Detonation/sputtering issue - Fourth Generation Pontiac Firebird (1993 - 2002) - Firebird Nation

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Detonation/sputtering issue


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5 replies to this topic

#1 avsfan4019

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Posted 09 April 2020 - 12:41 PM

I have a 99 Firebird 3.8 automatic. Issue im having is when I get to roughly half throttle or more the car sputters or detonates. Either way its running rough and not making any power at that point. It didnt start til after I put a full tank of gas in it one night and the next morning it started. So my first thought was maybe water in the tank or something. I have put a new fuel filter on it and cleaned the MAF sensor and it changed nothing. Plugs were changed a year ago or so. It wont act up til the car reaches normal operating temperature. I can also put car in park and rev the motor and it does the same thing. Only code its pulling is for the EGR valve but it has been that way for almost 2 years now and have also put a new EGR valve on it.



#2 SoCalTA

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Posted 10 April 2020 - 03:47 AM

fuel/air/spark

 

I'd probably start with checking fuel pressure



#3 sea dog

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Posted 10 April 2020 - 05:19 AM

If your scanner is capable of doing running sensor scans, I'd try doing a scan and seeing what the sensors are saying.

 

If you haven't a clue about what sensor data means, PM me with your email address and I'll send you the pdf file "scanner readings and what they mean". It was written by our member Injuneer, and should help you understand the data stream.



#4 avsfan4019

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Posted 10 April 2020 - 06:00 AM

my scanner wont do that. you can still send me the stuff and I can take a look at it. I may upgrade to a better scanner. I have read up some that it could be 1 of the o2 sensors. I have had cars with bad o2's before and never had issues like this. Which these motors may act different than other cars I had too. 



#5 Injuneer

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Posted 10 April 2020 - 07:10 AM

Please note the my “scanner” writeup is SPECIFICALLY for the 93-97 LT1 engine and may contain information the is not directly applicable to any other 4th Gen engine.  I have updated the current version to clearly indicate this.

 

What exactly do you mean by “detonation”?  That typically is characterized as “the sound of ball bearings rattling in a can”.  Very unusual in modern vehicles because they generally incorporate a knock sensor that allows the PCM to eliminate detonation in most cases.  I believe your 3800 V6 has dual knock sensors.

 

Running OK cold, then developing problems when hot can be related the heat soak of ignition components, including the ignition control module or ignition coils.  Heat soak can also affect the fuel pump.  Running poorly can also be caused by problems with the air/fuel ratio control system, which does involve the O2 sensor(s).  An engine that is running lean may exhibit detonation under load.

 

And you need to understand that the primary function of the EGR system is to prevent excessive combustion chamber temperatures with the engine under load, and in doing this, it prevents detonation.  What is the specific code you are (still?) getting for the EGR valve?.


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381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#6 avsfan4019

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Posted 10 April 2020 - 07:18 AM

The code im getting is p0401. Only reason I thought of detonation, and this is a totally different car and setup, is when I had a Honda Civic with turbo on it, if I tried to raise the boost to high it would detonate the motor so I would have to lower it back down. My Firebird is seems very similar in what its doing and sounds like. One thing I should add since you mentioned coil packs and ICM, my car had the issue of the windshield cowl seal getting worn out and when it would rain water would leak down onto the coil packs and would cause bad misfire. So I would avoid driving in rain til I got it fixed. Maybe over time one of the coils has went bad? I replaced the ICM about a year ago along with the crankshaft position sensor. Hope this helps.






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