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VY Berlina seems to misfire under load

Sdel179

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Hi all,
Before someone grills me for all the similar posts to this, I don't know what to try next..
Firstly the car starts easy and idles fine when cold.. Never an issue to start it.. It's fine when you first start driving BUT once it warms up its seems to miss thud under load.. I have replaced all leads and plugs when I got the car a month ago.. It did it during the test drive and a local mechanic said the Ecotec is bullproof it will just be a plug or lead well WRONG.. It's done only 149,000 and I have now replaced the inlet manifold gaskets that seem to fail on everyone's ecotec.. Brown oil sludge under the radiator cap and sure once the gaskets where taken off it was bad..I have swapped coil packs and the DFI with a mates and it's made no difference what so ever.. The resistance on the injectors is mostly the same on all average at 200 ohm is 13.9 to 14.0.. They all fire (click screwdriver test to ear ) BUT I can't see why it would be an injector only when hot..I have looked everywhere all vacuum hoses appear to be connected.. There is no check engine light on.. My mate hooked it up to his laptop and when it started thudding away the timing was retarding greatly.. There was one back fire sound today I noticed whilst revving it.. But that's the first time I have heard it.. There is not coolant in the oil inside the motor.. The inlet gasket was pushing oil into the radiator..I'm sure I'm not the only one with this issue any help welcome thanks
 

edals

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Id still consider the injectors. They do fail when they are hot. Many cases ive watched, car starts and runs when cold, fails to idle or start when hot.
Since you habe replaced all spark components, next step would be fuel.

Here is a excellent video showing the failure, corvette starts and runs cold, when hot, wont start or runs like a POS when hot. New injectors and all sweet.
http://youtu.be/G8M5jNy9KrA

Not say its the problem but dont rule it out as a problem.
 

jeepyrocks

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Likely crank angle sensor.
They can do strange things when hot and failing.
 

caaf

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Just thinking outside the box. When was your last transmission service? I say this as underload up hill it can pulse/surge as bands/clutches slip.. Just putting ini out there before you start pulling the engine apart ;)
 

Pollushon

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Coolant temp sensor and o2 sensor run open loop til she warms up. If either are failed or dodgy they continue open loop into hotter temps, which is a dump and retard mode. Likely to have a crusty coolant temp sensor if the LIM is stuffed and causing sludge.
 

Sdel179

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Thanks guys for your help :) today the check alternator and battery light come on then abs fault the dash died then ac and stereo..the alternator voltage was about 12.3 volts at idle, I have replaced the alternator but the miss is still there.. I was hoping it was voltage related..it's now at about 14.4 volts at idle. After another look at the computer results from yesterday not only was the timing retarding it was running rich and lean when it started to stumble..once it's warm if you sit in park and rev it then let it idle and give it a quick jab on the juice it misses and you can hear it from the exhaust.. I'm leaning towards 02 sensors now..the inlet manifold was just done the underside of the cap was brown with oil sludge.. I was hoping when the gaskets where replaced it would be fine :(.. Holden don't stock the two wire O2 sensors anymore and repco wants $90 each for Bosch or fuel miser about $110 each.. I'm think it's time to get a proper scan tool connected to it.. As so today it drove about 3ks fine then started to stumble so it's something I believe gives a 0 value at cold then bang onces it starts to heat up.. The temp gauge hadn't moved before it started to miss today :(
 
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Sdel179

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Coolant temp sensor and o2 sensor run open loop til she warms up. If either are failed or dodgy they continue open loop into hotter temps, which is a dump and retard mode. Likely to have a crusty coolant temp sensor if the LIM is stuffed and causing sludge.
What a PITA that coolant temperate sensors location is to test.. Without removing the DFI and coils.. It should throw a code anyways :)
 

lowandslow

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Sure you haven't got a cracked plug or a dodgey lead?

I replaced leads with brand new top guns only to introduce a missfire under load. Tested the new leads with a meter and they had more resistance than the old ones. In the bin with them and ordered a set of original leads.
 

Pollushon

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Are you certain it's the two wire? I was pretty sure they went four back on my model (s2) in 97 onward. eBay can net good results, this is where I got mine 12 months and a lot of boost ago.

http://www.ebay.com.au/itm/251154696974?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

What a PITA that coolant temperate sensors location is to test.. Without removing the DFI and coils.. It should throw a code anyways :)

The cts is a consumable like any other, for $15 it's more efficient to just swap it out. I've found the L27 and 36 pretty code scarce when something is degraded and not seen to be causing too much rukus with the ECU but the car runs like a dog. As a result I've been in your situation quite a few times over the years :)
 
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