Hello,

I get a backfire in the exh. when i rev it and let off or if I bring the rpms up to like 3500 when shifting. Just one pop when I let off the gas. seems worse when engine is not warmed up. Also get a vibration when under load or when driving at 1500 or so rpms. The vibration is not as bad if I drop a gear and bring the rpms up. feels like something in the drive train. any thoughts?? It is a 305 tpi 5 spd.

 

Check for vacuum leaks, and check your timing.

Sounds like a lean condition.

 

I will give check it out. I am going to tune it up over the weekend and see if this helps. Can it be a worn lobe on the cam?? Hope not!!

 

did a tuneup last night Plugs wires cap ect. and it still does the same thing Any other ideas???

 

Perhaps a sensor is making it run lean. What is your timing set at?

 

did you check for vacuum leaks? If you dont know how I'd be willing to explain

 

could you please explain? i've got some issue where the car runs fine as long as i set the idle to 900 or higher. sometimes it will idle ok at 800 but most of the time the rpms jump around and it wants to die when it gets under about 850. i've just left the idle at 900 when in gear and about 1150 in park and it runs fine but i'd like to idle about 650 or 7. sound like a vacuum problem?

 

Here is something real quick to check. Dead cyl. Pull the connector off one injector at a time and see if you don't get a simular result with one of them. Would indicate a bad injector or bad plug or bad plug wire. I know you changed plugs and wires but I have seen brand new ones fail right out of the box.

 

I am going to try the injector thing today. how do I go about cecking for a vacuum leak??

 

to check for a vacuum leak you turn the car on, pop the hood. Then take some carb cleaner and spray it around the engine bay. When the car acts different (might bog, or rev higher) when you spray it in a certain area then you have determined the general area of your vacuum leak

 

any way to do it without getting carb cleaner all over my engine? lol

 

it's inevitable

carb cleaner will evaporate on it's own. I wouldnt spray it too close to the coil and distributor though