Topic

Hi,

since a few days ago i've had a problem with my MGF (05/2001 1.8 VVC); it's stalling when driving. I'll try and describe to the best of my abilities how it feels, and would appreciate any pointers as to what it could be.

The car starts no problem, each time, cold or warm. When i pull off it feels to lose power almost proportionally to how much i accelerate, like being pulled back. If i over-rev in combination with slipping the clutch i succeed to get it moving but it still feels like pulling a two-ton trailer behind it. And when stopping in traffic the idle chases roughly until dying, unless accelerating hard (with a little gas it still hunts up & down roughly). When at 50km/h (thereabouts) i feel it's muffled and if i accelerate suddenly hard it doesn't go any faster and the exhaust sound changes to something turbo-like where it's just a suppressed whine instead of a roar of any kind.

It all started this saturday morning, out of the blue, never had any signs whatsoever before. So it felt like something that was caused by an event instead of just something that had degraded over time, as the change was so dramatic, if that makes sense.

So in trying to think what might have had happened, here's the last ten days of the history: i changed the whole of suspension last weekend (a week ago). For that i disconnected the battery, and then the ECU, and also the coolant overflow bottle. I did do the "reset" since (key to position 2, press on gaz 5 times in 10 seconds and key to 0). But could this maybe be the ECU or it's connectors acting up?

Also, i did work in confined spaces so could any of the tubes/wirings/etc around those areas cause this if disconnected? I've had a look around there since and don't see anything obvious but that doesn't say anything as i'm no expert. And i did drive the car with no problems for a whole week since, before it all started.

Aside that, in thinking what else had happened, i did remember having heard a "boom" from underneath the car at the end of a mounting ramp to the second floor of a parking building, either wednesday or friday (not sure which as i parked there every day this week), while going at it a tad too fast. Damn parkings have already caused a few casualties to the underside of the car. But while searching on the symptoms i realized it could maybe correspond to a dead catalytic converter which might have been the unlucky receiver of the aforementioned "boom". Or could it?

To finish, i've changed all plugs and leads recently (6 months) and cleaned the IACV valve the same time, and oil and coolant are clean and at stable levels.

Thanks in advance for any help you can provide

Sebastian.

Almost sounds like a timing issue but, with the history you mention, it does point to the cat being partly blocked/collapsed internally.

I think you need to investigate the exhaust system first. Has it had work done recently?(ie will it come apart easily?)

Also your car should be Mems3 so get an OBD reader onto it too.

Hi David, thanks for your reply

Sorry i forgot to mention, but i do have an OBD in the car that i'm using with the DashCmd app on the iPhone. It didn't report any error codes before/while/after my last drive yesterday. I'm going to go and do a full read/record session with my laptop either today or tomorrow to see if anything comes up.

Should i expect to be able to read from the results if the cat is gone (and if yes, what? error code? strange measures somewhere?) ?

As far as i can tell the exhaust has never had anything done to it (i have no previous bills for it and it's looking it's age although not bad by any means).

If it is the cat then you probably won't get any fault codes, but worth checking incase something else comes up.
How does the car rev up standing still?

It doesn't; i just started it, let it idle for a few seconds then pushed on the gas and it stalled. Left alone after startup it gets very rough after a minute.

I brought my laptop with me at the same time and recorded all available measures which proved to be very interesting, although somewhat too technical for someone like myself. Maybe you'd like to have a look and tell me if they speak to you?

The below link has a compressed folder with text files (no compromising pictures in there, promise) corresponding to each measure point, spanning over two-minute period, from startup to going rough to dying. Each measure is updated every 6 seconds so you'll see the evolution for all of them.

https://dl.dropbox.com/u/4662999/MGF/Data.zip

Let's take advantage of this modern equipment

Sounds like the cat's had it.

Your Fuel system brought up some errors:

11.25752 Empty data Fuel system #1 - Open loop due to insufficient engine temperature.
17.224921 Empty data Fuel system #1 - Open loop due to insufficient engine temperature.
23.33703 Empty data Fuel system #1 - Open loop due to insufficient engine temperature.
29.39829 Empty data Fuel system #1 - Open loop due to insufficient engine temperature.
35.584134 Empty data Fuel system #1 - Open loop due to insufficient engine temperature.
41.596691 Empty data Fuel system #1 - Open loop due to insufficient engine temperature.
47.783781 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
53.902779 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
59.860392 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
65.83191 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
71.771763 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
77.653011 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
83.550432 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
89.430397 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
95.432852 Empty data Fuel system #1 - Closed loop, using oxygen sensor feedback to determine fuel mix.
101.511928 Empty data Fuel system #1 - Open loop due to insufficient engine temperature.

Have you filled up at a supermarket recently?

And this from fuel trim bank 1

Time(seconds) % Percent
12.322213 0
18.197009 0
24.368902 0
30.403365 0
36.529716 0
42.580352 0
48.728491 -12.5
54.823612 -23.44
60.814495 -30.47
66.796039 -30.47
72.68918 -30.47
78.599188 -30.47
84.522033 -30.47
90.399922 -30.47
96.434531 -30.47
102.545694 0

David Aiketgate wrote: wrote:

Sounds like the cat's had it.

Thanks! If you don't mind me asking, for my own education, what leads you to this conclusion?

bensewell wrote: wrote:

Your Fuel system brought up some errors:

Have you filled up at a supermarket recently?

Can't say i have. I've always used the TOTAL stations. Why, do those measures indicate a possibly bad quality fuel?

I've had rough problems with bad fuel before. Changed to a tank of Total I think and mine was spot on so maybe its not that. The BOOM could have been the cat collapsing inside. You can't really tell until you get it off to see what state its in. If you think about it the cat is 12 year old part so could be that. The sensor data open / closed the last one looks a bit suspect. The lambda monitors this and adjusts the fuel mixture accordingly so usually starts open till the engine is warm then goes to close and works of the lambda to get the fuel mix right. I know I've had rich running for a while till I changed both lambda sensors.

The last time I had a car with total cat failure when shaken it sounded like a tin of marbles give it a shake and see if it rattles

sounds like a blocked/collapsed cat to me also had this same problem same dianosiitics on my old astra v6

midlife martyr wrote: wrote:

The last time I had a car with total cat failure when shaken it sounded like a tin of marbles give it a shake and see if it rattles

Ok, so i went to the garage, took position behind the car, grabbed it from the behind and lifted it above my head while shaking it and then... i woke up, went to the garage, gently tapped the cat with a wrench and it sounded perfectly solid. A few more motivated bangs and it still sounded dead solid.

I'll try and get the cat out tomorrow (i heard it's best to take it out with the silencer because it's the joint between them two that causes the most rust-trouble so easier to work on when off the car), to be able to give it a proper shake and then it'll be official.

Thanks everybody for your help, will keep you posted