Running Issues. Any ideas please?

Running Issues. Any ideas please?

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pb450

Original Poster:

1,301 posts

159 months

Friday 3rd April 2015
quotequote all
Never had any issues really, it's always run like a dream. Then a couple of weeks back I had the following....

The car starts well from cold and idles well. For a minute or so it won't rev freely and wants to stall with any throttle. (There was a thread on this symptom recently.) Then it clears after a short while. When warm, progress is good. Except... on the overrun there is bad shunting below around 1800 rpm when decelerating. So, change down and dip the clutch well before coming to a halt. Again, not a major problem but it shouldn't do this and it's a pain.

Then today I drove down to Portsmouth to collect my son from University. A 170 mile return trip. With 3 miles left I hit major traffic and crawled for an hour to complete the journey. (I know, Bank Holiday traffic, etc. Yuk!) This was a nightmare as the car constantly wanted to stall. Throttle blips kept the engine running but this wasn't clean. Pretty hacked off after an hour of that, I can tell you!

The journey home was fairly uneventful, except for shunting on the overrun as described. Then... approaching a major roundabout on the A3 I dipped the clutch, changed down and entered the roundabout. Foot off clutch and.... dead! Nothing! I came to a virtual stop trying to bump it in second. No luck. I turned the key and she roared into life again and off we went. I wasn't too popular with white van man behind me at the time but there was no reoccurrence during the remainder of the journey

At standstill when the revs are behaving, she idles at 1000, then 800, then back up to 1000 rpm, alternating for a couple of seconds on each, up and down. Occasionally on 1500rpm for a few seconds before returning once more to the up/down idle. Again, not right.

What I've done - which isn't much:
- Removed, cleaned and replaced the stepper motor.
- Checked that all plug leads are securely in place.
- Disconnected and reconnected the battery in case the ECU had it's knickers in a knot.
- Run a couple of tanks of Shell V-Power through on the TADTS principle, in the hope that it might be dirty petrol and would clear.

One last point, when I started up again an hour after arriving home to put the car back in the garage, it ran perfectly! Steady revs, no stutter, etc. Why do I think this won't be the end of it though? Simply because it does that occasionally, runs well for a short while.

I shall be on the phone to my friendly specialist next week but if anyone has a bright idea, I'd love to hear it. I should add that I won't be pulling too much apart myself and am pretty limited with my electrical testing skills.

Looking forward... if you're not bored reading this and haven't given up already. I wouldn't blame you. smile

Edited by pb450 on Friday 3rd April 19:40

jojackson4

3,026 posts

136 months

Friday 3rd April 2015
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Your not alone

ianwayne

6,243 posts

267 months

Friday 3rd April 2015
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A friend of mine had similar symptoms with his Chimaera 500. I strongly suspected the stepper motor but lending him mine made no difference. His car would just about start but then run terribly. We sorted it with a new battery!

Even though the old one had enough power in it to just about start the car, it was dragging all the electrics down. It was confirmed when after it stalled again, it wouldn't turn power enough to start and we had to bump it. With a new battery, the car was running smoothly after about 15 minutes (disconnect caused ECU reset of course).

pb450

Original Poster:

1,301 posts

159 months

Friday 3rd April 2015
quotequote all
jojackson4 said:
Your not alone
Some comfort, at least. smile

ianwayne said:
A friend of mine had similar symptoms with his Chimaera 500. I strongly suspected the stepper motor but lending him mine made no difference. His car would just about start but then run terribly. We sorted it with a new battery!

Even though the old one had enough power in it to just about start the car, it was dragging all the electrics down. It was confirmed when after it stalled again, it wouldn't turn power enough to start and we had to bump it. With a new battery, the car was running smoothly after about 15 minutes (disconnect caused ECU reset of course).
Interesting prospect. My battery is 3 years old and is on a trickle charger when the car is not in use. Never any starting issues. Spins like a good'un. I even left the headlights on in a service station today for 5 minutes when stopped for a 'comfort break' without any re-start issues.

BeastMaster

443 posts

186 months

Saturday 4th April 2015
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Hi Peter

Had much the same intermittent problem with mine, after a year of fluffing about thinking the problem solved only to rear its head again by either over or under revs I decided to do away with the stepper as the issue was spoiling my enjoyment of the car.

Decided that the stepper operation may have some relevance over other ecu control so decided to blank off the area behind, so that the ecu believes that it is controlling the stepper but has no influence over the engine running at all.

Since doing this 18 months ago the car seems totally transformed, even gear shifting seems more crisp and would not consider going back. Cold start up is unaffected but obviously cold tick over is a pain for a short while holding on throttle until enough temp is available to hold a steady tickover.

You can give it a try by disconnecting the stepper once a steady tickover has been achieved while the engine is running, but the ecu will know that it is disconnected and may throw up other issues, ie over / under fueling.

Andy

caduceus

6,069 posts

265 months

Saturday 4th April 2015
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jojackson4 said:
Your not alone
Olive?

skiver

656 posts

192 months

Saturday 4th April 2015
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I had the same problem and you have described my symptoms exactly.Replacing the coolant temperature sensor solved everything and is a cheap and simple fix; about a tenner for the sensor and 15 minutes work, well worth a try.

blitzracing

6,387 posts

219 months

Saturday 4th April 2015
quotequote all
Certainly over fuelling will cause the engine to stall and shunt. A temp sensor reading low or AFM output going high will cause to much fuel and the shunting would be the ECU trying to control the mixture. Id drop a plug out and see if its black.

pb450

Original Poster:

1,301 posts

159 months

Saturday 4th April 2015
quotequote all
skiver said:
I had the same problem and you have described my symptoms exactly.Replacing the coolant temperature sensor solved everything and is a cheap and simple fix; about a tenner for the sensor and 15 minutes work, well worth a try.
Now that's REALLY interesting Stuart. Thanks for the tip. Don't suppose you have a pic of where this little baby lives, do you? Certainly sounds like over fuelling.

skiver

656 posts

192 months

Saturday 4th April 2015
quotequote all
Unable to get a pic but it's situated behind the distributor cap: a brass plug screwed vertically down into the engine
with a red/black wire and green wire leading from it.

pb450

Original Poster:

1,301 posts

159 months

Saturday 4th April 2015
quotequote all
Excellent. Good description. I shall go looking for it.

jojackson4

3,026 posts

136 months

Saturday 4th April 2015
quotequote all
Buy the brass nut one the plastic ones are st

pb450

Original Poster:

1,301 posts

159 months

Monday 6th April 2015
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Sardonicus said:
The only one you will ever need and FAE are an OE quality item Ebay number 301434586462
From another thread but good advice here from Simon. For £9.99 I've bought one, even if it turns out not to be the culprit, it's a useful spare to have. It has the brass thread and there is only one left now from this source on ebay. thumbup

pb450

Original Poster:

1,301 posts

159 months

Friday 24th April 2015
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Quick update: The coil end of the king lead was VERY loose in the coil, to the point where it was not fitting properly. The coil was arcing to anything it could find, other than the king lead itself. This accounted for the rough running and resulted in damage to the coil as shown below.



New coil now fitted. Perfect running. thumbup A huge thanks to Dan Taylor for sorting this out for me. Although I should have picked it up myself, (I found the loose lead, shoved it in but missed the coil end) Dan had it sorted very quickly.

Also a huge thanks to Graham who lent me a bag of bits to replace. I simply ran out of time. Cheers mate!