Rough Idle; I have done full tune up, and it got worse

M81388 · Post by **M81388** » 14 Jul 2006, 14:03

Hi, I have a 1994 Volvo 850 Non-Turbo w/ 163000 miles. The car has had a relatively good idle ever since my father gave me the car a 1.5 years ago except when i put my foot on the brake at a stoplight while in Drive; where it would cycle between a good idle, and a rough one. It also began bucking when I put my foot on the gas, so within the last 6 mos. i have replaced: Spark Plugs (Bosche Platinum Plus), Wires, Distributor Cap, Distributor Rotor, EGR Valve, PCV Valve, Fuel Filter, Hose that connects Air Filter to EGR Valve. I was misfiring in one of my cylinders, so the plugs solved the bucking, but not only did the distributor cap and rotor not fix the intermittent rough idling, it got worse after i changed them.

Please help me out,
Mark.

Dacvolvo · Post by **Dacvolvo** » 14 Jul 2006, 15:03

M81388 wrote:i have replaced: Spark Plugs (Bosche Platinum Plus), Wires, Distributor Cap, Distributor Rotor, EGR Valve, PCV Valve, Fuel Filter, Hose that connects Air Filter to EGR Valve.

Might be a long shot here, but have you checked the condition of the actual air filter element itself?

If the engine idles rough, it may just be a simple case of it can't breath. Worth a quick 60 second check I reckon.

M81388 · Post by **M81388** » 14 Jul 2006, 16:26

Nah, its in decent condition. I'm just concerned that maybe i had somehow put the distributor rotor on wrong. It got noticibly worse after i changed that. The wires are in the right order - i'm sure of it because i followed the firing order (1-2-4-5-3). Could it be the Fuel Injectors?

Post by **MadeInJapan** » 14 Jul 2006, 16:51

Did you change the plug wires? Maybe to Bosch? Bougicord is the only way to go on our cars...others have mentioned degraded idle and other issues with Bosch wires. Also, Bosch Platinum's are known to cause problems. Change them out with simple and much much cheaper Bosch copper's and make sure to gap them correctly (.028 inches) and see what gives.

M81388 · Post by **M81388** » 14 Jul 2006, 18:37

i changed the Distributor cap and rotor and then the rougher idle began. I then changed the (needed) wires to some generic brand trying to maybe solve that problem. The spark plugs only have about 4500 miles on them, so i dougbt that they would cause any problems even if Platinums aren't so good.

cocka · Post by **cocka** » 14 Jul 2006, 19:00

M81388 wrote:i changed the Distributor cap and rotor and then the rougher idle began. I then changed the (needed) wires to some generic brand trying to maybe solve that problem. The spark plugs only have about 4500 miles on them, so i dougbt that they would cause any problems even if Platinums aren't so good.

If you still have the old bits replace them one at a time and see if that eliminates the problem, also a bad gasket on the throttle body can cause stumbling and bad idle problems so they tell me.

95autoturbo · Post by **95autoturbo** » 15 Jul 2006, 11:52

there is always that hose at the throttle body, I have seen a few with cracks in them........and pretty much had the same problem you had.

If it is cracked, go to your parts store and find a hose with similar bends and size, cut it down yourself - it will save more $$ than it would to buy the part from the stealership.

daveaherne · Post by **daveaherne** » 15 Jul 2006, 12:53

I had exactly this issue-and I changed all the parts you have-after this it also seemed to make the problem worse, I get stalling also. I'm planning on changing the throttle position sensor and the air idle valve. When I unplug the throttle position sensor the revs rise to above 1000rpm and stabilise so I'm fairly sure this part is a factor.

l33tDad · Post by **l33tDad** » 17 Jul 2006, 09:18

daveaherne wrote:I had exactly this issue-and I changed all the parts you have-after this it also seemed to make the problem worse, I get stalling also. I'm planning on changing the throttle position sensor and the air idle valve. When I unplug the throttle position sensor the revs rise to above 1000rpm and stabilise so I'm fairly sure this part is a factor.

I had some bad idle hunting about a month ago, replaced the throttle position sensor (50 bucks) and cleaned the throttle body itself. Idles like a dream now...

M81388 · Post by **M81388** » 17 Jul 2006, 13:56

I think that's what i'll do then. Replace the Throttle Position Sensor, and clean the throttle body itself; and just take a look at the lower engine mount - is this easy to change? I've seen the tutorial on Bay 13, but i'd like some opinions from people who have actually done it.

BTW, thanks so much for the input so far guys. I really appreciate it.