Poor running once getting up to temp

[Rockettvr]

Not posted on here for some time (since I sold up a couple of years back) but I still look in from time to time
Anyway my son still has a 390 recently back kn the road after being laid up since last year
Before being garaged it ran well but since it’s resurrection it’s running bad
Starts well and idles fine when cold but as soon as it starts to warm it starts to misfire/ run v lumpy and cuts out on occasion there’s also a strong smell of fuel - although if you bury the throttle it’ll take off like a scalded cat
Suspected and Tested the CTS which read 300ohms (warm) which should be fine but I’ve ordered a new one anyway
Any other thoughts ???

[Rockettvr]

Thanks for the reply
Positive input is always welcome
No one has money to burn but last Fridays lottery win has certainly helped

1 symptoms point to cts being most likely culprit
2 from bitter experience I know that just that something tests up ok at that point in time , doesn’t necessarily mean it operates correctly throughout its entire operational range
3 A decent CTS costs less than a gallon of premium unleaded - for the cost it makes sense to change it just to eliminate it from the equation
I’ll dig out the multi tester tomorrow and go through and make sure that I’m getting the right resistances and voltages at the right places
In the meantime if anyone has anything they think I should be looking at , that would be very welcome

Edited by Rockettvr on Saturday 14th May 21:13

[Rockettvr]

Hi
Thanks for the reply
Only had a quick look at it this afternoon so not got far into it yet
No sign of oil in water or water in oil but realise that’s not defintive of not having head gasket issues
Checked CTS and coil Various connections ht leads etc
Will spend an hour or two tomorrow going through checking everything with the multi meter
What are the symptoms and How do you diagnose a slipped liner ???

[Rockettvr]

Morning gents
Thanks for the replies
Unfortunately a misplaced multi-tester and persistent rain yesterday means I haven’t had a chance to get any diagnostics done as yet


I’m leaning towards it being on the fuelling side as the issue is only on cruising when warm - if you then give it a boot it’ll take off like a scalded cat
I would have thought that ignition issues would be present throughout but I may be mistaken - testing will tell

Hi Ray !!
Glad to hear that the car is running well for you now
I must admit the idle was never great on it but I just put it down to age/wear and tear
My apologies on the loose earth - I’m usually fastidious about such things but guess I must of missed it although I’m surprised it wasn’t causing issues sooner as it’s now 6-7 years since the heads were off
Hope it continues to run well for you
Ron

Edited by Rockettvr on Monday 16th May 07:52

[Rockettvr]

105.4 said:

Despite yesterdays rain, the good news is that now certainly doesn’t sound like a slipped liner.

[Rockettvr]

105.4 said:

Despite yesterdays rain, the good news is that now certainly doesn’t sound like a slipped liner.

[Rockettvr]

Quick update
Finally found my tester - tested everything (cold) all as should be
Took car out for a run - ran well for quite some time ran up to temp and seemed ok for a while then symptoms returned- hesitant /missing etc
Started back home to continue diagnostics and on the way back the fault suddenly cleared and car ran ok again
So drove past my house and a couple of minutes later symptoms returned but then cleared again before I could return home

I guess the only course of action is to take a tool kit and tester out with me and do the diagnosis on the side of the road

So it’s an intermittent fault causing missing/hesitation but clears when you boot it


Coil doesn’t seem hot
All connections seem good

Coil on its way out or failing ignition amplifier???

Frustrating!!!

Edited by Rockettvr on Saturday 21st May 18:18

[Rockettvr]

Solved
Traced to poor/inconsistent spark
Replaced coil amp and leads (tbh I think it was the leads )and now ok
Although another issue has now arisen for which I’ll make another post
Thanks for all the advice

[Rockettvr]

Hi all
Quick update
The replacement of leads etc seemed to be a cure but only temporarily alas
Been working on it from time to time but other stuff got in the way (doesn’t it always) so little progress for some time
Finally got some time to concentrate on the car and finally nailed the fault and the moral of the story is - Check your wiring very very very carefully !!!!
Knew the fault was on the ignition side and had replaced a lot of that side of things so started suspecting a possible issue with the aftermarket immobiliser so thought I’d delve deeper and thoroughly check the immobiliser and check and clean all connections and terminals on the ignition
Should have taken photos
I checked immobiliser action and found to be ok
the connections around the coil have been messed with at some point possibly due to the immobiliser being fitted but all wiring seemed to be factory rather than aftermarket. The connection to the + side of the coil, 2 cables white with black trace in a female spade connector seemed fine on 1st inspection but once tape removed found one of the wires attached by only 3 fine filaments of copper. Joint cut and re-terminated
Hidden further down in the tape was a nearly broken wire again just a few strands holding it together. Obviously the insulation had cracked at some point the copper had corroded and someone had affected a repair by just taping it up
The wire between the distributor and coil had a crimp on it probably the same issue as above again buried in the re taped loom - once the tape was removed the wire just fell out !!!
Re crimped and retaped
Car started on the button and a 30min run confirmed that the problem was fixed

A combination of failing old wire insulation (it is 40 years old ) poor repair and hiding everything in tape so it looked like part of the loom made this a very frustrating and time consuming issue to locate
Anyway problem sorted although my son has now lost all confidence and any pleasure in driving in the car and is probably going to sell up shortly , so unfortunately we’ll be a TVR less family for the first time in about 12 years.

[Rockettvr]

VyperSpace said:

And here I thought bending wrenches and chasing gremlins were the main attractions of TVR ownership. V8 howl, rocket-like acceleration, and white knuckle handling were 3rd, 4th, and 5th.

The attractions of oil embedded under the fingernails, skinned knuckles and smelling of old oil with a hint of momentum 99 appear to be lost on the young man !! He’s bought a Nissan 350z - newer more power Japanese reliability etc etc. (I’d still rather have his 390 )