'lumpy' constant speed running
Discussion
recently bought a 1994 m reg chimaera, full service history + bills, mots, etc. car is in excellant order - car is great in every respect except one...
when i try to drive on a constant trottle / speed (hot or cold though worse when cold) the car seems to lurch or hunt, i wouldn't describe it as a misfire as such but on some occasions it can feel similar.
I run the car on shell optimax - 98 octane, there is no apparent misfire @ tickover or when accelerating so it doesn't seem to be anything major.
does this sound familiar?
like i say, the car is great, starts everytime and drives / sounds brilliant just wondering if 'they all do that' or there is something i should be checking.
when i try to drive on a constant trottle / speed (hot or cold though worse when cold) the car seems to lurch or hunt, i wouldn't describe it as a misfire as such but on some occasions it can feel similar.
I run the car on shell optimax - 98 octane, there is no apparent misfire @ tickover or when accelerating so it doesn't seem to be anything major.
does this sound familiar?
like i say, the car is great, starts everytime and drives / sounds brilliant just wondering if 'they all do that' or there is something i should be checking.
No, Pete I'm not taking the piss. I have been a Chimaera owner, I now own a Cerbera.
If you click on the tab at the top of this screen marked 'search' and enter Stepper motor it will answer your questions.
Lump running is often caused by a dirty stepper motor and it is the most frequently asked question (or one of them) which is why I said All together now....
You might also have a problem with an air leak, the Ecu might need resetting, you might have an ignition problem, or any number of other things.
But try the stepper first.
If you click on the tab at the top of this screen marked 'search' and enter Stepper motor it will answer your questions.
Lump running is often caused by a dirty stepper motor and it is the most frequently asked question (or one of them) which is why I said All together now....
You might also have a problem with an air leak, the Ecu might need resetting, you might have an ignition problem, or any number of other things.
But try the stepper first.
Tyre Smoke said:
No, Pete I'm not taking the piss. I have been a Chimaera owner, I now own a Cerbera.
If you click on the tab at the top of this screen marked 'search' and enter Stepper motor it will answer your questions.
Lump running is often caused by a dirty stepper motor and it is the most frequently asked question (or one of them) which is why I said All together now....
You might also have a problem with an air leak, the Ecu might need resetting, you might have an ignition problem, or any number of other things.
But try the stepper first.
Thanks - i'll check out some of things you mentioned - your cerbera looks smart by the way, hope you enjoy it!
S/M is a good place to start provided the poor running only occurs at low revs. Beyond this point the S/M has no great influence on matters.
I chased a 'lump' around 2500rpm for months on my old 4.0HC and only really found relief by reseating all the electrical connections to do with the ignition system. There are a lot of them - made me wonder how it ever ran smoothly.
I chased a 'lump' around 2500rpm for months on my old 4.0HC and only really found relief by reseating all the electrical connections to do with the ignition system. There are a lot of them - made me wonder how it ever ran smoothly.
swisstoni said:
S/M is a good place to start provided the poor running only occurs at low revs. Beyond this point the S/M has no great influence on matters.
I chased a 'lump' around 2500rpm for months on my old 4.0HC and only really found relief by reseating all the electrical connections to do with the ignition system. There are a lot of them - made me wonder how it ever ran smoothly.
Thanks...this sounds similar to what i am experiencing as the constant speeds that are most common - 30mph and 60/70mph correspond to approx. 2000 to 2500 rpm (depending on which gear is selected obviously) - car is being tucked away for the winter soon so i should be able to start checking stuff like electrical connections.
Hope i dont open a can of worms!! if you know what i mean.
tovey said:
i had similar problems, turned out to be the coil, hope this helps. Best of luck with your new toy.
agreed...
I had the 2000rpm lumpy running thing & the guys at CDL did several trial & error fixes - the Ignition Module & Coil cured it 90% - Dan, then at CDL is now the new guy with Leven's
cosmoschick said:
It could be the oxygen sensors not working correctly causing the fuel mixture to be too rich or the fuel injectors could be dirty/blocked which in turn will prevent delivery of a fine mist of fuel into the combustion chamber.
I have this problem with the Griff at the moment, its fine on tickover & under power but at steady revs its lumpy.
Turns out to be the injectors, fuel cleaner has helped no end but they need a good clean or perhaps replacing - deep joy.
Nick
ncs said:
[quote=cosmoschick]It could be the oxygen sensors not working correctly causing the fuel mixture to be too rich or the fuel injectors could be dirty/blocked which in turn will prevent delivery of a fine mist of fuel into the combustion chamber.
I have this problem with the Griff at the moment, its fine on tickover & under power but at steady revs its lumpy.
Turns out to be the injectors, fuel cleaner has helped no end but they need a good clean or perhaps replacing - deep joy.
Nick
[/q The description of the problems with your griff sound exactly like the problem i am experiencing - not a massive problem, i can drive round most of the time - more irritating really.
i have just put some fuel cleaner in with the petrol -will see if it improves matters.
Thanks for your suggestion.
tovey said:
i had similar problems, turned out to be the coil, hope this helps. Best of luck with your new toy.
coil looks ancient on my car - maybe one of the things i replace as a matter of course over the winter.
Love the car - people said that you would love or hate a tvr (mostly people who had never even been in one let alone owned one!)- definately love.
Can also be the vacuum advance pump as already advised and covered in the Chimaera forum recently.
It`s the little "flying saucer" shaped thing on the the distributer housing. If this packs up,it can cause your problems at 2000 rpm. There is a pipe that runs from it`s centre to the top of the plenum (covered in the bible). To try it (you can always put it back) disconnect from both ends (noting which way round it goes as there is a one way valve built in) and block up the nipple on the Plenum with tape or similer and leave the advance pump end open. Take it for a drive and you will either be amazed at the difference (as I and many others were) or that won`t be the cure at all!
It is there apparently to aid fuel consumption on motorway/constant driving but does no harm taking it off.
It`s the little "flying saucer" shaped thing on the the distributer housing. If this packs up,it can cause your problems at 2000 rpm. There is a pipe that runs from it`s centre to the top of the plenum (covered in the bible). To try it (you can always put it back) disconnect from both ends (noting which way round it goes as there is a one way valve built in) and block up the nipple on the Plenum with tape or similer and leave the advance pump end open. Take it for a drive and you will either be amazed at the difference (as I and many others were) or that won`t be the cure at all!
It is there apparently to aid fuel consumption on motorway/constant driving but does no harm taking it off.
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