Date: Thu, 22 Aug 2002 09:12:12 -0400
From: KeithG <>
Subject: Re: My dealer hasn't got a clue, can you help? ('97 9000 Aero, Manual)

Lee, Still more musing on my part... If the MAP sensor lost a ground reference, I could imagine it exhibiting the symptom you describe. Why it does it only at WOT confuses it a bit. I am assuming that you have not driven another Aero which 'works correctly' to have a feel for it. I would disconnect the ECU and MAP and take a volt meter to verify that both the ECU and MAP get a low impedance connection to ground. If there is any variation, clean the bog engine ground cable at both ends and the ground connection for the FI system. It should be a single bolt with a number of ring connectors. To find this ground point, you'd have to have the electrical manual, guess, or ask the technician. It'll probably be near the battery or on the engine block somewhere. It COULD (very outside chance) be something INSIDE the short section of tubing or the nipple on the intake manifold which plugs the port and causes pressure to be under reported as well. If all these check out, swap in a known good MAP and see what it does. Please let us know what you learn as this is now bugging me. KeithG Lee Marshall wrote: > The problem is not intermittent, it always happens when the engine is under > load i.e. full throttle in 3rd, 4th and 5th, pulling from low revs, it > happens more if the car is carrying extra weight. Thankfully I never have to > tow anything. It is not affected by heat, road conditions or anything. > > I've never heard of the pressure transducer, where is it situated? It could > have already been replaced, so much has! BTW all the hoses have been checked > or replaced. > > My personal thought is that it is some kind of electronic connection > (probably to the BPCV) that can only be tested when the car is at full > boost, making it almost impossible to test in the workshop. > > Does anyone know where I could get hold of a wiring diagram for the turbo > system? > > > "KeithG" <> wrote in message > > >>Lee, >> >>They replaced the part I would suspect 3 times. It shows you how much I >>know... I think I would have to get to know Trionic a bit more to hazard >>another guess. I would disagree, though, with some of the previous logic >>used, but what do I know. Have they looked at the pressure transducer >>its hose, fitting or its wiring? Is it possible that the pressure >>transducer hose could be a problem or the transducer itself? From my >>limited understanding, I would guess that the system, somehow, does not >>know that the pressure has exceeded normal values. I could imagine a >>pressure transducer which is nonlinear and reports decent values back at >>idle and vacuum and becomes nonlinear and under reports pressure at >>higher pressures. A wastegate would stand an outside chance of causing >>this, a BPCV could do this, too. If the system is operating properly >>(still an IF, but mostly confirmed) and still overboosts, it HAS to be >>that the pressure signal is not reported correctly to the system. Does >>it do this all the time? Does it do it cold and hot? Over bumps and >>smooth pavement? >> >>Just some ideas YMMV! >> >>KeithG >> > > > > > --- > Outgoing mail is certified Virus Free. > Checked by AVG anti-virus system ( > Version: 6.0.380 / Virus Database: 213 - Release Date: 24/07/2002 > >

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