iam having a new idle problem with the new motor i got rebuilt it has mahle pistions with 9:1 compression and type s cams and it has a rough idle? is it suspose to be like that due to the low compression and the high lift of the cams?

 

are you tuned

 

no its not tuned the shop owner said you dont have to tune it you can just break it in with the stock computer and it has a walbro fuel pump and the car runs rich.....

 

what kind of spark plugs should i use and the gap for them?

 

So you are running 9:1 compression on a stock ECU. Hmmm. Dont think thats too good of an Idea, your ECU is going to want to run 10.0:1 or 10.6:1 - 11.0:1 depending on what motor you are running.

Your running rich as well? Sounds more like your mechanic wanted his money and you out of the shop. I take it to someone else and see what they have to say.

 

The initial curves will be way off any time you disconnect the battery, but after a few hundred miles, the ECU will take trim information from the O2 sensor and adjust everything out.

 

BTW: As pointed out above, 9:1 is pretty low compression for these engines (unless you are going to go with forced induction). The timing will be off a lot as well and it will take a while for the ECU to get everything in shape..... There is a possibility that this is beyond the adjustable limits of the ECU. I think that I read one or two of the engine models were in the 9:1 range, so it will probably work. I would give it a some miles and see what happens.

 

well i have been driving the car for about 10 miles now and it seems to be okay just the idle is kind of rough and when the car is at like 2500rpm it seems to sputter and have like a lag to it......... and called another shop and the guy said that it will be alright to drive it around just when i turbo charge it i need to tune it...... do you guys have any tips on driving to break in the motor?