94 Formula and summertime problem

[Zentech]

Was wondering if anyone has seen issues like this with thier firebird. Car runs fine most of the year except in the summer. Basically during the summer, once the car is driven maybe 30minutes it starts having some acceleration issues. Feels like it is bogging down when taking off from a stop. However, while sitting at a stop light, the engine sometimes starts reving up (maybe 1100 Rpms or so), feels like it just wants to take off.
Also, on the highway, when going up a steep hill, maybe at 60mph, it sometimes feels like the engine starts missing. The car is not overheating. I had the same issue with it last summer. However, it drives fine from fall to spring. I guess basically as long as it is cold/cool outside, I can drive it around and it has no problems. Does this sympton point to something in particular?

1994 Formula LT1 - 105k miles

No mods.

TIA

[knight7]

I am having a very similar problem too. When my car goes on a steep hill or where it needs acceleration it seems like the engine starts to miss. To avoid this i have to accelerate harder before the hill starts. If i continue on the hill with the same speed and same acceleration, or if i start to accelerate a little on the hill it starts to miss and i can seriously feel the engine.I changed my sparkplugs and wires about 2 months ago. So those cant be an issue. Hopefully some1 helps us.

[95firebird]

my car use to do that took it to the shop and they told me to use 5w-30 oil instend of 10w-30 in summertime now it works just fine

[ikeyballz]

dont you always use 5-30? and how does the oil mess that up..

[FormulaLT1]

Those symptoms sound like either a vacuum leak or a electrical issue in the ignition system or ground.

[CreepingDeath94]

Agreed...I think its in the ignition system. As it gets hotter, it starts losing the ability to fire. That tends to be the case with ignition anyway as it wears...it takes more energy to fire when hot as the resistance increases. Have the coils checked since theyre easiest to reach of the ignition system. Then work your way to the plugs. If the plugs are old, it could be that. I also had a problem once where my number 8 valve seal was leaking oil onto the plug and fouling it up...though that would probably start to become evident even in winter. It was more of a constant misfire as it got worse. But something to check out maybe.

[Zentech]

Originally Posted by CreepingDeath94

Agreed...I think its in the ignition system. As it gets hotter, it starts losing the ability to fire. That tends to be the case with ignition anyway as it wears...it takes more energy to fire when hot as the resistance increases. Have the coils checked since theyre easiest to reach of the ignition system. Then work your way to the plugs. If the plugs are old, it could be that. I also had a problem once where my number 8 valve seal was leaking oil onto the plug and fouling it up...though that would probably start to become evident even in winter. It was more of a constant misfire as it got worse. But something to check out maybe.

Thanks for the suggestions. My plugs and wires are the original plugs, have 105k on them. Bought new plugs and wires last year to put on, but then realized how difficult it looked to replace them So i haven't replaced them yet, but will get that done and see if it fixes the problem. If not I will take it to a shop and have them check it out. Thanks for the advice.

[superducky55]

Originally Posted by Zentech

Thanks for the suggestions. My plugs and wires are the original plugs, have 105k on them. Bought new plugs and wires last year to put on, but then realized how difficult it looked to replace them So i haven't replaced them yet, but will get that done and see if it fixes the problem. If not I will take it to a shop and have them check it out. Thanks for the advice.

Believe it or not, the chevy dealerships in my area gave me much cheaper quotes for doing the plugs and wires on the lt1 in a bird...
ended up getting mine done (LABOR only) for 320 + tax out the door.
Most local shops wanted a zillion dollars (600+) and each one gave me a half ass answer as to why. One even said they drop the whole motor out. ??? dummies. One said they remove water pump. One said they drop y-pipe. etc
either way.. like i said, dealerships usually know the tricks on the f-bodies.

Have them check your injectors since your about 100k and do the standard ignition testing (as stated above) since the 'coils' are so easy to get to on the lt1.

Again.. i'm beginning to trust the local pontiac dealer a lil more than backyard mechanics on my 95 lt1.. seem to give me *real* answers since there are so many screwy ass things with these f-bodies that backyard mechanics sometimes exaagerate or get completely wrong.

Best of luck to ya.

[97cavalier]

watch out for the optic spark!! it is a pain in the ass!!

[townguy]

I also own a 94 Firebird Formula, it has 135k miles on it, and I have had the same problem that Zenteck and many others have been talking about. This problem only happens during the summer months when the temperature outside is very high. As an example, I drove 5 hours today back to Southwest Virginia and had fuel stutters the whole way back after the initial "30 minutes" of driving. I have repaired the car a multitude of times, hoping, that every time would be "the one." I have replaced the ignition coil, the spark plugs (twice), the spark plug wires, the water pump, the fuel pump, have had a tune up, use 5W-30 synthetic (and switch off to regular just to see the difference) every 3000 miles, replaced the radiator (twice), radiator sensor (because I thought the car was overheating and the sensor wasnt accurately detecting the temperature), flush the radiator fluid (routinely), the EGR oxygen sensor (which was causing the check engine light to come on and then turn off), the gas/pressure regulator, and anything else under the sun. WHAT IS THE PROBLEM WITH MY VEHICLE? I think a fuel injector is bad and is possibly expanding when the temperature under the hood gets too high? Instead of a spray of fuel, it becomes more of a squirt? If it is a vacuum problem, where am I losing/gaining pressure? What hose might be expanding where this is happening? ANY help would be greatly appreciated. This has been an irritating problem for 3 years and I DO NOT know enough about cars and mechanics to fix it. I NEED YOUR HELP, PLEASE!