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car threatening to stall when warm
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doomer77  



Joined: 10 Jan 2006
Posts: 266
Location: Huskvarna, Sweden

PostPosted: Wed Mar 01, 2006 5:28 am    Post subject: car threatening to stall when warm Reply with quote

well, i pretty much said it in the title. whenever i drive my car around for a while, enough time for the temp gauge to reach middle the car has a tendency to threaten to stall whenever the rpms drop below 900 (lights flash on, oil pressure warning light comes on), normally it does this at around 500 rpms. as a result of this starting in 2nd gear when the engine is warm becomes difficult.

what could be the reason that the car is acting this way only when hot?

erik
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chris24  



Joined: 17 Jan 2005
Posts: 334
Location: boston/nottingham UK

PostPosted: Wed Mar 01, 2006 5:35 am    Post subject: Reply with quote

My revs are set at 950rpm when warm as per recommendations. maybe you could adjust that slightly...but your problem sounds a bit different to that.

I don't understand why your revs would drop below 900 if it idles at 900?

Quote:
as a result of this starting in 2nd gear when the engine is warm becomes difficult.


Maybe that answers it..?! Why would you start in 2nd gear? All you are doing is lugging the engine. Not a good idea to have the car in gear and below 2000rpm(except 1st). 500rpm and the oil light will come on and your car will want to stall, especially if it is in 2nd gear.

Hope that helps!
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Vince Ponz  



Joined: 03 Nov 2002
Posts: 3581
Location: Florida

PostPosted: Wed Mar 01, 2006 7:04 am    Post subject: Reply with quote

I think your fuel pump is overheating and stalling. It happened to me last year as I was trying to cross the GW Bridge and it stalled. Cooled off and ran another 200 yards and died. This was in busy Friday night at rush hour.

vince
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chris24  



Joined: 17 Jan 2005
Posts: 334
Location: boston/nottingham UK

PostPosted: Wed Mar 01, 2006 10:10 am    Post subject: Reply with quote

We need some clarity doomer! It doesn't sound like your fuel pump to me, but we need some more info as I may have read your question wrong.
Are you actually trying to drive your car at 500rpm (e.g. when going along slowly in a queue) or are the revs just dropping when you let the engine idle? Can you hear your fuel pump change note? Mine's a high pitched whirry pump that you can hear at 900 rpm. (Been like that for thousands of miles.)
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1985 - 924 (148K miles) - mint
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jpab924  



Joined: 03 Nov 2002
Posts: 1538
Location: Crown pt. IN. 50 miles southeast of Chicago Ill.

PostPosted: Wed Mar 01, 2006 3:05 pm    Post subject: Reply with quote

Check your basics first. Timing, and idle speed....do this with the engine warm. See what you got and go from there...
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doomer77  



Joined: 10 Jan 2006
Posts: 266
Location: Huskvarna, Sweden

PostPosted: Wed Mar 01, 2006 4:48 pm    Post subject: Reply with quote

it idles at 900 when cold, then slowly moves up to 1200 when warm. the thing is not that the car actually stalls, it just threatens to stall, the lights flash on and the engine goes shaky for a moment, it can be avioded by just giving it more gas. but still its a nuissance and i want to solve it if possible.

i can hear my fuel pump if i turn on the electric ignition only, then its a whirring noise, however i never hear it when the engine is running.
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Mike924  



Joined: 12 Aug 2004
Posts: 2601
Location: IoW UK

PostPosted: Wed Mar 01, 2006 7:51 pm    Post subject: Reply with quote

doomer77 wrote:
it idles at 900 when cold, then slowly moves up to 1200 when warm.


This is exactly the opposite of what should happen.

I would start by checking the operation of the AAV (auxiliary air valve), if this is OK I would suspect the WUR (warm up regulator). It could be that the PO (previous owner) has set the mixture too rich (to compensate for a broken WUR), just so that the car will start, making it too rich to run happily when it's hot (particularly when you put your foot down and get additional load enrichment.)

Just a theory...
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timstar92404  



Joined: 22 Sep 2004
Posts: 2075
Location: richmond BC

PostPosted: Wed Mar 01, 2006 9:42 pm    Post subject: Reply with quote

according to haynes the wur very rarely become inoperational. I have proplems with hot / cold starts as well I think could be my aav.

when its really cold the car starts but but it doesn't want to rev when I step on the gas and feels like it wants to shut off... when the engine sits after hot now I have to crank it for 10-30 mins sometimes to get it to start this is when it sits for 1-4 hours guessing after 6+ hours it starts easily.
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Mike924  



Joined: 12 Aug 2004
Posts: 2601
Location: IoW UK

PostPosted: Wed Mar 01, 2006 9:51 pm    Post subject: Reply with quote

timstar92404 wrote:
according to haynes the wur very rarely become inoperational.


The valve in my WUR was siezed and I know of a number of other board members who have had WUR problems. What might have been true when the Haynes manual was written doesn't seem to apply to twenty-plus year old cars.

timstar92404 wrote:
when its really cold the car starts but but it doesn't want to rev when I step on the gas and feels like it wants to shut off...


These are the classic symptoms of a WUR problem

timstar92404 wrote:
when the engine sits after hot now I have to crank it for 10-30 mins sometimes to get it to start this is when it sits for 1-4 hours guessing after 6+ hours it starts easily.


This is the normal hot start problem and has nothing to do with the WUR (or AAV).

timstar92404 wrote:
I have proplems with hot / cold starts as well I think could be my aav.


Don't hijack Doomer's thread, Tim.
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doomer77  



Joined: 10 Jan 2006
Posts: 266
Location: Huskvarna, Sweden

PostPosted: Thu Mar 02, 2006 2:54 am    Post subject: Reply with quote

lighten up, tim is only trying ot help

latetly it has had a reluctance to start when hot, yesterday it took about 5 minutes of cranking before it caught, today it started after only 10 seconds of cranking. but this might have to something with the injector cleaner i just poured into the tank?

lets have a vote here,

who thinks its the AAV and WUR causing this?

and who thinks its the fuel pump on its way out?
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1980 924 n/a - engine swap begun
1989 Volvo 480ES
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Belgian924t  



Joined: 07 Jan 2006
Posts: 104
Location: Belgium

PostPosted: Thu Mar 02, 2006 5:36 am    Post subject: Reply with quote

First to Tim: I thought you had sold your 924 or you were going to stop attacking this board?????

Then: Eric, go for basics: check all hoses, earthcables, sparkplugs, ignitiontiming, fuelpressure....

Start simple, then go further


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doomer77  



Joined: 10 Jan 2006
Posts: 266
Location: Huskvarna, Sweden

PostPosted: Thu Mar 02, 2006 5:43 am    Post subject: Reply with quote

will do man!
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Carpe diem. and if that doesnt work; get drunk!

1980 924 n/a - engine swap begun
1989 Volvo 480ES
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chris24  



Joined: 17 Jan 2005
Posts: 334
Location: boston/nottingham UK

PostPosted: Thu Mar 02, 2006 8:18 am    Post subject: Reply with quote

You say your car revs at 900 then 1200 when warm. Usually it is the other way round as Mike said, the AAV effectively holding the throttle open a bit more at first and the WUR keeping the mixture a bit richer while the engie is cold. When these are turned off the engine revs usually drop a bit (e.g. to 950) and the engine runs happily.

I'm still not clear...maybe I'm being a pedant...but you said that the revs drop to 500 and the oil light comes on. When is this? Does this happen when the engine is ticking over? Are you driving along in 1st or 2nd at 500rpm? When it goes down to 500 from 900, how long does it stay there for? Does it bounce back and forth?

Tim, to back Mike up...the WURs do go wrong/get disconnected etc etc. Don't believe everything in Haynes...
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1985 - 924 (148K miles) - mint
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Last edited by chris24 on Thu Mar 02, 2006 6:39 pm; edited 1 time in total
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924er  



Joined: 10 Jan 2006
Posts: 339
Location: Los Angeles California

PostPosted: Thu Mar 02, 2006 12:25 pm    Post subject: Reply with quote

my idle acts up when its warm too. the idle bounces up and down but i just think i have a minor vacuum leak.
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Mike924  



Joined: 12 Aug 2004
Posts: 2601
Location: IoW UK

PostPosted: Thu Mar 02, 2006 7:05 pm    Post subject: Reply with quote

Firstly: sorry, Tim, if I sounded a bit too harsh - I've done it again...

Secondly: Chris, thanks for backing me up.

Thirdly: 924er - Yes, your problem sounds like a vacuum leak.

Now back to Doomer's problem. I think we need a few more details here. Your car idles at 1200 when warm. This is a little fast - it should be somewhere between 900 - 1000 (depending on the electrical load on the alternator).

Does it always run at this speed when warm or just when it first warms up? If it's always fast, you need to tweak the idle screw in a bit. If you do this, it might not like idling when cold, given that it only runs at 900 rpm cold. It might be that the AAV is stuck and the idle speed has been adjusted to compensate.

You seem to have a problem starting from low revs; you say it tries to stall below 500 rpm. This isn't really surprising as the idle speed is nearly 1000; the engine can't really be expected to produce torque at half its idle speed. Is it simply your driving style? What about giving it more revs before bringing the clutch up?
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