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Discussion Starter #1
Hi there,

I want to replace the O2 sensor on my 1984 Saab 900s (not a turbo) and just want to confirm that there's only one.

I'm not a mechanic but I do have ramps and it sounds like a relatively simple thing to do. I already figured out how to reset the button that set off the EXH light in the first place. I know! I shouldn't have done this until after, but there I was, excited to have found it (went in through left speaker panel) and then just pushing the button like an idiot.

Also, I have a 16.6 gallon tank but have never been able to put more than about 12 gallons in. I know the tank was actually empty once (not just because of the flashing gas light) because the car was literally sputtering and I rolled into the gas station on fumes. (Wanted to see how far I could go once light came on. Not very, as it turned out.)

So:

1. Is there just one O2 sensor, and am I ok to replace it myself?
2. Why such a discrepancy with gas tank capacity? Air pockets? Other?

I'm guessing that these two questions could be intimately related.

Thanks much.
 

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UK cars did'nt have O2 on them as far as I was aware that early, but USA might, as had different emission laws but never heard of one on an 8V but everything was different to the 16v but if it's an early 16v it will be on the top side of the down pipe(uk is) just before cat
Your fuel tank is (14UK gallon)=16.8 USA gallon,there is usually about 1.5ish(UKgall) left when yellow light on permanently, so if you run out it's basically your fault, as it warns you early enough when getting close, and running it dry may cause the pump to fail prematurely.
It may be that your fuel pick up rubber (shaped like a sink unblocker plunger rubber) has perished etc, so cannot get all the fuel out of the tank, as the bottom of the main pump is higher, so it cannot reach the fuel in the tank, remove the cover and lift out the pump and see how much is in there on your low reading(when flashing) as you should be able to drive a fair way with low fuel light on permantly due to the pre set sender level, and I expect you will find either you have no rubber/or perished, or even dropped off, and there is a good 2" of fuel=2-3 gallon, in the bottom of your tank(on a level surface)
 

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There's only one o2 sensor.
 

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Use the cheapest universal one-wire O2 sensor your local parts store sells. It will work just as well as the high-priced spread.
Either your gas gauge is inaccurate or the fuel pickup doesn't reach the bottom of the tank.
 

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My Canadian market 84 8v turbo has an oxygen sensor.
I only had 8v i and cats did'nt come in till near 1990, although fitted they were not UK law till 1993 for GM900, so we can legally have a decat c900 or cat c900 as different emissions test for M.O.T.;ol;
 

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Also, don't sweat resetting the EXH light. It works off a mileage counter so it makes no difference when you reset it (and is NOT an accurate indicator that anything is wrong with the car)
 

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Discussion Starter #9
Bucking & Stalling & Charcoal Canisters, Oh My...

Okay, next question.

(Thanks for all the answers. I did end up replacing the O2 sensor myself, and it's been fine, but had to find somebody with the proper tool to get the old one off.)

My 1984 Saab 900S has 215k miles on it.

I've started to have some bucking over the last couple of months. I had a Saab pro in Salt Lake City look everything over. He recently flushed and replaced the clutch line, but otherwise gave the car a clean bill of health. He couldn't find a reason for the bucking or stalling (the reason I went in in the first place) and ended up sending me on my way.

The gist: the car loves being out on the open highway, and generally performs really well. I just put brand new tires on (studded winter tires were nearly dead) and got 34 mpg on a recent 300 mile trip. However, occasionally, when I'm climbing a bit of a hill on the highway, I'll get a bit of a stutter. It sometimes turns into a full-on bout of bucking, and I have to pull over for 5-10 minutes.

In stop-and-go traffic, the temperature jumps up, I sometimes get a stutter, and the car has actually lost all power a couple of times after a few minutes--once after sitting in a fast-food line for too long, and once when I was stuck in a traffic jam. By some miracle, I was able to steer over to the shoulder and stop just before everything died. I had the A/C button on to ensure a fan being on, and I think this was more of a contributing factor than a solution. I'm currently leaving it off, since it doesn't work anyway.

A mechanic here looked at the car yesterday. He found that the hose going to the charcoal filter was just hanging there, and looked as though it had been like that for a very long time. He fixed it, and told me to take the car home to see if that fixed the problem.

The bucking is now worse than ever. (I live about 20 miles from this mechanic, much of it highway.) His theory is that "gunk" is working its way through the canister, and that improvement is inevitable. He also said that the prior bucking was probably a result of air getting into the engine sporadically when that hose was disconnected.

I'm also guessing that I've lost about 1/3 of the power that I had before, and the idle feels choppy. The car bounces a little bit now. It didn't before. It was smooth.

He inspected the radiator (fine), fuel pump (strong pressure), the throttle (not pristine, but pretty clean--makes sense that a car this old would have some residual oil), the distributor cap (quite clean) and the coil--which may require further inspection in the future if the problem continues, he says.

I'm thinking that perhaps the throttle needs to be re-adjusted to where it was?

Also, from my reading on this forum, it sounds like people never replace the charcoal canister, and more often than not just end up disconnecting them altogether.

Any thoughts on all of this would be most welcome. As of right now, I'm tempted to just disconnect the brand new hose again in the hopes that the car will go back to the way it was two days ago, mysteries and all.
 

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You need to start with a fuel pressure gauge and measure the pressure of the pumped fuel
 

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Discussion Starter #11
Okay; I believe this was done yesterday, but I will confirm. So the fuel pressure gauge is completely separate from testing the fuel pump itself?
 

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One should reveal the other :)
 

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have you checked your plugs/gaps, as you could be running a bit rich so when you are stuck in traffic/or lights etc you are getting choked up a bit till you start accelerating and clear the engine out a bit, but if you advance/retard is'nt working, that will also cause a prob. dod you loose any water, as a slight HG leak will cuase a misfire(damp plug) but once you have sat and it's dried out from engine heat it works again fine, had that happen in a 1960's car
 

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The charcoal canister doesn't contain any 'junk'. There are 2 lines to it; a skinny vacuum line and a fat purge line. The skinny line could cause a vacuum leak, the fat line shouldn't do much (that you'd notice). There is no test for a bad charcoal canister, the people who really know what it does seem to be few and far between. It isn't causing stuttering, bucking.
Stuttering/bucking on turns or with low fuel indicates a bad fuel feed pump. Stuttering under load indicates bad cap/wires/rotor/plugs.
Dirty injectors cause hesitation, a dirty fuel filter will limit top speed.

As a pig-in-a-poke, spray some Windex on your spark plug wires and distributor cap in the dark, when the engine is hot and idling.
 

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Discussion Starter #16
Forgive me. I am a rube.

Please say more about this Windex test, and what the results are that I'll be hoping for/dreading. Assume I don't know what on earth you're talking about but wish desperately that I had more mechanic-ese in my brain.

Also, please tell me what you think has happened in the last couple of days. What are the steps? Did the mechanic's nosing around somehow send something over the edge and reveal the 99% bad cap/wires/rotor/plugs? How could the injectors and/or the fuel filter just now be revealing themselves as dirty as a result of the mechanic's hunt (assuming that these are the things causing a change in idle and loss of power)?

Is it easy to verify that injectors are dirty? I believe he checked the fuel filter, but will confirm that.

I don't think he meant that there was junk in the charcoal canister. Rather, I think he meant that the reconnection of the hose had changed the relationship of the flow to and through the canister. But what you're saying makes me think he was, perhaps, babbling.
 

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The Windex might reveal bad wires.
Don't chase symptoms you don't have. If top speed isn't limited, ignore the fuel filter. If your complaint is not hesitation, don't clean the injectors. Avoid replacing parts because they're cheap or easy to replace.
I can't tell you what happened before or after somebody looked at the car. Chase the symptoms you have, don't check/repair things at random or because it's easy.
First you need to determine if it's a fuel or ignition problem. Start with ignition, it's less obscure than the K-Jetronic which allows little testing without the right fuel pressure gauge and knowledge of the system.
Does the little valve on the inner fender by the air filter buzz all the time (it should)?
 

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In a dark, romantic setting :D, spraying Windex on the spark plug wires will show electrical arcing if there is a breakdown in their insulating properties.

The charcoal canister is an emissions device that shouldn't cause any adverse affect on the running at speed, and any 'stumble' at idle should be moderated, if not corrected, by the ecu and idle control valve.

If your tech goes about checking fuel pressure, have it done with the car being driven and not sitting on the rack in the shop. Ideally, you'll want it checked under load. You can also check the 'health' of the fuel pressure regulator by pulling the vacuum line and seeing if gas drips out.
 

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Discussion Starter #19
Yesterday, I did the Windex test; nothing. The car was continuing in its weirdness.

I have this smart neighbor I never see, but I know he's on his third Saab. He just happened to be standing outside yesterday, so I sidled up and explained the issues. He was curious, grabbed a can of starter fluid and came over to take a look. Sprayed that around; didn't detect any vacuum leaks. He ran back over to get his car stethoscope (Saabascope?) and listened around for a while. There was a strange click that he didn't like. He nosed around for a few minutes and eventually showed me what he had found: the hose for cylinder 2 was just hanging there! Ta da! The mechanic who looked at it a few days ago must have knocked it loose, which is why, after all he did was fix the charcoal canister hose, the car suddenly felt like a completely different car (clear loss of power, choppy idle, etc.).

I'm thinking that particular hose must have been loose for a long time. Could that looseness explain all of the bucking/stalling over the past couple of months? I hope? Anyway, that's back on, and I reconnected the fat hose to the charcoal canister (which I had pulled off yesterday). I drove it around for a while yesterday, and not a buck in sight. It felt like its old self. Smooth and happy.

So: did I do any damage in the 40 miles or so I drove the car on only 3 cylinders? What happens in that situation, exactly? (This Saab 900S is 1-3-4-2, yes?)

Also: the mechanic who left me on 3 cylinders... obviously knows a lot about Saabs, but maybe not the most careful. He has an A/C conversion kit that he's ready to put in for me for about $300. Assuming all goes smoothly on the installation itself, any misgivings about bringing the A/C back to life for a car this old? Will it be too hard on the engine and am I asking for trouble? (A/C is fairly important here in the desert--easy to hit 110 once summer comes.)

Hoping the car is happy again and on its way to 300k. Fingers crossed. Love to hear your thoughts. I also want to replace the fuel pick-up rubber at some point (mentioned in an earlier post) but don't want to ask for trouble on that front, either. If I should just leave it alone, and always plan to keep a certain amount of gas in the tank, I will.
 

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I read this a couple times and I'm stuck wondering what hose you are speaking of? Do you mean a spark plug lead was off the plug? I know (hope) you didn't mean a fuel line.

Glad the car's behaving and you'll be fine running a/c
 
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