Poor performance after 4000 rpm

[STE VR]

After having many problems with my car of late, I'm down to just 2 problems. 1. Stalling/nearly stalling when clutch dipped but will settle eventually if it doesn't stall and 2. No acceleration/fluffy from 4-5k rpm in any gear but 1st seems ok?.

Over the last 8 weeks its had:

Timing (confirmed and tested by Chassis 33)
Genuine coil, Genuine rotor arm, Genuine Dizzy cap, Lucas leads, plugs, extenders, plenum stripped and cleaned/sealed, stepper motor, ECU!!, AFM, coolant & temp sensor, new/ tidied wiring, fuel pressure/regulator tested, base idle set etc etc....

Just for info it's had a tank of fuel through it without doing any mileage so gave it a good 50 mile run to clear it a bit but still the same. Stopped at garage to fill up but when restarting it, it decided to misfire, pop, bang like crazy until i floored it, then it eventually picked up but still poor tickover as above.

HELP, seriously losing the plot now.


Steve

[Chimjunkie]

Interesting acceleration comment. Isn't there a road speed sensor which feeds back to the ECU? Really sounds as though it needs the attention of a rolling road diagnostic session

[JonathanT]

Chimjunkie said:

Interesting acceleration comment. Isn't there a road speed sensor which feeds back to the ECU? Really sounds as though it needs the attention of a rolling road diagnostic session

As I understand it, the road speed sensor is simply there to detect if the car is stationary or not (for emissions reasons I believe).

[Fire99]

well im not sure if, in your shopping list you have done this but i would get the error codes read from the ECU to check that any sensors arent failing...

Then if all the servicable parts (plugs, leads, dizzy cap etc) have been replaced perhaps get your ECU tested.

Mine had a fault where the ECU was reporting no error codes but when the ECU was tested it was running very rich.. When the ECU was sent off and tested there was a fault within the ECU..

All working fine now..

Just another possibility..

[Apache]

time for a compression check IMO

[blitzracing]

I still reckon its worth you while puting a DC test meter across the lambda probe outputs. (Black and White wires). You will find them comming up from the manifold downtubes. You are looking for .2-.7 DC volts switching at about 1/2 second intervals on tickover when the engines warm. Do this for both sides. It will help get a decent diagnosis and post the results. I do have access to a code reader, but they dont show a fault condition unless the fault is pretty bad.

Mark

[STE VR]

Many thanks for all your replies, however i have now admitted complete defeat after 8 weeks of and have given it to Ian at Torque RVT......I hope to have it back in the next couple of years!!!!!

Blitz, please let me know if you found anything wrong with the AFM just out of curiosity.

I will post the results once i get it back from Ian.

Many thanks

Steve

[blitzracing]

It basically works, but Im not sure of its calibration. Its output voltage is significantly higher than my one off my car, that would make it overfuel the engine. Funny thing is it has very simular output voltages to another "faulty" one I was sent. Ongoing project:

http://www.pistonheads.co.uk/gassing/topic.asp?h=0...

Mark

[v8 racing]

STE VR said:

After having many problems with my car of late, I'm down to just 2 problems. 1. Stalling/nearly stalling when clutch dipped but will settle eventually if it doesn't stall and 2. No acceleration/fluffy from 4-5k rpm in any gear but 1st seems ok?.

Over the last 8 weeks its had:

Timing (confirmed and tested by Chassis 33)
Genuine coil, Genuine rotor arm, Genuine Dizzy cap, Lucas leads, plugs, extenders, plenum stripped and cleaned/sealed, stepper motor, ECU!!, AFM, coolant & temp sensor, new/ tidied wiring, fuel pressure/regulator tested, base idle set etc etc....

Just for info it's had a tank of fuel through it without doing any mileage so gave it a good 50 mile run to clear it a bit but still the same. Stopped at garage to fill up but when restarting it, it decided to misfire, pop, bang like crazy until i floored it, then it eventually picked up but still poor tickover as above.

HELP, seriously losing the plot now.


Steve

Sounds like the cam to me?

[Chassis 33]

Hi Rob, cam yes possibly, especially given the mileage, but they don't fail over night which is pretty much what we've got here. I've not measured the cam lift while I've been at Steve's, however I have done a compression test, and I forget the exact figure but it was healthy enough.

Steve, sorry its not come good, I really thought we'd cracked it on Sunday, I feel a bit guilty really.

Regards
Iain

BTW Rob, did all the Rovertec SD1 V8 conversions have bulleted valve guides? (Sorry for the hijack)

[STE VR]

Iain, don't feel guilty you have been very helpful indeed. Yes, i thought we had cracked it too but on the few runs i've given it, it behaves differently every time so something is intermittantly wrong. It has ran ok once afterwards so i,m hoping to rule out anything too major like the cam etc..

Cheers

Steve

[JonathanT]

Chassis 33 said:

Hi Rob, cam yes possibly, especially given the mileage, but they don't fail over night which is pretty much what we've got here.

they don't, but on my limited experience of one failed cam, it "felt" ok on the way out to somewhere and "felt" wrong on the way back.....

[Corky]

v8 racing said:

STE VR said:

After having many problems with my car of late, I'm down to just 2 problems. 1. Stalling/nearly stalling when clutch dipped but will settle eventually if it doesn't stall and 2. No acceleration/fluffy from 4-5k rpm in any gear but 1st seems ok?.

Over the last 8 weeks its had:

Timing (confirmed and tested by Chassis 33)
Genuine coil, Genuine rotor arm, Genuine Dizzy cap, Lucas leads, plugs, extenders, plenum stripped and cleaned/sealed, stepper motor, ECU!!, AFM, coolant & temp sensor, new/ tidied wiring, fuel pressure/regulator tested, base idle set etc etc....

Just for info it's had a tank of fuel through it without doing any mileage so gave it a good 50 mile run to clear it a bit but still the same. Stopped at garage to fill up but when restarting it, it decided to misfire, pop, bang like crazy until i floored it, then it eventually picked up but still poor tickover as above.

HELP, seriously losing the plot now.

Steve

Sounds like the cam to me?

I agree, these were my symptoms (well the Griffs !) before I got the cam replaced.

[v8 racing]

Chassis 33 said:

Hi Rob, cam yes possibly, especially given the mileage, but they don't fail over night which is pretty much what we've got here. I've not measured the cam lift while I've been at Steve's, however I have done a compression test, and I forget the exact figure but it was healthy enough.

Steve, sorry its not come good, I really thought we'd cracked it on Sunday, I feel a bit guilty really.

Regards
Iain

BTW Rob, did all the Rovertec SD1 V8 conversions have bulleted valve guides? (Sorry for the hijack)

Hi Lain
sorry i didnt realise it happened like a switch? the rovertec heads did have bulleted guides, however we changed our name 15 years ago so there probably not as they where way back then!!

[Chassis 33]

Cheers Rob, I took the inlet off the other day to convert to EFi and went ooooooooooh!

I'll be intouch regards the Chim soon.

Regards
Iain

[STE VR]

Just an update and some information on the cure of my past problems. Took car to Ian at Torque RVT. It turned out to be a fooked AFM, knackered fuel pressure regulator, dodgy plug, and timing plus a few other things the 'yes mate, we've done loads of TVR's before' garage had messed up!!!. Moral of story:.. don't take it to just anyone to try and save that bit of money..it's just not worth it. I won't be that stupid again!!!!!!

Anyway just a thanks to Iain(Chassis 33) and everbody's posts/advice. Massive thanks to Ian and the lads at Torque(that man knows his stuff). The car came back much better than it's ever been and a few extra little jobs he didn't charge me for at a superb price.

Cheers

Steve

[dings]

Well done Steve, I am going through a frustrating time with mine just emailed RVT so hopefully they can help me out the garage I was going to use never got back to me so probably a blessing.

[blitzracing]

STE VR said:

Just an update and some information on the cure of my past problems. Took car to Ian at Torque RVT. It turned out to be a fooked AFM, knackered fuel pressure regulator, dodgy plug, and timing plus a few other things the 'yes mate, we've done loads of TVR's before' garage had messed up!!!. Moral of story:.. don't take it to just anyone to try and save that bit of money..it's just not worth it. I won't be that stupid again!!!!!!

Anyway just a thanks to Iain(Chassis 33) and everbody's posts/advice. Massive thanks to Ian and the lads at Torque(that man knows his stuff). The car came back much better than it's ever been and a few extra little jobs he didn't charge me for at a superb price.

Cheers

Steve

Did he specify how the AFM was "fooked"? Having now looked closely at units, there is not much to go wrong, unless they drop out of calibration or a component fails when it gets hot. (The main chip is rated up to 150'C) Once I had a decent test setup, all the test units I have give very simular voltages. No air flow gives .35 volts +/- 10mv. If this base voltage is higher or lower it could be out over the whole airflow range. If he fitted a new one can you measure this voltage for me (engine cold- ignition on for at least a minuteto let it stablise ) ?

Thanks

Mark

[Gaffer]

dings said:

Well done Steve, I am going through a frustrating time with mine just emailed RVT so hopefully they can help me out the garage I was going to use never got back to me so probably a blessing.

Call Ian, you will get a quicker answer that way.

Claire

[STE VR]

Claire.....you got a top man there (apart from the fact he's a complete nutter!!!)

Mark, I'm not allowed to open the bonnet anymore by order of the missus but will try and get readings prob early next week.

Steve