Date: Mon, 24 Feb 2003 13:42:44 -0400 From: Dexter J <lamealameadingdongnopsamlamelame.org> Subject: Re: '91 Saab 900 2.1 non-turbo w/poor performance on acceleration
Salutations: This is going to sound weird - but check for a ground somewhere in the spark lines.. I had - exactly - the same thing going on with a (non-DI) 1989 turbo and what was happening is that there was a small oil leak at the distributor that grounded out #4 piston spark under load and made the anti-knock/engine protection system cut in - exactly - as you describe.. The leak was so small that it didn't show after it cooled down a bit as the evidence evaporated leaving just the usual grime and the problem had been coming and going for years and at least one previous owner.. Worked great for my first year with it as long as I didn't step on it - was delivering fuel correctly at all other times - but the sensor was reading the shorting wire and missing piston under load so that it cut out under hard acceleration to protect the engine.. It could be a LOT of other expensive things - but run the car hard and hot and force it do that bucking thing for a little longer than you would normally allow it to go on - pull in and immediately pop the plugs and see if one of them looks different from the others or one smells of gas more.. It was so weird that I now mention it whenever a someone sees problems under hard acceleration.. It's sometimes the anti-knock system doing it's thing.. In mine - it turned out to be a 10 cent O-Ring at the distributor.. The DI unit may be a lot more expensive to figure out.. -- J Dexter - webmaster - http://www.dexterdyne.org/ all tunes - no cookies no subscription no weather no ads no news no phone in - Real Audio 8+ Required - all the Time Radio Free Dexterdyne Top Tune o'be-do-da-day Bill Monroe - Blue Moon of Kentucky http://www.dexterdyne.org/888/009.RAM Brian Dean wrote: > > "Lance Morgan" <alancemornopsamo.com> wrote in message > news:2a52f3e9.0302220739.70c192b5nopsaming.google.com... > > "Brian Dean" <BJDinNCnopsamsouth.net> wrote in message > news:<wii5a.5391$Ye6.2696nopsam.atl2.webusenet.com>... > > > I have a 1991 Saab 900, 2.1 non-turbo with 140,000 miles in good repair. > > > > > > Beginning several weeks ago, it began to lurch when accelerating under > load. > > > This lurching feels like momentary complete power cut-out by the engine > ... > > > sudden in nature with immediate resolution... i.e., it seems to studder > > > rapidly while accelerating under load. If the clutch is pressed in it > will > > > clear and rev freely. > > > > > > This occurs at start-up and continues, regardless of operating > temperature. > > > > > > There are NO problem codes set by the on-board diagnostics. > > > > > > The vehicle has a new dist rotor, dist cap, and spark plugs. All are > > > correct factory specified components. > > > > > > The head gasket was replaced about 10,000 miles ago without incident and > the > > > car ran faultlessly until just several weeks ago (probably less than 500 > > > miles with this problem). > > > > > > Any ideas would be appreciated... > > > Brian > > > > This type of problem can be difficult to diagnose, due to the number > > of possible causes, and the interaction between the (LH 2.4.2) fuel > > system and (EZK) ignition system. > > > > For DIY, you'll need to sequential trouble-shoot the two systems, > > using either a Bentley or Haynes service manual, on-line resources, a > > fuel-pressure gauge, a digital test meter, basic tools, and patience. > > > > I, too, would lean towards a fuel system problem, while not ruling out > > an ignition sys problem. A partial list of things to check: > > > > - fuel pump output > > - fuel pressure, including quick return of pressure after pinching > > line > > - air mass meter (AMM) > > - LH system and fuel pump relays (right-hand side kick area) > > - O2 sensor > > > > - vacuum leaks > > - ground points > > - general/physical wiring inspection & continuity and/or voltage drop > > testing > > > > - wiring and physical tightness of crank sensor behind crank pulley > > - ignition amplifier (sometimes called ignition module) > > - ignition coil > > - worn distributor > > > > Sometimes it's ultimately less costly and frustrating, and more > > expedient to take these type probs to a good saab mech - not only due > > to seasoned experience, but also being able to plug diagnostic > > equipment into the LH and/or EZK test harnesses [can help to pinpoint > > "ECU" (LH fuel control unit, right-hand side kick area) and/or EZK > > control unit (left front wheel area) failures, as well as other > > components], and other advanced tools like oscilloscopes, etc > > > > Lance > > 91 900S > ____________________________________________________ > > Lance, Simon, and darkpoter - > > Nothing simple like a clogged, wet or mouse infested air cleaner element, > also ... no potato in the exhaust pipe... > > I agree it does sounds like a fuel supply problem and I will investigate > further. > > To start with ... > I disconnected the fuel return hose from the fuel pressure regulator and > rigged a simple on/off switch from the hazard light fuse (#27) to the fuel > pump fuse (#30). This was described in detail in the Bentley manual. It > allowed me to run the fuel pump when the car was not running. The fuel pump > delivered exactly 900 mls of fuel in 30 seconds... which is listed as the > "minimum" delivery rate specification. > > Does anyone else have any experience with this test ??? ... and is 900 mls > "marginal" performance for the pump delivery rate ... ??? > > Also just poking around, ... I pulled the access panel under the rear > luggage compartment to inspect the condition of all the fittings and > electrical hook-ups to the fuel pump ... they all look to be in perfect > condition ... so no easy fix to be found there ... > > I plan to go ahead and replace the fuel filter just for good measure....not > knowing when this was done last and that I've put 40K miles on it without > replacement... > > Since I don't have a good diagnosis as of yet (feul system versus ignition > system ...etc...) ... I will also replace the ignition wires... as I don't > really know how old they are either. So again, this is a reasonable thing > to spend money on even without a clear diagnoses. > > Thanks for your comments. > Brian
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