Will a bad Idle Stabilizer affect drivability???
05-08-2006, 09:46 AM
#1
Got Nothin'
Rennlist Member
Rennlist Member
Thread Starter
Will a bad Idle Stabilizer affect drivability???
I know you are all getting tired of reading about how poorly my car runs when cold. I checked the TPS and AFM over the weekend. The TPS is OK, and the AFM has a spike in voltage as the "barn door" opens.
I adjusted idle which was a bit low.
This morning, the car idled horribly but stayed running. It had low power all the way to work, until the engine was fully warmed up, when the idle smoothed out.
The question is: Will a bad Idle Stabilizer affect drivability???
I adjusted idle which was a bit low.
This morning, the car idled horribly but stayed running. It had low power all the way to work, until the engine was fully warmed up, when the idle smoothed out.
The question is: Will a bad Idle Stabilizer affect drivability???
05-08-2006, 02:09 PM
#2
Got Nothin'
Rennlist Member
Rennlist Member
Thread Starter
As a bit of an update. Even after the engine is warm and running smoothly, it will sometimes revert to a horrible idle after letting up on the throttle, as in when I am coming to a stop.
The question remains, is this an Idle stabilizer problem?
The question remains, is this an Idle stabilizer problem?
05-08-2006, 04:59 PM
#5
Three Wheelin'
You need to make sure that the mechanical idle is set properly first. To do this you need to install a jumper wire between pins B and C of the diagnostic connector. This jumper disables the ISV.
Connect a dwell/tach to the coil (green is +, black is ground), and start the engine. Use the idle by pass on the throttle body to adjust the idle to 840 +- 50 RPM. DO NOT adjust the mechanical stop screw. The mechanical stop is the small screw with the lock nut.
With the mechanical idle set, remove the jumper wire. Idle should stay within +- 50 RPM of 840.
Now that the idle is set I would start looking at the DME Temp Sensor II. This is the sensor with the BLUE connector. Look near #1 intake runner. This sensor is an NTC, or Negative Temperature Coefficient device. In plain English this means that as coolant temperature goes up, the resistance of the device goes down. Use an ohm meter to read the sensor when the engine is cold, and then again when the engine is hot. The hot reading should be less than the cold reading.
This sensor measures coolant temperature and sends a signal to the DME. The DME will adjust the fuel/air mixture based on this temperature. For cold starts the mixture will be rich.
If the engine is running poorly when cold, then I would suspect the DME "thinks" the engine is up to temperature.
You may also be having a problem with the O2 sensor. These things do wear out, or get slow to respond. You can back probe the sensor connector with a Digital Volt meter. With the engine running you should see the reading vary between 0.30 and 0.80 or even 0.90 volts DC.
Finally, check for vacuum leaks. A sever vacuum leak will cause all sorts of problems....
Connect a dwell/tach to the coil (green is +, black is ground), and start the engine. Use the idle by pass on the throttle body to adjust the idle to 840 +- 50 RPM. DO NOT adjust the mechanical stop screw. The mechanical stop is the small screw with the lock nut.
With the mechanical idle set, remove the jumper wire. Idle should stay within +- 50 RPM of 840.
Now that the idle is set I would start looking at the DME Temp Sensor II. This is the sensor with the BLUE connector. Look near #1 intake runner. This sensor is an NTC, or Negative Temperature Coefficient device. In plain English this means that as coolant temperature goes up, the resistance of the device goes down. Use an ohm meter to read the sensor when the engine is cold, and then again when the engine is hot. The hot reading should be less than the cold reading.
This sensor measures coolant temperature and sends a signal to the DME. The DME will adjust the fuel/air mixture based on this temperature. For cold starts the mixture will be rich.
If the engine is running poorly when cold, then I would suspect the DME "thinks" the engine is up to temperature.
You may also be having a problem with the O2 sensor. These things do wear out, or get slow to respond. You can back probe the sensor connector with a Digital Volt meter. With the engine running you should see the reading vary between 0.30 and 0.80 or even 0.90 volts DC.
Finally, check for vacuum leaks. A sever vacuum leak will cause all sorts of problems....
05-08-2006, 08:47 PM
#6
Got Nothin'
Rennlist Member
Rennlist Member
Thread Starter
Cliff
I reset the idle speed according to Clark's instructions.
Also just finished a HG replacement which included a new O2 sensor and DME II sensor.
Will a bad DME II sensor have any ill affect when the engine is warm? Will it occur intermittently?
Now, for vac leaks...will they dissipate when the engine is warm? Will they cause an intermittent problem. For the life of me, I cannot figure out where such a leak could be, I have been all over the intake and vac systems, with no obvious leaks.
I reset the idle speed according to Clark's instructions.
Also just finished a HG replacement which included a new O2 sensor and DME II sensor.
Will a bad DME II sensor have any ill affect when the engine is warm? Will it occur intermittently?
Now, for vac leaks...will they dissipate when the engine is warm? Will they cause an intermittent problem. For the life of me, I cannot figure out where such a leak could be, I have been all over the intake and vac systems, with no obvious leaks.
05-08-2006, 09:36 PM
#7
Rennlist Member
pete,
do you know if your car is running rich [or lean]? extra soot in the tail pipe? worse gas mileage than usual? i'm leaning toward fuel delivery [pump, filter, FPR, FPD, injectors]. have you checked all those out? also, i've seen a TPS and AFM check out within specs and still cause problems.
allen
do you know if your car is running rich [or lean]? extra soot in the tail pipe? worse gas mileage than usual? i'm leaning toward fuel delivery [pump, filter, FPR, FPD, injectors]. have you checked all those out? also, i've seen a TPS and AFM check out within specs and still cause problems.
allen
Trending Topics
05-09-2006, 08:13 AM
#8
Got Nothin'
Rennlist Member
Rennlist Member
Thread Starter
Haven't done fuel delivery per se. However, fuel economy sucks. The pump is fairly new. But FPR etc have not been tested. I will need to find procedures for that. But honestly, I think it is an air delivery issue/vacuum.
05-09-2006, 08:56 AM
#9
Three Wheelin'
Pete:
When everything is working properly these cars get pretty good mileage. My turbo gets in the mid 20's around town and in the low to mid 30's on the highway.
I would start off by measuring the signal from the O2 sensor. Since this is a later model you can back probe the sensor by inserting a test lead into the back of the connector. Connect the + lead to the sensor, and the - lead to a good bround. Connect a dwell/tach to the coil. Set the volt meter to read the 2 volts DC scale and start the engine. As the sensor comes up to temperature you should see the meter display cycle across 0.50 volts. At this point unplug the sensor (leave the meter connected) and install a jumper between pins B and C of the diagnostic connector. The O2 sensor reading should go above 0.50 volts. I like to see between 0.60 and 0.70 volts. If the voltage is too high, say 0.80 or 0.90, try adjusting the CO (carbon monoxide) by-pass at the AFM. Opening the by pass will make the idle mixture lean, closing the by pass will make the idle mixture rich. Set the by pass to get between 0.60 and 0.70 volts. NOTE: You may need to adjust the mechanical idle screw on the throttle body to maintain idle RPM. Reconnect the O2 sensor and remove the jumper from the diagnostics connector. The volt meter display sould start to cycle across 0.50 volts.
Vacuum can be a little more involved, but I would start off by checking vacuum at the fuel pressure regulator. If you do not have vacuum here, fuel pressure will be maxed out and your mileage will suffer. A common problem with NA cars in cases were the intake had been off is connecting the line to the damper and FPR to the wrong port on the throttle body. On the NA cars there are two vacuum ports on the throttle body. The first port is for the evaporative emissions purge system and the second port is for the FPR and damper. The difference between these ports is the first port is above the throttle plate and the second one is below the throttle plate. What this means is that while the second port will alwyas have a good vacuum signal, the first port will have a much smaller signal (I've measured about 5" HG) just as the throttle is opened. Once the throttle plate gets past a certain point this vacuum signal goes away. This is necessary to give a monentary signal to the purge system.
The easiest way to test the ISV is to connect a dwell/tach to the coil, start the engien, and then load the engine by turning on the head lights, fog lights, rear window defroster and the A/C. If the ISV is working properly the engine RPM should be fairly constant. I have not seen a situation where a faulty ISV caused driveability issues, but I have seen hose leaks cause the engine to run lean.
You might also try doing cold and warm compression checks.
What do the spark plugs look like?
When everything is working properly these cars get pretty good mileage. My turbo gets in the mid 20's around town and in the low to mid 30's on the highway.
I would start off by measuring the signal from the O2 sensor. Since this is a later model you can back probe the sensor by inserting a test lead into the back of the connector. Connect the + lead to the sensor, and the - lead to a good bround. Connect a dwell/tach to the coil. Set the volt meter to read the 2 volts DC scale and start the engine. As the sensor comes up to temperature you should see the meter display cycle across 0.50 volts. At this point unplug the sensor (leave the meter connected) and install a jumper between pins B and C of the diagnostic connector. The O2 sensor reading should go above 0.50 volts. I like to see between 0.60 and 0.70 volts. If the voltage is too high, say 0.80 or 0.90, try adjusting the CO (carbon monoxide) by-pass at the AFM. Opening the by pass will make the idle mixture lean, closing the by pass will make the idle mixture rich. Set the by pass to get between 0.60 and 0.70 volts. NOTE: You may need to adjust the mechanical idle screw on the throttle body to maintain idle RPM. Reconnect the O2 sensor and remove the jumper from the diagnostics connector. The volt meter display sould start to cycle across 0.50 volts.
Vacuum can be a little more involved, but I would start off by checking vacuum at the fuel pressure regulator. If you do not have vacuum here, fuel pressure will be maxed out and your mileage will suffer. A common problem with NA cars in cases were the intake had been off is connecting the line to the damper and FPR to the wrong port on the throttle body. On the NA cars there are two vacuum ports on the throttle body. The first port is for the evaporative emissions purge system and the second port is for the FPR and damper. The difference between these ports is the first port is above the throttle plate and the second one is below the throttle plate. What this means is that while the second port will alwyas have a good vacuum signal, the first port will have a much smaller signal (I've measured about 5" HG) just as the throttle is opened. Once the throttle plate gets past a certain point this vacuum signal goes away. This is necessary to give a monentary signal to the purge system.
The easiest way to test the ISV is to connect a dwell/tach to the coil, start the engien, and then load the engine by turning on the head lights, fog lights, rear window defroster and the A/C. If the ISV is working properly the engine RPM should be fairly constant. I have not seen a situation where a faulty ISV caused driveability issues, but I have seen hose leaks cause the engine to run lean.
You might also try doing cold and warm compression checks.
What do the spark plugs look like?
05-09-2006, 09:28 AM
#10
Got Nothin'
Rennlist Member
Rennlist Member
Thread Starter
The O2 sensor is new. I will check it as best I can.
As for the idle stabilizer, it could be part of the problem.
I need to find out why the idle goes bad, on occasion after the car is warmed up.
This is really frustrating. I am getting close to seeking professional help. (For the car)
As for the idle stabilizer, it could be part of the problem.
I need to find out why the idle goes bad, on occasion after the car is warmed up.
This is really frustrating. I am getting close to seeking professional help. (For the car)
05-11-2006, 03:29 PM
#12
Got Nothin'
Rennlist Member
Rennlist Member
Thread Starter
The problem seems temp related, although even when the engine is warm, I will get bad (rough running, low idle, no power) performance.
So the questions are:
Could it be a bad cap/rotor? They are old.
Idle stabilizer? That explains the bad idle, but not the poor performance under acceleration etc.
AFM - How would a bad AFM affect the engine performance?
FPR - How do you test the FPR? What should happen if I pull the vac line while the car is running.
VAC leak - Would I get the variable problems with a vac leak, or would the problem be constant?
Plan is to replace cap/rotor/fuel filter.
So the questions are:
Could it be a bad cap/rotor? They are old.
Idle stabilizer? That explains the bad idle, but not the poor performance under acceleration etc.
AFM - How would a bad AFM affect the engine performance?
FPR - How do you test the FPR? What should happen if I pull the vac line while the car is running.
VAC leak - Would I get the variable problems with a vac leak, or would the problem be constant?
Plan is to replace cap/rotor/fuel filter.
