Hi, 

 

I bought my Skoda Felica Fun back in Janurary. The first 6 weeks were aces, but then I started to notice an issue with idling. When parked up sometimes it would idle fine for 15 - 20 minutes but then it would struggle and cut out. 

 

Another example might be when slowing down to turn a corner, I'd put my foot on the clutch and the engine would start to struggle, not always, just sometimes, however drop the clutch and boot the gas and you can keep it alive, otherwise it would cut out, and power steering would go.  

 

Another symptom, when starting either hot or cold it would occasionally rev wildly between 800 - 3000 revs for the first 60 seconds and then sort it self out.

 

My first through was maybe the idel control valve was on the fritz. I cleaned and then eventually completely replaced the throttle body. However this did not solve the problem. 

 

I then suspected the ECU, I sent the ECU and both the old and brand new throttle body off to be diagnosed, however all came back with no fault found on any of them. 

 

Having given a glance around the engine bay and checked the hoses as best I could, not finding any issue or sign of an air leak I began replacing things in the hope this would solve the issue. So far I replaced (in no particular order);

 

- Spark Plugs

- HT Leads

- Ignition Coil

- Distributor

- Alternator

- Fuel filter

- Map Sensor

 

I then had the timing checked... still no love. 

 

I took the pickup into get the Fuel pump swapped out but then the throttle body refused be reset, so I thought, well maybe it's an intermittent fault with the ECU, so I purchased a reconditioned one from a place called "Lynx", (it ended up costing a lot more that they originally advised and took four weeks to arrive!!!!) but today it's turned up... and unsettlingly while they can now reset the throttle body, the car now revs wildly from 800 - 3000 rev's constantly and is un-drivable.

 

It revving like there is a MASSIVE air leak, however it I put my hand over the throttle body to starve it of air it cuts out almost instantly. 

 

I'm really starting to think that I might have to bin this truck, which is a shame but I've wanted one since they first came out and it's taken me this long to be able to buy one and have a place to work on it, and give all I've replaced it *feels* like it's going to be something small! :(

 

It's been in the garage several times to be plugged into the proper VAGCom software stuff and they've wandered around the engine bay and none of us can work it out - I'm confident that the guys at the garage are competent enough, but is there something we're all missing? 

 

Any advise on possible solutions would be gratefully received. 

 

- Matt

It's been in the garage several times to be plugged into the proper VAGCom software stuff and they've wandered around the engine bay and none of us can work it out - I'm confident that the guys at the garage are competent enough, but is there something we're all missing?

Matt

The list of parts you changed is quite long. Any prior diagnosis and evidence associated with it?

With such wild behavior, I am expecting there are errors stored by ECU. Tell us all about them for a proper advice.

Some more questions:

Did you check the coolant sensor?

How did you check for vacuum leaks?

Any test on fuel pressure?

What proof you have the 'new' ECU is good?

Edited 16 October, 201510 yr by RicardoM

Igniton timing is out.

Igniton timing is out.

Why woult that be with such different issues list?

Matt

The list of parts you changed is quite long. Any prior diagnosis and evidence associated with it?

With such wild behavior, I am expecting there are errors stored by ECU. Tell us all about them for a proper advice.

Some more questions:

Did you check the coolant sensor?

How did you check for vacuum leaks?

Any test on fuel pressure?

What proof you have the 'new' ECU is good?

Hi RicardoM

Plenty of new parts :( - no warning or evidence (that I can find of prior issue).

No codes stored on the ECU now or previously except failure to reset, if there were I'd have actioned against them. Only most recent one was not being able to reset the throttle body so I got the reconditioned ECU.

Some answers;

Nope, not checked the coolant sensor, will do that.

Both myself and the garage checked for leaks, none found.

Ive not checked the fuel pressure myself, but the garage did and suggested there was no issue found. We change the fuel pump because it was one of the only things we hadn't done.

No evidence to prove or disprove that this ECU is solid other that it responds to the vagcom software and will store a fault if we trigger one on purpose.

Pretty sure its not a timing issue as I bought a strobe to check the timing and purposeful set it wrong to see what it sounded/acted like, and it doesn't sound like this. This sounds/acts more like when you pull the vacum hose off, but they're all sealed.

If there's anything else you need to know to offer further advice please ask. Thanks for your time.

- matt

Plenty of new parts :( - no warning or evidence (that I can find of prior issue).

Nope, not checked the coolant sensor, will do that.

Please don't buy a new one, just check in VAG-COM for proper, smooth readings.

Both myself and the garage checked for leaks, none found.

I know that, but please tell me what method did you use? Just visually?

Pretty sure its not a timing issue as I bought a strobe to check the timing and purposeful set it wrong to see what it sounded/acted like, and it doesn't sound like this. This sounds/acts more like when you pull the vacum hose off, but they're all sealed.

That makes me insist on this issue. Based on your findings, vacuum leaks is my 1st option. Sometimes they are hard to catch. The engine acts fuel starved, randomly lean.

If there's anything else you need to know to offer further advice please ask. Thanks for your time.

We'll fix it if you are very determined. I know I am.

Just to be sure, I need additional info related to VAG-COM readings:

What values for short term fuel trim / long trim fuel trim at idle?

Is the throttle valve angle showing smooth values around idle position? No jumps? How about idle switch?

What voltage range for lambda values at idle?

 

If you pump quickly the brake pedal at idle, will the engine stall?

Hi RicardoM, 

Thanks for the response. The car is currently at a garage 100 miles away from me. I'll pass on the requests for information, but it might have to wait until I'm stood in front of it myself.

 

I'm pretty determined to resolve the issue, but funds are getting lower and lower... :(

 

I'll come back to you Asap. 

 

Cheers!

- Matt

I'm pretty determined to resolve the issue, but funds are getting lower and lower... :(

Well... that is the downside of changing parts without proper diagnosis. Sadly, most mechanics are part changers.

Anyways, my impression is that the fault should be clearly visible for somebody knowing how to analyze and corelate live data using an ECU scanner

One more thing to check. Any leak in exhaust system between catalytic converter and cylinder head?

Hi RicardoM,

Found the issue! Small vacum pipe hidden behind the engine had split. Fixing that solved the reving issue. Unfortunately on the drive from my place to the garage the engine went pop. :(

Found a new one with 50k on the clock for cheap so that's going in tomorrow. Hoping once this goes in everything will be squared away.

Thanks for your time.

- Matt