ISCV Workings?
Discussion
J-LLO has started to misbehave. She will start but as soon as you try and drive away there are coughings and splutterings and the car wants to stall if you do not dip the clutch. When hot you can feel a hesitation on constant speed running. If you drove it like you stole it it is fine. It is fun to give her a good thrashing around my local country lanes but some more relaxed cruising would be nice occasionally.
My first feeling was that it was over fuelling and I have taken off the idle speed control valve (ISCV) and have started to clean the unit for the first time. There was some carbon coming out of it. However I am confused as to the physical operation of the unit. I understand that the solenoid operates a rod to open a valve at the other end of the casting. There are two ports on the side which were connected to each other in the body of the unit by the spindle hole. So,some enlightenment of the workings of the ISCV would be welcome.
I have a copy of the 2.9 diagnostics article from Car Mechanics (?) which I am attempting to follow.
If I cannot sort the problem I will have to join the bank robbers on Euro Tour!
My first feeling was that it was over fuelling and I have taken off the idle speed control valve (ISCV) and have started to clean the unit for the first time. There was some carbon coming out of it. However I am confused as to the physical operation of the unit. I understand that the solenoid operates a rod to open a valve at the other end of the casting. There are two ports on the side which were connected to each other in the body of the unit by the spindle hole. So,some enlightenment of the workings of the ISCV would be welcome.
I have a copy of the 2.9 diagnostics article from Car Mechanics (?) which I am attempting to follow.
If I cannot sort the problem I will have to join the bank robbers on Euro Tour!
TurboTony said:
So,some enlightenment of the workings of the ISCV would be welcome.
Forgive me if this is TOO elementary, but when the engine is idling, the throttle is almost completely shut, so no air can get in. The ISCV has two holes - one is on the outside of the throttle butterfly, the other is on the plenum (vacuum) side.The engine needs air to run, and the ISCV is just a solenoid controlled by the ECU, that opens a valve between those two holes, to allow air to bypass the throttle in varying quantities, controlled by the various other signals the ECU receives - engine temperature, engine speed, air flow meters (or lambda sensors on cat-equipped cars), etc.
All works great when it's new. When it's all 20-odd years old, not so much.
Mine has similar symptoms to yours, so I'll be doing the same sometime soon.
I'd start with a voltage check (see your Car Mechanics article) on the Throttle Pot.
A good blast of Carb Cleaner up the airflow metres would probably do no harm?
ICV just lets a bit of air past when throttle flaps are fully closed, no harm in giving it a clean but possibly not the cause of your issues
Another thought, are your air hoses from Air Flow metres ok, any air leak will create all sorts of "funny" behaviour?
Hope you get sorted soon and J-llo is fighting fit again
I've had no end of problems getting my S3c to run properly Tony. I've recently replaced the lambda sensors, cleaned every sensor connection and it still ran like a pig, very frustrating. I was resigned to taking it to a garage, but I had one more read of the bible and found a section on resetting the ecu. This simply entails unplugging the main, multi pin connector and then plugging back in. Apparently, this resets the ecu to its original map. I did this (awkward as above the passenger footwell), and started the car and it's been running perfect ever since. Might be worth a try..
tel595 said:
I've had no end of problems getting my S3c to run properly Tony. I've recently replaced the lambda sensors, cleaned every sensor connection and it still ran like a pig, very frustrating. I was resigned to taking it to a garage, but I had one more read of the bible and found a section on resetting the ecu. This simply entails unplugging the main, multi pin connector and then plugging back in. Apparently, this resets the ecu to its original map. I did this (awkward as above the passenger footwell), and started the car and it's been running perfect ever since. Might be worth a try..
I believe disconnecting the battery for 20 mins does the same thing. But I also read somewhere that when you start it for the first time you should not touch the throttle but allow it to tick over until warm and the fan cuts in. Something to do with the ECU learning parameters. Did this the other day after a battery change and it's running better than ever. TurboTony said:
J-LLO has started to misbehave. If you drove it like you stole it, it is fine. It is fun to give her a good thrashing.
If I cannot sort the problem I will have to join the bank robbers on Euro Tour!
Here you go Big Tony. You'll need these accessories. If I cannot sort the problem I will have to join the bank robbers on Euro Tour!
If you're looking for a safe job, Nobby & Stan are doing one next Friday night. Seriously, does J-LLO have a porous or leaking vacuum pipe? Try spraying carb cleaner or Bradex Easy-Start around the hoses with the engine running and see if the idle speed increases. Or use a spare length of hose as a stethoscope.
Oops, forgot the piccy!
Edited by glenrobbo on Friday 15th April 10:10
Sorry if this is stating the obvious, but have you tried a fault code reader to interogate the ECU
(Of course being a 1991 Ford, this isn't a modern ODBC type reader, but a special bit of kit known as a Star Tester)
There are at least a couple of these in the community - I have one and maybe Philpott?
It does give codes which can indicate if the ECU is happy and point to things like faulty sensors or readings as well as allowing a test where you shake and pull the wiring to see if anything is intermittent.
(Of course being a 1991 Ford, this isn't a modern ODBC type reader, but a special bit of kit known as a Star Tester)
There are at least a couple of these in the community - I have one and maybe Philpott?
It does give codes which can indicate if the ECU is happy and point to things like faulty sensors or readings as well as allowing a test where you shake and pull the wiring to see if anything is intermittent.
Well,firstly thanks to all for your advice. I now understand the workings of the ISCV. When I looked more closely I could see that the rod had a bulge which seats in between the two apertures.
I cleaned all this and re-installed the unit which gave a little improvement but did not provide a complete cure.
This afternoon, I removed the two airflow meters and the hoses to the plenum. Although the Meyers were pretty clean I still have them the once over. The tubes are fairly sad having some rub marks and a couple of places where these could be pin holes. I have wrapped the dodgy areas with self amalgamating tape. I also sprayed the butterflies. She is now running very well, even when cold.
I will replace the two hoses. TVR parts list them:
http://tvr-parts.com/tvr-parts/part-details/tvr-s2...
although I suspect that there may be alternatives which have been used? Did I read somewhere that smooth or convoluted hoses gave better airflow or am I dreaming this?
I cleaned all this and re-installed the unit which gave a little improvement but did not provide a complete cure.
This afternoon, I removed the two airflow meters and the hoses to the plenum. Although the Meyers were pretty clean I still have them the once over. The tubes are fairly sad having some rub marks and a couple of places where these could be pin holes. I have wrapped the dodgy areas with self amalgamating tape. I also sprayed the butterflies. She is now running very well, even when cold.
I will replace the two hoses. TVR parts list them:
http://tvr-parts.com/tvr-parts/part-details/tvr-s2...
although I suspect that there may be alternatives which have been used? Did I read somewhere that smooth or convoluted hoses gave better airflow or am I dreaming this?
These people: http://www.autosiliconehoses.com/ do a twin wall wire reinforced silicon hose in black or blue outside/orange inside in various diameters which should do the job.
I fitted some of their 75mmm hose on Austin's air inlet a few years ago. It's robust stuff.
.
I fitted some of their 75mmm hose on Austin's air inlet a few years ago. It's robust stuff.
. glenrobbo said:
twin wall wire reinforced silicon hose in black or blue outside/orange inside in various diameters
One thing to check if you're fitting silicon intake hoses is where the crankcase breathers come out - the breather hoses are often taken down to the air filter, which means the gases are drawn back up the intake hoses. They contain fuel and combustion byproducts which will degrade normal silicon hoses unless you fit the expensive stuff with a fuel-resistant liner. The ones glenrobbo mention obviously have a liner, which I guess will be a fuel-resistant liner, which is great. I suspect the wire reinforcing may be overkill since these hoses shouldn't ever see suction, but there's no harm in it except maybe pushing the price up a bit.glenrobbo said:
Tony, if you no longer need the bank robbers accessories, please could you return the blue rubber gloves?
I may need them.......
I will send them back after the weekend as I am drilling some large holes to get into a bank vault, but please do not tell anyone else.I may need them.......
I think that I will wrap the entire length of the intake hoses in self amalgamating tape to give a neater finish as a temporary (!) solution.
Oil change next on the list followed by new brake shoes.
Niiige said:
How is J-LLO doing ?
Have you given her some TLC today or did you turn into Basil Fawlty and motivate her with a branch ?
Cold today, so I carried out some chores in the house. Started J-LLO this afternoon and she sounded nice. Should be able to play in the garage tomorrow.Have you given her some TLC today or did you turn into Basil Fawlty and motivate her with a branch ?
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