Stalls when warm and in gear
04-19-2018, 04:10 PM
#1
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Stalls when warm and in gear
I have 1995 Camaro z28 with 176k miles on it. I have been having problems with it ever since I bought it. Stalls out when it's warm and in gear idling. Just installed a new tps and harness that goes to the opti spark. Previously replaced sparkplug, wires, icm, coil, egr, pcv valve and grommet, cleaned iac, new air filter, new fuel filter. I also replace the vacuum lines for the timing advance. (Previously backfiring.) Has lower oil pressure but not causing my problem. I have new oil pump but just have to install it. Compression 150. (Across all cylinders) Lower than normal. When I take off air filter the car stalls even in park. When I unplug maf car stalls. I think there is a slight misfire, but not sure. Rpms are about 1100 when first started. But if I put it in gear it goes down to 6-700 rpms. I cleaned my iac but nothing. When I took the air filter off and tried to start it wouldn't start. Then I saw smoke coming from engine bay. Maybe intake manifold is bad? I'm lost. Any help would be appreciated.
04-19-2018, 06:23 PM
#2
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Join Date: Aug 2017
Posts: 9
Re: Stalls when warm and in gear
I have 1995 Camaro z28 with 176k miles on it. I have been having problems with it ever since I bought it. Stalls out when it's warm and in gear idling. Just installed a new tps and harness that goes to the opti spark. Previously replaced sparkplug, wires, icm, coil, egr, pcv valve and grommet, cleaned iac, new air filter, new fuel filter. I also replace the vacuum lines for the timing advance. (Previously backfiring.) Has lower oil pressure but not causing my problem. I have new oil pump but just have to install it. Compression 150. (Across all cylinders) Lower than normal. When I take off air filter the car stalls even in park. When I unplug maf car stalls. I think there is a slight misfire, but not sure. Rpms are about 1100 when first started. But if I put it in gear it goes down to 6-700 rpms. I cleaned my iac but nothing. When I took the air filter off and tried to start it wouldn't start. Then I saw smoke coming from engine bay. Maybe intake manifold is bad? I'm lost. Any help would be appreciated.
04-19-2018, 07:42 PM
#3
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Location: Hell was full so they sent me to NJ
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Re: Stalls when warm and in gear
At any point have you scanned it for codes?
What “vacuum lines for the timing advance”? Do you mean the vacuum/vent harness for the Opti? If so, that's all it is - a vent. All ignition advance is controlled by the PCM based on RPM and engine load (MAP).
Does it smell rich when it’s stalling? That could relate to a faulty coolant temp sensor for the PCM. If the PCM thinks the engine is cold, it can run rich enough to cause it to stall.
When does the engine transition form idling OK to stalling? When the PCM transitions from open loop (ignoring O2 sensor input) to closed loop (adjusting A/F ratio based on O2 sensor feedback) a faulty O2 sensor can cause the engine to run rich and rough. The open to closed loop transition typically occurs at 206 seconds after cold start, assuming the coolant temp has reached at least 140°F.
If all else fails, data logging with Scan9495 may show up the problem. Free download, just need a cable. We can review the data log for you.
https://www.camaroz28.com/forums/com...95-lt1-874306/
What “vacuum lines for the timing advance”? Do you mean the vacuum/vent harness for the Opti? If so, that's all it is - a vent. All ignition advance is controlled by the PCM based on RPM and engine load (MAP).
Does it smell rich when it’s stalling? That could relate to a faulty coolant temp sensor for the PCM. If the PCM thinks the engine is cold, it can run rich enough to cause it to stall.
When does the engine transition form idling OK to stalling? When the PCM transitions from open loop (ignoring O2 sensor input) to closed loop (adjusting A/F ratio based on O2 sensor feedback) a faulty O2 sensor can cause the engine to run rich and rough. The open to closed loop transition typically occurs at 206 seconds after cold start, assuming the coolant temp has reached at least 140°F.
If all else fails, data logging with Scan9495 may show up the problem. Free download, just need a cable. We can review the data log for you.
https://www.camaroz28.com/forums/com...95-lt1-874306/
04-19-2018, 08:11 PM
#4
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Thread Starter
Join Date: Aug 2017
Posts: 9
Re: Stalls when warm and in gear
At any point have you scanned it for codes?
What “vacuum lines for the timing advance”? Do you mean the vacuum/vent harness for the Opti? If so, that's all it is - a vent. All ignition advance is controlled by the PCM based on RPM and engine load (MAP).
Does it smell rich when it’s stalling? That could relate to a faulty coolant temp sensor for the PCM. If the PCM thinks the engine is cold, it can run rich enough to cause it to stall.
When does the engine transition form idling OK to stalling? When the PCM transitions from open loop (ignoring O2 sensor input) to closed loop (adjusting A/F ratio based on O2 sensor feedback) a faulty O2 sensor can cause the engine to run rich and rough. The open to closed loop transition typically occurs at 206 seconds after cold start, assuming the coolant temp has reached at least 140°F.
If all else fails, data logging with Scan9495 may show up the problem. Free download, just need a cable. We can review the data log for you.
https://www.camaroz28.com/forums/com...95-lt1-874306/
What “vacuum lines for the timing advance”? Do you mean the vacuum/vent harness for the Opti? If so, that's all it is - a vent. All ignition advance is controlled by the PCM based on RPM and engine load (MAP).
Does it smell rich when it’s stalling? That could relate to a faulty coolant temp sensor for the PCM. If the PCM thinks the engine is cold, it can run rich enough to cause it to stall.
When does the engine transition form idling OK to stalling? When the PCM transitions from open loop (ignoring O2 sensor input) to closed loop (adjusting A/F ratio based on O2 sensor feedback) a faulty O2 sensor can cause the engine to run rich and rough. The open to closed loop transition typically occurs at 206 seconds after cold start, assuming the coolant temp has reached at least 140°F.
If all else fails, data logging with Scan9495 may show up the problem. Free download, just need a cable. We can review the data log for you.
https://www.camaroz28.com/forums/com...95-lt1-874306/
It stalls when in gear. The rpms will go from 900-1000 to 500-600 when I put it in drive.
Ill try to get that cable to connect to the computer. I'll also test the o2 sensors, maf and map. And I'll replace that coolant temp sensor near waterpump. Also if the map sensor is bad could it be the reason why my car won't start at all with the maf disconnected? Thx for reply it was helpful. I'll keep it updated.
04-19-2018, 10:45 PM
#6
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Join Date: Nov 1998
Location: Hell was full so they sent me to NJ
Posts: 70,648
Re: Stalls when warm and in gear
It's not OBD-1.5. That would involve additional sensors, and would set codes that are in both the OBD-1 DTC xx format and some in the OBD-2 Pxxxx format. Only the LT1's used in the 94/95 Corvette were true OBD-1.5. GM must have planned to use OBD-1.5 in the F-Body LT1, installed the 16-pin connector, but never installed the required PCM.
Scan9495 is specifically designed to effectively communicate with 93/94/95 OBD-1 PCM's. For your 95 you would need to by the recommended OBD-1 cable with the 16-pin connector.
If you have access to an OBD-1 scanner with a 12-pin connector, you can use a 12-pin to 16-pin adapter, or simply use two jumper wires.
Courtesy of Shoebox
http://shbox.com/1/xraycable.jpg
As I indicated, the vacuum line from the Opti to the manifold and the air supply line from the intake elbow to the Opti are simply a vent system to remove ozone from the Opti. Nothing to do with ignition advance. The vacuum line obviously caused a vacuum leak.
Yes, the coolant temp sensor in the water pump is the one that supplies the PCM data. The coolant temp sensor in the driver side head is for the gauge.
When the engine is cold the PCM does two things - 1) provides a rich A/F mixture for cold start and warmup; 2) elevates the idle RPM. Idle RPM is programmed as high as 1,200 RPM in neutral at sub-0°F temps. Another sign that your coolant temp sensor may not be providing accurate readings to the PCM. Look through the link I posted.
Stock programming for an auto trans,with the engine fully warmed up sets idle at 550 RPM in gear and 650 RPM in neutral.
Scan9495 is specifically designed to effectively communicate with 93/94/95 OBD-1 PCM's. For your 95 you would need to by the recommended OBD-1 cable with the 16-pin connector.
If you have access to an OBD-1 scanner with a 12-pin connector, you can use a 12-pin to 16-pin adapter, or simply use two jumper wires.
Courtesy of Shoebox
http://shbox.com/1/xraycable.jpg
As I indicated, the vacuum line from the Opti to the manifold and the air supply line from the intake elbow to the Opti are simply a vent system to remove ozone from the Opti. Nothing to do with ignition advance. The vacuum line obviously caused a vacuum leak.
Yes, the coolant temp sensor in the water pump is the one that supplies the PCM data. The coolant temp sensor in the driver side head is for the gauge.
When the engine is cold the PCM does two things - 1) provides a rich A/F mixture for cold start and warmup; 2) elevates the idle RPM. Idle RPM is programmed as high as 1,200 RPM in neutral at sub-0°F temps. Another sign that your coolant temp sensor may not be providing accurate readings to the PCM. Look through the link I posted.
Stock programming for an auto trans,with the engine fully warmed up sets idle at 550 RPM in gear and 650 RPM in neutral.
Last edited by Injuneer; 04-19-2018 at 10:48 PM.
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