Date: Sun, 23 Feb 2003 14:34:25 -0500 From: "Brian Dean" <BJDinNCnopsamsouth.net> Subject: Re: '91 Saab 900 2.1 non-turbo w/poor performance on acceleration
"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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