Ok so I just bought this '95 with the massive 3.4L. When I start it and get it warming up, the car perrrs. When it just sits and idles it is fine.

When i head down the road and it gets warmer, eventually it sounds like a VW bus. rough idle and shakes a bit.
Friday I put in new plugs (gapped at 0.45) and new wires thinking it would solve this issue. It hasnt.

Suggestions?

 

Any codes? What is fuel pressure? Changed fuel filter? Have you test the coil packs? Could be a number of things. Get it scanned for codes to see if it shows anything. Until then, its like throwing money in the fireplace.

 

Unknown fuel pressure. I know 1 pack is new from previouse owner. Fuel filter looked new when we had it in the air. Is there more than 1 on these? Just seems fine until its all warmed up and driving. No engine lights on.

 

yep call around and see if any of the parts stores have a scanner that will work on your car. it sounds like when you go into closed loop and it runs off the sensors something is not right. so you have a cam sensor, intake air temp sensor, throttle position sensor, 02 sensor, map and maf sensors and the knock sensor. gona need to test them. it is a really good idea to try and find the area the problem is in or it can get spendy quick. it could be any of the mentioned sensors or not.

 

well i also noticed the oil pressure is normal until the car is warmed up. when im driving the oil pressure seems lower than it shouls be. at idle its just above the lowest line. so i may start with the oils sensor. sound good to you?

 

Sonds like the idle air controller motor/valve could use a good cleaning. Also seafoam the TB or use throttle body cleaner. And, change your PCV valve.

 

If you think it may be bad, get a mechanical guage to test for real oil pressure. Oil pressure will vary with engine wear, weight of oil and type filter you use, outside temps, engine rpms, etc. Those oil sending units are not that accurate if they have several years of age on them but that don't mean that yours is reading wrong. Only way to tell is with the use of mechanical guage or by replacing it with a new one.

 

All good suggestions. Thanks guys. I'll start replacing/cleaning some of these things. they are all looking old and OEM.

 

Ok guys this car is becoming embarrasing. I paid more attention to the issue today.

I started my car this morning and let warm up for a few min. Idle was awsome and it drove nicely to the store 1000 feet away. I left it running and went inside. Was inside for about 5 min talking to the clerk and drinking coffee. Got back into the car and it was more than warmed up. Everything was perfect. I drove to destination 1 which was about 3 miles/5 min. and turned the car off for 10 min. Still with me?

I got back into the car, started it and it idled like crap. I drove to destination 2 which was 4 miles/5 min. Loss of power and sounded like my dads old VW bus. Like a 5 cyl car.

Got to destination 2 and turned car off for 4 to 5 hours. Came out, started it and it was running **** again. Is something expanding and creating a vacume leak or something? I hadnt been able to get to someone with a scanner, but now wondering if im chasing the wrong frog.

 

A leaking intake manifold (between the manifold and heads) will act like that. If the gaskets are juuuuuust barely sealing when cold, they can leak once the engine heats and things start to tweak. Just for fun, check the torque on the intake manifold bolts.