Thread: 91 Grand prix with problems...

So I just purchased a 91 GP with only 59K on the clock... So far I can tell the front clip has been replaced (wrecked).
It idles rough then jumps to 3000 rpm....
The shift indicator in the dash is stuck indicating drive....

And ohhhh yeah... it blows billowing white smoke out the exhaust and I can feel the whoosh of air coming out of the radiator with the cap off LOL....

So tomorrow I begin the great tear down...

I tested compression and got 90 , 140, 130 on the front three Left to right...
and 90,90,120 on the rear three left to right.

So I wanted to know do these engines (3.1L) crack the block easy?
Or am I gonna get lucky and just need to pull the heads?

I will be scouring the local junk yards for a new front bumper cover and grills etc. tomorrow as well.

Is there anything I should do while I have the heads off that you GP gurus recommend? I saw somebody make a suggestion that the 3.4 intake will help the 3.1 breath better but I would like confirmation.

Any suggestions would be awesome!

Thanks JC

Originally Posted by iroc2

a s/c'd 3.8 may fix er up good.

back to topic,
white smoke sounds like a head gakset to me that could be your problem, 2 bad head gaksets(?), but im not sure what the compression specs are on our engine. i can look it up and have it for you tomorrow tho

Thanks... but the news is grim........
Crack between two rear cylinders all the way up to the deck surface and looks like a crack in the front....

Now I need to find an engine sigh.... otherwise I wasted close to $400 on an old car with a non repairable engine.

they dont crack too easy as long as they dont get super hot
the whooshing sound you hear could be because it doesnt have a lot of coolent in it whitch caused it to get hot blow the head gaskets and crack the block
it sucks but ive seen it time and time again, how much coolent is in it and what color is it?

just woundering and iroc correct me if im wrong but arn't those motors all iorn, heads and block, or just the block

The motor is iron and the heads are aluminum.
I was pulling the intake off and noticed all the gaskets were brand new so I asked the previous owner if he tried to fix it.

"But in all honesty yes, when it was parked at my old office last year I had
a friend pull the intake down for me and then signs pointed to the rear
cylinder head. Think there was a crack between cyl 1 & 2 on the deck-(rear
head toward passenger side) and think also in the cylinders. Didn't have
much time to devote to it but researched block repair online and how people
were repairing this. We tinkered awhile with it. Using welding and even some
epoxy. We reassembled with new gaskets but to no avail. At that point I
lacked further resources and it had gotten beyond the scope of my ability,
funds, or time."

So basically he told me that he knew the block was cracked and that he had visually inspected it and tried to weld it......

Welding cast iron is tough unless you really pay attention....

So I guess I was screwed....

yea you were f-ed form the get go

So do I try to find a CHEAP and I mean CHEAP engine or just part this car out....

I don't have time to part the car and really needed something that got more than 10 miles to the gallon.... sigh.... decisions...

im sure you can find a cheap motor and i would put a lg8 in there if you want to stick with a 3.1 but those motors are all OBD2 i belive so it may be more work, it really just depends on how attached you are to your car

Originally Posted by dpzelenak

im sure you can find a cheap motor and i would put a lg8 in there if you want to stick with a 3.1 but those motors are all OBD2 i belive so it may be more work, it really just depends on how attached you are to your car

Not really attached to the car... just my money LOL...

then i would scrap that one and put the money towords something better

So I am looking online for bare blocks (looks cheapest) Is there much difference between the bare blocks on the 3.1 years?
I can find 92 and 93 bare blocks but not 91.... a few claim to be 92 and up?

no there all the same, but i think the LG8 block is bigger but thats in the late 90's

Well I can't find any decent (cheap) 3.1l around here but I can find a bunch of 3.4L down at the pick a part places. If I find one with good compression will it bolt up to the 3.1L transmission?
Are the computers different or anything really strange like that?

Would the heads bolt up?

I am willing to swap in a different motor if I don't have to jerk around changing wires, computers hoses mounts and stuff.
As long as only a few changes are needed (not every darn thing under the hood LOL)
\
Thanks JC

Originally Posted by iroc2

tisk tisk... great car as long as they run solid lol haha i knwo the feeling. so many people talk about theyre bad 3.1's but i (fingerscrossed and knocking on wood) havent had a single problem with mine yet. just turned 158,8xx... im not sure how scared i should be yet...



not 100% sure if the heads would bolt up but the trans should bolt up fine. im not sure about the harness tho. ill try to see if its the same



makes sense

trans will bolt up to 3400s but you will need your computer reprogrammed for the older non electronic transmission. 3400 heads will bolt up to a 3.1 motor.... but youd need the upper and lower plenum too.... as well as the obd2 electronics.... id suggest going to a junk yard getting a motor for like 3-400 and going from there usually they run if you can find a good enough/ complete enough one. just a cleanup and tune up.

i was tinkering one nite on the comp. and typed in 3100 gm engines and saw one with 30,000 miles on it for 450 bucks,or put a 3400 in it

Originally Posted by blown gt

i was tinkering one nite on the comp. and typed in 3100 gm engines and saw one with 30,000 miles on it for 450 bucks,or put a 3400 in it

WOW I just found a 3.1 about 40 miles away for 400 but its 159K on the odo... i am pulling the old one this weekend so I have a core for direct swap.

Tnx JC