interchanging a 3.4 L with a 3.1 L in a 03 grand prix

Asked by Mar 06, 2014 at 01:04 PM about the 2003 Pontiac Grand Prix SE

Question type: Maintenance & Repair

8 Answers


3.1L refers to pre-'95 motors fwd and rwd. 3.4L refers to pre-'95 DOHC fwd motors and OHV rwd motors. The 3100 and the 3400 are interchangable fwd motors. They will run without modifying the computer but you should do this.

12 out of 12 people think this is helpful.

Now if you change the motor do u have to change any of the wording for sensors


"change any of the wording for sensors" ? What are you asking


Sorry the wireing on the harness or block


The '94 (3100) and '96 (3400) through '05 are very similar engines. They use the same block, the 3400 is bored out. I cannot confirm that the wiring harnesses are the exact same through out the 11 years but that is easily fixed by putting your sensor on the new motor. There are some small differences in the 3100 after '00. But nothing a tuner can't fix. I would need to know the years and trims of the cars to help you further and which way your swapping. The main issue will be tuning the car as the computer is only setup to correctly fuel the stock motor. The simplest option is to swap computers. Next is to tune the stock computer for the larger motor, using a handheld programmer or better yet, tuning software. But they are close enough that it would run decent until you had time to tune it. The 3.4 DOHC would require a harness swap and lots of other work. The 3.4 rwd is all cast iron and has no benefits of being swapped.

1 out of 1 people think this is helpful.

I have a 99 Chevy Malibu with the 3.1 and would like to put the 3.4 in it if it would work. Cuz I know how to do all of the repairs due to working at a repair shop as a mechanic for so many year its just that oi have never seen it done before. And I would be using parts from a grand am about the same year cuz I will be doing other things to the car to improve the handling and power from the car. I will be putting rear disk brakes on it and trying to make it a sleeper cuz of all the rice burners out here.

3 out of 3 people think this is helpful.

I just found your other question. I'll reply there.

2 out of 2 people think this is helpful.

OK thanks

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