Help - Not fun to drive anymore

[taylormj4]

I've used my Chimaera daily for 2.5 years and enjoyed it a lot but over the last year or so the chugging thing has got worse and worse. It's been through 2 TVR indy services (the last with an engine management specialst with a rolling road) and they haven't found the problem.
It used to happen just a low revs but now it happens in every gear at every rev, so that I now spend more time in neutral than in-gear. It really is spoiling the driving enjoyment let alone knackering the transmission. Only time it isn't noticeable is when you floor it.

I've changed the dizzy cap / rotor arm / plugs / plug leads, checked the connecions to the coil and the igniter. It's been on one of those units that plugs into the ECU and all the parameters were fine (i.e. lambda sensors etc). I've checked the resistances of the temperature sender and the injectors and the throttle pot - all OK as per Mr Heath's book. I did find high resistance values for the air flow meter but at last service the garage found it to be OK and the rolling road showed 245bhp (engine is the 450).

This chugging is doing my nut though - any ideas chaps?
Anyone tried a Krypton tuning expert.
Anyone have a spare airflow meter that I could try or know of one in a scrap yard etc?

Cheers,
Matt

[TVR+Bubblecar]

Two thoughts come to mind

1. Vacuum advance

2. Coil

Can you describe the symptoms in a bit more detail

I have a 450 which used to misfire below 2000 revs

I fixed by changing dizzy cap / rotor / coil / leads /temp sensor /and those metal connectors on the plugs - not sure what fixed it but it changed the cars characteristics completely

I also found it ran smoother by disconnecting the vaccum advance pipe and blocking off the hole at the inlet end (left the dizzy end "open"

Hope you get it fixed

Chris

[AlexB]

My Chim was hesitating at part throttle. Took it to Austec in Crawley and they checked it over on the RR with the various engine diagnostic kit attached.

All the sensors were fine and doing their job, but the car was running lean at part throttle - this was diagnosed as being due to partly blocked injectors. Had the injectors cleaned and refitted and all seems well.

They also found that I wasn't getting full throttle and sorted that with a healthy rise in power as a result.

It's expensive to have the injectors removed, cleaned and refitted, but worth investigating rather than getting rid of an otherwise great car. Particularly as any test driver will probably notice the symptoms.

Good luck sorting it!
Alex

[GreenV8s]

What is the "chugging" thing you talking about?

Is it drive line shunt? This occurs when the engine 'bounces' violently against the transmission making the car kangaroo at low rpm. It will normally only occur at low RPM and part throttle - say below 1500 rpm or so. It can be made a lot worse if there is any play in the transmission, either from a worn gearbox/diff/UJs/CV joints, or from worn or loose engine or diff mounts.

[joospeed]

is it an intermittent thing or is it there all the time at part throttle?

[chimtvr]

im assuming the chugging you are talking about started only happening at low revs in high gears and then over a period of time the problem started happening at higher and higher revs when you changed the plugs and leads it seemed to get a bit better then got worse again?????
we get this a lot on gas converted cars because of the high octane its always ignition so replace the coil with a proper landrover one and i will bet my boots the problem goes away

[taylormj4]

Guys,
Thanks for all the replies, I'll try and answer you all...
Chris: The symptoms are regular misfiring (approx once or twice per second) at any rev in neutral, the misfiring causes the power to go on/off/on/off... when in gear which gives an effect similar to pressing and removing your foot from the accelerator - not comfortable.

Alex: The last service was done by Austec - I took it all the way there from Cardiff in an attempt to sort out this problem but to no avail.

GreenV8s: "Chugging" as above, a bit like when you see a learner driver trying to pull off, also known as kangarooing. It used to only do it at very light throttle, eg going down a hill but now does it at moderate throttle or no throttle. If I'm trying to do say 35mph in traffic I can't use any gear that will make it stop. Also does it at motorway speeds.

Joospeed: The problem is constant but the misfire is not constant enough for loss of power just annoying.

ChimTvr: I believe the coil is the original and not a cheap replacement, but would be 7 years old now. Wouldn't a bad coil give me poor acceleration though?

Other symptoms are:
1. The car actually shaking at idle because of the misfiring - the 3.5l V8 in my 1973 RangeRover is sooooo much smoother.

2. The idle is so poor that if I pull off two of the plug leads I can't tell the difference, which suggests very poor ignition??

3. I tried removing those plug shroud things and the little (suppressors) at the dizzy end - things seemed to improve but I could smell like burning rubber as if the leads were getting hot (This happens quickly, before the exhaust manifold has had chance to warm up so I don't think it's because the leads were closer the block) - is this due to increased current from the coil?

Thanks for the help guys. I've spent hours trying to figure this one and its getting annoying now.
Cheers,
Matt

[GreenV8s]

That sounds like a severe misfire, not the usual sort of problem. What did Austec make of it?

[IPAddis]

I had the same effect when I managed to get water inside the dizzy. Definately sounds like an ignition problem.

Have the plugs been checked for fouling?

Ian A.

[taylormj4]

GreenV8s said:

That sounds like a severe misfire, not the usual sort of problem. What did Austec make of it?

Well,strangely, they thought it was OK - certainly the peak bhp was 245, which seems OK but then it doesn't do it with a lot of throttle on (or maybe I just can't feel it when I'm being pressed into the seat like that!)

When I picked up the car, the mechanic who had done the service wasn't around but he hadn't left any notes on the record card. I wonder whether the message had been passed on that he was supposed to investigate an engine problem? Someone had definitely been in the car doing a test drive or something as there were oil marks everywhere. Service was done well though, no complaints there at all. When I enquired after getting home and still finding the fault, one of those remapped ECU chips was suggested. I don't want more power though, I just want it to run properly!

Another interesting symptom is that the revs don't drop much as I dip the clutch to change gear. Could this be an air leak.

Cheers,
Matt

[chimtvr]

Matt as you have a range rover just swap your known good coil for the one on your Chim it will cost you nothing apart from 10 mins then at least you can rule out one more thing

[joospeed]

It sounds fascinating. I guess you're willing to try anything to fix it? I'd love to have a look at it .. no fix / no fee .. sound tempting? .. all it will cost you is the cost of getting it here and back, a long way I know but you only owe me if i fix it!

[colinrob]

I did have a similar problem with mine not as bad as yours though, I changed all the parts that you have turned out to be the plug extensions, I think the cheapest place to get these was ACT

[taylormj4]

joospeed said:

It sounds fascinating. I guess you're willing to try anything to fix it? I'd love to have a look at it .. no fix / no fee .. sound tempting? .. all it will cost you is the cost of getting it here and back, a long way I know but you only owe me if i fix it!

Hi Joospeed,
Now that is tempting. Very generous of you. You must like what you do. Just looked at your profile to find where you are - hilarious comments on there!

I'd be really embarrassed though if I brought it all the way up there and then found it was just a knackered coil or stepper motor or something - things is there seems to be so many possibilities and whilst they might all individually not be that expensive, I don't want to trial by error replace them all.

Could you give me some pointers of things to check before wasting your time? Sod's law I'd drive it up to you and the problem would go away!!

Thanks ChimTVR for the suggestion of changing for my RRover coil - I'd not wanted to risk that as its a 1973 model, but will they be similar - can't find any markings?

Matt

[chimtvr]

yes it will work just fine

[PeterC]

If you read the bible you will discover that the original coil supplied by TVR is CR*P. It is prone to breakdown (due to the high engine bay temperatures) causing mis-fire problems.

If you remove the HT lead is there any trace of oil leaking from the coil? This is one of the first signs of a failing coil.

Hopefully this might be your problem, but I am surprised this has not been mentioned to you before?
The recommended replacement is a BOSCH unit and costs around £45 and is easy to fit.

[taylormj4]

PeterC said:

If you read the bible you will discover that the original coil supplied by TVR is CR*P. It is prone to breakdown (due to the high engine bay temperatures) causing mis-fire problems. If you remove the HT lead is there any trace of oil leaking from the coil? This is one of the first signs of a failing coil. Hopefully this might be your problem, but I am surprised this has not been mentioned to you before? The recommended replacement is a BOSCH unit and costs around £45 and is easy to fit.

I have read about the coil in SH's book and have done the recommended check for leaking - no leak.
I've also tested the resistance of the HV and LV windings and these also seem OK. This doesn't check for on-load or HV breakdown though, of course. There's certainly no visual signs of breakdown (ie sparking at night etc).
Have also been fiddling with an oscilloscope trying to look at the waveforms out of the coil and into each spark plug but the current clamp I have doesn't seem to be sensitive enough.

Thanks for the info on the Bosch part, do you happen to know the part no. ? Cheers.

[victormeldrew]

Yup, my 500 ran like a pig for a while until my local fettler fitted a new coil. Symptoms were a severe misfire under load.

[chimtvr]

as the misfire mainly happens under load you wont see it unless you are on a rolling road just change it for your working known good one and save yourself a massive amount of hassle

[taylormj4]

chimtvr said:

as the misfire mainly happens under load you wont see it unless you are on a rolling road just change it for your working known good one and save yourself a massive amount of hassle

Hi, sorry must have confused you....
It used to happen only on overrun and light loads but now also occurs under moderate load too.
I will try changing the coils over this weekend and let you know.

Thanks.