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TPI running and idling rough

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Old Aug 15, 2015 | 09:18 PM
  #1  
Logan Bryant's Avatar
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From: Cambridge City, IN
Car: 1991 RS
Engine: 355
Transmission: TH350
Axle/Gears: 4.11
TPI running and idling rough

When I start it, it won't want to idle. It will want to bog down. I will unplug the maf sensor and the idle will go up to about 800-900 rpm. Also when I go and drive it, with the sensor out, it will want to bog down while trying to get on the gas. Once it reaches about 200F it will run right. I just changed the fuel filter and nothing changed. The only thing I want to know is if I should try and clean the maf, or just replace it.
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Old Aug 15, 2015 | 11:09 PM
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Car: 86 Trans Am WS6
Engine: 383 stroker
Transmission: 700r4
Axle/Gears: 9 Bolt Torsen 3.70
Re: TPI running and idling rough

Originally Posted by Logan Bryant
When I start it, it won't want to idle. It will want to bog down. I will unplug the maf sensor and the idle will go up to about 800-900 rpm. Also when I go and drive it, with the sensor out, it will want to bog down while trying to get on the gas. Once it reaches about 200F it will run right. I just changed the fuel filter and nothing changed. The only thing I want to know is if I should try and clean the maf, or just replace it.
No check engine light? You can try and clean the maf with maf cleaner before shelling out the $$$ for a re manufactured one but I wouldn't get my hopes up on it.
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Old Aug 16, 2015 | 06:58 AM
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vinny R's Avatar
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From: Florida
Car: 1991 Z28
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: 3:42 Auburn
Re: TPI running and idling rough

Does it act the same with the sensor plugged in? at 200 does it run right?
I had a problem with my ECM not coming out of start mode. I would have to wait until the temp came up and had to shut the car off and start it up again. This would restart in normal operation as the temp would be up. I would not get a Check Engine light as start mode is a normal operation. I don't think the MAF sensor is your problem, There is a Idle Air Control sensor that does get crappy, you may want to clean that one also.
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Old Aug 16, 2015 | 08:31 AM
  #4  
Logan Bryant's Avatar
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From: Cambridge City, IN
Car: 1991 RS
Engine: 355
Transmission: TH350
Axle/Gears: 4.11
Re: TPI running and idling rough

The check engine light has always been on due to having headers and not putting the o2 sensor back on. Once it reaches 200F it I'll run perfect. No bog or anything.
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Old Aug 17, 2015 | 01:49 PM
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Car: 86 Trans Am WS6
Engine: 383 stroker
Transmission: 700r4
Axle/Gears: 9 Bolt Torsen 3.70
Re: TPI running and idling rough

Originally Posted by Logan Bryant
The check engine light has always been on due to having headers and not putting the o2 sensor back on. Once it reaches 200F it I'll run perfect. No bog or anything.
thats your problem

Last edited by TylerSteez; Aug 17, 2015 at 06:24 PM.
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Old Aug 17, 2015 | 03:13 PM
  #6  
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Car: 85 T/A
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: BW Limited Slip 3.27 w/disc brakes
Re: TPI running and idling rough

The O2 sensor needs to be hooked up. The ECM relies on the MAF and O2 input to operate the motor effectively.
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Old Aug 17, 2015 | 03:38 PM
  #7  
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From: Stafford, Connecticut
Car: 87 Iroc
Engine: modified 350
Transmission: high performance built 700R4
Axle/Gears: Strange S60 3:73
Re: TPI running and idling rough

Dude the O2 sensor is your main controller for your fuel system.
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Old Aug 17, 2015 | 07:19 PM
  #8  
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Re: TPI running and idling rough

Originally Posted by Logan Bryant
The check engine light has always been on due to having headers and not putting the o2 sensor back on. Once it reaches 200F it I'll run perfect. No bog or anything.

I find it interesting that your set up can work without an 02 sensor hooked. It is beyond my understanding! Your AFR must be inaccurate because your ECM can not correct the AFR under normal cruise and idle. In WOT and open loop it won't matter but in normal drive you can be too rich or too lean which will have consequences on your spark plugs, engine temperature and cat converter.


Regards
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Old Aug 17, 2015 | 08:23 PM
  #9  
Logan Bryant's Avatar
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From: Cambridge City, IN
Car: 1991 RS
Engine: 355
Transmission: TH350
Axle/Gears: 4.11
Re: TPI running and idling rough

So.... Went and looked at the headers again and found the o2 sensor down by the collector. The owner told me that is why the check engine light was on, when I bought it. So I guess it leaves one thing left....
Attached Thumbnails TPI running and idling rough-tmp_11117-20150817_211302-1992187411.jpg  
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Old Aug 26, 2015 | 06:36 PM
  #10  
Logan Bryant's Avatar
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From: Cambridge City, IN
Car: 1991 RS
Engine: 355
Transmission: TH350
Axle/Gears: 4.11
Re: TPI running and idling rough

I checked the codes and i got a code 34, and I also changed to toast new Bosch maf sensor.
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Old Aug 27, 2015 | 11:52 AM
  #11  
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Car: 85 T/A
Engine: 305 TPI
Transmission: 700R4
Axle/Gears: BW Limited Slip 3.27 w/disc brakes
Re: TPI running and idling rough

If your still getting code 34 after the MAF was changed it may be the burn-off relay, 85 was the last year GM used the combined power/burn-off unit.
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