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Discussion Starter #1
I have a bit of an interesting problem. My Saab idles at 800-900rpm. When I drive it and slow down to a stop the rpm will drop low enough the car might end up stalling. If I put it in neutral as it coasts to a stop and blip the gas pedal before its rpm drops too much, it will catch itself and idle as it should (nice steady idle). Best way to describe it is that it behaves as if the bypass/blowoff valve is leaking and you press the gas pedal and then let it go back to idle. In my case it does not do that if the engine is unloaded. Problem is that I put a new one and it does work.

So, after reading http://www.saabcentral.com/forums/showthread.php?p=1121054, I have replaced the vacuum lines, the one way valve between the valve cover and the intake manifold, and checked the grounds on the engine. Still no luck. I have not checked the idle control valve yet because it does not have a loopy idle, but I might as well do it today.

Not knowing what else to check, I was then thinking it could be the throttle position switch because upon inspection I found out its contacts were quite filthy:


Thinking that was the problem, I took it out and apart,

cleaned the contacts both at the switch and the harness connector, and put it back. I tested it manually for both the famous click and continuity at idle and full throttle, and it seemed to be working fine.

With that taken care of, there was another issue I when I release the throttle, only after almost a second the switch's idle switch would then click. So, I turned it a bit to make it click just as the throttle plate would snap back close. It felt like I was forcing the switch to turn; it could be I was also pushing the throttle plate open.

So, I started the car. Now it would not stall anymore but its idle was now 1500rpm, whch made me think I had indeed opened the throttle plate with my adjustments.

So, what else can I do?
 

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A car that stalls when the brakes are applied is most often a sign of a bad brake booster (the large black donut on the fire wall at the brake master.
 

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Discussion Starter #3
Actually it does not stall when I press the brakes. I can have the car idling while parked and press the brakes all day without ill effects. Also, if the car is on neutral while I decelerate to stop, I will have no problems. But, if I am slowing down (engine braking) and then press the clutch, it might stall.
 

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I have the same problem...

I see that this problem appears to be unresolved. My 89 saab 900S n/a has the same issue. I haven't done anything to it yet but I was considering doing just a basic tune-up (plugs,wires, maybe fuel filter) and see if that does it. I was also thinking it might possibly just be a batch of bad gas as I haven't had any issues until now and I have the owned the car for multiple months now.
 

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I just had a similar problem that went to a check engine light- turned out my O2 sensor went. Actually caused a weak acceleration though. In the midst of finding it I cLeaned both the AMM and the AIC valve. Hooked up an old connector to the valve and opened and closed it while cleaning. You may also want to checkthe idle adjust locknut on the throttle body- it may have worked loose aand given a slight vacuum leak for the minor hunting you have.
 

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I'm revisiting this because I have the same symptoms.

Precisely, the engine speed would fall so far as to cause it to stall when decelerating. It would idle well, and would not stall if I lifted the gas and depressed the clutch while cruising. It also got worse as the car warmed up.

I figured the whole automatic idle control system was working as idle was good, and even compensated for AC and other variations (such as turning the throttle adjustment screw). Plus the problem was when the car was moving, when the idle control is... well, idle.

I focused on the turbo bypass valve as it comes into operation while there is vacuum, which is maximum when decelerating in gear.

I found this on the underside of the throttle-body end of the turbo bypass hose...



I looked at a spare, used, hose and it had the same problem.

It appears that metered air was leaking from the turbo bypass hose when the bypass valve opened. It was worst under deceleration while in gear, which created the highest vacuum and hence opened the valve the maximum. And even worse when the engine was warm as the throttle body tube would expand and make the crack bigger.

I taped the crack temporarily and the problem disappeared.

Anyone with a fair, used bypass hose they can spare?
 

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I'm revisiting this because I have the same symptoms.

Precisely, the engine speed would fall so far as to cause it to stall when decelerating. It would idle well, and would not stall if I lifted the gas and depressed the clutch while cruising. It also got worse as the car warmed up.

I figured the whole automatic idle control system was working as idle was good, and even compensated for AC and other variations (such as turning the throttle adjustment screw). Plus the problem was when the car was moving, when the idle control is... well, idle.

I focused on the turbo bypass valve as it comes into operation while there is vacuum, which is maximum when decelerating in gear.

I found this on the underside of the throttle-body end of the turbo bypass hose...



I looked at a spare, used, hose and it had the same problem.

It appears that metered air was leaking from the turbo bypass hose when the bypass valve opened. It was worst under deceleration while in gear, which created the highest vacuum and hence opened the valve the maximum. And even worse when the engine was warm as the throttle body tube would expand and make the crack bigger.

I taped the crack temporarily and the problem disappeared.

Anyone with a fair, used bypass hose they can spare?

mine was split as you pictured (if thats the side that goes to the TB). I put some red silicone at the slip and put the clamp on it and screwed it closed and all was well.
 

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TBV appears fine, but the bypass hose appears to be the problem in both cars. Plus it's gone super hard, unlike the other hoses around the area.

Does anyone know if replacements in silicon are available?
 

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The turbo-bypass hose is the thick one between the bypass valve and the throttle body, not 5/32 hosing...
Saabturbo92 said something about BPV hose replacement and associated vacuum line replacement

The question was asked about silicone hose non specifically, B202 I guess assumed that the OP was asking about silicone for the vacuum line replacement not BPV, B202 responded with the vacuum hose diameter which is 5/32

HENCE why I said vacuum line not BPV line in my post regarding the 5/32 being original spec when someone asked what 5/32 was.
 

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Still begs the question - are there any turbo bypass hoses in silicone, since they seem to be a weak point?
Unlikely - it's a low demand part. As far as I am aware they are on available new old stock - OEM @ $70 approx IIRC.

They definitely aren't a weak point, probably one of the best lasting pieces of rubber on the entire engine. Think about how long cooling hoses last, how long power steering hoses last, rubber suspension bushings (I've listed them from shortest to longest approximate lifespan) The rubber of the BPV hose you should last much longer (and there is proof by the fact they are failing now over 20 years since manufacture). Those that have failed have probably had exposure to petrochemicals/solvents/oil in their life and thus shortened their lifespan.
 

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The rubber of the BPV hose you should last much longer (and there is proof by the fact they are failing now over 20 years since manufacture). Those that have failed have probably had exposure to petrochemicals/solvents/oil in their life and thus shortened their lifespan.
True...
 

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I would be interested to know who is going to take over making spare parts as originals dwindle, I say we are at the toughest point now with decreasing OEM new old stock yet there isn't high enough demand for companies to create aftermarket products (I don't know if there ever will be :(). This is just insane in Australia, no chance of getting anything Saab at a decent price, except brake pads. I blew heaps of money buying 2nd hand parts from a wrecker in Aus that sometimes cost me more than new parts would from the US just because I needed my car back on the road. Absolutely ridiculous. Now I buy parts from the US in advance and get them ferried back by my Dad who visits the US every now and then.
 

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short answer ... No one ...

If it has not been profitable to date to make and sell certain aftermarket items , it certainly wont be in the future .
I cant recall the last time I purchased a *saab* part In Australia for the reasons you list .
Even some of the places that had developed a reasonable name for supplying *new* at reasonable prices have either stopped stocking the consumables or now want your first born .

WHAT I have often considered ... without having delved too deeply ...

Is some sort of franchise/reseller style arrangement with say .. EEURO and or PFS where a small quantity of the common consumables are stocked locally .. they discount the freight based on a bulk shipment ... and the middle man applies a realistic mark up for his Investment ..and distribution.

BUT we live in a climate of Net shopping .. where we are all guilty of cutting out Middle men , and ultimately strangling local supply .
You Do it ... I do it ... The result .. we save a $ on this purchase ..

the consequence .. Saabwreck .. Volvsaab .. No more demand ? dont stock it ...

Its classic chicken and egg .. and an issue that will only get worse ,
 
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