1999 1.6 8V Engine idle problems - Thingy
Hi, I really hope someone can help me out!

My Vauxhall Astra 1.6 8V with engine X16SZR has been driving me absolutely nuts.
I came from holiday to find my MOT was overdue since over a month, the engine management light came on just before the MOT test and failed because of Lambda reading high exhaust emissions due to misfire in the second fast idle test and the fast idle test. I bought a new Lambda sensor and replaced it, the engine started running alot better with no engine lights coming on and exhaust fumes were more neutral. Went for a MOT retest but failed again for the same reason and the light came back on while driving back home!

I did some research and found out about the paper clip test, I tried it and got fault code P0505 Idle air control malfunction. I bought a new Idle Air Control but unfortunately when it arrived it was slightly banged up with a few marks on the casing (very poorly packed) but couldn't get a replacement because it had already been signed for! I tried it anyway hoping it would be okay. Engine was running better so i figured it must be fine but after about 15 mins when the engine got hot it started to idle very roughly. I fitted new spark plugs, HT Leads, Coil Pack, Air Filter, I cleaned out the air intake pipes throttle motor and replaced the EGR Valve but still have the same problem. When the temp gets to around 90 the engine management light comes on with fault code P0505 (engine clearly struggles with idle speed going up and down and exhaust backfiring lightly every once in awhile with abit of blackish smoke). Is the Idle Air Control causing the problem? Why would the fault only occur when the temp reaches around 90? The engine management light goes on and off every once in a while when the engine is hot. The fans don't always come on when temp reaches 92 but it sometimes jumps down to around 85 (without fans coming and me reving the engine slightly). Could the ECU be at fault? I really need to get my car back on the road again, i've been unable to work the last 2 weeks and keep spending more money which i don't have!

Any help and suggestions would be greatly appreciated!

Thank you

Edited by Pugugly on 16/09/2008 at 21:41

1999 1.6 8V Engine idle problems - Screwloose

Check for a failed throttle body gasket - they rarely make a sound.

The breather vent into the same body is also worth rodding-out.

Check the ECU plug for corrosion too.
1999 1.6 8V Engine idle problems - Thingy
I will replace the throttle body gasket tomorrow and see if that cures it.
I've cleaned out the breather vent and checked the ECU plugs for corrosion but everything is fine... I had a diagnostic scan to see if anything else would show up but still only got the P0505 fault. I decided to check the ABS and immobiliser while the scan was being done anyway but got no response from the car for both? When i bought the car it was advertised with ABS and immobiliser... does this point to a faulty ECU or did the previous owner just all sorts of extra's which don't exist?!?
1999 1.6 8V Engine idle problems - Screwloose

If it's got ABS; then there'll be an ABS warning light coming on/going off at key-on.

The immobilizer is chip-in-key and was universal fit in '99.

Can this scanner read manufacturer P1xxx codes as well as EOBD's P0xxx? That P0505 is flagged simply because it can't control the idle - for whatever reason..
1999 1.6 8V Engine idle problems - topbloke
these engines were quit prone to inlet manifold gaskets leaking may be worth sraying some wd 40 around the manifold area with it running and see if the engine/rpm settles briefly, it sounds like an air leak somewhere thats why you get the idle code and a rich mixture
1999 1.6 8V Engine idle problems - Thingy
I used a mates Vauxcheck which I'm sure it reads manufacture codes because i used before and got fault code P1540 AC refrigerant pressure sensor - circuit malfunction.

If i listen very carefully i think i can hear a slight hiss from some air leaking and it seems to get better very temporarily with WD40. Went to Vx to buy gaskets but was told my engine doesn't have a throttle motor gasket listed on the parts computer thing!?! He gave me one which said might be the one but when i got home and checked it wasn't the same shape. I will go back on Saturday and try and get the correct one along with a inlet manifold gasket and see if that does the trick.

When i turn the ignition the ABS light does not light up, guess the previous owner added a few extra features on the advert! Sigh*!

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