poor running, misfire?

[honestjohntoo]

I agree, its a likely cause, just wonder how a TVR auto technician would overlook that, unless the crankshaft damper has become damaged making it impossible to set up timing correctly.

By the same token a part worn camshaft will affect idling performance but act normally at wider throttles, albeit with some loss of power.

[johntom]

Thanks for your replies, i have bought a temp sensor off fleabay just in case - awaiting delivery. The Tvr specialist replaced the coil, plugs and ignition module as they said the plugs weren't the right ones (although it ran fine on them before) and the module and coil brought back the rev range (original fault was not reving past 2000rpm). They rebuilt the dist. due to a rusty/worn gear on the top, they have set and rechecked the timing, co. etc. I surpose i am trying to replace suspect parts because its cheaper to buy them/fit myself (via ebay and if they don't improve the situation i have spares) than take it to a garage and pay £45+vat/h and top price for the parts ie new plugs, coil, ign. module, rebuild dist = £576.00!
Will fit the temp sensor asap and report back. Many thanks

[johntom]

Hi
this afternoon i have fitted a new engine temp. sensor and throttle pot, still no difference. Your can feel the engine is running rough even with the bonnet up. I have tried a second hand coil and another ignition module, again no difference.

New parts so far, HT leads. dist cap, rotor, plugs, coil, ignition module, throttle pot and engine temp sensor.

Interestingly i had the bonnet up and the coil -ve lead off, with the intention of testing the coil. I unlocked the passenger door and as i opened it the alarm (sigma S30) started to beep and the engine cranked over - moving it forward on the starter ! I went round to the drivers side and pressed the blipper to make it stop! What is happening - could there be a circuit from the immobilsor effecting the car's running?
Sometimes you can try and start the car without knocking off the alarm and it will turn over and make the alarm sound today it happened and it carried on after i removed the key!

[combine]

If you aren't sure about a fault its best to take her to an auto electrician that has experience with v8 tvr's , you will save yourself a lot of time and money . Is there a Tvr Indy near you ?

[convert]

Could it possibly be an air leak on the afm to plenum pipe?

Just finished putting mine back together after fitting new exhaust manifold gaskets, and I hadn't quite got the pipe on the AFM correctly. Was running a bit ropey, but ran great after re-seating the pipe.

[adam quantrill]

I wonder if the immobiliser could be affecting the ignition?

On mine the rev limiter knackered it - I just disconnected it and haven't had a problem since.

Check the coil primary feed with an oscilloscope over the rev range.

[honestjohntoo]

Normally an immobiliser/alarm interrupts the ign feed to either/or both the coil and/or the starter relay.

You had a lead OFF the coil negative then you triggered the immobiliser/alarm by opening a door which in turn energised the starter relay. Ooops!

Its impossible to say how/why the starter relay responded to the opening of a door other than removing coil negative has clearly upset the alarm system or speculating that the alarm system might be faulty.

Suggest you switch the immobiliser/alarm off and leave it off whilst troubleshooting. That should allow you to move on.

If not and it is an aftermarket system and you have circuits for the immobiliser you could pull the relays and rejoin the wires that were cut to effect the installation.

Otherwise the yellow pages are full of car alarm companies who can troublshoot it.

Then you can get back on track with your Efi trouble shooting as per my earlier suggestions. 10th post.

[johntom]

Hi
it was a Sigma S30 - was, as i have removed the whole thing. Unfortunately the car still has some hesitation at a constant throttle, particularly at lower revs ie under 2000rpm. Could the ECU be responsible, it's still the original one, can't think of anything else to change?

[adam quantrill]

What fuel are you running - is it old? You could try some super in there.

[Richybaby]

Hi, perhaps the fuel pressure is now not correct, you said that the mechanic re-set the fuel pressure, you also said that it was running fine before, bar the 2000 rpm issue, whatever the state of tune is of your engine, perhaps the fuel pressure was correct for your setup before and now is not, had a few fuel pressure related issues a little while ago, some of your issues sound similar, do you know what the pressure was before? what it is know? hope this helps, Rich.

[dickymint]

Richybaby said:

Hi, perhaps the fuel pressure is now not correct, you said that the mechanic re-set the fuel pressure, you also said that it was running fine before, bar the 2000 rpm issue, whatever the state of tune is of your engine, perhaps the fuel pressure was correct for your setup before and now is not, had a few fuel pressure related issues a little while ago, some of your issues sound similar, do you know what the pressure was before? what it is know? hope this helps, Rich.

Now that sounds like sense. Most problems can be traced back to the last thing adjusted.

[johntom]

Hi
the fuel pressure was set to 36psi? by RTR. I tried to test it prior to taking it into them and it was 30 psi with the old pump and 32psi with the new one (which i've left on). Yes the fuel is new and i have tried injector cleaner. I will look at the regulator.

Would you assume the pressure is too high or too low and which way would you turn the allen screw?

Edited by johntom on Thursday 3rd July 19:50

[honestjohntoo]

johntom said:

Could the ECU be responsible, it's still the original one, can't think of anything else to change?

Yes, the ECU could be responsible and the best way to check it is by substitution with a known good unit.

Honestly though, the answer to your problem is not based on thinking of other things to change.

What concerns me is that you have bypassed several prior suggestions, some of which are on the 10th post on this thread.

honestjohntoo said:

The majority of all Efi faults have two root causes: ie.

o Air leaks and

o Wiring/connection issues.

Both these are covered in detail on the mentioned website.

http://www.vintagemodelairplane.com/pages/Download...

o For Leaks - go to the plenum chamber article under Efi components..

o For Efi wiring/connector maintenance - see the main article index.

Wiring/connector issues will affect the ignition circuit also.

o An unusual problem, easily overlooked - the suppression capacitor, if there is one, across the coil may be breaking down.

o Has the Ignition amplifier been fitted with the correct thermal conductivity compound to prevent local overheating of the unit.

o Earth straps to the chassis can also be an issue as can the Efi system earth at the rear of the block below and behind the LH rocker cover.

o And quite a common issue is dry joints inside the ECU which can be addressed with the judicious use of a small soldering iron.

Unfortunately, now, I am getting trapped into my pet hate, the scattergun approach to problem solving, suggesting some likely things at random. Usually this process does not work unless by luck! In the long run its usually better to use a structured test program, whereby the whole system is reviewed/tested in a logical sequence.

Help can be found on the mentioned website index under Efi Testing and Adjustment Program.

To add further detail all the components mentioned in that essay are examined in detail under the Efi system components index.

It seems now would be a good time to review all the testing that has been done and what remains.

You also need to re-review:

honestjohntoo said:

I agree, its a likely cause, just wonder how a TVR auto technician would overlook that, unless the crankshaft damper has become damaged making it impossible to set up timing correctly.

By the same token a part worn camshaft will affect idling performance but act normally at wider throttles, albeit with some loss of power.

Despite the apparant boredom of routine testing because your engine actually runs and idles the suggested tests are simple to perform.

An airleak not testable other than by visual inspection (or using a squirt of WD40) is the integrity of the main air input hose between the AFM and the plenum air intake tunnel.

Finally, the design limits for fuel pressure are 26 to 36 psi. If you set the maximum to 36 psi then blip the throttle and check that it falls to 26 psi, you have it about right.

Higher or lower than those two figures will be outside the normal original fuel pressure for the bog standard flspper.

[johntom]

Hi
i decided to check the plugs (fitted by the specialist). The NGK website recommends BPR5E, the car had B7ECS (which are a shorter reach plug) and according to NGK are for the 4.0, 4.5 and 5.0 engines?
I have fitted some BPR5ES tonight and the car drives much better, certainly more responsive. Still a slight hint of 'judder' but definitely much better.
www.ngk.co.uk

Edited by johntom on Saturday 5th July 12:59

[dickymint]

johntom said:

Hi
i decided to check the plugs (fitted by the specialist). The NGK website recommends BPR5E, the car had B7ECS (which are a shorter reach plug) and according to NGK are for the 4.0, 4.5 and 5.0 engines?
I have fitted some BPR5ES tonight and the car drives much better, certainly more responsive. Still a slight hint of 'judder' but definitely much better.

Strange as I and many others swear by B7ECS for all Wedges (V8's that is).

[gun metal]

dickymint said:

johntom said:

Hi
i decided to check the plugs (fitted by the specialist). The NGK website recommends BPR5E, the car had B7ECS (which are a shorter reach plug) and according to NGK are for the 4.0, 4.5 and 5.0 engines?
I have fitted some BPR5ES tonight and the car drives much better, certainly more responsive. Still a slight hint of 'judder' but definitely much better.

Strange as I and many others swear by B7ECS for all Wedges (V8's that is).

Dicky, how the feck is it going with you, you are my sool mate. Gretings from the dutchie's

[Campbell]

I have has the same problem with back firing when holding constant throttel, on a cripton tuner the problem with the dizy nocking out the fire sequence, not at the correct timmings, proble best getting a spare from the net or borrow a good working unit and try, it mey fixe your problem.

Good luck

[Richybaby]

johntom said:

Hi
the fuel pressure was set to 36psi? by RTR. I tried to test it prior to taking it into them and it was 30 psi with the old pump and 32psi with the new one (which i've left on). Yes the fuel is new and i have tried injector cleaner. I will look at the regulator.

Would you assume the pressure is too high or too low and which way would you turn the allen screw?

Edited by johntom on Thursday 3rd July 19:50

By no means an expert, but speaking from experience, personally I would up it, very slowly, see how she goes, keeping an eye out for leaks if your fuel lines are old. Cheers, Rich.

[adam quantrill]

Hmm, poor running for me now, looks far too rich. I have a Coolant Temp sensor on order but I've checked its resistance anyway and it seems OK, varies normally with temperature etc (besides I shorted it out and it's still rich). So - planning ahead what's next? I have a spare ECU to try out so I'll give that a go in the morning. After that, a spare AFM. Then it's probably worth checking the wiring loom I spose.

[rev-erend]

adam quantrill said:

Hmm, poor running for me now, looks far too rich. I have a Coolant Temp sensor on order but I've checked its resistance anyway and it seems OK, varies normally with temperature etc (besides I shorted it out and it's still rich). So - planning ahead what's next? I have a spare ECU to try out so I'll give that a go in the morning. After that, a spare AFM. Then it's probably worth checking the wiring loom I spose.

Too much petrol in the tank .. it's just trying to use it quicker