[Corsa B 1993-2000] Runs like crap from cold

[Alanco]

Hi,

put this in mechanical, sory if thats not right,.

I've got a Corsa b 1.0 12v

car was running fine (ish) - only problem i've had in 2 years is that when under load in high gear (top) going uphill on say M.way ( ecu light comes on) once load taken off engine light goes out and car drives normally. but noticed that had loads of mayonase on rocker cover plug, so thought i'd investigate

removed rocker cover and loads of crap in there - cleaned out as best i could - cleaned from rocker cover and blew out pipes to injection unit.

seamed much better for a few days, but now every time i start from cold - it goes fine for couple of hundred yards and then just seams to bog down, if you press clutch and rev it revs freely but as soon as you put under load it goes slower and slower until you clutch it again,. rev it a bit and it picks up and drives perfectly

ecu light dosn't come on when this happens and i am ignorant when it comes to paper clips etc etc.

where should I start ?

ta

Al

[CorsaEdi]

That mayo is normal on those engines it's just condensation, just keep an eye on oil and coolant, if they mix you have a problem and watch for smoke from exhaust

As for the bogging down I would get the codes read, try the pedal test (can't remember if it works on your car)
When was it last serviced?
Is it like a misfire?

[Alanco]

HI Edi,

Last serviced about 2-3k ago, - its not a missfire just absolutly no power - if it had carbs I would think it was almost overfuelling !

I'll have to check out the diagnostics as thats an area I'm ignorant on, No idea what pedal test, paper clip test is - reading tuts today for more info,

[Taurus]

Pedal test and paper clip test won't work on yours. Only way is a diagnostic kit. Buy yourself opcom, very cheap and it's very capable.

There's not a lot of information to go on, does it run fine once it's warmed up?

Did you check & clean the throttle body after you blew all the much out of the pipes leading to it?

Keep a close eye on your coolant level. As said, mayo is usually nothing worse than condensation, but on those there is a weak spot behind the water pump where the timing cover gasket can leak coolant into the oil. That results in excessive mayo, so it's worth making sure.

The issue with the ECU light coming on at higher load is often a EGR issue, which may also cause the cold running problem you've got. You can take it off and clean it, you'll need a new gasket to refit.

[Alanco]

HI Taurus,

thanks for the info.

THrottle body was mucky, cleaned with carb cleaner - laugh ( I did blow away from throttle body ) !!!!

Coolant level has been steady

EGR valve was removed cleaned (again with carb cleaner - left soaking overnight ) aprox 6 months ago.

I'll try and track down opcom and go from there. ta muchly

[Alanco]

Well, good news guy I work with has OPCOM, so can hopefully run diagnostics in next few days and go from there -

Al

[Alanco]

HI All,

Arranged to go to Watford this morning to do the opcom test, car ran like a real pig this morning hopping down the road for first 1/2 mile before sorting itself out and driving ok for rest of journey

Ran opcom , only stored fault was O2 sensor not reading, but it was reading fine when we did the test - reset ecu and took for road test, far better, pulls away cleanly with no bogging down, thyrottle response appears far better - no lag.

Just when I was a happy bunny got to an uphil bit of road, engine under load - Missfire, ECU light comes up ! - goes as soon as loading reduced - Did twice on way home.

So will repeat opcom later in week and go from there

Al

[santa]

Sounds similar to a problem I had on a 1.2 (same induction system). Error codes kept complaining about the O2 sensor when the real culprit was the MAF.

Try disconnecting the MAF. You will get an engine warning light on the dash, but if driveability improves then you have your culprit. If it is still no better, then you at least know what it is not.

[Alanco]

Hi Santa,

cheers !

I got my dumb head on today - whats a MAF ?

I got another 1.0 corsa on my drive for next week or so so can substitute bits

al

[Alanco]

hi sorry,

lazy just ebayed - yeah, will swap MAF's and c what happens

Al

[Alanco]

HI Santa,

changed MAF from donor car, started revs went right up then settled which i can't remember it doing before.

todays been sponsored by 1664, so no road test but will check out tommorrow

cheers

al

[Alanco]

Sounds similar to a problem I had on a 1.2 (same induction system). Error codes kept complaining about the O2 sensor when the real culprit was the MAF.

Try disconnecting the MAF. You will get an engine warning light on the dash, but if driveability improves then you have your culprit. If it is still no better, then you at least know what it is not.

HI Santa,

JOb done - MAF changed car drives sweet - opcoms not as clever as it should be -

thanks

Al

[Taurus]

HI Santa,

JOb done - MAF changed car drives sweet - opcoms not as clever as it should be -

thanks

Al

Opcom can only tell you what codes the ECU has stored. The problem with O2 codes is that it's a feedback system so usually it's a problem elsewhere that throws the exhaust gases out of parameter. Opcom is a tool which can help you figure out what's going on, the problem is that we've gotten lazy with car diagnostics expecting them to tell us what the problem is. In reality the weakness is the ECU not Opcom. If the ECU can't see that it's the MAF causing the O2 sensor to be out of parameter then Opcom can only tell you what the ECU tells it.

Which is why good old fashioned 'mechanicing' still counts. You'll find a number of things the ECU doesn't always spot, most frequent are O2 issues, EGR issues and CTS issues. But using Opcom's live data reading you can usually spot what's going on even though there are either no fault codes or codes which are seemingly unrelated.

It takes time - which is why many workshops won't do anything other than instant diagnostic fixes - customers don't want to pay for the hour it took figuring it out. They just want to pay for the 10 minutes it took to replace the sensor.

[gb33]

opcoms not as clever as it should be -

OPCOM isn't the problem -- all it does is read codes stored on the ECU.

The problem is that the MAFs can go bad yet appear to be functioning normally to the ECU. The faulty airflow reading caused by the bad MAF then results in the wrong metering of fuel, which causes the exhaust gases to run excessively rich or lean, which goes beyond what the 02 sensor is capable of monitoring. The ECU then thinks the O2 sensor sn't reading properly and stores a code as such.

Ironically, Bosch is the maker of the MAF and the 02 sensor on our cars...how convenient is it for them that their MAFs fail this way so that most motorists/dealerships/mechanics end up replacing both MAF and 02 sensor when the MAF fails?

[Alanco]

cheers TAuras / gb33

yeah., i agree with both your comments, I was also lucky to have a bit of advice from santa, and more importantly a donor car to nick bits from

FUEL INJECTION IS A DARK ART -

Al