back to the drawing board- still not running right

[Zapper2003]

Alright. Here we go again. 1997 Firebird Formy lt1, a4, 105k miles. Idles at 1200-1300rpms but seems to have an audible miss, as i can hear it and feel it when sitting in the car. Smells rich at the exhaust. when cold, it starts right up great the first time, but when it gets warm (tonight, around 160*) it wont start unless i hold the throttle wide open, and when it starts, it sounds flooded, blows black smoke and idles high for a few seconds then idles back down to 12-1300. When I step on the throttle at idle it stumbles, can sometimes stall if i dont play games with the pedal, and blows black smoke that smells rich and even wet/moist (leaves black droplets on the floor behind the car). I have replaced the optispark, water pump, plugs and wires and intake air temp sensor. Had the ICM tested and it tested out fine. I have not tested fuel pressure or tested for a vaccuum leak. Have not tested coil. I plan to put in some fresh gas as well as a new fuel filter, as well as change the oil and filter. So, what is left?

Is it possible an injector is stuck? What abou the throttle position sensor? mass air sensor? Is there any way to test any of these items?

[Zapper2003]

Also, i've been told to spray the intake area with carb cleaner as to check for a vacuum leak as well.

[86 IROC-Z]

I some how got linked here.

I'm scared.

How do I get back to the AAG?

[pajeff02]

I would probably go over all the vacuum lines real good and look for any splits -- could be the mouse from hell also had a taste for rubber. Carb cleaner, soapy water, and other stuff will help find a vacuum leak. You can even use a propane torch (unlit, of course) as the RPM will increase if it sucks the gas into the engine through a vacuum leak. If that checks out, I would look at fuel pressure. Any chance the timing chain is stretched all to hell? That could give you starting issues. Another freak thing is a broken camshaft that still engages but has enough slop to move around a bit.

If you can make it run long enough to color the plugs -- I would pull them all to see how they read. Hopefully someone here will come up with a diagnosis and a fix...

[Zapper2003]

car will idle all day long. soon as i touch the throttle it wants to die, or does die.

[Zapper2003]

the plugs are a son of a bitch, i could get to a few of them easily but the rest are nut-uh.

[pajeff02]

car will idle all day long. soon as i touch the throttle it wants to die, or does die.

Silver mentioned the O2 sensors in the Train -- but on start-up it would be running closed loop and not accepting feedback from the sensors until it is warmed up if I recall correctly.

[Zapper2003]

That I honestly don't know. If i could convert to carb with a regular distributer, it'd be done already.

[JaycenK]

The LT1's had a problem with the intake gasket leaking at the back passenger side. I also have a 97 and the dealer had to replace mine at 50k. Has yours ever been done? This may explain why you have to hold the throtle wide open to get it to start, and why it wants to die when you touch the gas. Call the dealer and ask them if there are any notes on that problem and what the symtoms are.

[Zapper2003]

I've had the car for 2 and a half years give or take and only put 5k on it, bought it from the bank so i have no idea the history of this car. I plan to pull the EGR off tonight and clean that, as well as check the intake for leaks.


Intake gasket job can be done with motor in car, right?

[bigrondownhiller]

The intake can be done with the engine in the car. I would try checking the fuel pressure and for any vacuum leaks at the manifold or even the injectors. The hard start could be an injector leaking down. Does it start hard if you shut it down for a minute after running and then restart?

[Zapper2003]

The only time it starts hard is after its been running long enough to build up any engine temps. I just got home with my oil filter and fuel filter (had the wrong oil filter on the shelf ). Gonna throw them on tomorrow and start it up. I cleaned the EGR tonight, it was really black and sooty. Blasted the hell out of it with carb cleaner and worked the plunger a number of times, i almost wonder if it wasn't stuck.

[JaycenK]

EGR shouldn't cause that, but why not right. Take throtle body cleaner and hit that back side of the intake while the car is running and see if there is any change in the idel while it's cold.
You have been f-en with this car for a while and I thought you said in a previous thread that you all ready checked fuel pressure, right?
Could be a leaking injector as well, you could take them out and have them tested and cleaned and that would eliminate that. Have you cleaned the maf?
you can test the TPS but they are so cheap you could just replace it but if not then the test requires a multimeter. How to test it is in the Chiltons manual. you can also test the MAPS sensor. One thing you could look at is the MAPS sensor and see if the ruber gromet is seated right. just unbolt it and pull it out. If the gromet is F-ed then GM sells it for 8 bucks.
Lets us know what you find.

[Zapper2003]

I will check those things out when the car cools down. I've been doing a fix here, a fix there, and starting after each to see if its the cure . Just tried it after a fuel filter change, oil/filter change, and cleaning the EGR. I did notice SOME improvement in certain areas. 1. the exhaust does not smell near as rich as it did. 2. the idle is still fast, 1100. It wont idle down to 'normal' (its been so long i forget where normal is..850?). It still will not start after its warm. I hit the key, it rolls maybe 2x and fires but dies right away, long enough to fool you into thinking its going to start. After that point I have to floor the pedal to get it to start, and that is the only way.

List of parts replaced, cleaned, or checked.
1. opti
2. plugs/wires
3. water pump/thermostat
4. Intake temperature sensor, not manifold absolute pressure sensor.
5. cleaned egr
6. changed fuel filter
7. oil/filter

To be done:
1. check for vacuum leaks
2. check MAP sensor grommet
3. pull 02's and look for something?
4. TPS sensor

I have not checked fuel pressure yet, I don't have a tester.

[bigrondownhiller]

How is the air filter?

[Zapper2003]

Fairly clean (k&n). I've even started the car with the air intake tube on, but the filter/box off, no difference.


Speaking of which...what type of cleaner do i use on the MAF? Since it has a k&n in it (in when i bought the car), i should def. clean the maf (prolly oiled down).

[pajeff02]

CRC (and others) make a MAF cleaner. It does not leave any residue.

[Zapper2003]

I'll have to pick up some. I know autozone carries CRC products and i'm fairly certain i've seen it there.

[Zapper2003]

Also, since cleaning the egr and changing the fuel filter, the car is less likely to stall when blipping the throttle. Before, when warm, i could blip the throttle and the car would just die for a split second then rev up while stumbling and proceed to smooth out, sometimes accelerating smoothly, othertimes stalling. Now, I can blip the throttle and it still stumbles all over itself til it accelerates, but its less apt to stall. I also have some popping out the exhaust that I never had before. I'm going to get some maf cleaner tomorrow and try that, as well as see what I can do about testing the rest of the stuff. If I can't find anything, or what I do find is inconclusive, I'm going to have a chase-car and gonna go run the shit out of it and put a half tank or so of fresh fuel in the pig, and see if it will throw a CEL.

[Zapper2003]

bear with me, i'm trying to make myself clear with my descriptions as to how the car is actually running.



when idling, 1100-1300 rpms, the motor runs smoothly, but every now and again (kind of like every 2nd firing of a cylinder) it will 'bloop' out the exhaust a bit and the engine will shake a bit. I will try to get a video/sound clip if i can. I don't know how much that will help.