1995 LeSabre part throttle hesitation problem L27 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat
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1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 08-27-2010, 06:43 PM   #1
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Default 1995 LeSabre part throttle hesitation problem L27

This is a car I bought for my daughter to use. This is a long post, but I would rather give too much information than too little, so bear with me. I bought a 1995 Buick LeSabre Limited with the Series I L27 in March with 129k on it. It intermittently would move under its own power and you would have to let it cool off for an hour then you could drive it again. I thought it was the Fuel Pump. I changed the oil, air filter, put in new plugs (turns out they had been done recently), new 8mm plug wires (old ones were original), fuel pump, fuel pump sock, and fuel filter. The issue still happened, but it started throwing codes at least. Its ODB I but has the ODB II connector with different pinouts, but the code reader at O'Reilly Auto worked and said TPS sensor out of range and Camshaft sensor. I replaced both but the issue still happened. Remembering my 89 Olds Royale 88 had a bad crank sensor but said cam sensor on the codes, I replaced the crank sensor which was a pain because I couldn't buy or rent a puller that worked, had to modify one to make it work. This fixed that issue, but I wanted to list all the parts that have been recently replaced and why. I also replaced the radiator (cracked tank) upper and lower hoses and a leaky master cylinder.

A new issue started, my daughter said it would barely run sometimes and sometimes it wouldn't start. It is not throwing any codes. I found it had a corroded battery terminal that was causing so much resistance that the plastic boot actually burned and melted. After cleaning the terminals the issue went away, so I assumed the alternator couldn't put out enough power to support the ignition system. And I charged the battery overnight. But the problem soon returned, and is now constant and not intermittent at all. At part throttle it just lugs or hesitates, and if you go to 1/2 throttle or more it takes off like gangbusters. So basically its undrivable. If you don't just punch it it takes literally 2 blocks to reach 30 mph and it feels like lugging the engine in high gear on a stick shift car. But I have put the tranny in 1st and it still does it. I replaced the TPS sensor again, and no change. I checked the voltage on both TPS sensors and it gives smooth continuous change in voltage throughout the range of motion. I have cleaned the throttle body, the MAF sensor, the IAC and the ERG, and checked for vacuum leaks.

After reading another post on here, I disconnected the knock sensor hoping it was faulty and pulling timing, but there was no change in drivability.

Based on another post I unplugged the MAF sensor to see if it would drive differently when using the maps based on TPS sensor and RPM only. It did drive a little different, but still has like only 30 horsepower until you get to half throttle and it suddenly takes off like a spotted butt ape. With the MAF plugged in it feels like 15 horsepower. So my question is how well is it supposed to work with the MAF sensor unplugged? I assume that puts it in limp home mode, but I would think it would still be more drivable. BTW unplugging either the knock or the MAF sensors does turn on the SES light, plugging them back in the light is out again. O'Reilly lists a MAP sensor for this, but for the life of me I can't find it, it is not on the intake manifold anywhere, and I doubt they hid it in the lifter valley like the starter on a Northstar V8. The issue seems to be solely throttle based, not RPM or speed related. It does it from a rolling start or from a stoplight. You can punch it right away and off you go. Should I try a junkyard MAF? Or ignition module? I can't imagine why the ignition module would only fail to deliver under light loads. I also put water on the motor and touched my hand across the wires to check for arcing, and I was not shocked. I am out of work, so I don't have money to keep throwing parts at this. Any help or suggestions are greatly appreciated.

Being ODB I I don't remember it having in cool features on the scan tool like showing me the current RPM, etc, so I have not rented the tool to drive around with. I assume with ODB I its only going to read codes and there are none since the SES light is not on.
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Old 08-27-2010, 08:53 PM   #2
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Try manually shifting the car in to 1st gear. Almost sounds like the torque converter is stuck in lock up.
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Old 08-28-2010, 09:36 AM   #3
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I did try that because I thought it might not be downshifting, made no difference. If the torque converter was staying locked up it would stall and buck when stopping. But maybe its locking up really, really early. Does the 4T60-E lock up in all gears or just overdrive? I will unplug the TCC plug and see if it changes anything. Thanks.
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