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1993 850 RPM pulsing up and down at idle Topic is solved

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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Paul-93-850
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1993 850 RPM pulsing up and down at idle

Post by Paul-93-850 »

1993 850


Check engine light came on and code indicated the MAF.
RPMs were very high at idle.

I bought a re-manufactured Bosch MAF and now the RPMs pulse up and down at idle.

What might this indicate?
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bmdubya1198
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Re: 1993 850 RPM pulsing up and down at idle

Post by bmdubya1198 »

Is your check engine light still on? When was the last time your IACV was cleaned?
'00 V70R Venetian Red/Charcoal M56 Swapped 199k
'03 S60 2.4T Silver/Black 117k
'07 XC90 V8 AWD Sport Titanium Grey/Black 174k
'91 944 Turbo Dark Green/Beige 175k
'92 245 Base White/Beige 249k
'99 BMW 528i
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misha
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Re: 1993 850 RPM pulsing up and down at idle

Post by misha »

Paul-93-850 wrote: Wed Oct 04, 2017 12:58 pm ...I bought a re-manufactured Bosch MAF and now the RPMs pulse up and down at idle.

What might this indicate?
That indicates that re-manufactured & aftermarket MAF will not work on these cars.
Only brand new or even good known used OEM BOSCH.

1993 n/a should use just an insert.

Disconnect the MAF and see if it runs better.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
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Paul-93-850
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Joined: Sat Oct 27, 2007 3:20 pm
Year and Model: 1993 850 non-turbo
Location: Beach

Re: 1993 850 RPM pulsing up and down at idle

Post by Paul-93-850 »

Disconnected the MAF and it idles too fast.
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erikv11
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Re: 1993 850 RPM pulsing up and down at idle

Post by erikv11 »

But it doesn't surge? Bingo - the MAF is the problem.

Remanufactured MAF will have non-Bosch electronics, and they usually (like 90% + of the time) don't work right in these cars.
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misha
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Re: 1993 850 RPM pulsing up and down at idle

Post by misha »

Fast idle with maf disconnected could indicate a clogged iac valve or a vacuum leak.
The fact that fluctuating up & down rpm goes away with maf disconnected indicates that maf is bad.
NEVER use aftermarket sensors on these cars.ONLY oem....new or good known used.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
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misha
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Year and Model: '97 850 2.5 20v
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Re: 1993 850 RPM pulsing up and down at idle

Post by misha »

Somehow my post has been duplicated.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
Paul-93-850
Posts: 96
Joined: Sat Oct 27, 2007 3:20 pm
Year and Model: 1993 850 non-turbo
Location: Beach

Re: 1993 850 RPM pulsing up and down at idle

Post by Paul-93-850 »

I removed and cleaned the idle air control and the throttle body. No apparent bad vacuum hoses. High idle speed has only dropped slightly. Still rough and hesitating acceleration. When first starting, the idle goes up and down a few times and then stays high.

Before doing the cleaning the code only showed 1-1-3 short term fuel trim upper limit.

Assuming MAF is OK, what would these symptoms indicate?
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misha
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Re: 1993 850 RPM pulsing up and down at idle

Post by misha »

Re-manufactured or aftermarket Maf CAN'T be ok for these cars.
It's better to run the car with it disconnected.
Other that...large vacuum leak somewhere like ribbed plastic hose from air filter housing,vacuum tree,pcv system,hose for fuel evaporation...
On how much rpm it is idling?
N/a idles around 900(+-50) rpm.
'97 850 2.5 20v / fully equipped / Motronic 4.4 from the factory / upgraded with S,V,C,XC70 instrument cluster / polar white wagon
'91 Citroen XM 2.0 SI /fully equipped/mandarine red metallic
History of Volvos in the family:
'71 144 S
'73 144 De Luxe
'78 244 DL
'78 244 DL
'79 244 GLE
'85 340 GLS
Paul-93-850
Posts: 96
Joined: Sat Oct 27, 2007 3:20 pm
Year and Model: 1993 850 non-turbo
Location: Beach

Re: 1993 850 RPM pulsing up and down at idle

Post by Paul-93-850 »

RPM at idle goes from around 1200 to 1800.
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