Still won't idle properly

[Alex Gurr]

Unfortunatley my car is still rather poorly. Basically it doesn't want to fire on start up and it idles horribly, always on the verge of stalling unless you give it some revs. This happens hot or cold. The strange thing is that it seems to pull fine at higher rev's (2,000rpm +), but just does not want to idle at all.

I have:
- checked and cleaned all the plugs (although not checked the gaps)
- replaced all of the HT leads, including the king lead
- quickly cleaned the stepper motor housing at the back of the pelumn chamber
- swapped the air flow meter for one lent to me by dnb

Where should I be looking next? People have mentioned that the coil can pack up, but I am guessing it is OK, because the car still pulls well at higher revs. Any other ideas? Could it be ECU related?

Any help would be very greatfully appreciated. If any RV8 gurus live around Hertford and fancied poping over to help me look at it then that would be very much appreciated - there might even be a few beers in it for you too

I am just getting a bit frustrated now as I really want to get out and enjoy it some more.

Cheers,

Alex

[350Matt]

Sounds like an air leak somewhere, any joint after the airflow meter if it leaks will pull in air and lean the engine out, at higher revs / throttle the percentage of air isn't enough to effect it so it runs over that point.

Check all the rubber hoses onto the plenum and any joints / t-pieces etc.

One of the best ways to find air leaks is to spray lighter gas around the joints with the engine running, if it revs up when you spray the joint, then you've found the leak as the engine will pull the gas in and use it as fuel.

Matt

Edited by 350Matt on Monday 18th June 21:22

[Alex Gurr]

Thanks Matt. I will have a look at the air lines into the pelumn and see what I can find. I did casually check the pipe from the AFM to the pelumn and it seemed OK, but I will look more carefully tomorrow.

Interestingly enough, when I unscrewed the stepper housing on the back of the pelumn slightly the engine revs increased, but when I removed it the engine died all together. Is this common?

Cheers,

Alex

[NicBowman]

Hi

The stepper motor could be knackered. This lets air past the throttle buterfly, to allow tickover. If the stepper is broken and closed, the idle will be 500rpm (or should be) so may stall. When you muck around with teh stepper housing you are letting air in, thus increasing the tickover.

Airleaks would normally go the other way, too high tickover.

Suggest new stepper motor.

Nic

[Alex Gurr]

NicBowman said:

Hi

The stepper motor could be knackered. This lets air past the throttle buterfly, to allow tickover. If the stepper is broken and closed, the idle will be 500rpm (or should be) so may stall. When you muck around with teh stepper housing you are letting air in, thus increasing the tickover.

Airleaks would normally go the other way, too high tickover.

Suggest new stepper motor.

Nic

Nic, is there an easy way to test whether the stepper motor is broken or is it simply a case of replacing the unit? Is this something an ECU fault reader would pick up?

Cheers,

Alex

[NicBowman]

Hi

Reading from Steve Heath, ECU fault 48 would point to stepper motor. You can also test for the correct resistance at the ECU plug. I would get a copy of the Steve Heath book, it helps!

Cleaning the stepper is the easy bit, I think this is mainly a placebo, but worth a try.

Steppers are medium expensive, around £90 I recall, so on the limit of a 'buy to try', unless you have lots of cash!
Best of luck.


Nic

[Slacey]

There are steppers on eBay at the moment for £25

[Jay Ayegees]

Silly question - did you reset the ECU after all that fiddling?

[Alex Gurr]

Jay Ayegees said:

Silly question - did you reset the ECU after all that fiddling?

Er no I think I need to go off and read Steve Heath's book . I have got a copy, but have been limited on time and stupidly attacking this by trial and error. Obviously I will find out later, but is it easy to reset the ECU?

Cheers,

Alex

[Hoover.]

I'm no expert at all..... new stepper motor though on ebay approx £30....

http://cgi.ebay.co.uk/Idle-Air-Control-Valve-Range...

[Griff Boy]

Part no 25527077 or 73312A

Anyone know which of the two part numbers for a serp 5.0 v8?

Cheers

Ian

PS Was just about to pay £90 from ACT for one!, cheers Hoover

[mrcosmos]

Hi Alex,had exactly the same symptoms with my Griff.I changed the Dizzy cap and Rotor arm for genuine Lucas ones.Now perfect.Hope this helps.Regards,Dave.

[Alex Gurr]

mrcosmos said:

Hi Alex,had exactly the same symptoms with my Griff.I changed the Dizzy cap and Rotor arm for genuine Lucas ones.Now perfect.Hope this helps.Regards,Dave.

Thanks Dave. The Dizzy Cap and Rotor look OK to me, but if the ECU reset doesn't work then I will look to replace these too.

When cleaning the inside of the stepper housing is it simply a case of covering a rag in white spirit and wiping it around the inside (say on the end of a screwdriver), or do you need to take the housing off the back of the plenum and give it a really thorough clean.

Cheers,

Alex

[Johno]

Check the servo hose . . . .

[Hoover.]

Griff Boy said:

Part no 25527077 or 73312A

Anyone know which of the two part numbers for a serp 5.0 v8?

Cheers

Ian

PS Was just about to pay £90 from ACT for one!, cheers Hoover

I got the lead on this from the Chimp boys.... they are buying 73312A as its what listed on their parts page and also the number on their removed ones.... no idea if the 500's have a diff one though.

Hoover

[Jay Ayegees]

Reset ECU by:-

1). Turn off ignition,
2). Locate ECU in passenger footwell.
3). Carefully unplug connector from ECU.
4). Go have a quick cuppa or make mad passionate love to your partner (several times if you're not into foreplay)
5). Reconnect the connector to the ECU.
6). Put all the spaghetti back as tidy as you can.
7). Go lie down if you're shagged or go for a good run.

Jay

[Alex Gurr]

Well, I have tried everything I can thing of and don't seem to be getting anywhere. I know it will sound defeatest, but I am going to send it to a garage for them to look over. My fear is that I could end up replacing half of the injection system before finding the fault, which would cost me more both in hours and pounds.

Does anybody know any good TVR indies near Hertford.

Cheers,

Alex

[Hoover.]

Not an independant as such..... but very knowledgable on TVRs... looks after a fair few....

Kimberly Motors
17-18, The Service Rd, Potters Bar, Hertfordshire EN6 1QA
Tel: [phone]

or you have Offords nr St Neots, TVR Centre at Arlkey (Barnet)

Hoover.

[Uncle Fester]

I had some very similar, but not identical symptoms.
It turned out to be worn distributor.
Is your Tacho reading stable?
If not, can a tacho, the kind garages use to put on the leads under the bonnet get a stable reading?
Is there any play in the distributor shaft bearings?
Fester

[Alex Gurr]

Thanks Hoover, much appreciated

Uncle Fester - The idle isn't stable. Basically the symptoms are:

- Reluctant to fire on start up. The engine churns over more than it would do normally, then it coughs into life.
- The idle isn't stable, hunting slightly, often coughing on what feels like 6 or 7 cylinders. This can happen for a few seconds, or a few minutes, before eventually dying.
- The engine seems to run fine under load, reving up cleanly, or so it appears.

I have tried:
- Cleaning the plugs (in all fairness they weren't that bad in the first place)
- Replacing the HT leads and King Lead (which had a slightly split casing)
- Cleaned the air flow stepper motor
- Cleaned the throttle butterfly housing
- Re-set the ECU

None of these seem to have made any difference.

I have decided to try the fault reader that a fellower Pistonheader lends out for a few quid and see what it comes up with. If I have no joy with that then I think it will have to go into a specialist.

Thanks for all your help so far guys.

Cheers,

Alex