other cylinder (which presumably is in the exhaust part of the cycle when the other is nearing TDC for the power stroke) is 'lost'.

My TF developed a very bad misfire a few years ago, enough to bring on the yellow MIL light. It turned out it was the ignition leads. Since the plugs needed replacing anyway, I just replaced the spark plugs first (no effect), then the ignition leads (which solved the problem). If that hadn't worked I'd have bought new coil packs, except they aren't cheap so I was saving that for the worst case outcome.

However, what you say about swapping coil packs or leads over should work. There are two ways to do it - one is get the engine running then pull a coil pack (don't get shocked). If the engine stops or runs even rougher that coil pack is OK. If the engine continues running as before, the other coil pack is at fault. Same technique can be used with the ignition leads.

The second way is to remove one plug at a time from the head, turn the engine over and check for a spark. The exterior of the plug needs to be in contact with an earth of course.
 

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'10 TF135
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DSCF8811.jpg

Thought I'd better include a pic in case anyone's confused about there being 2 coil packs and 2 leads...
It sounds a bit like one's 'gone'. I think I'd be a 'chicken' and substitute a known good one, tho'
 

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MG TF 135 '03
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Discussion Starter #7
So checked the plugs and coils today, all four plugs sparking on all four ignition coils/leads. So I know I've got ignition.

Going to check the fuel pump tomorrow, I can hear it prime but want to make sure it's squirting. I'm praying it's fuel pump failure because if not I'll have to check the injectors.

We managed to bump it again today but once started the throttle has no input and once the pedal is released she dies again. I did have fuel trim errors for the past few months, could this suggest a dying fuel pump?
 

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MG TF 135 '03
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Discussion Starter #8
What's the likelihood of a crank sensor failing? I can't see it from the engine bay, but would that cause symptoms like this?

Put some more petrol in her just, just on the off chance she'd ran out, she sounds like she wants to start but don't want to burn out the starter motor or flatten the battery 😖
 

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mg_tf
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Long shot, but if your timing turns out to be way out (i.e. you have a spark but it's at the wrong time), it has an outside chance of being because the timing belt jumped a few teeth. It is not unknown, I'm told, for the alternator belt to fail, whiplash the timing belt cover and get inside and cause the timing belt to jump. I doubt that's your problem but it's one to bear in mind.
 

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MG ZT, Rover 25
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5,679 Posts
I'd be tempted to change all the plugs first and maybe even the coil packs as they can get intermittent.

If the TF is similar to other k-series the tacho works from the Camshaft Position Sensor (CPS), so when cranking, if the tacho flicks the CPS is not dead.

Is your air filter unclogged - try without

When was the fuel filter changed - change if ages/ never. Try adding some fresh petrol if it's stood a while. If it starts running ok, run through some cleaner product like Forte.

Is your exhaust ok, the baffles can collapse blocking them internally. Give it a shake. If it sounds like it's got sand in, try with that box disconnected.
 

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Crank sensors can fail and are difficult (in my instance) to change as in an awkward position if you have an aftermarket oil cooler in place. I agree with the comments above that there are several things to check first regarding the coils/sparkplugs, leads et al. However, if you get under the car and have small flexible (double jointed) hands, it may be worth replacing the crank sensor as a precaution (I tried to replace mine as a form of prevented maintenance and failed miserably - I just could not get to the sensor with any tool and my hands are just too big).

It is rare for crankshaft sensors to fail reading the comments on this forum over the years. They do not suffer from oil contamination or heat like the cam sensor but the crank sensor can pick up a lot of other crap which can be cleaned off the head of the sensor.

I am not sure that the engine would run at all if the crankshaft sensor was unable to generate a signal. If it generates an irregular signal. I guess that the engine would stutter along...
 

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MG TF 135 '03
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Discussion Starter #12
Hi All,

The mechanic came out on Wednesday and spent the day searching round the car for the cause. We replaced the MAP sensor in the intake manifold which made her run a little better but then eventually she still gave up and refused to start. He also checked the IACV which was working fine. As for exhaust, when she runs as described later the gas comes through as expected so there's no blockage in the system.

Ignition:
Having checked the spark plugs and coils again, we determined that we had a good spark and that the ignition system was working as it should be, so that was the first thing out of the way.

Compression:
Performed a compression test and each cylinder was within range so was good to know that the engine wasn't leaking and that none of the gaskets had gone. (Massive sigh of relief 😅)

Air:
Having removed the air tube from the airbox to the throttle body, the throttle body and engine were getting enough air, but she still wouldn't start.

Fuel:
We removed the fuel pipe from after the fuel filter, cranked the car and fuel sprayed everywhere so we knew we had fuel entering the system. The spark plugs were also wet with fuel after each crank.

After diagnosing that we had the four things to make the engine run we were a bit stumped as to why she wouldn't start and decided to check the ECU.
With the fuel pump relay removed from the rear left panel in the boot, she roared into life before stopping as she ran out of fuel. As soon as the fuel pump relay was put back in she refused to start. The relay is working as the fuel pump engages as it should. Therefore the final verdict was that the ECU was over fueling the engine causing her to flood and drown.

This backs up the various fuel trim errors I've had over the past few months which would suggest that the ECU was slowly dying wrt to the fueling of the engine.

Theres a guy on ebay that will copy your ECU data to a new unit so that the immobiliser doesn't have to be changed and so should be plug and play. It's only £50 for the job so cheaper than the camshaft sensor was to replace. I've read that the ECUs are prone to dying, I imagine this is due to their location close to the engine with the heat.

Does this sound like good logic to you all? I don't mind the price for the ECU replacement as this will tick one of the things of the list.
 

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Hi All,

The mechanic came out on Wednesday and spent the day searching round the car for the cause. We replaced the MAP sensor in the intake manifold which made her run a little better but then eventually she still gave up and refused to start. He also checked the IACV which was working fine. As for exhaust, when she runs as described later the gas comes through as expected so there's no blockage in the system.

Ignition:
Having checked the spark plugs and coils again, we determined that we had a good spark and that the ignition system was working as it should be, so that was the first thing out of the way.

Compression:
Performed a compression test and each cylinder was within range so was good to know that the engine wasn't leaking and that none of the gaskets had gone. (Massive sigh of relief 😅)

Air:
Having removed the air tube from the airbox to the throttle body, the throttle body and engine were getting enough air, but she still wouldn't start.

Fuel:
We removed the fuel pipe from after the fuel filter, cranked the car and fuel sprayed everywhere so we knew we had fuel entering the system. The spark plugs were also wet with fuel after each crank.

After diagnosing that we had the four things to make the engine run we were a bit stumped as to why she wouldn't start and decided to check the ECU.
With the fuel pump relay removed from the rear left panel in the boot, she roared into life before stopping as she ran out of fuel. As soon as the fuel pump relay was put back in she refused to start. The relay is working as the fuel pump engages as it should. Therefore the final verdict was that the ECU was over fueling the engine causing her to flood and drown.

This backs up the various fuel trim errors I've had over the past few months which would suggest that the ECU was slowly dying wrt to the fueling of the engine.

Theres a guy on ebay that will copy your ECU data to a new unit so that the immobiliser doesn't have to be changed and so should be plug and play. It's only £50 for the job so cheaper than the camshaft sensor was to replace. I've read that the ECUs are prone to dying, I imagine this is due to their location close to the engine with the heat.

Does this sound like good logic to you all? I don't mind the price for the ECU replacement as this will tick one of the things of the list.
A bad signal from a sensor or related wiring/connections making the ECU think the engine is cold will give an extended opening time for the injectors causing over-fueling of the engine. Personally, I would get access to Testbook/T4 to be sure that you are not throwing good money after bad.
 

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MG TF 135 '03
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Discussion Starter #14
A bad signal from a sensor or related wiring/connections making the ECU think the engine is cold will give an extended opening time for the injectors causing over-fueling of the engine. Personally, I would get access to Testbook/T4 to be sure that you are not throwing good money after bad.
The engine is cold though so even with the extended opening time it shouldn't flood the engine, do you know which sensors have an input into the fueling of the engine?
Also you wouldn't happen to know anyone with a T4 around the Leicester, Hinckley area would you?
 

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MG ZT, Rover 25
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Yeah, a mobile T4 check would seem sensible to see if that points at the ECU. I assume you would have to buy a new ECU (expensive?) and pay the £50 for data transfer?
 

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MG TF 135 '03
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Discussion Starter #16
It's £50 for the ECU, transfer is free. They benchmark the ECU to make sure it's all good and if it's fault when you get it then they'll happily replace it.

Here's the listing:
 

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Yeah, a mobile T4 check would seem sensible to see if that points at the ECU. I assume you would have to buy a new ECU (expensive?) and pay the £50 for data transfer?
The engine is cold though so even with the extended opening time it shouldn't flood the engine, do you know which sensors have an input into the fueling of the engine?
Also you wouldn't happen to know anyone with a T4 around the Leicester, Hinckley area would you?
On the cold engine point, you are right so I assume that the issue is not related to faulty temperature-related sensors. If you are right about the over-fueling, it can be due to a faulty sensor/wiring of the TPS, vacuum leak, faulty IACV, faulty throttle body ie Too much air = Too much fuel

I would do a Google search to find someone with Testbook in your area. It may find other problems that you are not aware of yet.

As I have said many times before on this forum, it is amazing what Pscan can do to help you identify problems. By the time you have thrown money at the problem (a few quid here and a few quid there...........), both money and time can be saved investing in Pscan in the first place. It shows many metrics in a live format, recording as it goes so a post-run analysis is possible.
 

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MG TF 135 '03
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Discussion Starter #18
On the cold engine point, you are right so I assume that the issue is not related to faulty temperature-related sensors. If you are right about the over-fueling, it can be due to a faulty sensor/wiring of the TPS, vacuum leak, faulty IACV, faulty throttle body ie Too much air = Too much fuel

I would do a Google search to find someone with Testbook in your area. It may find other problems that you are not aware of yet.

As I have said many times before on this forum, it is amazing what Pscan can do to help you identify problems. By the time you have thrown money at the problem (a few quid here and a few quid there...........), both money and time can be saved investing in Pscan in the first place. It shows many metrics in a live format, recording as it goes so a post-run analysis is possible.
Thanks for help both, I've just contacted a garage in Atherstone as they are MG specialists, just waiting for a call back, according to their website they have a T4. He might have some pointers as to what it could be and if needs be get a T4 connected.

These cars and their sensors ay, I think the mechanic checked the IACV yesterday and said it was working fine. I had attempted to reset it and could hear it moving so perhaps that's crossed off the list. The throttle body seemed to be performing well to throttle inputs when we were checking it.
Now TPS was interesting, it did start with it disconnected at one point and then when it was reconnected the engine died. I'm just hoping its not a cascade failure (I don't actually know if this can happen on cars) as the camshaft sensor had failed and the MAP sensor had failed as well. Although with the car being almost 18 years old, perhaps they've decided to just conk out at the same time.

I definitely need to look at investing in PScan, especially after all this fiasco, from watching the mechanic work it doesn't seem as hard or as scary to work on it as I first thought. (That's coming from a design engineer who's scared to work on his own car 😣) I guess its just take everything slow and use common sense.

Hopefully can get her back on the road soon, missing how she stuck to the road and took the miles on. I'm currently condemned to a Peugeot 107 and its just not the same...
 

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MG TF 135 '03
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Discussion Starter #19
So bad news, the new ECU didn't do the fix that we were hoping for. The car got towed yesterday to an MG specialist in Atherstone, fingers crossed he can get her living again quickly. You don't realise how great she was to drive until you're forced to drive a conventional car.

Here she is leaving me, hopefully to return soon :(
136535
 
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