stepper motor!
Discussion
As some are aware I've had various issues with the car, I sorted a vacuum leak which was the stepper plenum hose, ran loads better after that, it cured most of the erratic idling, but still revving high when I turned the car on , then settles after a few mins, same coming up to junctions, revved high, before it settled, a bit of a pig to drive smoothly too, lots of shunting etc, plugs were changed as soon as i got the car, its got magecor leads that don't look that old, the symptoms were as regular as clockwork, exactly the same every time I drove it, so took the plunge and bought a new stepper motor, fitted it correctly and started up, there was half a second of something sorting out then tick over settled to 1000 on cold start straight away, drove up the road, no shunting, so much soother then tick over dropping to 900rpm, happy days, it sorted it, lovely drive, still a tad lumpy tick over but that can be sorted any time, I was overjoyed, for the first time since I got it, its running pretty good..... until tonight, popped to the shops (well an excuse to go for a drive really) and back to normal, high revving before dropping, lots of shunting and a pig to drive smoothly yes it was a genuine stepper motor from Motaclan, wrapper even said OEM, so it better be, worse still there was a distinctive bit of misfire too just before I got home when the engine was warm, I'm gutted, the car is going in the garage on the 7th, but I do like to try and sort stuff myself if possible...
I did swap the leads over that were recommended a while ago, angled ones but they made no difference at all, ran exactly the same as before I put them on, well until they gave up as they were rubbing on what i think was a really hot pipe possibly going to the heater matrix maybe? on the drivers side this is, so put the old leads back on. I still recon there is a vacuum leak somewhere, but I'm not sure where all the vacuum hoses are. The was a tatty looking short hose hose right behind the stepper motor, that was tatty so cut some off that... so where do I look?I have a new elbow going into the plenum too, a smooth bore ACT one
I did swap the leads over that were recommended a while ago, angled ones but they made no difference at all, ran exactly the same as before I put them on, well until they gave up as they were rubbing on what i think was a really hot pipe possibly going to the heater matrix maybe? on the drivers side this is, so put the old leads back on. I still recon there is a vacuum leak somewhere, but I'm not sure where all the vacuum hoses are. The was a tatty looking short hose hose right behind the stepper motor, that was tatty so cut some off that... so where do I look?I have a new elbow going into the plenum too, a smooth bore ACT one
Any fresh air that does not go through the maf sensor can be a source of a vacuum leak.
Hoses to the plenum area include the fuel pressure regulator to stepper housing, brake servo, charcoal canister, crankcase breather system.
The vacuum advance module on the distributor can fail too meaning this can draw in more air than normal, this is the small pipe from dizzy to plenum.
A basic test is to remove the pipe from the plenum and suck on it, if you cant feel any resistance it may have failed.
Basic timing checks should be carried out too.
It may be worth waiting for your garage visit to stop you pulling your hair out, do you have it booked into a specialist?
Hoses to the plenum area include the fuel pressure regulator to stepper housing, brake servo, charcoal canister, crankcase breather system.
The vacuum advance module on the distributor can fail too meaning this can draw in more air than normal, this is the small pipe from dizzy to plenum.
A basic test is to remove the pipe from the plenum and suck on it, if you cant feel any resistance it may have failed.
Basic timing checks should be carried out too.
It may be worth waiting for your garage visit to stop you pulling your hair out, do you have it booked into a specialist?
Belle427 said:
Any fresh air that does not go through the maf sensor can be a source of a vacuum leak.
Hoses to the plenum area include the fuel pressure regulator to stepper housing, brake servo, charcoal canister, crankcase breather system.
The vacuum advance module on the distributor can fail too meaning this can draw in more air than normal, this is the small pipe from dizzy to plenum.
A basic test is to remove the pipe from the plenum and suck on it, if you cant feel any resistance it may have failed.
Basic timing checks should be carried out too.
It may be worth waiting for your garage visit to stop you pulling your hair out, do you have it booked into a specialist?
It's a classic car specialist that are quite familiar with TVR's, I know they do sell them and service them etc, but probably not quite TVRSW level, but surely a decent old school mechanic should know their way around an old V8? After all, its not necessarily a TVR type issue, rover V8's were in loads of cars, any way, I'm sure they are up to the job, but take your point, probably worth waiting, its just frustrating that's allHoses to the plenum area include the fuel pressure regulator to stepper housing, brake servo, charcoal canister, crankcase breather system.
The vacuum advance module on the distributor can fail too meaning this can draw in more air than normal, this is the small pipe from dizzy to plenum.
A basic test is to remove the pipe from the plenum and suck on it, if you cant feel any resistance it may have failed.
Basic timing checks should be carried out too.
It may be worth waiting for your garage visit to stop you pulling your hair out, do you have it booked into a specialist?
Edited by Andy70 on Friday 27th September 20:56
adavy said:
Have you done a proper smoke test to check for leaks?.also have you used roverguage as this will point you in right direction.
bob boberson kindly brought his roverguage software around when I got the car and everything the system checks was all good, not done a smoke test, maybe that will be one for the garage?Belle427 said:
You only have to search here for Tvr Chimaera shunting and it will show hundreds of threads on the subject, some of which are very interesting.
The god damn shunt is killing me one is very good.
That was the most informative thread I read in shunting. The god damn shunt is killing me one is very good.
I was lucky in that my car never really shunted, but I was interested to try the vacuum signal change, and I found the car smoother on the pick up through the lower revs.
It’s a really cheap and easy change to make, but it’s important to be able to check the timing - which is also super simple but it requires a decent timing strobe gun.
I bought one from Amazon for around £40 and it was nonsense. I was lucky to have made friends with a nearby Griff owner who has better kit than me and we got it right.
Basically set the non advanced idle to 8degs BTDC and everything fell into place.
It’s also easy to check where TDC is - which is also a worthwhile exercise.
That goddamn shunt thread basically leads to those steps, but gives a lot of background info and theory in the mix.
As I understand it, the two most obvious culprits for shunt are the timing and advance combo (that thread), and the type or condition of the can shaft (and potentially timing chains), which is a bigger job of course.
Do you know if the can shaft is original, and how many miles are on your car?
I am confident that there at much more educated folk on here that would give alternative things to check, but that’s what I know if shunting.
Misfiring, again as I understand it, is 99% down to ignition system. Which is easy from coil to amp to dizzy to leads to spark plugs. Harder with injectors.
As a very basic trial, run a couple of shots of Redex through the tank when you fill up. You never know. And it won’t hurt anything.
Please also report back on what the mechanic finds. It’s all helpful for your learning as well as ours!
PabloGee said:
That was the most informative thread I read in shunting.
I was lucky in that my car never really shunted, but I was interested to try the vacuum signal change, and I found the car smoother on the pick up through the lower revs.
It’s a really cheap and easy change to make, but it’s important to be able to check the timing - which is also super simple but it requires a decent timing strobe gun.
I bought one from Amazon for around £40 and it was nonsense. I was lucky to have made friends with a nearby Griff owner who has better kit than me and we got it right.
Basically set the non advanced idle to 8degs BTDC and everything fell into place.
It’s also easy to check where TDC is - which is also a worthwhile exercise.
That goddamn shunt thread basically leads to those steps, but gives a lot of background info and theory in the mix.
As I understand it, the two most obvious culprits for shunt are the timing and advance combo (that thread), and the type or condition of the can shaft (and potentially timing chains), which is a bigger job of course.
Do you know if the can shaft is original, and how many miles are on your car?
I am confident that there at much more educated folk on here that would give alternative things to check, but that’s what I know if shunting.
Misfiring, again as I understand it, is 99% down to ignition system. Which is easy from coil to amp to dizzy to leads to spark plugs. Harder with injectors.
As a very basic trial, run a couple of shots of Redex through the tank when you fill up. You never know. And it won’t hurt anything.
Please also report back on what the mechanic finds. It’s all helpful for your learning as well as ours!
Cool interesting, the mileage is 62,2500k, timing is one for the mechanics i think, but I'm happy to change serviceable components as I didn't get much history with the car dizzy and rotor seem new, but having said that for the sake of 20 quid I can change them for piece of mind, no idea regarding coil, looks a bit crispy possibly, so again no harm in changing, new plugs so ok there and done redex ages ago, twice.. I was lucky in that my car never really shunted, but I was interested to try the vacuum signal change, and I found the car smoother on the pick up through the lower revs.
It’s a really cheap and easy change to make, but it’s important to be able to check the timing - which is also super simple but it requires a decent timing strobe gun.
I bought one from Amazon for around £40 and it was nonsense. I was lucky to have made friends with a nearby Griff owner who has better kit than me and we got it right.
Basically set the non advanced idle to 8degs BTDC and everything fell into place.
It’s also easy to check where TDC is - which is also a worthwhile exercise.
That goddamn shunt thread basically leads to those steps, but gives a lot of background info and theory in the mix.
As I understand it, the two most obvious culprits for shunt are the timing and advance combo (that thread), and the type or condition of the can shaft (and potentially timing chains), which is a bigger job of course.
Do you know if the can shaft is original, and how many miles are on your car?
I am confident that there at much more educated folk on here that would give alternative things to check, but that’s what I know if shunting.
Misfiring, again as I understand it, is 99% down to ignition system. Which is easy from coil to amp to dizzy to leads to spark plugs. Harder with injectors.
As a very basic trial, run a couple of shots of Redex through the tank when you fill up. You never know. And it won’t hurt anything.
Please also report back on what the mechanic finds. It’s all helpful for your learning as well as ours!
All good info guys, I'll tinker where i can then see what the garage can do if i fail, I'm just so frustrated as last night after replacing the stepper it ran so sweet until I started it up this evening. I'll change the gearbox oil tomorrow if I can jack the car up level (sorry wrong thread, see sticky gear change) I got some mobil ATF 220 is it? off ebay for 22 quid for 3l), thn look ito swapping dizzy and rotor arm
No idea regarding cam shaft, but the car seems peppier than my old Chim i had before, so assume it's ok
Belle427 said:
Its been mentioned before if you pinch off the stepper to plenum hose, the one that you replaced when the engine is running the revs should drop to roughly 600 rpm and almost stall out.
This is a pretty good indication of vacuum leaks but a smoke test is a much better option.
Ah ok, I thought doing that was to set the base idle, ill try that tomorrow, done for the day no, just changed the gearbox oil and tried to seal some leaks, ok, onto my other thread now, 'sticky gearshift' is it? lolThis is a pretty good indication of vacuum leaks but a smoke test is a much better option.
Belle427 said:
It is how you set the base idle too but can be some kind of indication you have a vacuum leak.
, ok i didn't know that, so if it stalls that could indicate a vacuum leak? I'd like to know more about the smoke test, is it a DIY thing that can be done, rent or but a kit or something? or is it one for the garage? I did RG data analysis back in August for the OP and all the iNputs and outputs indicated that all the parts were working correctly except the stepper was running very low at idle (ie open only around the 1% mark) suggesting a vacuum leak.
A smoke test is very worth while doing at this stage. Its a bit of kit that a lot of enthusiasts have so maybe ask around your area to see if you can borrow one, with garage rates at circa £80/hr you'd be better off buying your own for about 120 GBP.
Once you've sorted any leaks then set the base idle and that will shift the stepper upto a much more healthy 20 to 40 % at idle providing much more head room either way for the stepper to do its job.
A smoke test is very worth while doing at this stage. Its a bit of kit that a lot of enthusiasts have so maybe ask around your area to see if you can borrow one, with garage rates at circa £80/hr you'd be better off buying your own for about 120 GBP.
Once you've sorted any leaks then set the base idle and that will shift the stepper upto a much more healthy 20 to 40 % at idle providing much more head room either way for the stepper to do its job.
blaze_away said:
I did RG data analysis back in August for the OP and all the iNputs and outputs indicated that all the parts were working correctly except the stepper was running very low at idle (ie open only around the 1% mark) suggesting a vacuum leak.
A smoke test is very worth while doing at this stage. Its a bit of kit that a lot of enthusiasts have so maybe ask around your area to see if you can borrow one, with garage rates at circa £80/hr you'd be better off buying your own for about 120 GBP.
Once you've sorted any leaks then set the base idle and that will shift the stepper upto a much more healthy 20 to 40 % at idle providing much more head room either way for the stepper to do its job.
yeah, that vacuum leak was the pipe from the plenum to throttle body, I replaced that with a noticeable difference afterwards.. I seen a couple on ebay for about £60, or are they rubbish?A smoke test is very worth while doing at this stage. Its a bit of kit that a lot of enthusiasts have so maybe ask around your area to see if you can borrow one, with garage rates at circa £80/hr you'd be better off buying your own for about 120 GBP.
Once you've sorted any leaks then set the base idle and that will shift the stepper upto a much more healthy 20 to 40 % at idle providing much more head room either way for the stepper to do its job.
adavy said:
I had same symptoms as you. Smoke test revealed several leaks. Solved them which helped but core was to change the electrical connection to the afm. The wires had gone crispy. A $10 land Rover part cured it completely.
,yeah, mine don't look to healthy as it happens, Bob Boberson noticed it too when he popped around with his roverguage, is there a link any where for this please?
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