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Discussion Starter #1
Had the car in garage ( not someone I have used before ) to have rear wheel bearing done and asked the guy, whilst you are at it can you see if you can determine why the engine at idle is coughing a bit now and then. Picks car up that afternoon, guy says I am down on compression on 1&2 cylinders after doing a compression test, and said it would be more expense than its worth to get it looked at further to just drive it into the ground. Mmm, at this point it was all I needed to hear,so drives back home no problem.

Early start the next morning and I had a job to get up our hill, almost as if it was firing on one let alone anything else, when it did pick up there seemed to be a lack of power but the misfiring had stopped. Leaving work that afternoon again the engine was lumpy as hell, and this time engine light comes on. Calls into scrapyard and spoke to one of the guys there, he put his meter on it and said it was misfiring and thought it was highly unlikely to be a drop in compression. He cleared the codes. Drives back home and all seemed a tad better but still not right. So I fitted a new Maf sensor and plugs to start with, plugs had seen better days but were all burning just fine. Off for a drive the next day and things seemed much better, but on the odd ocassion even doing about 50-60 there would be a slight jerking momentarily as if it was being starved of fuel. At idle the car was not missing a beat and sounded as quiet as a sewing machine, no smoke or moisture coming from exhaust and I have had no loss of coolant either. On my return journey things were about the same, with the ocassional glitch at high speed, and the odd one or two just as I would pull away.

Ok on to this morning and I took off the throttle body, to say it was coked up is an understatement, it was just not stained with carbon but had quite a layer built up inside of it. Gave this a real good clean with carb cleaner and a soft bristle brush and is now shiny shiny. I disconnected every possible connector I could get at and sprayed with a high quality electrical cleaning spray, let dry and put them all back. All ground earth wires I coul get to have been cleaned up, although they were not too bad. Gone out for a drive again, runs like a dream and again idles as sweet as a nut, however :( there seems to be one point just as the accelerator is pressed slightly pulling away, or gets to the point where the pedal is just before the fully up position when slowing down from whatever speed, that seems to be causing this slight stutter on the engine still. Just wondering if anybody had any other suggestions before taking it in to my usual garage to get it checked out, the only other thing I have not got around to doing yet is the EGR valve.
 

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Discussion Starter #3
Coil pack could be failing, what was the fault codes?
Cheers, tbh I never took much notice, the guy down the yard just said 1 and 2 had shown missfires. Not sure if I can do a pedal test to show anything or not, the warning light has not come back on since and like I say it`s running so much better other than that slight niggle. Judging by the crap that was in the throttle body I am guessing the EGR is not gonna be that clean. From what it was running like I feel like I am almost on top of it by elimination, and that whatever is causing this now is probably something simple.
 

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If its losing coolant then I wonder if head gaskets gone between cylinder 1 and 2. It would explain the misfires and the garages comment about the low compression.
 

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Discussion Starter #6
If its losing coolant then I wonder if head gaskets gone between cylinder 1 and 2. It would explain the misfires and the garages comment about the low compression.
As per my OP, it`s not losing any coolant at all,had the car for a year and it`s still on the correct level. Or if it is leaking because the rough idle which was what I was first getting only started a couple of weeks back,then it must be a very small leak, but then again I guess small leaks turn into bigger leaks at some point. :)
 

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Discussion Starter #7
Try cleaning the EGR then if that doesn't work, keep driving it until the EML comes on

Just a quick update, found a pretty blocked breather pipe which has now been cleaned out and the car seems to be running much smoother. Still have just a very slight sticky spot on the throttle which makes the car chug a bit for a second, but as far as I can tell it`s not a missfire. Did a pedal test which throws up 0100. I have a brand new MAF sensor coming this morning, hoping it is that and not a fault with power going to the sensor. I did take off the connector off whilst the car was ticking over and it still kept on ticking over, that is supposed to be a sure sign the sensor is shot apparently, but how much truth there is in that I don`t know. My question is though, if I fit the new sensor do I need to get the error code erased? Just to point out that I have no warning lights on the dash, the code is just via the pedal test.

Cheers for any more info.
 

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Discussion Starter #9
You will need to get the code erased, yes
Cheers, well I cleared the code via disconnecting battery for half an hour. Fitted Maf and took it out for a drive, all seemed fine for 10-15 minutes and then that slight fault returned. Again the car still seemed to have an improvement in performance with regards to acceleration, other than that one spot on the throttle. Got back home and did a pedal test again, no error code showing up. Seems like it happens once the car has warmed up a bit, possible EGR valve I wonder? I know they can be cleaned to a certain degree, but as it looks like a bit of a pain to remove, I have ordered a new replacement, pretty pointless cleaning and fitting back on only to find it`s still happening. If the EGR was just starting to play up, would it necessarily give me an error code or trip the engine warning light do you know?
 

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When you remove the battery, ecu clears the long term fuel trims. When you start up again, ecu takes time to relearn the long fuel trims, maybe wrong ones. You’ll shoot bullets in the dark without opcom and make others pockets rich by shooting the parts cannon.
 

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Discussion Starter #11
When you remove the battery, ecu clears the long term fuel trims. When you start up again, ecu takes time to relearn the long fuel trims, maybe wrong ones. You’ll shoot bullets in the dark without opcom and make others pockets rich by shooting the parts cannon.

Cheers for that, I have ordered an op-com but wont be here till middle of the week, what readings should I be getting with the fuel trims, and when you say it takes time for the ecu to learn the new trims, does that time vary on mileage?
 

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Discussion Starter #13
It varies on a lot of things. Before you say anything else here, spend 50m of your life watching this:

Why was I half expecting something like this? :) To be honest I had no intention of changing anything with regards to the trims, but was just wondering what they should be hence my question. Oddly enough things seem to be running a much better today, although thats only a short journey of a few miles. Will take it out for a good drive and give it a bit of stick on Wednesday and see how things work out.
 

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You can’t change the trims but the video is gold, it explains what are the trims and what they do. Flat lines you see directly in the short term trims, so make sure you make an opcom recording, it has this facility.
 

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Discussion Starter #15
You can’t change the trims but the video is gold, it explains what are the trims and what they do. Flat lines you see directly in the short term trims, so make sure you make an opcom recording, it has this facility.

Thanks once again, will there likely to be a comprehensive list of instructions with the Op-Com CD do you know? From what I have seen elsewhere the majority of it is self explanitory. I was wondering though, if I do a recording is that just with car running stood still and at different revs, or are you supposed to drive the car while it`s recording?
 

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Discussion Starter #17 (Edited)
You would want to record when the problem occurs, otherwise there’s no point to record when engine runs nice.
Well I got the op-com come through, and although I can scroll through the blocks and as far as I can see everything looks normal, for some reason it will not go into record mode, just flashes up with a message briefly and shuts the software down. Took it for a spin and floored it a bit, seemed like it was running fine other than a couple of instances where the engine bucked a bit, this seems to happen more at low speed 30-40mph and at 2000rpm. Anything above or below that and there is no problem.

Got back home and checked fault codes and it showed P0135 (8) Not present, and P0100 (1) not present. Cleared these codes and off for a drive again, ran the op-com and it now shows P0571 (8) present. I know what the codes are, I am just wondering if, is it just throwing up random codes for no apparent reason, or the ecu is malfunctioning which is causing this, or is it a case of it being normal that it will throw up another code after I have cleared the previous one`s?
 

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Discussion Starter #19
A lot of words but no info on short term and long term fuel trims.

Well tbh, as I was unable to record anything whilst driving I thought it was pointless. But as you ask, with car stationary I get the following.

LTFT ......... Stays at -7% at idle or revving.
STFT.........Fluctuates 0 to -6% at idle and between 0 and -12% when revving.
 
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