high revs

[Dan Andrews]

evening all 

After some advice I have a S4s starts from cold with no problems now (God knows why) but new issue still has hot start problem, but is now revving on its own and randomly between 900 to 2.5k when stationary. It's getting undrivable any advice help welcome. 

This car is really turning me to drink you sort something out another appears.

[Chillidoggy]

What are the IAC valve readings like?

It is a good excuse for drinking, though!

[Gjk]

Long shot….. but, could it be a dirty TPS?

[shaunw]

Sounds like it could be either an  Idle air valve control issue or a TPS ( throttle position sensor ) issue to me?  I had similar problems that were resolved by replacing the TPS 

[Chillidoggy]

Dan, have you done a Freescan yet?

[Dan Andrews]

Morning all sorry for delay and thanks for answers. Regarding freescan I have managed to get it on my laptop but can’t seem to get a reading. Took it to a show in Margate last week never been so embarrassed it just starting revving itself at the lights, must of looked like I was having a midlife crisis.

[Gjk]

Stupid question but you have the ALDL lead don’t you?

it could be, you have my pet hate of needing to assign a com port on the laptop!

[Chillidoggy]

Which show did you go to in Margate?  I wasn’t aware there were any!

Otherwise, I’d echo Grahame’s comments. 

[Dan Andrews]

I wont be going again it was a show at the jet ski world car park. Loads of cars of all makes quite a few modde. Nice bunch of people but nearly left my front spoiler at the bottom of the entrance slope and even worse on way out. Just looking to see if I need to format the port.

[Dan Andrews]

Well got it working (I hate computers) car threw up one fault code 24 vehicular speed sensor (Voss) circuit

24 TIP a weak idle mixture or bad missfire can cause this

below few screen shots

thanks 

 

[Chillidoggy]

I warned everyone on the East Kent group about the likely damage to an Esprit front spoiler at Jet Ski World. Hopefully it’s not too bad.

[sailorbob]

As your erratic idle speed is occurring when stationary you can discount error code 24 as being related to that.

[Dan Andrews]

On 06/08/2024 at 15:36, Chillidoggy said:

I warned everyone on the East Kent group about the likely damage to an Esprit front spoiler at Jet Ski World. Hopefully it’s not too bad.

Yep think I missed that post I got half way down thought nope but too late lucky no damage done.

Spoke to someone who comes highly recommended he has asked for me to try and get it saved on freescan on a drive. So good excuse to take out might try on my way to motors at the moat on Sunday.

[scottytwo]

I have a similar issue on my 89SE. Sometimes it will maintain about 2000 rpm. It then seems to work properly.  When at lights it idles OK then goes up to 1200 and brings on the CEL giving an IAC Valve issue. The strange thing I have noticed (and why I'm replying to this) is that if I am approaching a junction or lights and I am coasting while out of gear, the idle is spot on. It is only when the car stops moving that the erratic idle starts to occur. Any ideas on that one?

[Dan Andrews]

Yep starting to do my head in a wee bit. Did a freescan the other day the car ran and ticked over at around 1000 revs for ages spoke to someone who had a look at the screen shots and said they all looked normal. Drove to Motors by the moat about 30 miles and she ran great no issues, then on way home first stop begfore getting out the castle gates and up went the revs to about 1800 and stayed like that till i got home.  

[Gjk]

Do you get a CODE 22 TPS voltage low when car is hot?

 

[Gjk]

I don’t know if this has any bearing upon your high idle problem but, when I had a similar fault I replaced all of the vacuum hose in the engine bay. I found that the 90 degree elbow that attaches the thin hard plastic tube to the MAP sensor was cracked and split.

[Chillidoggy]

45 minutes ago, Gjk said:

I don’t know if this has any bearing upon your high idle problem but, when I had a similar fault I replaced all of the vacuum hose in the engine bay. I found that the 90 degree elbow that attaches the thin hard plastic tube to the MAP sensor was cracked and split.

That would cause a loss of power, too. Especially if it became completely dislodged like mine did.

[Dan Andrews]

16 hours ago, Gjk said:

I don’t know if this has any bearing upon your high idle problem but, when I had a similar fault I replaced all of the vacuum hose in the engine bay. I found that the 90 degree elbow that attaches the thin hard plastic tube to the MAP sensor was cracked and split.

Thanks for replys no code 22 TPS showing on freescan. Think it has a vacuum leak as the compressor keeps running every 30 secs or so for 1 or 2 secs when ignition is on, also front flap under windscreen opens but shuts within 10 mins once turned off.

[Gjk]

Have to admit Dan, I used the paper clip method to get the code 22. I also used to get the engine check light come on when at idle but it extinguished as I opened the throttle.

what readings do you get from the tps when the engine is hot?

is it 0 at closed throttle and 100 at wide open and do the numbers climb sequentially when the throttle pedal is slowly pressed from off (idle) to on (100%)?

[Chillidoggy]

Is the compressor you’re referring to the vacuum pump in the boot?

[Escape]

3 hours ago, Dan Andrews said:

Thanks for replys no code 22 TPS showing on freescan. Think it has a vacuum leak as the compressor keeps running every 30 secs or so for 1 or 2 secs when ignition is on, also front flap under windscreen opens but shuts within 10 mins once turned off.

As Ian says, that's the vacuum pump you're talking about, it has nothing to do with engine management. 😉 So any leaks there cannot cause a high idle.

[Chillidoggy]

3 hours ago, Escape said:

As Ian says, that's the vacuum pump you're talking about, it has nothing to do with engine management. 😉 So any leaks there cannot cause a high idle.

It does have something to do with engine management in respect of the EBPV and throttle jack, so perhaps it's worth a check.

Dan - has your car still got it's EBPV and throttle jack? I know a lot of them have been binned, mine included.

[Dan Andrews]

2 hours ago, Escape said:

As Ian says, that's the vacuum pump you're talking about, it has nothing to do with engine management. 😉 So any leaks there cannot cause a high idle.

Yes it is the vacuum pump I was talking about so that one thing less it could be I suppose. I hope to do a run in it on Tursday so will try and save the data on freescan. I will have to get it looked at soon. Someone has said might be the map.

[Escape]

16 hours ago, Chillidoggy said:

It does have something to do with engine management in respect of the EBPV and throttle jack, so perhaps it's worth a check.

Dan - has your car still got it's EBPV and throttle jack? I know a lot of them have been binned, mine included.

You are of course right Ian that the vacuum is used for the throttle jack and EBPV. 😳 But most have been removed and a leak in the system is unlikely to lead to high idle as it uses vacuum to open the throttle.