Hello Gents,

The ole' 1990 Volvo 240 at 190K miles has been running like a top for awhile, so I've been scarce on this forum...but:

Problem: Very rough hot idle. Oil light will even flicker, its so rough. Searched the archives for secret fixes and advice, and am fairly stumped at this point.

- Starts fine. No changes here.

- Idle is fine when cold.

- No problems with acceleration, either cold or hot.

- Fine at higher (off idle) RPM.

- No fault codes showing.

- No "check engine light." Although after a couple of hours at highway speeds, stop for gas...the light comes on briefly (<5 seconds) after starting the engine back up.

- New wires, cap, rotor, plugs, air filter.

- Clean throttle body and flame trap (including that little brass nipple ;-). No change.

- Old and new plugs all look similar and look good.

- Been running Amsoil 1W-30. No noticeable oil consumption.

- AMM wire impedance within spec at 3.4 ohms. (Wires 2 and 4? Followed Bentley procedure.)

- Idle air valve clean and works like a top off the car. Impedance and action OK.

Vacuum hoses not all new, but look OK. There is a small RTV patch on the main air line bellows between the AMM and the throttle body.

- No loss of mileage, either highway or commuting around town.

- No change in rough idle when car is put in N and brakes applied/ unapplied.

- Run a couple of types of injector cleaner (Techron, Valvoline) through on recent trips.

- Cold front today in Austin (below 60 degrees) and the idle is not so rough after 20 mile commute.

- Color of car is white.

Any advice and suggestions will be appreciated.





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Paul Despres, 1990 240 DL 190K, Austin, Texas