94 firebird hesistates

I have a 94 firebird formula, its got about 119k miles on it. when it is cool outside it runs great but if it gets over 90 out, when it heats up, it hesitates. at idle it runs fine and after about 3k rpm it runs fine, but anywhere between 1200 and 3000 rpm it sputters... the odd part is only when its really hot outside. I had my father check it with a computer reader and its no giving me any codes. We are kinda lost on what the problem is and any help would be appreciated

Thanks

Nick

That is strange. I'd check the fuel pressure on it. When the problem occurs and it turns out to be ok, I'd hate to say maybe the good ol optispark.

I had a similar problem on my '95 TA except mine would hesitate when cold, I cleaned out my air flow sensor and it seems to have fixed the problem so you could always try that :dunno:

thanks for the advise, I'm hoping its not the opti, we replaced the waterpump shortly after I got the car.. not fun and all that would have to be done again in the process. So far, I have cleaned the intake sensors and all the black stuff from the front of the intake, we did that last year and it wasn't half as dirty this time. I also had my father check the fuel pressure and thats fine.The cooling system seems to be working, it gets it upto around 240 and the fans all turn on and sounds like a leaf blower and cools it back down some.

1 thing about the opti, wouldn't it be throwing codes for misfires? right now I don't get any.. it only happens when its hot out and the car gets hot, I live in new england, we had a really hot week last week and this week has been cool, haven't had any problems this week

thanks for the advise, I'm hoping its not the opti, we replaced the waterpump shortly after I got the car.. not fun and all that would have to be done again in the process.

Ooops, that's when it's time to do it. :grinno:

If the W/P, opti, or timing set require attention, unless you are a glutten for punishment and love spending an afternoon getting covered, laying in muck, you do all 3. They all have about the same life span.

it wouldn't neccisarily throw a code.

You are 110% positive that there is no way you're running lean?

its acting like its running lean, but the fuel pump is fine, and it only happens when it gets really hot out.
I did a search for the problem on the web and another person on another forum said they have the same problem all the time, and the people there said the oxygen sensor, my problem is that its only happening when its hot.. maybe something cloging it that expands when it gets really hot

ok, I got the info from my father's computer scanner
from a while ago/when it had the problem
desired idle: 650 rpm / 750
engine rpm 675 / 775
coolant temp 190.80 / 242.10
manifold air temp 59.90 / 151.70
a/c pressure 73.00 psi/ 118.00
map sensor 1.48 volts/ 1.43
throttle sensor .64 volts/ .64
throttle angle 0/0
batery voltage 13.20 volts/ 12.70
barometric pressure 4.93 volts /4.84
left o2 sensor 118.00 mVolts /114.00
right o2 sensor 162.00 mvolts /409.00
block learn cell 16/16
left block learn value 130/132
right block learn value 120/128
left integrator value 130 / 128
right integrator valeu 127/128
left inj pulse 3.9 ms/3.7
injector pulse 3.5 ms/3.6
mass air flow 8.00 gr/sec 8.00
ccp duty cycle 0/0
idle air mtr pos 23 steps/37
learn idle pos 13 steps/21
spark advance 16/14
knock retard 0/0
knock sensor 148.00/147.00
a/c clutch enabled/disabled
a/c requested/not requested
fan #1 on/on
fan #2 off/on
air swtich selenoid off/selenoid on
loop status closed/open
o2 sensor ready/ready
r oxy sense ready/ready
learn control enabled/disabled

ok, I got the info from my father's computer scanner
from a while ago/when it had the problem
desired idle: 650 rpm / 750
engine rpm 675 / 775
coolant temp 190.80 / 242.10
manifold air temp 59.90 / 151.70
a/c pressure 73.00 psi/ 118.00
map sensor 1.48 volts/ 1.43
throttle sensor .64 volts/ .64
throttle angle 0/0
batery voltage 13.20 volts/ 12.70
barometric pressure 4.93 volts /4.84
left o2 sensor 118.00 mVolts /114.00
right o2 sensor 162.00 mvolts /409.00
block learn cell 16/16
left block learn value 130/132
right block learn value 120/128
left integrator value 130 / 128
right integrator valeu 127/128
left inj pulse 3.9 ms/3.7
injector pulse 3.5 ms/3.6
mass air flow 8.00 gr/sec 8.00
ccp duty cycle 0/0
idle air mtr pos 23 steps/37
learn idle pos 13 steps/21
spark advance 16/14
knock retard 0/0
knock sensor 148.00/147.00
a/c clutch enabled/disabled
a/c requested/not requested
fan #1 on/on
fan #2 off/on
air swtich selenoid off/selenoid on
loop status closed/open
o2 sensor ready/ready
r oxy sense ready/ready
learn control enabled/disabled

Looking at that, I want to say vacuum leak, especially toward the left side of the motor (intake :dunno: ) Reason I say is all your left readings point to it being lean and your idle is higher than preffered.

I have an update, we checked for vac. leaks and found none, since the problem only happens when its hot, we decided to think in the manor of keeping the car cool, we tested the coolant and it was mixed to strong for the summer temps, so we syphened some out and added some water, also, I noticed that there was alot of dirt in the radiator, so we blew out the radiator and the ac condensor out with an air hose... so far I haven't had the temp go past 220, and rarley over 210 but then again, we've been lucky here not to have a day as hot as the days I had the problems. At this piont, I have no clue if the problem is from the car getting to hot for the whole thing to work right or to hot for some component... so my theory is to not let the car get that hot, if it happens again, I'm going to get the thingie that turns the fans on earlier

thanks for the advice, I'll keep you guys updated

Nick

I have a '95 firebird with a 3.4L engine, 173K miles, with the exact same problem. My car never runs hot (max coolant temp about 180) but the hesitation has gotten a lot worse since the outside temp has been in the 90's. From my reading on the net I'm nearly convinced it has to be the O2 sensor. Have you found any solution to the problem? Mine hasn't been hooked to a code reader. Thanks, Brad

Check out your Distributor. There is a vacume hose running to it which may have filled the distributor with oil. Would account for the power loss. if this is the problem, you may want to bypass the vacume hose so that it isn't running into the distributor.

Huh? Distributers have'nt been vacuum advanced since the late 70's???

my problem, I think was heat related, its gotten as hot outside and I haven't had it happen again yet

Its not vaccum advance its an after market solution to the optispark moisture problem its not factory but it does work if you replace your water pump at the same time but it will cause a vaccum leak if not installed properly.