Stepper motor

[Flames7607]

Hi Everyone,

Have just got a very nice 1998 Chimaera 4.5

Can anyone tell me what the symptoms are for needing the stepper motor cleaned please ?

My car is a bit "lumpy" when at low throttle positions, either in town traffic or cruising on the motorway. There doesn't seem to be a mis-fire or anything, it just doesn't seem totally happy unless accelerating.

Cheers

[StarmistBlue400]

Loads of threads on steppers of late so probably worth a search. I could be wrong but would a dirty stepper make it lumpy. I would have thought the dizzy would be more to blame. Do you know the last time the plugs and dizzy were changed.

[Flames7607]

It's got new leads and plugs. Has no problem under power, just seems a little lumpy on those throttle positions just off idle

Regards

[Harrytsg]

This thread might help http://www.pistonheads.com/gassing/topic.asp?h=0&a...

It's sounds like a more possible culprit (as mentioned) may be ign/spark, worth checking the simple things like distributor cap and rotor arm for condition - bearing in mind there is mentioned on here that cheap copies of these parts can cause problems in themselves, particularly with rotor arms breaking down electrically.

Plug extenders ok?

[Flames7607]

Dark now so will check in the morning - good link to the stepper post though - something to check first.

Much appreciated

[chris1972]

Check out all the ignition components; dizzy cap, rotor arm, cleanliness of plugs, plug extenders, leads etc. Nothing wrong with taking the stepper out, giving it a clean and replacing with some fresh PTFE tape... another box ticked. Once you've gone through the ignition, if unresolved, start on the fuelling.

[Robert Lees]

"just doesn't seem totally happy unless accelerating",,,, they all do that! ;
lovely colour car by the way.

the stepper is usually related to idle rather than driving. Mine had this rough running at low revs. i disconnected the afm and it was right as rain?
ecu mate gave me a clue to be fair!

[Flames7607]

Please excuse my ignorance, what is ECU mate ? Is that like OBD2 ?

[shpub]

http://ecumate.com/shop/product_info.php/cPath/22/...

[Flames7607]

Great thanks for that, will have to try and source one :-)

[QBee]

Flames, "they all do that, Sir. It's a feature".

The stepper controls the idle.

If your stepper motor starts sticking in the OUT position, you will get a high idle on start up that then doesn't go away, and high idle at other times when you really don't want it, like when waiting at the lights or in slow crawling traffic.

If it sticks in the IN position your car won't hold any idle, and you will need to grow an extra foot for crawling up hill in a queue.

[Flames7607]

OK, seems my symptoms are not pointing to the stepper motor. Will check the distributor first, as it has new plugs and magnicore leads fitted before I bought it.

[QBee]

There are loads of other PH owners in Kentshire - just start a new thread headed Kent Chimaera owners - help please..... and explain your issue, then meet up and compare. If yours is excessive they might have suggestions, or part swaps you can try, and if it is just standard TVR rough idle at least you will know.

[QBee]

One futher thought - check all your plug leads are fully on the plugs - the number 8 one has a habit of popping off and costing you a rough idle and 30 bhp when giving it beans.

[Flames7607]

QBee,

Thanks so much, just going to check the leads and take her out for a spin. Will do a post for Kent owners too :-)

Regards

[Trevor450]

I had a cracked plug extender that wasn't visible to the naked eye until I went to change the leads and it came apart. It caused a hesitation and lumpy running around town.

[Flames7607]

Thanks Trevor, will check mine when the engine bay has cooled down, having just come back from a run.

Regards

[Flames7607]

My next question associated with this is how hot does the exhaust manifold get. I have Magnocor KV85 leads fitted which are fully suppressed, but if I remove the extenders, the lead boots will touch the manifold on some cylinders. If the problem is a faulty plug extender I would like to remove all of them to see if it fixes it.

Regards

[chris1972]

Flames7607 said:

My next question associated with this is how hot does the exhaust manifold get. I have Magnocor KV85 leads fitted which are fully suppressed, but if I remove the extenders, the lead boots will touch the manifold on some cylinders. If the problem is a faulty plug extender I would like to remove all of them to see if it fixes it.

Regards

Very, very hot. You can purchase heat protective sleeves if you no longer to use extenders, however, you may then find that the leads no longer reach the dizzy.

[QBee]

chris1972 said:

Flames7607 said:

My next question associated with this is how hot does the exhaust manifold get. I have Magnocor KV85 leads fitted which are fully suppressed, but if I remove the extenders, the lead boots will touch the manifold on some cylinders. If the problem is a faulty plug extender I would like to remove all of them to see if it fixes it.

Regards

Very, very hot. You can purchase heat protective sleeves if you no longer to use extenders, however, you may then find that the leads no longer reach the dizzy.

Been there, tried that, now have extenders AND heat sleeves