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1988 volvo 740 idling high after new IAC valve

volvo 4 life

volvo 4 life

Active member
Joined
Aug 9, 2007
Location
Northwest Connecticut
My dad recently purchased a 1988 740 with a five speed and after 2 weeks it developed a problem where after driving the car for a little while it will idle really high (2500 rpm) like the iac valve is stuck completely open. I hit the valve with a hammer when it was doing this and the idle came right back down to normal so I assumed it was a problem with the valve. Now we replaced the valve and its doing the same thing. Is it possible the valve is bad again or is there something else that would be telling it to idle high?
 
Check for vac leaks, and clean out the hoses leading into the IAC. Also, clean the electrical connector to the IAC.

Check your base idle as well.
 
Check the throttle linkage length.

Although it would be better to adjust TPS and throttle stop before doing this. Easier to do with throttle body off the car.
 
I will check the tps adjustment. When it idles high like this and you shut the car off it is sometimes very hard to start afterwards. I had luck holding the throttle to the floor and cranking it but it seems like it floods itself.
 
andysbeta said:
1988 should be LH2.2. No codes in that case, ECU doesn't have a CEL or store fault codes. Good luck , internet repairing a car = impossible.
Click to expand...

^^ * YUP * ^^

a late production or Califas/EGR car *may* be LH 2.4...
never underestimate the power of missing information...
 
Realized something else. When the car is warm it's really hard to start. What's the chance of the coolant temp sensor being bad? Seems to make sense because it would increase fueling and raise the idle if it thought it was cold right? And that would make it start hard warm and idle high.
 
I had a 2500 RPM idle on my '87 740 turbo when the IAC valve died. I was 500 km from home too, made starting out really exciting with an automatic. Shift to drive, CLUNK! WHEE!

Replacing it with a non-busted one from a junkyard made everything happy again. It sounds to me like you just got another broken one or something's not hooked up right.
 
slipstream3d said:
I had a 2500 RPM idle on my '87 740 turbo when the IAC valve died. I was 500 km from home too, made starting out really exciting with an automatic. Shift to drive, CLUNK! WHEE!

Replacing it with a non-busted one from a junkyard made everything happy again. It sounds to me like you just got another broken one or something's not hooked up right.
Click to expand...

Those guys are easy - just block off the IAC hose and dial-an-idle with the hand valve. Not ideal, but works until you get it fixed and safer than trying to drive w/ a 2k5 idle.
 
check for cracked spark plug wires. almost always the culprit of a rough idle. even if not cracked, could be worn out, change em if you haven't done so in last 5K miles
 
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