1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Members do not see ads below this line. - Help Keep This Site Online - Signup
My 1991 900S surges after being driven at freeway speeds for about 20 minutes. That is, while holding the throttle steady on level ground, the car seems to first loose power and then regain it.
I replaced the head gasket about 10,000 miles ago, when I got the car at 108,000 miles. I did the head gasket, water pump, alternator brushes and mounting bushings along with cooling system hoses and one of the vacuum hoses that was cracking. I also did a major service with plugs, cap, wires, all filters and belts replaced as well as the thermostat and all fluids. I verified the hose to the vacuum container was newer and leak free at the canister and that the ventilation system held vacuum. I also cleaned the battery terminals and the ground bundles at the cylinder head. The car ran fine after the head gasket job except for the first two minutes after start-up when it was just a little balky. I checked for vacuum leaks again and swapped in a known good Air Mass Meter with no effect. Since the problem seemed minor I let it go.
Five months ago the idle started to vary slightly, just enough to notice movement in the tach needle and a slight change in the engine note. I cleaned the AIC (again) and changed all the vacuum hoses and grommets on the engine. I found the hose to the vacuum canister had pulled off (?) and reattached it and verified the canister to be leak free and hold vacuum. I also found the relay for the A/C to be dead but since it was the end of the season I let it go. Subsequently I discovered that the heater can not be put into the recirculate mode. There appeared to be no vacuum leaks.
About 800 miles ago the car started to surge at freeway speeds. It seemed fuel related so I verified fuel pump delivery pressure and fuel pressure regulator operation. Then I pulled codes from the ECU and got 12112 – oxygen sensor self-compensating circuit problem (incorrect air-fuel ratio at idle) and 12111 – oxygen sensor self-compensating circuit problem (incorrect air-fuel ratio while driving). I again checked for vacuum leaks and found the large hose running from the throttle body to the valve cover “PCV” held vacuum but was cracking and so replaced it. I also found oil seeping from the valve cover and removed and resealed it with anaerobic sealer. I tested the ELCD system and found it OK. I used a propane torch to look for additional leaks around the manifold, injectors and hoses and found none although I have never used this method before and am not sure I would have found leaks this way. I verified operation of the coolant temperature sensor and the oxygen sensor heater and output at idle. I again swapped in the known good air mass meter and also swapped in a good working but older relay for the fuel pump. The idle is steadier but varies slightly on almost exactly a 5 second cycle. I have read on this bulletin board that removing the oil filler while the engine is running should cause it to run poorly. I am puzzled that opening it makes no difference on this car. Neither does closing it with the palm of my hand. I do not find any evidence of leakage where the filler tube enters the block.
My plan now is to clean the grounds on the radiator cross member, the gearbox and in the luggage compartment. I don’t know where to go from there. Because the main problem occurs at 2500 to 3000 RPM I don’t think vacuum leaks are a big concern. Should I do the injector O-rings, they might be original? I used a little bit of anaerobic sealer around the water passage at the intake manifold gasket and wonder if that could cause the adjacent intake ports to not seal? Then I wonder if I should do the oxygen sensor and perhaps put a brand new relay in for the fuel pump and the main system?
posted by 206.183.2...
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
