Hey folks, first time posting. Got a 1992 Volvo 940 non-turbo which I bought a few months ago. When bought the idle was ok but soon after changing wires and plugs (which were gapped correctly) it now idles much worse, bouncing between 400-900rpms. This is only the case at idle, when the throttle body is open or when cruising it runs fine.

Ive cleaned IAC, checked the MAF, and cleaned around the tbrittle body, any ideas?

also while I’m here does anyone know why they made two different IACs for the 940 series?

 

The 940 may have Bosch or Regina ignition, that's why, the distributor maybe in the back of the head or in front ala 240.

Make sure you use OEM wires, Bougicord, and cheap NGK copper plugs, that maybe your issue.

 

Yes it’s located at the back of the head, but that’s been replaced along with the wires, and NGK plugs, I’ve also checked for vacuum leaks, of which I couldn’t find any

(edit: The wires I admittedly cheaped out on with O’reillys brand), could that be the cause maybe? It only got worse when I did the sparks and wires but the sparks I know are gapped and proper ngks

 

Ok, so we're a year later into the thread Tony, and Just in case you're still having (bad idling, hesitation, bogging down & shutting off at stop lights, sputtering & chugging especially after the car has warmed up, backfiring and/or heavy fuel smell, check engine light etc etc..) here's a simple fix...

1. Start by (and here's the real culprit) checking the "Throttle Position Sensor, or TPS as it's called " typically located on the back of the throttle body, and may require either small hands, or a bit of contortionism to get to it... It may also require spray cleaning with a can of electrical components cleaner... (at Walmart)...

NOTE: If cleaning or replacing with a new TPS (about $30.00 bucks, BOSCH!!) be sure to INSTALL IT CORRECTLY !!! You'll notice while connected to the vehicle, the TPS is screwed to an ADJUSTABLE SLIDING PLATE, and if installed correctly with the engine OFF, gently turn the throttle **** "just a touch", and you should hear a slight "CLICKING SOUND" coming from the TPS which tells you that its lined up correctly! Tighten the little screw (Allen Key Required) and you're off to the races my friend !!

2. Be absolutely sure to Check your Spark Plugs as well! If you notice there's corrosion, or heavy carbon buildup or appears burnt ,change them out "and use BOSCH PLUGS and not NGK !!! If you've been driving around with a Bad OR Mis-Aligned TPS, it'll foul-up your Spark Plugs for sure!

Have Fun with your classic 240
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