929nitro

It's not my Vette but my 92 Camaro. I pulled the stock 305 motor and replaced it with a rebuilt 350 with mild cam, correct heads for 92 intake. I cannot get the car to run right. It will start ok but does not idle constant, idle fine then die down and come back to normal. I have been checking for vacumn leaks but have not found any. My suspicion is that the ecu will not handle the bigger motor with cam but am not sure. With OBDI system I no of no way to change the programming. Any help from the experts hear would be greatly appreciated.

madeintheusa

I have changed out a few of these and never had to change out the computer. I would check for a vacuum leak or see if there are any codes coming up maybe a sensor got damaged in the swap.

southernflyer

sounds like a vac leak. I agree, could be sensor, check vac sensor. also, how mild is "mild". I believe that that computer will need to see some vacume at idle... just a guess. good luck

929nitro

Thanks for the input guys. I'll have to find the specs on the cam. My engine builder felt it was about as much as he could go without affecting the computer. The couple of times I did drive it I would get about 15 to 20 miles and it would die. Engine power didn't seem any better than with the 305. I prefer the older cars much easier to work on.

southernflyer

on second thought, I had a very similar problem with my aftermarket system. I searched and searched for a vacume leak and or a fuel pressure or leak problem. I started with a standard tune up and went from there. In the end, the coil that i bought was bad from the store. it would run like that untill it got hot and about 15 to 20 miles down the road. at that point it would break down and not run at all. replace the coil and see what happens. (my aftermarket system uses that same coil)

929nitro

I'll try a new coil but this one was new and was running fine with the 305, 305 was only pulled because oil pan rotted out and engine ran with very low oil no other reason was running strong for 185K miles. I forgot to mention that the car is running rich but there is no way to adjust it. I have also checked timing 3 times and have to adjust by ear as it will not run if set according to specs.

southernflyer

Does not sound like a timing problem to me. A bad coil can make the car appear to run rich due to the unburnt fuel in cylinder. Also it is possible that the O2 sensor could have been damaged during the swap. The O2 sensor would affect the mixture but should not make it run the way that you describe because the computer will be programed with a generic fuel mapping specifically in case of that issue. Also cant hurt to double check all of your grounding straps and the wiring for the ignition module. The ignition module itself should work or not so I dont think it would give you an intermittent problem. good luck

terry82

i would look at your sensor for your temp for the computer [not the gauge ]and check the o2 sensor .both can make your car run rich .have you checked for codes?after you get it running right you can change to the bigger injectors for the 350.