Question Lt1 has bad idle and and power at low rpm - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums

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post #1 of 19 (permalink) Old 09-10-2010, 01:06 AM Thread Starter
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Lt1 has bad idle and and power at low rpm

Hey guys I just bought a 94 camaro and it has been running good for the most part, but recently Ive had a problem with the car running rough. if I punch the gas the car sputters until it hits 2500 rpms then takes off. Ive searched and have been thinking it could be a dirty MAF or bad Egr valve. The weird thing is the car runs perfect when I first start it up, then I drive around for awhile and everything is running great until I hit normal operating temp, then it runs like crap and sputters when I punch it. Im not very knowledgeable about cars. Any help would be appreciated!
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post #2 of 19 (permalink) Old 09-10-2010, 05:23 AM
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Get some spray injector cleaner open the Throttle blades on the t body clean everything and the MAF let dry 20 min. Pull the egr valve and clean without getting anything on the rubber diaphram. Reinstall.

When it warms up could be a bad oxygen sensor giving bad signal to the PCM and fuel mixture getting screwed up.
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post #3 of 19 (permalink) Old 09-10-2010, 11:24 AM Thread Starter
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Alright Ill try that and see what happens, thanks!
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post #4 of 19 (permalink) Old 09-10-2010, 02:12 PM
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you could see if its a sensor problem. let the car get to operating temp. when it starts acting up. turn the car off and unplug the maf sensor. turn the car back on and it will run in open loop. if it still runs crappy (besides very rich) then most likely your sensors are ok and you should check into other things

1994 Z28 A4
383 LT1 - LE Trickflows - LE Ported Intake - Jones Cam Designs Solid Roller
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post #5 of 19 (permalink) Old 09-10-2010, 02:15 PM
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also do not spray anything onto your maf other than CRC Maf cleaner or CRC electrical cleaner. its a very sensitive sensor that needs to function 100%. spraying anything else onto it is taking a gamble in my opinion.

1994 Z28 A4
383 LT1 - LE Trickflows - LE Ported Intake - Jones Cam Designs Solid Roller
Strange s60 4.30 - 4L60e - SS4000 - 3400 lb - 28" MT Radial
Best ET 10.87 @ 123.66 - 1.49 60 ft - +1600 DA
Under the knife again... LE Victor EFI, Holley Dominator ECU, 13.5:1, E85, Custom SR

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post #6 of 19 (permalink) Old 09-10-2010, 04:48 PM
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If it only starts running bad when it gets up to operating temp, it could also be a closed loop issue.

You can easily narrow that down by unplugging both O2 sensor connectors (keeps it open loop) and drive it while it's warmed up.

If it continues to run well like it does when it's cold, with the O2s unplugged, then it could be bad/fouled O2 sensors, bad O2 sensor wiring, or an exhaust leak.

If there is no change while running it with them unplugged, then it's probably an ignition issue (ICM over-heating is common).
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post #7 of 19 (permalink) Old 09-12-2010, 09:27 PM Thread Starter
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Well after the car warmed up I unplugged MAF sensor and drove the car around. It seemed like there wasnt any noticable change and it ran bad as usual under 2000 rpm, I just replaced all the intake manifold gaskets and cleaned the egr valve, what else could this be? plugs and wires? opti?
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post #8 of 19 (permalink) Old 09-12-2010, 09:56 PM
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Its sounding like O2 sensors, try this-



Quote:
Originally Posted by JSK333 View Post
You can easily narrow that down by unplugging both O2 sensor connectors (keeps it open loop) and drive it while it's warmed up.

If it continues to run well like it does when it's cold, with the O2s unplugged, then it could be bad/fouled O2 sensors, bad O2 sensor wiring, or an exhaust leak.

If there is no change while running it with them unplugged, then it's probably an ignition issue (ICM over-heating is common).



Yep its slow.

Making the world a warmer place one gallon at a time.
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post #9 of 19 (permalink) Old 09-12-2010, 10:32 PM Thread Starter
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I thought unplugging the maf sensor is the same thing? If not, where do I unplug the 02 sensor? Do I unplug the sensor it self? Im confused
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post #10 of 19 (permalink) Old 09-12-2010, 10:56 PM
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The MAF sensor measures the amount of air coming into the engine and the O2 sensors monitor how much fuel is being added to the air after its burnt. When you unplug the MAF the computer runs off of the VE tables (preprogrammed tables in the computer) but still uses the O2s to help adjust the fueling.

You'll need to leave the MAF plugged in and unplug the O2s at the sensors connector.



Yep its slow.

Making the world a warmer place one gallon at a time.
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post #11 of 19 (permalink) Old 09-12-2010, 11:12 PM Thread Starter
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where is that at?
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post #12 of 19 (permalink) Old 09-14-2010, 09:44 AM
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i cant remember exactly how the OBD1 setups are but i think there should be 2 O2 sensors on your exhaust system, 1 upstream of the catalytic converter and 1 downstream of it. i know for sure the OBD 2 systems have 4, one at the back of each exhaust manifold, and one after each of the catalytic converters

Last edited by 96_T/A_WS6; 09-14-2010 at 10:00 AM.
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post #13 of 19 (permalink) Old 09-14-2010, 11:31 AM
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my 94 caprice wagon has 2 o2 sensors, one on each pipe going to the catalytic converter. you can get to them from under the car, look for a sensor sticking out of the exhaust pipes right before the cats (my car has dual exhaust from the factory, dont know if camaros will be different)

1A2 wagon, 383K miles and counting
Apparently an F body LT1 swapped, reman. PCM with unknown tune.
(speedo accurate with 2.56 gears, but has it been tuned for the F body cam??)
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post #14 of 19 (permalink) Old 09-14-2010, 12:25 PM
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Quote:
Originally Posted by 96_T/A_WS6 View Post
i cant remember exactly how the OBD1 setups are but i think there should be 2 O2 sensors on your exhaust system, 1 upstream of the catalytic converter and 1 downstream of it. i know for sure the OBD 2 systems have 4, one at the back of each exhaust manifold, and one after each of the catalytic converters
OBD 1 has 1 sensor for each bank before cat, no post cat ones.



Yep its slow.

Making the world a warmer place one gallon at a time.
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post #15 of 19 (permalink) Old 09-15-2010, 12:15 AM
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oh ya my bad, ive been in iraq for the last year so its been forever since ive even touched a car, especially an OBD 1 car
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