High Idle on 5.7TBI - Pirate4x4.Com : 4x4 and Off-Road Forum

cj8scrambld · 10-25-2001, 06:40 AM

Hello, any GM techs out there? My '94 5.7TBI has an intermittent high idle when warm. I had changed the IAC without any improvement. I did not get any SES (service engine soon) light. I then changed the engine coolant sensor/Tstat/ coolant all at the same time. AFTER that I now have a SES and it would only start if I press on the accel. to the floor, then when it starts it has a very high idle and sounds as though it will cut out if I give it gas to soon. After driving for a short distance it runs ok but still has the intermittent high idle. Then if I were to shut it down and start it again I would have to press the accel to the floor again as above. I had the battery disconn. over night and I am going to see how it is now. I tried that yesterday for about 15" (battery disco) without any change. When I jump the term for the code it appears to be this: flash/pause/flash/flash/flash/flash/flash for a total of six flashes in I think 3 sets in a row (?) Any ideas? Thanks! John

Leader · 10-25-2001, 06:50 AM

Most of the time a high idle is from the gasket under the tbi getting sucked in.Have you checked it out yet? The code you gave was a 15...I dojnt have a book here to tell you what a code 15 is or I would try and help..I just love chasing ghosts on those damn things!!NOT~~~

cj8scrambld · 10-25-2001, 07:42 AM

Leader, thanks for the input. *** I had just put the old coolant temp sensor back in and guess what...no SES dash light!! It must have been a bad new sensor. The high idle is intermittent, I had changed the TBI gasket also a short while back. This SES light and starting trouble is only since I had changed the sensor/Tstat/coolant yesterday, prior to that it was just an intermittent high idle. Thanks again for your input, my NAPA dealer was out of the temp sensor and will have one in an hour...I will try a new - new one!!

fj40mon · 10-29-2001, 10:35 PM

cj8scrambld:

Code 15 is coolant temp. sensor circuit. The signal voltage is to high. Your right on the money. Congrad's

fj40mon <IMG SRC="smilies/bounce2.gif" border="0"> <IMG SRC="smilies/bounce.gif" border="0">

Ken Bernstein · 11-08-2001, 12:41 AM

Check for any vaccuum leaks on your intake manifold. Use brake clean (non flamible type) or carb cleaner and spray around vaccuum lines and your EGR valve a slight leak will cause this when you spray the lines if the engine stumbles or loses rpm ya gotta leak

10-25-2001, 06:40 AM	#1 (permalink)
cj8scrambld Rock God Join Date: Mar 2000 Member # 343 Location: Conway, MA US Posts: 1,947	High Idle on 5.7TBI Hello, any GM techs out there? My '94 5.7TBI has an intermittent high idle when warm. I had changed the IAC without any improvement. I did not get any SES (service engine soon) light. I then changed the engine coolant sensor/Tstat/ coolant all at the same time. AFTER that I now have a SES and it would only start if I press on the accel. to the floor, then when it starts it has a very high idle and sounds as though it will cut out if I give it gas to soon. After driving for a short distance it runs ok but still has the intermittent high idle. Then if I were to shut it down and start it again I would have to press the accel to the floor again as above. I had the battery disconn. over night and I am going to see how it is now. I tried that yesterday for about 15" (battery disco) without any change. When I jump the term for the code it appears to be this: flash/pause/flash/flash/flash/flash/flash for a total of six flashes in I think 3 sets in a row (?) Any ideas? Thanks! John

10-25-2001, 06:50 AM	#2 (permalink)
Leader Registered User Join Date: Jun 2001 Member # 5091 Location: Decatur TX. Posts: 51	Most of the time a high idle is from the gasket under the tbi getting sucked in.Have you checked it out yet? The code you gave was a 15...I dojnt have a book here to tell you what a code 15 is or I would try and help..I just love chasing ghosts on those damn things!!NOT~~~ __________________ It's as close to a 1ton as you can get and still look like a jeep!!

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10-25-2001, 07:42 AM	#3 (permalink)
cj8scrambld Rock God Join Date: Mar 2000 Member # 343 Location: Conway, MA US Posts: 1,947	Leader, thanks for the input. *** I had just put the old coolant temp sensor back in and guess what...no SES dash light!! It must have been a bad new sensor. The high idle is intermittent, I had changed the TBI gasket also a short while back. This SES light and starting trouble is only since I had changed the sensor/Tstat/coolant yesterday, prior to that it was just an intermittent high idle. Thanks again for your input, my NAPA dealer was out of the temp sensor and will have one in an hour...I will try a new - new one!!

10-29-2001, 10:35 PM	#4 (permalink)
fj40mon Registered User Join Date: Mar 2001 Member # 3929 Location: longview,WA. Posts: 170	cj8scrambld: Code 15 is coolant temp. sensor circuit. The signal voltage is to high. Your right on the money. Congrad's fj40mon <IMG SRC="smilies/bounce2.gif" border="0"> <IMG SRC="smilies/bounce.gif" border="0">

11-08-2001, 12:41 AM	#5 (permalink)
Ken Bernstein Registered User Join Date: Oct 2001 Member # 7534 Location: El Dorado County Posts: 222	Check for any vaccuum leaks on your intake manifold. Use brake clean (non flamible type) or carb cleaner and spray around vaccuum lines and your EGR valve a slight leak will cause this when you spray the lines if the engine stumbles or loses rpm ya gotta leak