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        General >> Problems >> Idle problem
        
(Message started by: Mike_Floutier on Aug 1^st, 2008, 12:10pm)

Title: Idle problem
Post by Mike_Floutier on Aug 1^st, 2008, 12:10pm

Hi all,

It starts beautifully and idles perfectly - for about 20 - 30 seconds - then it suddenly becomes a little lumpy.

Any ideas?

Mike

Title: Re: Idle problem
Post by bizzay1 on Aug 1^st, 2008, 12:42pm

Air Hose ??

Title: Re: Idle problem
Post by Mike_Floutier on Aug 1^st, 2008, 1:21pm

Which one do you mean?

What I'm focussing on is the fact that it can and does idle perfectly, BUT something changes, every time - exactly after 20 seconds.

I'm after this thing that changes, what happens 20 seconds after start-up?

Mike

Title: Re: Idle problem
Post by peteHull on Aug 2^nd, 2008, 12:06am

Could it be air con switching in.... sudden extra strain on engine? whatch the clutch onthe front of the compressor....

Title: Re: Idle problem
Post by Tompion on Aug 2^nd, 2008, 1:54am

Possibly when the oxygen sensor is up to temperature.

Title: Re: Idle problem
Post by Mike_Floutier on Aug 2^nd, 2008, 6:22am

The air-con is already on.

I'm interested in the o2 sensor, I wondered about that; it's been on there for 313,000 miles, maybe it's tired of life, sounds like it might be. It feels like that sort of problem.

Thanks

Mike

Title: Re: Idle problem
Post by kev2scorps on Aug 2^nd, 2008, 9:36am

Hi Mike,

Does the same problem occur if the engine is started from cold, e.g. in the morning after being idle all night, or only on a warm / hot start?

Why do I ask?

Well the lamda or ho2s sensors should not come into play on a cold start for 180 seconds after start up. The engine is running in "open loop" where fueling is controlled by calculations based on Intake Air Temperature, IAT, Engine Coolant Temperature, ECT, and Mass of Air Flow into the engine, MAF. After 180 seconds of running from cold start, the engine swithes to "Closed Loop" where stoichometric (lamda) levels comes into play. This is when the lamda or ho2s, (heated oxygen sensors), come into play. See this page on the main site for a much more comprehensive explenation... http://www.fordscorpio.co.uk/ho2smonitor.htm

If you have access to an OBD Scan, the performance of the HO2S sensor can be monitored, a graph can be run showing the sensor switching from slightly rich to slightly lean, approx 0.8volts to approx o.2 volts. This switching should be about once per second. If a second oxygen sensor is fitted on your 2.3 (after the CAT, though any 97 Scorp which I have seen has not got the second sensor), it should be "flat lining" around 0.4 or 0.5 volts if the catalytic converter is doing its' job corretcly. The second sensor is only a monitor, and does not have an effect on fueling, I guess that Ford made cutbacks.

I hope I haven't confused the issue any further here.

Hope you sort it soon,

Kev.

Title: Re: Idle problem
Post by Mike_Floutier on Aug 2^nd, 2008, 5:31pm

Ok, thanks for that. A few things spring to mind:

1. How does it define cold start - coolant temp?

2. Now, on a NORMAL working car, assuming it's up to temperature and idling ok, IF you were to disconnect the Lambda sensor AT IDLE, what reaction would you expect?

Reason for asking 2. is that I can disconnect the sensor with no change noticable.

I removed the sensor just to see if I could since I'm thinking of replacing it - that was easy!

After removing the heat shields I noticed that the compression joint between the exhaust manifold and the EGR valve was "dry". I discovered that it had never been properly made. Maybe this explains the slight smell of exhaust gases in the cabin at idle. Anyway, I remade it properly with a new, undamaged olive BUT that made no difference.

I also took advantage of the lack of heat shields to check that the exhaust manifold to cat nuts were easy to undo. They were; this is good news for the possible impending auto-box change.

Anyway, I'd be interested in what you think about 1) & 2).

Thanks as always,

Mike

Title: Re: Idle problem
Post by kev2scorps on Aug 2^nd, 2008, 8:36pm

Hi Mike,
I really don't know what temperature the engine Coolant has to be below to define a cold start, but the mechanic where I work, who teaches apprentices and is a bit of a whiz on electrics, diagnostics etc. once told me that the only way to be sure was to leave the car for many hours or to be safe - over night.

If the lamda sensor is disconnected on a normally running car, the emissions will be excessive, the car would fail an M.O.T. but the engine would run in "Open Loop" where the onboard computer would make calculations about fueling based on Engine Coolant Temperature, Intake Air Temperature (Cool air is more dense than warm air), and MAF, (Mass Air Flow) readings. The lamda sensor only fine tunes the mix.

There are 2 engine coolant temperature sensors on your car, 1 talks to the ECU, the other to the temp display on the dash.

Sorry if this hasn't been of much help, I am no expert, I have just learned bits from this site, the mechanic at work, "Car Mechanics" magazine and of course by tinkering with cars myself.

With regards to the compression joint on the pipe from the exhaust manifold to the EGR valve, try sealing around it with "Gun Gum", I have used this on a cracked exhaust manifold for a while and so far so good. Alternatively, you could get some gasket seal in a tube, (like the sealant used around baths and in showers, but of course designed to be used on manifolds, cam covers etc). Make sure though that none of the product drops into the manifold down onto the cat or lamda sensor. The mechanic at work warned me that that wouldn't be so good for either.

Kev.

Title: Re: Idle problem
Post by Mike_Floutier on Aug 2^nd, 2008, 9:25pm

Thanks Kev, hopefully someone else will come along knows the answer, I would like to get this sorted before I sell the car.

Regards

Mike

Title: Re: Idle problem
Post by davem on Aug 2^nd, 2008, 10:09pm

Sounds like the oxygen sensor or ERG system. Get an OBD2 scan on it and read the codes. Anyone in your area with an OBD lead?

Dave

Title: Re: Idle problem
Post by Tompion on Aug 8^th, 2008, 12:59am

Mike

I believe the 2.3 should have a planar oxygen sensor fitted (mine has) these get up to temperature quicker than the sensors on the 2.9.

I ran some tests via the OBD with a cold engine (stood for at least 12 hours overnight):
Engine coolant temperature 68F
Inlet Air Temperature 70F
Time taken to exit open loop 58 seconds.

After letting the engine warm up, I turned it off & let it stand for 10 minutes before restarting:
ECT 185F
IAT 113F
Time taken to exit open loop 31 seconds.

Dave

Title: Re: Idle problem
Post by Mike_Floutier on Aug 8^th, 2008, 7:39am

Thanks for that info. Tompion!

I got a new Lambda sensor on Wednesday and fitted it but it made no difference.

It was then that I started to realise that the problem seemed to be that it was maybe only running on 3 cylinders. So I disconnected each HT lead in turn until I found the one that made no difference. Sure enough it was the rear coil pack one that I'd replaced 13k miles ago.

The thing is that this time it was only that one cylinder whereas when the coil went before it affected both under it's control.

I removed the spark plug under it and found it to be covered in oily mess. Also I noticed that there were bits of insulation from the LT ignition wiring that had been pinched between the plug and it's seating in the head. I cleaned everything up and replaced the plug BUT still no difference.

At least I'm on the right track now. Today I'll swap the coils over to see if it's coil related or cylinder/plug related. If the former, I'll replace the coil. If the later I'll swap the plugs to rule that out although it doesn't feel like a compression issue.

I'd like to get this sorted as this is my last thread after 10+ happy years of Scorpio motoring with the site as my tutor. The car is going on e-bay on the 13th.

Will let you know how I get on.

Thanks

Mike

Title: Re: Idle problem
Post by Highlander on Aug 8^th, 2008, 3:35pm

Mike, I dont suppose running on three cylinders might be the cause of your lack of power and the vibration you're feeling??

Title: Re: Idle problem
Post by Mike_Floutier on Aug 8^th, 2008, 4:54pm

Stuart, you may be right! I just picked up a new coil pack on the way back from the airport and popped it in. The idle is perfect now (but then it has been occaisionally - frustrating).

It's interesting to hypothesise about why the coil failed after only 14,000 miles. My favourite is related to the fact that the bracket that held my gas injectors in place broke (due to my continually bending it when replacing spark plugs!!). Since they sit just above the coil/plugs cover I wanted to protect them from the vibrations of the engine and so placed a large, folded, thick towel on top of said cylinder head cover for the injectors to rest on. Thinking about it this must have made an already hot place quite a bit hotter; and then there was summer. I know it's not been the hottest sumer but I'm guessing that what with my towel and all it was just a bit too much for my coil packs.

Anyway, I'm picking up a passenger from Stansted airport shortly so a 120 mile round trip should prove to be a suitable test-drive. Will let you know how it goes.

Oh and btw, the "bearing noise" that I thought was part of this diff/prop-shaft/auto-box scenario turned out to be a badly worn tyre - lol! - when I replaced some of the steering rods recently I got a garage to do the tracking. They did it perfectly apart from one thing, instead of 3mm toe-in, I got 3mm toe-out!!! I only noticed it at oil change. I did the tracking myself after that but I hadn't associated the "noise" with the tyre until a couple of days ago when I finally changed it - bingo "bearing noise" GONE!

As I said, I'll let you know how it goes.

Mike

Title: Re: Idle problem
Post by Mike_Floutier on Aug 8^th, 2008, 9:38pm

Ok, do you want the bad news or the bad news - hehe!

Well, firstly it still acts like it's running on 3 cylinders - ie. the new coil pack made absolutely no difference.

So, I'm on the M25 on the way to Stansted when the coolant blows a hole you can put your fist through in the side of the radiator.

I got off onto the A10 and safety and stopped the engine within about 2 minutes. The lump is very hot.

I'm now at home wondering what to do next.

Mike

Title: Re: Idle problem
Post by Mike_Floutier on Aug 9^th, 2008, 8:32am

Ok, first things first, I compression tested each cylinder this morning and the back one (where I thought the coil was to blame) has 6 bar where the other three are around 13 bar.

Looks as if this explains the "firing on three" and "vibration" problems. Also perhaps why the radiator blew yesterday.

I looked at the "head gasket replacement" sheet on the site last night and it looks a bit beyond me; I'm worried about not messing up the timing chain. I didn't really understand some of the terms, eg. TDC (I know what it means, I just don't know how to measure it/set it) also the angles they talk about.

Do you think I should try or give up?

I'll see if I can get a cheap rad today, at least I should be able to change that.

Any ideas about the head would be very welcome.

Thanks

Mike

Title: Re: Idle problem
Post by Mike_Floutier on Aug 9^th, 2008, 8:47am

Thought you might like this pic http://www.exhortations.co.uk/images/PICT0038.jpg of the bust rad - hehe!

Title: Re: Idle problem
Post by scorpio_man on Aug 9^th, 2008, 9:04am

hi mike

you'd be better of trying to find a new engine than fitting a head gasket.

i'd bet good money that the head is damaged. i'm still off the road nearly 2 months later after mine went.

don't run it as if the oil gets into the water ways and pipes, if will rot the rubber and it will never hold pressure.

i hope you have better luck than i've been having. :(

Title: Re: Idle problem
Post by Mike_Floutier on Aug 9^th, 2008, 10:42am

Ok, I have to decide what to do. The rad I can do and I can get one today. The same place also has a head gasket kit in stock.

Since what I can earn with the car until my new one get's it's gas installation plus whatever I can get for selling the car in two weeks must far exceed the cost (£200) of buying the rad & gasket kit, I'd like to have a go. What have I to lose?

I'm going to start a new thread called "Head Gasket replacement since I'm now off topic.Mike