Login Register

1986 240 DL fluctuating idle

Help, Advice, Owners' Discussion and DIY Tutorials on all Volvo's "mid era" rear wheel drive Volvos.

1975 - 1993 240
1983 - 1992 740
1982 - 1991 760
1986 - 1991 780
1990 - 1998 940
1990 - 1998 960
1997 - 1998 V90/S90
Post Reply
mhgreen
Posts: 82
Joined: 15 December 2014
Year and Model: 240 DL 1986
Location: Portland, OR

1986 240 DL fluctuating idle

Post by mhgreen »

I don't have a tachometer, but I can feel and hear my engine fluctuating up and down during idle. No conspicuous vacuum leaks, and I am wondering where I should start on hunting down this issue. Any thoughts?
“Some cannot loosen their own chains and can nonetheless redeem their friends.”
Top
User avatar
93Regina
Posts: 2813
Joined: 18 January 2014
Year and Model: 93:240/940
Location: Sunflower State
Been thanked: 65 times

Post by 93Regina »

mhgreen wrote:where I should start on hunting down this issue.
Salvage Yard - Look for another MAF (aka AMM)

ECU and AMM information
Last edited by 93Regina on 01 Feb 2015, 21:31, edited 1 time in total.
Top
mhgreen
Posts: 82
Joined: 15 December 2014
Year and Model: 240 DL 1986
Location: Portland, OR

Post by mhgreen »

Replaced amm a month ago - known good.
“Some cannot loosen their own chains and can nonetheless redeem their friends.”
Top
User avatar
93Regina
Posts: 2813
Joined: 18 January 2014
Year and Model: 93:240/940
Location: Sunflower State
Been thanked: 65 times

Post by 93Regina »

mhgreen wrote:Replaced amm a month ago - known good.
Replace injectors' o'rings
Top
mhgreen
Posts: 82
Joined: 15 December 2014
Year and Model: 240 DL 1986
Location: Portland, OR

Post by mhgreen »

Sprayed penetrant around injectors during idle... No change
“Some cannot loosen their own chains and can nonetheless redeem their friends.”
Top
mhgreen
Posts: 82
Joined: 15 December 2014
Year and Model: 240 DL 1986
Location: Portland, OR

Post by mhgreen »

Sorry - I am not trying to counter every piece of advice you give. And maybe the penetrant trick isn't failproof.
“Some cannot loosen their own chains and can nonetheless redeem their friends.”
Top
User avatar
93Regina
Posts: 2813
Joined: 18 January 2014
Year and Model: 93:240/940
Location: Sunflower State
Been thanked: 65 times

Post by 93Regina »

mhgreen wrote:...engine fluctuating up and down during idle..
Classically speaking....AMM is the issue....and fuel burn (aka mpg) tends to drop.

Classically speaking...a vacuum leak tends to increase RPM, but not up/down.

Classically speaking...DIYers who screw the pooch via twitching throttle plate (etc) create their own problems.

Hence, throttle plate must be in OEM position. I don't know spec for 1986 LH, but if someone has been twitching throttle plate, I'd set it closer to closed position, 1/4 turn at a try. Of course, throttle switch needs to be in adjustment.
Top
mhgreen
Posts: 82
Joined: 15 December 2014
Year and Model: 240 DL 1986
Location: Portland, OR

Post by mhgreen »

Let me make sure i understand. Throttle plate - inside throttle body - has two flathead screws on it. You're suggesting I turn both screws 1/4 turn clockwise?
“Some cannot loosen their own chains and can nonetheless redeem their friends.”
Top
mhgreen
Posts: 82
Joined: 15 December 2014
Year and Model: 240 DL 1986
Location: Portland, OR

Post by mhgreen »

Tps is adjusted correctly, and throttle plate seems fine. I did notice a hissing from the intake manifold somewhere. Can't pinpoint it.
“Some cannot loosen their own chains and can nonetheless redeem their friends.”
Top
mhgreen
Posts: 82
Joined: 15 December 2014
Year and Model: 240 DL 1986
Location: Portland, OR

Post by mhgreen »

What about IAC?
“Some cannot loosen their own chains and can nonetheless redeem their friends.”
Top
Post Reply
  • Similar Topics
    Replies
    Views
    Last post

Return to “240, 740, 760, 780, Bertone, 940, 960, V90, S90”