I Really Need Help Here Guys

[87TIGN]

I have been fighting this problem for a very long time (over a year) and I no longer know what to do. I am at the end of my rope here and ready to ditch the car for good. Ok so the problem is basically when the car goes into closed loop it begins to stutter, backfire and fall on its face even with just a slight bit of throttle but it will idle just fine. It runs perfectly while in open loop but as soon as the thermostat opens and it goes into closed loop it runs like sh*t. I have the fuel pressure set at 42 lbs line off however it seems like its running very rich (O2 readings are around 800-900 at about 1/8 to 1/4 throttle which just seems way too high). After changing many of the sensors on the vehicle just trying to fix the problem, I finally got a crappy reading on the coolant temp sensor (the single prong sensor on the passenger side of the intake manifold) while the car was running crappy so I replaced it and it seemed to fix the problem... for about 24 hrs and then it started again. I replaced the sensor once again thinking it could have been a bad sensor to begin with (I was really hoping haha) but it happened again so I replaced the entire engine wiring harness (this car was pretty abused when I got it and alot of stuff was hacked apart including the harness) thinking there was maybe a short in the wiring that was frying sensors. I got the car running again after a long winter and just like clock work it happened again... This time with most of the sensors already replaced and a new wiring harness I only had the ECM left to replace. I replaced the ECM thinking maybe it was bad and tonight it happened yet again. I did not replace the coolant temp sensor before I ran it with the new ECM so I am not sure if the sensor got burned out from a bad ECM but I have a feeling that if I replace the sensor I will just get the same result. I have put alot of time and money into this vehicle and I have always wanted one since I was a kid. I have owned this car for over 6 years now and I don't want to get rid of it but I will if I can't get this figured out. The car is just killing me and I want to get it fixed because when it runs its scary!! Please help me figure this out... I love this car and want it to run right. I have rebuilt the engine, tranny, rear end and there are way to many parts in this car to take a loss on it. I am also willing to pay someone that really knows these cars to come over to Greeley and put their eyes on it for me. HELP!!
Thanks in advance
-Andrew

 

[pdzz]

List the sensors that were replaced, please. Phil.

 

[87TIGN]

From memory, IAC (Idle Air Control Valve, Coil Pack, C3I (Computer Controlled Coil Ignition), Fuel Pump Relay, ESC (Electronic Spark Control), O2 Sensor, TPS (Throttle Position Sensor), Single Prong Coolant Sensor, Crank Position Sensor, MAF (Mass Air Flow Sensor), Knock Sensor, Mushroom Top Sensor on driver side of intake manifold.

 

[Powder]

In your signature you list a "HO coilpack", what is that? Do you have a scanmaster? If so list the readings in open and closed loop for comparison. This will give the guys on here something to work with.

 

[87TIGN]

Also the other black plastic 2 prong (I think it controls the fans) sensor. Does it matter if some of the sensors I have used are BWD and not ACDelco? Should I put a new coolant temp single prong in with the new ECM. Doesn't the single prong coolant temp sensor tell the ECM what temp the block is at?

 

[boostingbuick]

The coolant temp sensor for the PCM is the two pin or two wire sensor. But the ignition module would have been my first guess. And the Mass air will also give you a run. If its a aftermarket unit it my not fix anything. Is it? And have you checked for a voltage drop at the pcm for a loss of ground? The cam sensor will also cause some issues, I will still make sure its set correctly. I have seen it set just off a little and make some funny issues. And remove and reinstall the prom. I hope to help get you down the right track.

 

[pajo]

codes

What are your readings on your scan master when this happens and is there any fault codes that pop up.Does the open-close loop cycle and how often./.

 

[DougP]

What brand MAF lots of problems with after market ones.

 

[IrvJr]

Check grounds? Swap the chip? I had a bad IAT sensor kill me for months til i noticed on Directscan that the temp never changed.

 

[Heath]

Shot in the dark but I had one of the metal prongs on my module bent just enough that my car drove like what your describing. I was getting in a hurry and did not plug it in strait I guess.

 

[87TIGN]

In your signature you list a "HO coilpack", what is that? Do you have a scanmaster? If so list the readings in open and closed loop for comparison. This will give the guys on here something to work with.

Yea the HO coil pack I got from a Buick website but I have since removed that and have a new stocker on there currently. I do have a Scanmaster and I will post those readings tomorrow.
Thanks
-Andrew

 

[87TIGN]

What brand MAF lots of problems with after market ones.

I believe its a reman Delco and I got it from G-Body parts I believe

 

[87TIGN]

Shot in the dark but I had one of the metal prongs on my module bent just enough that my car drove like what your describing. I was getting in a hurry and did not plug it in strait I guess.

Yup checked that when I plug the Prom and Chip into the new computer

 

[87TIGN]

Check grounds? Swap the chip? I had a bad IAT sensor kill me for months til i noticed on Directscan that the temp never changed.

The grounds all looked good but I will double check them and I will watch the IAC on the scan master to verify that the temperature does change when I list my scanmaster readings tomorrow.

 

[87TIGN]

The coolant temp sensor for the PCM is the two pin or two wire sensor. But the ignition module would have been my first guess. And the Mass air will also give you a run. If its a aftermarket unit it my not fix anything. Is it? And have you checked for a voltage drop at the pcm for a loss of ground? The cam sensor will also cause some issues, I will still make sure its set correctly. I have seen it set just off a little and make some funny issues. And remove and reinstall the prom. I hope to help get you down the right track.

Which terminals do I read across in order to check for a voltage drop? I will double check the cam sensor tomorrow as well to make sure it is set correctly. Do you have a link for that article on Gnttype for setting that sensor?

 

[boostingbuick]

Put a volt meter on voltage and put the red lead on the pcm casing and the black on the battery ground. Anything more than .15 volts should be looked into.

Cam Sensor Information For the cam sensor.

 

[Phoneguy]

Check the balancer bolt to make sure it is tight. Balancer could also be cracked. If the balancer is wobbly it will cause these symptoms. Good luck.

Bryan

 

[87TIGN]

This was written on the bottom of the cam sensor set instructions:

"Several people have found that when running a bigger cam with advanced valve timing, it sometimes will help cure a popping or sputtering symptom by advancing the cam sensor a few degrees. The above values give you an idea of what to shoot for."

Could this be the issue as well? I am running the comp cams roller set up from full throttle, I believe its something like .515 lift maybe and a 216 duration.

 

[RobS]

I finally got a crappy reading on the coolant temp sensor (the single prong sensor on the passenger side of the intake manifold)

Doesn't the single prong coolant temp sensor tell the ECM what temp the block is at?

No. The computer uses the 2 prong sensor to read engine coolant. If you got a bad coolant reading on your scanmaster, replacing the single wire sensor will not correct this. The single wire coolant sensor is to light up the idiot light. The mushroom coolant sensor is the cooling fan override. Hope this helps. Rob

 

[Dabigguy]

Just a thought, spark plug wires or maybe a blown head gasket between two cylinders?