Symbol engine running problems

Hello all. I have a long-standing problem with my 1999 AS Symbol. Intermittently the engine is ‘racing’ / running too fast. Sorry for the lack of technical terminology! When driving the engine speed seems to stick at a high level, is very noisy and remains constant even if I accelerate, brake or change gear. I don’t think it’s the accelerator because it’s not actually causing the van to go faster. My local garage, which is usually brilliant at caring for the van, has just changed the Stepper Motor and previously cleaned out the combustion chamber. Now a bit stuck with diagnosis of the cause of this. Has anyone experienced a similar problem or have suggestions for me? As usual, thank you very much for taking the time to read this post. Cheers.

The description doesn't sound logical. If an engine is revving fast it will move the vehicle fast, depending on the gear it's in. Unless the clutch is in use or the gearbox is in neutral you cannot disconnect the engine from the transmission and through that, the wheels. In other words, it's only if the driver does something to disconnect the drive via clutch or gearbox that the revs can rise and not pass those higher revs to the wheels. The only way that can happen without driver input is if the clutch is worn out and slips.

As to the engine actually revving faster, contrary to the actual accelerator inputs, that is a highly dangerous characteristic and there can be a multitude of causes, from air leaks somewhere on the induction side to a sticking throttle cable and probably all sorts of other possibilities, What is certain is that the problem must make the vehicle a danger and as such it should not be used 'til the issue is identified and resolved.

I've never heard of a Stepper Motor, though a starter motor sounds like it, but can't have any connection to the described issue. And each of the four engine cylinders has a combustion chamber but you don't clean out just one and if you clean them all it's referred to as a decoke and is a comprehensive job that's rarely done these days. Again even if it was done it's difficult to see how it might affect the issue in question. The terminology is maybe suspect here.

Garages usually supply an invoice with details of the work undertaken and that might help clarify what they've actually done to the vehicle.

Sorry I've not been much help but the post is somewhat confusing.

I dont know the answer ,but it would help to say what engine you have. Petrol/diesel and maybe size.Milage and any other factors.

Micky

Thank you Steamdrivenandy for such a comprehensive response. I apologise for the poor description of the symptoms but I am not a technical person. The problem is in itself confusing, especially as it only happens intermittently. The only thing I can add is that the problem most often kicks in 15 minutes or so into the journey. I must correct what I said originally. It was the throttle chamber that was cleaned out, not the combustion chamber. The garage has not been able to replicate the problem on a short road test so I need to ask them to accompany me for a longer drive and hope they can see the problem for themselves. Thanks again.

Hello Micky. Thanks for your comment. It’s a 1998cc petrol engine with around 69,000 on the clock. Sorry didn’t think to include that information in the post. Cheers

Hello ROB.

Had a problem almost like that years ago on Fiat. Traced by a dealer to a vacume hose rotting.

Brian

Try a search. Many members have had that 2l petrol engine.Including me. I seem to remember a stepper motor problem.
This will bump it up .

Micky

Hi all. So, finally have resolved this problem - thanks to the perseverance of my local garage. They investigated and found that there are two sensors which measure engine running temperature. The first one feeds the temperature gauge on the dashboard. The second one influences the supply of fuel to the engine. It was this second one which needed to be replaced. And now all seems good - fingers crossed. Giving feedback in case anyone else has the same issue. Cheers again for the responses. Rob