3.1 design changes

[TeeJay3800]

I recently read a thread in this section about a difference between the intake manifold or plenum gaskets on '90 3.1's and on later model 3.1's. I am wondering if there are more differences between '90 and '91+ than that. For example, everywhere I check, the '90 has a HP rating of 135, while all '91+ 3.1's have a rating of 140. Is there a difference here (MAF, etc.)?

[Robby1870]

na, MAF was only in 88 with 2.8s The AC circuit changed from 90 to 91 and I think in late 93 they made the letters on the plenum thicker. And, they changed PCV hole locations from on the lower intake to under the plenum. Changed from Vacuum to Digital EGR in 91. Thats all I can think of, minus the gasket changes already mentioned

[TeeJay3800]

Wow, how do you know all that? Must done a rebuild or five. Based on your knowledge, does it seem likely that there is a 5 HP difference between '90 and '91?

[Robby1870]

I wouldnt trust any numbers you see on the internet. Ive seen one site that says that GTPs didnt come with the DOHC! 3.1L is 140HP. And, even if it is 135, its no big deal. Any motor brand new from GM could have 135 or even 145 for that matter.

[gp90se]

88-90 the plenum bolts are different (91+ they have rubber boots).

 

that +/- 5 horses means jack squat. they rated the 86 fiero 2.8 at 140 horse, and it prolly is about there. I dont worry bout 3.1 numbers, there not high output motors (minus the vin V, but were not talking bout that).

 

-Jeff

[Brian P]

Digital EGR = 1990. 1991 the plenum went to a "floating" type, with rubber sleeved bolts, rubber/metal gaskets. PCV changed in '90 to the type that clamps to the plenum, not the lower intake. The block was also strengthened in '91

[TeeJay3800]

While we're on the 3.1 topic, my manual states there is a 4,000 rpm limiter in Neutral, which I've verified is correct. Doesn't seem to be any limiter in Park. My question is if there are any limiters in gear and if the limiter cuts in at different revs in different gears (I've heard something like 6250 in 1st, 6225 in 2nd, something like that)?

[Guest TurboSedan]

While we're on the 3.1 topic, my manual states there is a 4,000 rpm limiter in Neutral, which I've verified is correct.

 

not with a manual trans

joshua

[Brian P]

the way some of you people drive, there should be!!!!!!!!!!

 

Oh, right. There should be a 4k limiter in park for your year

[Baddflash]

Mine have 4k limit in park and neutral, unless moving I can put in neutral and go to 6k if I want. Never hit 6200 rev limiter, I don't think the engine would like it.

[TeeJay3800]

I dunno, the manual specifically states there is a 4k limiter in N, but says nothing about P. I've revved it to 5k+ in P, so I don't think a limiter exists in Park.

[jeremy]

I dunno, the manual specifically states there is a 4k limiter in N, but says nothing about P. I've revved it to 5k+ in P, so I don't think a limiter exists in Park.

 

my cutty stops at 4k in Park....

[GnatGoSplat]

I dunno, the manual specifically states there is a 4k limiter in N, but says nothing about P. I've revved it to 5k+ in P, so I don't think a limiter exists in Park.

 

It's not unusual for the Park/Neutral switch to be slightly out of alignment or have bad contacts. This can cause the ECM thinks the car is still in gear when it's in Park or Neutral.

My car had the same problem. It didn't seem to affect anything until I added the automatic locking/unlocking and it was locking me out in Park. I had to rotate the P/N switch just a hair and then all was well.

[Z34door]

ok i have an issue.......... my parts car is a 90' 3.1 in a euro. i was thinking about taking the intake halves and gasket matching them and puting it on my 92 motor. will it work given the changes???