after car warms up it runs badly what could cause this

10

Asked by Apr 11, 2010 at 10:02 PM about the 1994 Pontiac Firebird Formula

Question type: Maintenance & Repair

When I first start my car up in the morning it runs great for about 5-10 mins or until warm.  After this it starts to run rough and backfire at low rpms.  At high rpms it seems to be missing and has lowered power.  It is an LT1 with headers and a cold air intake(slp) with dual cones.  It has new plugs and wires from last summer(car has too much power to drive in pa winters) I ran it for two days before this happened.  It also has bigger injectors and fuel pump.  It also gets a little hard to start once it is warmed up as well.

9 Answers

9,570

Sounds like an electrical problem. Check you plug wires along with the distributor cap and the coil. Look for any burning or loose connections.

5 of 5 people found this helpful.
Best Answer Mark helpful
45

coils are bad

2 of 2 people found this helpful.
10

Thanks guys, turns out that my headers burnt two of the spark plug wires. I also found out that the ground for my fuel pump wasn't right, so I am glad it went to the shop and I found out before the fuel pump burned up.

1 of 1 people found this helpful.
3,265

Same thing happened to the 94 LT1 Camaro we built. Routing wires in f-bodies suck. Are you running the stock opti? You run the quarter with it?

1 of 1 people found this helpful.
10

Yes it is the stock opti, but it has other things done to it. The friggin headers are what keep burning the wires, and when burned I have to put the car on a lift to replace because the car is only about five inches off the ground(3 inch exhaust is only about 3) The first time I ran it with the new stuff on it I ran 12:07sec in the quarter. The 4.10 rear and the racing clutch make all the difference in the world. I think I am gonna go with a 3.73 and a supercharger next. That way I can go faster on highways, but who knows. Exhaust, suspension, cam, intake, and all the SLP stuff made a big difference. As well as the 800lbs less weight, the opti and piston are about all that is left that is stock.

225

I would look for a vaccum leak, causing a lean situation

1 of 1 people found this helpful.
30

i had a 1994 firebired that did the samething as your after it warms up it ran poorly and had no power and backfired. it turns out that cadalletic converter was plug up and need to be replaced. After i replaced it she ran perfect.

3 of 3 people found this helpful.
15

check r timing,or this might sound crazy,but a 40 year mechanic told me u might have too much iol in r pan.sounds nuts,but check r oil anyway

1 of 1 people found this helpful.
10

I'm having trouble with my 1997 trans am it runs good cold but when it warms up its skipping&want go. I replaced fuel pump,filter,plugs&wires,distributor&ignition coil

1 of 1 people found this helpful.

Your Answer

Firebird

Looking for a Used Firebird in your area?

CarGurus has 723 nationwide Firebird listings starting at $1,649.

ZIP:

Pontiac Firebird Experts

  • #1
    Samuel Moore
    Reputation
    990
  • #2
    dandyoun
    Reputation
    840
  • #3
    Tom Demyan
    Reputation
    750
View All

Related Models For Sale

Used Chevrolet Camaro
499 Great Deals out of 30,899 listings starting at $995
Used Chevrolet Corvette
134 Great Deals out of 16,101 listings starting at $3,000
Used Ford Mustang
413 Great Deals out of 41,513 listings starting at $1,488
Used Ford Mustang SVT Cobra
6 Great Deals out of 297 listings starting at $4,795
Used Pontiac Grand Prix
12 Great Deals out of 2,482 listings starting at $950
Used Porsche 911
118 Great Deals out of 5,222 listings starting at $12,995
Used Ford F-150
3,159 Great Deals out of 223,315 listings starting at $1,000
Used Dodge Viper
251 listings starting at $29,999
Used Chevrolet Monte Carlo
7 Great Deals out of 1,237 listings starting at $1,585

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.