[MrBoJangles]

Hi all,
At wits end.
1998 SE with bad engine surge at idle and low speed - no codes show, no Check Engine light.
Good 'indie' has done following:
Cleaned TB (twice)
Renewed vacuum lines
Replaced fuel filter
Replaced fuel pump
Replaced Ignition pack

So lots of money spent - but fault is proving elusive, and I'm ready to trade-in a car I love.

 

[hacker-pschorr]

Does it feel like you are varying the throttle during light acceleration?

I thought a popular fix was repairing the wires in the TB?

 

[MrBoJangles]

Does it feel like you are varying the throttle during light acceleration?

Not really, it's mostly a bit more 'abrupt' than that. And sometimes as I am coming to a stop at a corner or light, it will almost stall, so that seemed like the other threads that pointed to fuel filter or pump - but those have now both been changed + regulator. And it is often bad just sitting motionless at idle - worse when engine is cold.

 

[MacNoob]

Check the turbo bypass valve:

Should hold vacuum at the small vacuum fitting.
Should only pass air between the two large fittings when vac is applied to the small one.

Having said that, it still could be the throttle body. rebuilt ones are available. After 216,000km my '01 wagon is starting to do this.

 

[xianbei]

Surge > Sticky Waste Gate?

I talked to an experienced Saab indy about this issue, he mentioned that a sticky waste gate could be the source.

He said he usually checks this with a screwdriver. The gate should open and close smoothly.

I haven't checked mine yet because it hadn't acted up all winter. Now that it's spring again here in Vermont I've seen it start to flake out again.

 

[Route 17]

Your symptoms sound similar to what Saabcog went through.

http://www.saabcentral.com/forums/showthread.php?t=162199&highlight=surge

If I recall he was finally able to find the cause and I think it was a vaccum check valve but you would have to contact him to confirm.

 

[SaabNineThree]

unplug the battery for an hour thats what i did it worked tbh.

 

[MrBoJangles]

unplug the battery for an hour thats what i did it worked tbh.

What and how does unplugging the battery do????

 

[Jssaab]

Cleaning the Throttle body often does little, try replacing it ( its an easy DIY)

 

[SaabNineThree]

What and how does unplugging the battery do????

resets the ecu

 

[MrBoJangles]

resets the ecu

And how and why does that help? And why does the ecu need a reset?

 

[Spurs75]

Have you tried replacing the maf?

 

[MrBoJangles]

Have you tried replacing the maf?

No not yet. Is that a likely candidate? I'm guessing it's not such an expensive part, so we could do that next.

 

[Spurs75]

I recently had a problem where i started the car and it would rev up to 3k then drop down to 750 then rev upto 2.5 k then stall. No codes, no check engine light. Replaced the maf with one off ebay problem sorted. I actually ran the engine with the maf unplugged to fault find this and i had no surge, but obviously a check engine light showing the maf was unplugged (malfunctioning). Hope this helps.

 

[MrBoJangles]

I recently had a problem where i started the car and it would rev up to 3k then drop down to 750 then rev upto 2.5 k then stall. No codes, no check engine light. Replaced the maf with one off ebay problem sorted. I actually ran the engine with the maf unplugged to fault find this and i had no surge, but obviously a check engine light showing the maf was unplugged (malfunctioning). Hope this helps.

Well that's definitely a likely next step, many thanks.
(A next step down the depressing road of a near re-build of this car.
So far:
- new turbo
- exchange head, with all the associated and expensive work that goes with that
- new neutral position switch
- new starter motor
- new fuel pump
etc etc

 

[mt.aero]

No not yet. Is that a likely candidate? I'm guessing it's not such an expensive part, so we could do that next.

Its a very likely candidate. Try just cleaning the MAF first. Its a pretty expensive part to replace. ($300+)

 

[SaabNineThree]

And how and why does that help? And why does the ecu need a reset?

i dont know but it tends to work for me when the ecu is adaptive

 

[mt.aero]

i dont know but it tends to work for me when the ecu is adaptive

If you are reseting the ecu to cover up a problem, you are likely going to run into bigger problems down the road. If you are reseting to lose the standard adaptation on a good running engine, then torque away!

 

[MrBoJangles]

Its a very likely candidate. Try just cleaning the MAF first. Its a pretty expensive part to replace. ($300+)

What parts do I have to take off to get to the MAF? I've read how to clean it, but where is it exactly? I realize it is in a large air intake line, but not having worked on the engine yet -just need to know what parts need to come off to get access....

 

[mt.aero]

This is a nice and easy job. In reference to the pic below, it is in the bottom left corner.... its attached to the rubber intake pipe. It the thing with the barcode on top. Simply undo the clamps on either side and unclip the wiring harness to it. Then its just a matter of following the directions on the can of MAF cleaner. CRC cleaner works great for me. Just to note, its easy to put it back in backwards (ask me how I know :lol: ), so they include an nice airflow directional arrow (that I pretty much ignored).