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Discussion Starter · #1 ·
Just finished putting everything back together after changing the head gasket, timing chain, timing and balance chain guides, water pump and 5 hydraulic lifters on my Aero. I cleaned the throttle body (and turned the throttle stop screw) and AIC valve whilst it was apart and gave the wastegate rod a couple of turns up (i.e. increase base boost slightly) also changed the BPC valve as the old one was open circuit on one side and engine regularly hit overboost. Also fitted oil pressure sender for oil pressure gauge, new tensioner pulleys/belt and one valve between cam cover and inlet (old one was two way!)

Started her up (first time) and everything was OK apart from the idle control, went up to 3k, after a few minutes it would then hunt from 2k to 2.5k every second so I guess the ECU was trying to set the speed but was outside its parameters. There was NO check engine light. Playing with the throttle stop screw eventually got things controlling to 1100rpm. Came back after an hour and the idle was back to 3k, resistance across the AIC gave 7 ohms (right value). Problem was AIC as when I block it the idle speed was OK. I then fitted an AIC from a 91 2.0L turbo, different type of AIC but resistance across it was the same. Idle now controls without a problem. Drove 30miles last night, everything very good, no overboost, sweet. Then this morning I pull out of the drive – spun the wheels in second which surprised me, then check engine light comes on and has stayed on even after switching engine off for a couple of minutes. Car runs great though, idle OK, boost correct, a dream but now with check engine light, no hesitation.

Any ideas? Lambda sensor broke after removal refitting, why did old AIC valve give up after being cleaned. Has the AIC from the 91 upset the ECU? Can I pull the error codes or is it a dealer visit? Help.
 

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Have you left the ignition on (engine not running) and waited for the Check Engine light to flash the code at you?

It may be the AIC, although if it's working well, it's just as likely a connector has fallen off a sensor, wire broken or something, since you've obviously had a lot of things disconnected recently.
 

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Adrian,

Won't turning the throttle stop screw affect the point at which the 'Throttle Position Switch' detects the 'closed' position? It's a while since I had the ICV version of engine (on a 1994 2L ECO), but I found unless there was enough 'travel' to ensure the throttle position switch was clearly triggered, when parts get warm and/or worn the 'stop position' may not be detected, and the floating rev scenario (as per your description) occurs.

In summary, the throttle stop screw should not be adjusted, without ohming out the closed and open positions of the throttle position switch and ensureing correct resistances/switching occurs. Haynes manual describe test method/values.
 

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Discussion Starter · #5 ·
Thanks guys - I think turning that throttle stop screw was a bad idea.

What is the procedure to read the error codes - turn ignition on wait and count flashes?
Is there a list of what the flashes mean somewhere?
 

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Turning throttle stop screw back would be the easy test/solution - after checking error codes.

To adjust throttle stop position switch is easy too. Just loosen locking nut, and rotate the unit slightly clockwise and retighten locking nut. Best to check switch resistance against haynes manual figures before and after - and ensure a spare 'degree' of rotation is included to allow for any play in the mechanism when unit is hot under running conditions.

I leant this process the had way when an 'Indie' Saab specialist in south west tried being smart, by turning throttle stop screw to reduce tickover - at least he did it free of charge!! My guess was he didn't even know what a throttle position switch was! I had to set it back when the 'floating rev' scenario occured - itermittently - mainly when engine was up to temp, etc.
 

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Discussion Starter · #8 ·
Cheers Paul.

Just checked codes and I get three flashes which means intake air temp sensor. Will swap sensors between cars - that's the advantage of his 'n hers motors, and my folks, and folks-in-law, and sister
 

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Originally posted by Adrian:
[qb]Do error codes automatically reset when sensor values are back in range or do I have to unplug battery or is it a dealer visit? [/qb][/b]
Once the fault is removed, it should clear after a number of engine starts. 10, I think.

I had the same problem shortly after replacing the head gasket on my Aero - broken wire at the connector on the sensor.

Spooky, eh?
 

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Discussion Starter · #12 ·
Spooky.
Mine is a silver with black interior Aero as well.

I disconnected the battery and sensor plug, reconnected and its running perfectly. Fitted new exhaust and rear poly antiroll bar bushes last night plus top engine mount poly bushes. Wow I'd forgotten how great the Aero is. Just need to keep an eye on the BCP and hope that this one does not get blown if it does it will be an ECU repair.

New discs and Pagid pads still to fit - thanks for the speedy delivery Elkparts - very efficient.
 
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