So I recently bought a mk1 1.4 MPI 8v, its a 2003 with 37k on clock (which is backed up by the service history and overall condition) 9 months test - intention to be a 1st car for step son

 

I didn't really notice when I bought it that there could be an issue, I test drove it and it seemed fine. Its been sat on my drive for a couple of days and decided to start it and let it run up to temp so as keep the battery topped up and make sure it got up to temp with no issues.

 

It didn't sound too bad on startup, but I noticed after it had been running for a few minutes that the rev counter needle on idle was moving about quite a lot and sounded noisy and rattley & shaking the car. Lifted bonnet for a closer listen and it sounds like an old diesel. Also noticed that when I turn the engine off it seems to over run for a second or 2 and shudders when it stops running. 

 

Car seems to drive ok, doesnt seem to lack power or cut out but feels a bit hesitant a lower revs, doesnt sound too noisey inside the car when driving, also the EML is not illuminated, and it doesn't smoke. I have seen on here that rough idle is a characteristic of these engines, but it sounds really bad. I bought a 1.2 HTP for my other step son a few years ago that has now done 120k and still going, doesnt sound as rough as this. I did try to plug my cheapo ebay obd2 reader in with the torque android app but it didnt find any new or old codes - it's fairly cack tbh

 

So i'm now wondering if it could be a misfire / coil pack / bad spark plugs / crank sensor/ fuel pump etc even wondered if it could be a collapsed cat or a bearing although I can't imagine that one of these engines would have a major failiure at just 37k, I have seen others on here with 120k + and still going. 

 

I'm thinking the next thing to do will be to get my mechanic mate to plug it into a proper reader to see if there are any codes showing - but wonder if that is likely given the EML light is not on, and wondered if anyone on here has any thoughts on what could be the cause of this please. I can see it had new spark plugs 2 years and 10k ago. I'm going to take a closer look at the weekend when I have time and will report back if I manage to work it out or if I can get it plugged into a proper computer in the mean time.

 

Thanks in advance! :-) just hoping I haven't had my fingers burnt with this one!!

Check for air leaks in the brake servo vacuum pipe before doing anything else, the pipes can split letting unmetered air in and making an already rough idle worse.

For a quick reference, this is mine idling at 70,000 miles. Original timing chain....

 

 

22 hours ago, sepulchrave said:

Check for air leaks in the brake servo vacuum pipe before doing anything else, the pipes can split letting unmetered air in and making an already rough idle worse.

Thanks I never thought of that I will have a look at weekend when I get more time. Might try and film it and put it in here so people car hear it. I did see a YouTube clip of a before and after new timing chain fitted and mine sounds very similar to the before. I've got a stethoscope and will try and get the probe on the chain cover to see if that's where the clatter is coming from but would be odd at 37k I think.

1 minute ago, Piescoffer said:

but would be odd at 37k I think.

 

Not at all, they start rattling long before that. It's a poor design with no chain tensioner.

3 minutes ago, TMB said:

 

Not at all, they start rattling long before that. It's a poor design with no chain tensioner.

Yeah if it turns out to be that I will probably do it myself. I guess the car is 17 years old and has only done loads of very short journeys most likely which could have stretched it out over time. 

Yeah, they stretch pretty quickly. Never heard of one snapping though.

The shonky idle is caused by cam scatter, it's not worth worrying about, those engines are crude but bulletproof.

My understanding is that it's a result of being tuned for EU emissions legislation. It depends how rough we're talking, it shouldn't be much more than slight lumpiness or something is wrong.

34 minutes ago, TMB said:

My understanding is that it's a result of being tuned for EU emissions legislation. It depends how rough we're talking, it shouldn't be much more than slight lumpiness or something is wrong.

 

Whoever told you that didn't understand the effect of cam scatter at idle when the chain's slapping about and the cam timing is randomly varying, all pushrod engines with simplex chains do it, it's why we used to fit duplex chains when doing performance upgrades.

16 minutes ago, sepulchrave said:

 

 all pushrod engines with simplex chains do it, it's why we used to fit duplex chains when doing performance upgrades.

 

They don't have a simplex chain. It's duplex.

 

Edited 3 November, 20205 yr by TMB

Then you're stuck with scatter and a sick idle because there's no way to improve it without changing the cam profile and increasing fuelling at idle.

https://youtu.be/l4HNv4NiyXo

 

This is what it sounds like. I have had a good look around the engine bay and cannot see any vacuum leaks the hoses are all in excellent condition. Also took spark plugs out and they are like new. Plugged it into Obd scanner and no stored codes. Put stethoscope on chain cover and it does sound very rattly.  Any thought anyone please? In the mean time I have fixed the boot release (wires broke off tailgate button) and reset the gear linkage following the guide on here as was stiff getting into reverse, that's lovely and smooth now.