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Discussion Starter · #1 ·
For the second time in 6 months, yesterday my Astra H (Z16XER), started but didn't accelerate up to normal idle, remaining at around 500rpm.
No missfire but just very lumpy. If lightly press on throttle, revs drop. Left it like this for a minute or so, then pressed throttle a bit and it died.
It then won't start. Even with throttle wide open and 20 secs of cranking - nothing.
Left it for 20 mins and it just springs into life like nothings happened.
I was at work and had no tools but last time this happened, I took plugs out and they were wet from fuel.
So I think it's sort of over fuelling on cold start, very occasionally.

Anyone else had this?

Any Thoughts?

No fault codes, live data (normally) shows everything as it should be. Get 45mpg+ on my run to and from work on fast A roads.
 

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You can get problems like that when the engine temp sensor is faulty, the ecu under fuels as it thinks the engine is warm eventually flooding the engine and plugs. Try getting the engine temp up on the hidden menu, see youtube for hidden menu.
 

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Discussion Starter · #3 ·
Thanks Redman, that's a good suggestion.

I've therefore plugged in OPCOM at home and had Torque app running on trips to and from work. Temps seem accurate for coolant and intake both on start-up and running. I did however notice that the catalyst temp gauge (CatB1S1 on torque app) was reading -33oC (minus 33 C) before start yesterday but think this wouldn't be used by ECU for fuelling?
The other anomaly I found was on the ECC page (It's the ELITE model) where outside temp recorded '0' degrees when it was about 12. Is this wrong - anyone know where this temp sensor found?
Long term fuel trim never strays more than 4 points in either direction and is often 0, and lambda readings look totally normal.
It's perhaps possible that one of the temp gauges (presume coolant temp must be main one for fuelling..??) might be intermittent.

I'm using Torque now trying to catch the point when it happens again.
 

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Well you seem to be doing all the right things.
Have you wobbled the connector to the coolant sensor? to see if it is a loose connection.
When the engine starts from cold it runs in open loop and ignores the 02 sensors until they get hot (o2 sensor heater reduces the open loop time by accelerating temp) The engine control then goes to closed loop and uses the 02 sensor signals.
Have heard of bad connections at coil pack causing poor running and starting without throwing a fault code.
 

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Discussion Starter · #5 ·
Hi Redman
Thanks for your continued interest -
I caught it yesterday - wiggled all connections and no change.
I immediately got torque app up and did a screen recording (not easy for me I assure you!)
Left it running with no peddle throttle input at about 450rpm for about 4.30 (on the recording). As it warmed up I tried the throttle and - as always - it died.
I then tried to start again, without resetting the ignition switch i.e. just turn key back to start position. Turns over but nothing.
Had an inkling to remove key, re-insert and try again. It started straight away like nothing happened!
Rest of video is me driving down the road normally and as can be seen, everything works perfectly.
I'm now concerned that it's ECU. Reason I got rid of my old Astra G was that after owning for 11 years, it needed a 3rd ECU and I'd had enough - thought the Astra H was supposed to have ironed out the unreliable ECU issues...
I don't know if it's a coincidence but this happened after a start, turn car round and back up drive - perhaps 30 secs of engine run the day before. However last time it did this it was at work after I'd driven 35 miles that morning...
Things I noticed:
Mixture ratio hovering around 0.69 which is clearly incorrect as it wouldn't run at all. Normal should be 14.7.
Cat temp remains at -33 C
Fuel in seems normal for tick over as does MAP Pressure
O2 Sensor values remain level.

Anyway, here is the video
 

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That intermittent issue is strange. A better diagnostic monitor might help but this is a start.

Maybe a bad ECU or wire.

On our z81xer, I don't recall the barometric pressure deviating much from 14.7 psi. So maybe the sensor and wiring is a place to investigate. Maybe a red herring.

An easy place to start is to check that your battery and alternator are in good nick. Low voltage will knock out some control systems in haphazard ways. There are a bunch of grounds that corrode rapidly and can cause major voltage drop so you might clean them along with the battery terminals. Some of the major connections to clean are under the battery, under the UEC, at the engine block, alternator, starter.

Two comments on the ECU:

- Not sure if water enters from the meek UEC cover or the bottom but it is a popular problem. You can remove and inspect the board, pins, and connectors easily. Post below gets you started. We had to remove and dry off the board a few times. Some people have corrosion to clean


- There are some ECU replacement posts here that you might want to browse. I don't sense this is such a common problem as the water ingress is.
 

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Discussion Starter · #7 ·
Hi Dripping

Some good points you make. I'll have a look at UEC and grounds this weekend and check voltages. The UEC: have heard of this before, definitely worth a dry out and a contact clean...
As an easy change, I've swapped over the coil pack from the wife's car this evening. That's a brand new Delphi (mine was an old looking Lucas) as I do notice that it (her car) consistently gets a few extra MPG on the same work run of 70 miles per day when I take that instead to give it a run. I'd always put it down to mine being the Elite (hers a breeze) and being a little bit heavier with leather heated seats etc but worth a go anyway.

Thanks again
 
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