Regal chugging and hesitation during acceleration

My car chugs around 30-45 mph sometimes very lightly. It got less noticeable after I had my mass airflow sensor replaced recently. A while ago I had the torque convertor replaced and it was good for a week then started again. Someone told me it could be a dirty valve body. It only happens once every blue moon and when I take my foot off the gas real quick and re accelerate at the same speed the chug isn't there. I can go weeks without it happening. I've had my car hooked up as well to a scanner and had no codes come back.
 
xFallenx said:
My car chugs around 30-45 mph sometimes very lightly. It got less noticeable after I had my mass airflow sensor replaced recently. A while ago I had the torque convertor replaced and it was good for a week then started again. Someone told me it could be a dirty valve body. It only happens once every blue moon and when I take my foot off the gas real quick and re accelerate at the same speed the chug isn't there. I can go weeks without it happening. I've had my car hooked up as well to a scanner and had no codes come back.
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Unfortunately mine is not lightly at all. It is a pretty obvious chugging and jerking. I haven't cleaned the throttle body on this car since I got it so I will give that a shot as well. I have a GMC Envoy that dies on me when I turn on the A/C when the throttle body gets dirty, so it definitely something to look into.

That being said I beginning to get very discouraged about this car. I just can't seem to narrow this issue down. I'm beginning to think it may not be ignition related but that still investigating all areas.
 
Don't get get discouraged, there a lot of things left to check and mostly free. Since you did have an EGR code, it would be worthwhile removing it and check the pintel for smooth action when pressing it with a small fillips head screwdriver. If you feel any resistance in the spring action, try cleaning with carb cleaner and then dry completely before spraying the pintel with PBblaster. Sometimes this will help for several months, but you will eventually have to replace it.

BTW, since you have a scanner, look at STFT & LTFT @ idle (engine warm and in closed loop) and see what you have. If you are showing positive (+) trims 10-15% the engine is running lean and the PCM is trying to compensate by enriching the fuel trim. If you are showing negative (-) trims you are running rich and the PCM will command less fuel in order to bring the trims back to near zero (0). This is another free diagnostic function & gives a lot more info for troubleshooting.
 
cckeeler said:
Unfortunately mine is not lightly at all. It is a pretty obvious chugging and jerking. I haven't cleaned the throttle body on this car since I got it so I will give that a shot as well. I have a GMC Envoy that dies on me when I turn on the A/C when the throttle body gets dirty, so it definitely something to look into.

That being said I beginning to get very discouraged about this car. I just can't seem to narrow this issue down. I'm beginning to think it may not be ignition related but that still investigating all areas.
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I will say this before I got the torque convertor done it was pretty bad. Then I got that done it was lighter then the mass airflow sensor and now it is extremely light and only happens once and a blue moon.
 
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alright, well a bit of an update. Today I took the throttle body off and cleaned it as well as the EGR valve. The EGR valve didn't look too bad. Had a few hiccups but everything is back together.

The STFT and LTFT are running around 16 at idle. Based on what you were saying it appears to be running lean. Unfortunately I don't know exactly what that means.

Also, I decided to throw in a gauge in my scanner that showed me what gear I am in. The jerking and chugging seems to actually happen in 3rd gear, not overdrive. Hitting the brake though, does cause it to drop into 4th, but once I downshift it jerks around a bit again in 3rd. The scanner did not show any misses while all this was happening.
 
You must have a vacuum leak, but in order to save a bunch of key strokes, Click Here for a pretty good explanation of what the fuel trims mean.

Also, I decided to throw in a gauge in my scanner that showed me what gear I am in. The jerking and chugging seems to actually happen in 3rd gear, not overdrive. Hitting the brake though, does cause it to drop into 4th, but once I downshift it jerks around a bit again in 3rd. The scanner did not show any misses while all this was happening.
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I am sorry, but this does not make any sense.😕 The 4T65E trans is a 4-speed auto trans with a convertor lock-up which takes place between 45-50- mph under light acceleration. If you hit the brake while in OD (4th gear) with the convertor locked up, hitting the brake peddle simply unlocks the lock-up in the converter, and at that speed the trans should remain in 4th gear until such time the speed drops below the threshold for demanding shift into 3rd gear. If you lightly accelerate after hitting the brake peddle at that speed, the converter should soon lock again.
 
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I am probably not doing a very good job explaining it. I was accelerating in 3rd and it would start chugging. But I could hit the brake and it would drop into 4th and be ok. Now I could have eased up in the gas as well causing it to just shift into 4th as it should. So the lockup of the torque converter I keep hearing about happens in 4th? I was also cruising in 4th gear and I would give it a ton of gas and it would downshift and start jerking around.

I'm going to have to see if I can track down a vacuum leak. From my reading it seems it could also be the catalytic converter right? I'll have to see if I can find an exhaust place open today and just have them test it for me.
 
Let me ask you this. If you unplug the MAF sensor, does it automatically force the LTFT to 0?

I was trying to track down the vacuum leak and was watching the scanner as I was trying things and I decided to see what unplugging the MAF sensor did to the fuel trim and the O2 sensors. Unplugging it forced the O2 sensor to a more normal up down pattern and the LTFT went and held at 0. I'm just trying to get an understanding of how the system works.

BTW I think the vacuum leak is between the throttle body and the supercharger. I keep trying to torque those bolts but every time I spray carburetor cleaner on it the engine stumbles. I put a new gasket on that after cleaning the throttle body.

I also took off the hose going to the throttle body and the LTFT started going negative. Not sure what that means but thought I'd throw that out there as well.
 
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Let me ask you this. If you unplug the MAF sensor, does it automatically force the LTFT to 0?
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If you unplug the MAF sensor, the PCM will operate with predetermined fuel maps and will not use air flow as part of the equation. So with that being said, I would think that the LTFT in that map would be set at 0.
BTW I think the vacuum leak is between the throttle body and the supercharger. I keep trying to torque those bolts but every time I spray carburetor cleaner on it the engine stumbles. I put a new gasket on that after cleaning the throttle body.
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Use some silicone on both side of the gasket!
I also took off the hose going to the throttle body and the LTFT started going negative. Not sure what that means but thought I'd throw that out there as well.
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I am not sure which hose you are talking about, but if it was the main air flow from the air cleaner, check the air filter for obstruction.
 
Alright where there is where my lack of knowledge shines through. I tried looking around to see if I needed to put anything on the gasket but couldn't find anything. Easy fix.

That being said just with my continued torqueing the LTFT is showing just above 5. Didn't change much however.

My observations while driving this thing seem to be all over the board but the more I drive it seems to start just before, or immediately following the shift into 4th. It only seems to happen though when I maintain the same gas on the pedal. If it lift it off and back on the problem is not there.

As far as the hose going into the throttle body, I guess I could have been a little more specific. I was referring to the hose going from the air filter into the throttle body. But that was more or less just me tinkering trying to make sense of all this.
 
Just to help you understand, the STFT is what makes the LTFT move up, or down. If your STFT is constantly high, the LTFT will continue to move up, if the STFT is below 0, the LTFT will decrease. I hope this helps.
 
Check the TPS with a scanner. What is the voltage with ignition on, closed throttle? Accelerate lightly while watching the voltage increase all the way to WOT. Did you see a smooth linear increase all the way up to open and 4.2v+ at that point? If all that that looks good, disconnect the MAF and see if it starts any better.
 
I am going to run the test of the throttle position sensor tonight. I'll respond after I do it.

So does the torque converter lockup in 3rd of 4th gear? Can I rule out the Torque Converter from my diagnosis if the problem starts in 3rd?
 
If you drive the car in 'D' (3-rd gear) the convertor will lock at the same speed as mentioned earlier, but normally the rpm's are high enough to prevent ignition misfire chugging. If you have not tried it yet, drive it with the trans selector in 'D' rather than 'OD' and see what happens.
 
Oh and I'm still not logging any misfires. The throttle position shows as % rather than voltage on my scanner but it seems to be functioning properly. I'll keep testing.

Is there a way to disable the TCC lockup?
 
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Yeah no change in 3. I hit. 35 ish and it starts jerking and bucking. It seems to be getting worse. It does seem worse when I have less than a quarter tank
 
Yeah no change in 3. I hit. 35 ish and it starts jerking and bucking
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Well in that case, let's forget about the TCC, or trans and focus on some other things previously mentioned. Have you had the CAT back pressure tested? Have you tried driving with the gear selector in 3rd with the MAF disconnected?
From my reading it seems it could also be the catalytic converter right? I'll have to see if I can find an exhaust place open today and just have them test it for me.
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