Mechanics

'98 1.0L CORSA: INTERMITTENT CHECK ENGINE - AIR FLOW METER

1998 Opel Other

Hello,

I am a newbie to motoring, but I have a problem that I apparently need to research with my own hands (garages either want to pump money by replacing everything in sequence, or tell me not to bother).

I have a 1.0L 1998 Opel Corsa; right hand drive as common here in Ireland. The car runs fine; has a few known problems which I'll list later - first, the one I'm struggling with.

The Check Engine sometimes lights up for a time. And I know how to reliably " make" it light up:

- get up into high gear. 5th will do the trick all the time, 4th sometimes

- speed up so that the speed is not low for the gear. About 60 kmh for 4th, about 90 kmh for 5th

- release the accelerator pedal and let the car slow down gradually without changinggear (or sometimes, *slightly* press the brake)

This brings the Check Engine light on. Then if I press the accelerator (with otrr without changing the gear down), the light goes off again.

I took the car to a garage, where they took a computer reading which said " Air Flow Meter". (I think it was " low voltage" ). They told me to replace the air flow meter; their price was through the roof but I found a cheaper one (insert only) in a shop and got it fitted. No change!

I need to get rid of this as I want to use the car for a driving test, and one can be failed on the test if " a system warning light comes on at any time".

Here are the known problems, in case any of them may point to the cause:

- the accelerator is somewhat stiff compared to newer cars (but still manageable)

- a compression check (in a garage) showed low compression (100 psi) in one of the cylinders; but the car still has enough power to run for now

- the battery is weak; if the car is left alone for several days, it needs a jumpstart to get moving again

What should I check for, try, etc? I have a more experienced friend who can help me with the tricky manual work, but I need directions.

WIll be most thankful for any advice on fixing this.
Avatar
Michael_Ireland
August 20, 2007.



Check for vacuum leaks, when you let off the gas in a manual trans it creates a high vacuum in the intake, which could be sucking air in somewhere causing the MAF to think it is out of range. Look for cracks in the boot between the MAF and the throttle body and inspect all vacuum lines

Tiny
Jack42
Aug 20, 2007.
Thanks!

I have found nothing on visual inspection; but not all parts are visible. I'll get the friend and try disassembling the vaccum lines to inspect them more closely.

What should I check for, apart from a crack? (I just want to inspect as much as I can when I get the friend to help me - I would not risk disassembling anything myself)

Tiny
Michael_Ireland
Aug 20, 2007.
Besides cracks. Loose fit, oil saturation, anywhere they have been rubbed against something.

Tiny
Jack42
Aug 20, 2007.
Could you elaborate on " oil saturation" in this context?

The others are about the vacuum lines and I will make sure to check them externally very carefully, but how do I check for oil saturation?

Tiny
Michael_Ireland
Aug 20, 2007.
Also, it seems that the light goes on much more readily in wet/humid weather. Today is dry and I had to get it up too 100 kph then release gas pedal (in 5th gear) to light it up; but on a rainy day th elight came up readily with pedal released in 4th gear at 60 kph.

Tiny
Michael_Ireland
Aug 20, 2007.
They will be spongy if oil saturated. The only thing that bothers me is the less expensive MAF meter. Ifit is still giving the same codes, might need a pin to pin wiring check or possibly a factory MAF

Tiny
Jack42
Aug 21, 2007.
What will be spongy? I'm sorry but I have lost the plot now; I thought this was about the air intake pipes, going from the MAF to the engine?

(Really sorry about this, I'm a complete newbie).

Tiny
Michael_Ireland
Aug 21, 2007.
The vacuum lines will be spongy if oil saturated. The air intake boot, look for cracks

Tiny
Jack42
Aug 21, 2007.
Thanks very much! Within some weeks (holiday season has intervened) I'll get my friends, examine the vacuum lines and box very carefully, and revert with result : )

Tiny
Michael_Ireland
Aug 21, 2007.
I have mustered the courage to remove the air box myself, after reading in the (paper, Haynes) manual that it's an easy task. Easy it was.

And what I found was no mere crack.

The rubber hose, described in the manual as the " breather pipe" and connecting the air box to the engine, has a gaping hole, about the size of a finger. I suspect that this was accidentally created by a mechanic who welded the exhaust some months ago; I now remember that the light problem started back then.

This apparently explains everything. Bad that I spent 150 euro on replacing the air mass meter which was never at fault at all - but this is the cost of getting experience. I will seek a replacement ASAP.

Question: is it safe to put the broken pipe back and drive the car before I find a replacement?

Tiny
Michael_Ireland
Sep 3, 2007.
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