ok, here it goes, i have a 92 firebird with a 305 tbi in it, it has 90k miles on it and is in great condition. I am starting this thread because seems to have an issue that i cannot figure out. when the motor is cold in the morning, i start it up and it runs great!!! now after it warms up a bit it starts to feel like it has a miss, the tac doesnt sit still and i can hear a puh...puh..puh puh puh...puh (not a pop or bang) sound at the exhaust. (best typed sound i can do sorry). it only does this at idle in drive! throttle repsonse is amazing for a 305tbi, it has plenty of power and runs amazing...other than at a red light...it just feels like it wants to die, but it never does. as soon as i give it any sort of throttle..up up and away i go....it never misses during driving, shifts sooo smoothly and im scratching my head because i get very bad gas milage...like 8 mpgs...and the miss can shake the whole car sometimes...although the motor is running great i dont understand. i have replaced the following:

cap and rotor
spark plugs and wires (2 sets of wires to be sure)
intake job was done
water pump (didnt replace to fix this issue just needed a new one)
radiator & thermostat (didnt replace to fix this issue just needed a new one)
egr valve
air temp sensor
tps sensor
iac sensor
alternator (didnt replace to fix this issue just needed a new one)
battery (didnt replace to fix this issue just needed a new one)
welded up all exhuast leaks
car does have a hollow cat converter (i live in colorado no emissions)
doesnt burn oil or loose coolant ever.

im at a loss and i cant figure out why its doing this...

i know ive replaced more than that but i cant remember off the top of my head.

any advice or help would be very appreciated.

im so done throwing money at this issue.


only code i get every now and then is the egr code 32. but i already replaced that.

 

Check all your vacuum lines. They may LOOK good, but may be bad. If you get nasty black crap all over your fingers when touching the lines, ya need new ones.

 

i have replaced most of my vaccuum lines already, i knew the first reply would be to check the vac lines but i have a millions times and just cant find a leak....any hidden vacuum lines i may be missing?

 

I knew that sound....."puh...puh..puh puh puh...puh (not a pop or bang) sound at the exhaust." It was the EGR Solenoid to EGR Vavle line.

Also check the line that runs over to the vacuum ball in the front drivers fender

 

do u have any pics to show this vacuum ball? and whats the best way to test the solenoid?
also i thought the EGR was not active during idle?

 

test the solenoid with a 9 volt battery, 3 wires 1 to open, 1 to close and a ground.

And yes, not active at idle

I was just suggesting more vacuum lines.

 

if its not active at idle, would it still have vacuum running to it, considering my issue is only at idle

 

You are still supplying vacuum to the solenoid no matter what position the solenoid is commanding the EGR to. If you cap the port supplying the solenoid at the intake, you eliminated all EGR/EGR Solenoid vacuum lines and functions. It would be just a test of those lines in that system.

 

ok so i will go over the entire vacuum system again does anyone have any other ideas to check for?

 

so your saying if cap the line from the intake to the solenoid and the issue goes away there is a leak somewhere and if it doesnt go away thats not the issue?

 

EGG ZACKLY!

 

alright ill give it a shot. any other ideas if it ends up not being a vac leak?

 

Other than the IAC being bad.....not really. Shorted out ignition wire against something so on each firing of that cylinder, it shorts,skips, etc.

I am picturing something like this....

something is "pulsing" to give you a ""puh...puh..puh puh puh...puh". So, maybe the pintle of the IAC is "chattering" or the EGR solinoid is "pulsing" the EGR at idle and THAT is not likely.

 

i replaced the IAC and it didnt change a thing, also did the wires 2 times. to be sure.

 

Just a thought.I didn't see O2 sensor in the replacement parts list. You mentioned:"i start it up and it runs great!!! now after it warms up a bit it starts to feel like it has a miss."

So with that, it's in "CLOSED LOOP" Your O2 is now warmed up and sensing and telling computer what to do as in rich,lean, or whatever. IDK, without a analyzer that shows whats going on, it's hard to say.

 

Every new car, and most cars produced after 1980, have an oxygen sensor. The sensor is part of the emissions control system and feeds data to the* engine management computer. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.
A gasoline engine burns gasoline in the presence of oxygen. It turns out that there is a particular ratio of air and gasoline that is "perfect," and that ratio is 14.7:1 (different fuels have different perfect ratios -- the ratio depends on the amount of hydrogen and carbon found in a given amount of fuel). If there is less air than this perfect ratio, then there will be fuel left over after combustion. This is called a rich mixture. Rich mixtures are bad because the unburned fuel creates pollution. If there is more air than this perfect ratio, then there is excess oxygen. This is called a lean mixture. A lean mixture tends to produce more nitrogen-oxide pollutants, and, in some cases, it can cause poor performance and even engine damage.
Th*e oxygen sensor is positioned in the exhaust pipe and can detect rich and lean mixtures. The mechanism in most sensors involves a chemical reaction that generates a voltage (see the patents below for details). The engine's computer looks at the voltage to determine if the mixture is rich or lean, and adjusts the amount of fuel entering the engine accordingly.
The reason why the engine needs the oxygen sensor is because the amount of oxygen that the engine can pull in depends on all sorts of things, such as the altitude, the temperature of the air, the temperature of the engine, the barometric pressure, the load on the engine, etc.
When the oxygen sensor fails, the computer can no longer sense the air/fuel ratio, so it ends up guessing. Your car performs poorly and uses more fuel than it needs to.

 

ive considered the 02 sensor. would that create the same issue im having now?

 

sometimes it does it right away and not after its warmed up...seems like it all depends on how cold it was the night before determines how long it takes to start acting up, its been colder here at night lately and i have noticed that it takes longer to act up when thats the case

 

you've done everything else, another $20 ain't gonna matter. You need to change it anyway.......well its suggested.

can't answer that for sure

 

can you here the engine go into CLOSED LOOP?? Its pretty distinct if you start it up and sit and listen. 2 min maybe

 

no i havent, what should i be listening for? and would that still explain the warm nights that it starts doing it right after i start the engine?

 

When cold, the idle will gradually fall to normal (around 650rpm). When warm, it takes much less, sometimes right into closed loop after start up.

 

ok so i snooped around the vac hoses a bit more, found a few things, the egr valve has 1 hose coming off of it which goes to the solenoid. there is one other hose that goes from the bottom of the tbi to the solenoid also, the ends of these 2 houses are connected by one connector that goes to the solenoid. couldnt find one on the intake itself, also i followed the vacuum line to the vacuum ball, the hose that comes off the ball to a T junction has completely collapsed......i unplugged the line from the T junction going to the vacuum ball....there was no vacuum at the end of it. should there be?.................does anyone have a vacuum line map for my engine?

 

Yes, while the engine is on. The other end from the Tee goes to the Cruise Control. Where did you pick that line up at? It should also be tee'd where the EGR Solenoid gets its vacuum....from the TBI.

 

no sir it is one hose that goes from the front of the tbi to the solenoid. the solenoid has 2 ports, one goes to the egr valve and the other goes to the front of the tbi unit. these 2 hoses are connected at the solenoid end of the hose. then a long hose goes from that to the cannister tee and thats where i found the collapsed hose going to the ball from the tee i followed from the egr thingy...

 

 

my question is, could this collapsed vacuum line going from the tee to the vacuum reservoir be causing my issue? the main hose on the tee has good vacuum so im assuming the collapsed hose is where that one is trying to suck vaccuum from....

 

anyone? i need help on this bad.

 

come on someone out there has to be able to answer this for me

 

I know it's a pain. But on both my TBIs I took each vacuum hose off and checked the individual hose with a hand vacuum pump. I had leaks on some that "looked" good. On my '88 I even put mini clamps where they connected, helped out alot. Also, have you checked your fuel pressure?

 

no i have not checked my fuel pressure as i it drives so perfectly when i give it gas, no shudder, plenty of power and torque all day long...i guess i could give it a shot but i just dont think thats it...considering how perfectly it runs otherwise.

 

My recomendation is to fix the vaccumm line that you found bad. Then at idle see if your EGR valve is opening, you can do this with your finger under it by feeling the diaphram. If it is opening then replace you EGR silinoid (not the valve). It sounds to me like your EGR is opening when it should be closed causing your comuper to dump more fuel to compensate for the added vacuum.

 

ok so I replaced the bad hose....no change. but I tested the egr solenoid and got a resistance of 43 ohms. I tested the connector for the solenoid......nothing...not 1 volt...I tried and tried to get a reading...tested battery and got 14.3 volts steady....so I know how to use the meter lol, but that connector didn't read ****. I also had my wife rev the engine up and down and I saw nor heard anything from the EGR valve...the inside didn't move at all....wtf man

 

Here is were the vacuum for the cruse control on my car starts. I don't use cruse control so its been plugged off. Its not pretty but it works.


You can pull the hose and cap it off ether with a hose like I did or a cap on the nipple. That eliminates anything down line that could be leaking.
If that does not help then just put it back together.

 

ok ill give it a shot and report back after work.

 

but pretty sure my EGR isnt opening or is not closing...it doesnt move at all and the connector to the solenoid didnt have any voltage

 

could i have a bad 02 sensor???

 

still trying to solve this issue...any help is appreciated

 

did you fix the collapsed vacuum connection, and T/S the EGR/SOL yet? New O2 sensor?
The EGR Solenoid is commanded by the computer. No volts should be there until the computer tells it to open/close....at highway speeds

 

yes i did fix the collapsed vacuum hose. i didnt replace the 02 sensor because im not getting any assistance or how to test it or even know if this is causing my issue...i dont want to replace it unless im sure that its bad. also i already replaced the egr valve and i tested the solenoid and i get 43 ohms of resistance....how else can i test it

 

im still getting a egr code at highway speed...

 

There are two types of tests you can do to an an oxygen sensor: 1) on the car , 2)off the car (bench test). The easiest method is to do it on the car but it would require the sensor to reach 600°F and a scan tool to get the accurate readings. The bench test is more of a quick test to determine if it works or not. To do the bench test you will need a propane torch and a DVOM. The main idea is to connect the red leed of the meter to the black wire of the sensor, and the black leed of the DVOM to the body of the sensor.


Turn on the meter and set it to the lowest voltage scale, light the torch and place the tip of the oxygen sensor in the flame. Since there is no oxygen, the sensor will produce .9v or 9/10th's of a volt within 1 minute. This will indicate a rich mixture because the voltage is climbing. As you pull away from the flame,the voltage must drop within 3 seconds to it's original reading ,the voltage drop indicates a lean mixture.

If there is no reading or if the sensor voltage is not changing, then it indicates a bad or sluggish O2 sensor that needs replacing.


Note: Some O2 sensors have a heating element with more that 1 wire connected. Always connect to the black wire on the sensor to do the bench test.

Also read post 16 in this thread, or better yet, read it all. It's good stuff to know

https://www.thirdgen.org/forums/tbi/...t-bad-egr.html

 

because the solenoid is not opening the EGR or the EGR itself is bad. you will set a code 32 at a steady highway speed of 50ish. The solenoid pulses many times a minute to regulate the EGR position

 

well the egr is new i doubt its that....so solenoid must be bad right? unless im still missing a vacuum leak?

 

if the solenoid isnt opening the egr and its closed...then that wouldnt be causing my idle issue right? it would need to be stuck open to cause my issue correct?

 

correct....closed at idle

There is only 2 vacuum lines: port vacuum to Solenoid, Solenoid to ERG Valve, that's it

1 thing to look at.the steel port on the Solenoid should go to vacuum port, the black nipple port on the solenoid goes to EGR valve

 

ok well the way mine is set up doesnt let you switch the hoses by accident and the port vacuum goes to my tbi...just like the vacuum diagram i posted a few back...both my ports are plastic too on the solenoid. im still wondering what would cause my car to throw an egr light at hwy speed....im going to put in a new solenoid tonight but i have a feeling its not gonna fix anything.....

 

im now thinking that because the cat has been hollowed out and there is less back pressure causing that code 32 to be set...which is leading me to think my egr system is not the issue at all

 

Understand about the only one way on deal, molded rubber boot looking connector

See post 43 about throwing code

Good luck

 

thanks for the help...