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  #16  
Old 10-31-2004, 08:30 AM
possumfat9
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There is no gas in the oil. Disconnecting coolant temp unit will cayse the car to barely run. My understanding of knock sensor operation is this. Computer retards timing until sensor picks up knock, computer then advances timing just enough to stop knock. I have removed coil pack from no.1 cylinder, I mounted this coil pack onto air filter assembly. I ran spark plug wire from coil pack back to no. one plug. I can now hook up my timing light to no. 1 plug. Although flywheel has no timing marks, plate behind it does at 10-30 btdc. While car is warm and operating properly I have placed mark at 10 btdc on flywheel. Upon applying gas timing will retard about 17 degrees. During the approx 5 minutes that car runs bad the timing is almost 35 degrees btdc. I am no mechanic but have done many shade tree jobs on points type ignition. This just seems like my problem is premature firing or pre-detonation. Specs state that computer is only capable of 12-28 degree adjustment. Still looking for answers. Thanks
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  #17  
Old 10-31-2004, 10:19 AM
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Is it possible that the belt jumped a tooth? Just a guess.
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  #18  
Old 10-31-2004, 10:25 AM
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Well...... actually, and I'm saying this to help, you're backwards. Timing is advanced with rpm, the mixture burns at a fairly steady rate so it needs to begin earlier to stay ahead of the increasing piston speed. So... Timing will advance normally and if the knock sensor(s) detect pre-ignition (detonation) the computer will gradually retard the timing. No knock, no retard. The 12-28 advance limit is in addition to the base timing.

An added benefit to reducing oxides of nitrogen through the EGR system is that the introduction of an inert gas into the mixture reduces flame propagation speed and results in knock reduction also.

Your timing measurement is right on and doesn't indicate any problems. Next thing I would try is disconnecting the MAF and see how that affects the problem (disconnect with key OFF, then restart.)
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  #19  
Old 10-31-2004, 10:26 AM
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Quote:
Originally posted by michael
Is it possible that the belt jumped a tooth? Just a guess.
That wouldn't account for a 'slot' problem, ie only runs bad for a certain period.
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  #20  
Old 10-31-2004, 11:17 AM
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I assume that MAF is Mass Airflow Sensor. If I disconect it then car will go dead. Thanks for the info on Knock sensor and timing. I think I have been mis-lead about knock sensors.
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  #21  
Old 10-31-2004, 11:28 AM
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OK, Just cranked car with airflow sensor disconnected and car will run. It will not idle and runs bad with it disconnected. Thanks
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  #22  
Old 10-31-2004, 11:53 AM
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I have test for Mass airflow sensor but it makes no sense.
Notice that on svx it does not tell where to test to or from. This is from service manual. Thanks

Legacy
Key On ................ Red & Black/Red ............ 10-13 Volts
Engine On ............. Red & Black/Red ............ 13-14 Volts
Key On ............... Black & Black/Red ............ 0-0.3 Volt
Engine On ............ Black & Black/Red ......... 0.8-1.2 Volts
Key On .............. White & Black/Red ............. Zero Volts
Engine On ........... White & Black/Red ............. Zero Volts
Loyale
Key Off ............... Black & Ground ............... 0-10 Ohms
Key On ................. Red & Ground ............ 10 Volts Min.
Key On ................. White & Black .......... (1) .1-.5 Volt
SVX
Key On ................... Black/Red ............... 10-13 Volts
Key On ..................... White ................. 0-0.3 Volts
Key On ..................... Black .................. Zero Volts
Engine On ................ Black/Red ............... 13-14 Volts
Engine On .................. White ............... 0.8-1.2 Volts
Engine On .................. Black .................. Zero Volts
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  #23  
Old 10-31-2004, 12:34 PM
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Backprobing (with straight pin - my preference is 'T'-headed mattress pins but any stout, thin pin will work) the sensor connector while connected to the sensor with the key on, engine off (KOEO.) Since your problem, if I recall correctly just occurs for around five minutes at a time it sounds as though the engine temp sensor would be bad but it could also be most anything that is going through a warm-up situation. The symptoms point to a/f ratio problem. I need to read back through again but I have a busy schedule today. I'll try to pick back up later tonight.
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  #24  
Old 10-31-2004, 05:10 PM
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Hi Possium, a bit more info. The bits that you have said that can be factored in are;

Facts; Runs good for about 3 minuits from start. Before it happens, runs ok after.
Back fires into inlet manifold.
does not do it if let run for 10 min, to warm up.
timing 10 btdc advances to 35 btdc.
exhaust gets very hot.


Well just sumerising as we go, the back firing into the inlet, points to either retarded spark or a very lean mixture.

Both will keep the burning going on till the inlet valve opens, when it ignits the fuel in the manifold, this will pressurise the crank case through the breather system, to push the oil out.

Both will heat the exhaust due to the still burning fuel.

The spark seems to be ok. 10 btdc at idle, advancing to 35 btdc when the throttle is opened, is normal. I can't see any thing else in the spark dept. that would do it.

So the fuel is the most likely one. If it is left to warm up it is ok. It is only when the throttle is opened that it goes lean, and only during a small window of time, during the warm up peroid. Once past this time it is ok.

Trying to eliminate some of the causes, the MAF sensor is the main controller of mixture, and signals the increase in air, if it was faulty, it would be faulty all the time, not just at this small time window. There is nothing different happening to it during the warm up peroid.

The throttle position sensor signals the throttle opening to go with the MAF signal, but it is not affected during this warm up time either.

The temp sensor plays a major part of the warm up peroid, and can cause all sorts of problems, but why does it run ok if it is left to warm up on its own.

When the warm up cycle is running, the fuel is increased, tapering off as the temp rises, the EGR, Purge and closed loop are enabled, once warmed..........F.I.I.K.

Gee I wish I could hit it for you, but it seems that during this time it can't handle an opened throttle, the result is either the amount of fuel is not rich enough, or there is air being leaked into the system from some where that is sending the mixture lean.

Wish I could be of more help, may be Beav has had some experence that he can remember.

Harvey.
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  #25  
Old 10-31-2004, 08:40 PM
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I've been at the same impasse Harvey. The only thing I can lay my feeble mind onto is a lean backfire but that doesn't allow for the overheating exhaust. Either late timing, excessive fuel or a plugged cat/muff does that. I was hanging my hat on an ECT with transitional/intermediary dropoff. I'm still not sold that it isn't. An overheating electrical part would continue to worsen, which isn't happening and I hate condemning an ECU without solid validation. I only had brief access to the database and I hate pushing the issue since I was sneaking in. I would expect that an intake backfire could dislodge hoses or even split them and cause erroneous MAF data, for that matter the MAF may also have suffered damage. You're right, most MAFs are bad across the range, save for some Mits and the old Bosch hotwire MAFs (BTW - what is it with Europeans and electrics anyway? Bosch, Marelli and, my all time fav, Lucas, aka 'The Duke of Darkness'.) I think the best bet is some time spent with a GMM, a vacuum gauge, a fuel pressure gauge and maybe a gas analyzer - nothing like a live datastream.
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  #26  
Old 10-31-2004, 09:48 PM
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Long distance troubleshooting.

Yes it is hard to get the full picture, over the net, its a bit like someone describing a night at Hooters, ok, but you really got to be there and taste it for yourself.
Ya know what I mean.

Harvey.
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  #27  
Old 11-01-2004, 06:11 AM
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What year is your SVX? Did you try resetting your ECU? Have you tried cleaning your intake pipes, throttle body, MAF & IRIS. I also had a similar problem caused by a bad 02 sensor, I don't want to send you on a goose chase. Just giving you some possible leads. I might have missed it but did you check for codes?
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  #28  
Old 11-01-2004, 08:14 AM
possumfat9
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Ok as of now, I have replaced egr valve, egr reg, plugs, timing belt, upper intake gaskets, pvc valve and oxegen sensors. ( Note: Sometimes after engine runs bad, maybe 3-5 min after, car will set code of left oxgen sensor. I have on order new knock sensors and lower intake gasket set. Computer has been reset many times. I have tested everything that can be tested (or is listed) in component test section of service manual except mass airflow sensor. I have enclosed copy of test proceedure in previous post and svx listing only gives 1 point of test and does not state what to test to Ground or Etc. When I state that car backfires into intake. It is not real bad backfire but continuous as long as you try to force the car to gain speed. Sometimes the 5 min of running bad is worse than others. This acts like an old car with carb and it is at operating temp and you try to drive it with choke completely closed. except for the blowing of oil. The oil thing is not near as bad since I replaced pcv valve.
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  #29  
Old 11-01-2004, 03:12 PM
oab_au oab_au is offline
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Hi, If it sets a code for the left oxygen sensor, then the trouble must be occuring in closed loop. Still thinking. How long have you had the car? has it had any other strange happenings?Did this trouble just start, out of the blue, Was anything done to it before this started? anything you can think of, before we get out the diagnosistic dice.

Harvey.
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  #30  
Old 11-01-2004, 04:44 PM
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I figure left sensor problem was because of all the oil and smoke. My first post ever on here concerned this same problem and it has been going on about 8 months. I have just been starting car 5 minutes before going places and I am just tired of it. I love my svx and my son just bought one.
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