Failed emissions on a 951. 21 times the limit.
07-15-2005, 11:46 AM
#31
Three Wheelin'
Running rich can be caused by any one of several things, most of which have been mentioned in previous posts.
However, what has not been mentioned is using the proper test equipment, like Diogital Volt Meters and Dwell/Tachs.
First off, you can use the DVM to "prove" your Fuel/Air meter and O2 sensor. At idle you should see the DVM display a voltage that varies across 0.50 volts when the engine is at idle.
Second, you cannot use the in-dash tach for setting the engine idle, it just isn't accurate enough, you MUST use a Dwell/Tach.
Third, to set the engine idle you need to put a jumper wire between pins 'B' and 'C' of the diagnostics connector to disable the Idle Stabilizer Valve, and then use the Idle By-Pass on the throttle body to set the idle to 840 +- 50 RPM.
Personally I would start by removing the throttle body and verifying that the throttle plate mechanical stop is set properly. I've seen more thatn one P-Car that wouldn't idle properly because a "mechanic" used the mechanical stop to compensate for a problem he couldnt' fix other wise.
To set the mechanical stop you need to remove the TB and loosen the TPS screws. Make sure the throttle plate moves freely and does not bind. Loosen the 7mm jam nut, hold the throttle plate closed and back the stop screw out until it does not touch the stop arm. With the throttle plate closed, turn the stop screw IN until it touches the stop arm, and then turn the stop screw IN an additional 1/2 turn. Tighten the jam nut. Verify that the throttle plate opens and closes freely and that the stop arm touches the stop screw. Now you can set the TPS so that it clicks just as the throttle plate opens and closes.
When you get the TB reinstalled you will need to set the mechanical idle. Connect a dwell/tach to the coil and put a jumper wire between pins 'B' and 'C' on the diagnostics connector. Start the engine and use the idle by-pass on the throttle body to adjust the idle to 840 + - 50 RPM. When you have the mechanical idle set, remove the jumper from the diagnostics connector. Engine RPM may vary slightly, but should stay within +- 50 RPM. If the idle is stable, load the engine by turning on the A/C, headlights, and so forth. If the ISV is functioning properly the idle should stay within the spec.
Before you tear into the AFM you might what to try adjusting the Idle CO (Carbon Monoxied) by-pass on the AFM. To do this you need to disconnect the O2 sensor and connect a DVM to the O2 sensor's signal (black) lead. You can do this by inserting the red meter probe tip into the back of the connector. The connector is a soft rubber and will hold the meter probe. You also need to have the ISV disabled (jumper wire at the diagnostic connector).
To get the the CO adjustment you need to remove the snorkle from the air box, and you may need to drill out the plug. With the plug out you should see a 6mm Allen head screw. Turning the screw clock wise richens the mixture, and turning the screw counter clock wise leans the mixture.
With the engine at idle, use the CO adjustment to get the DVM to read between 0.6 and 0.7 volts DC. This should get your CO into the .02 to .04 range (In April my 951 tested at .02 with Guru chips, 3.0 BART FPR and a ReliaBoost set at 15 psi, and before that my '87 NA tested at .03 in stock trim.). Note: Engine RPM will vary as you adjust the CO, so you need to make a CO adjustment and then re-set the mechanical idle with the idle screw on the TB. Let the system stabilize between adjustments, and GO SLOW! Make small CO adjustments (1/4 turn at a time).
If after all of this you are still having mixture problems, then I would look at the FPR. Try using an external vacuum source like a Mity Vac. If the FPR will not hold a vacuuml, then you need to replace it.
With the engine at idle and with a DVM connected to the O2 sensor, you can apply a vacuum to the FPR to change fuel pressure. As vacuum to the FPR goes up, fuel pressure goes down. At the same time, the O2 sensor should start indicating towards more lean.
If all of this checks out and you are absolutely certain that you do not have any intake or vacuum leaks, then the only other engine component that could be causing a rich mixture is the DME Temp Sensor II. This is the sensor at the front of the block with the Blue connector. You can test this sensor with a DVM. The sensor is an NTC, or Negative Temperature Coefficient device. All this means is that as the temperature goes up, the sensor's resistance goes down, and when temperature goes down, resistance goes up. If this sensor is not functiong properly, or if there is an open circuit to the DME, the DME will not see the correct coolant temperature, which will cause the fuel/air mixture to be "off".
However, what has not been mentioned is using the proper test equipment, like Diogital Volt Meters and Dwell/Tachs.
First off, you can use the DVM to "prove" your Fuel/Air meter and O2 sensor. At idle you should see the DVM display a voltage that varies across 0.50 volts when the engine is at idle.
Second, you cannot use the in-dash tach for setting the engine idle, it just isn't accurate enough, you MUST use a Dwell/Tach.
Third, to set the engine idle you need to put a jumper wire between pins 'B' and 'C' of the diagnostics connector to disable the Idle Stabilizer Valve, and then use the Idle By-Pass on the throttle body to set the idle to 840 +- 50 RPM.
Personally I would start by removing the throttle body and verifying that the throttle plate mechanical stop is set properly. I've seen more thatn one P-Car that wouldn't idle properly because a "mechanic" used the mechanical stop to compensate for a problem he couldnt' fix other wise.
To set the mechanical stop you need to remove the TB and loosen the TPS screws. Make sure the throttle plate moves freely and does not bind. Loosen the 7mm jam nut, hold the throttle plate closed and back the stop screw out until it does not touch the stop arm. With the throttle plate closed, turn the stop screw IN until it touches the stop arm, and then turn the stop screw IN an additional 1/2 turn. Tighten the jam nut. Verify that the throttle plate opens and closes freely and that the stop arm touches the stop screw. Now you can set the TPS so that it clicks just as the throttle plate opens and closes.
When you get the TB reinstalled you will need to set the mechanical idle. Connect a dwell/tach to the coil and put a jumper wire between pins 'B' and 'C' on the diagnostics connector. Start the engine and use the idle by-pass on the throttle body to adjust the idle to 840 + - 50 RPM. When you have the mechanical idle set, remove the jumper from the diagnostics connector. Engine RPM may vary slightly, but should stay within +- 50 RPM. If the idle is stable, load the engine by turning on the A/C, headlights, and so forth. If the ISV is functioning properly the idle should stay within the spec.
Before you tear into the AFM you might what to try adjusting the Idle CO (Carbon Monoxied) by-pass on the AFM. To do this you need to disconnect the O2 sensor and connect a DVM to the O2 sensor's signal (black) lead. You can do this by inserting the red meter probe tip into the back of the connector. The connector is a soft rubber and will hold the meter probe. You also need to have the ISV disabled (jumper wire at the diagnostic connector).
To get the the CO adjustment you need to remove the snorkle from the air box, and you may need to drill out the plug. With the plug out you should see a 6mm Allen head screw. Turning the screw clock wise richens the mixture, and turning the screw counter clock wise leans the mixture.
With the engine at idle, use the CO adjustment to get the DVM to read between 0.6 and 0.7 volts DC. This should get your CO into the .02 to .04 range (In April my 951 tested at .02 with Guru chips, 3.0 BART FPR and a ReliaBoost set at 15 psi, and before that my '87 NA tested at .03 in stock trim.). Note: Engine RPM will vary as you adjust the CO, so you need to make a CO adjustment and then re-set the mechanical idle with the idle screw on the TB. Let the system stabilize between adjustments, and GO SLOW! Make small CO adjustments (1/4 turn at a time).
If after all of this you are still having mixture problems, then I would look at the FPR. Try using an external vacuum source like a Mity Vac. If the FPR will not hold a vacuuml, then you need to replace it.
With the engine at idle and with a DVM connected to the O2 sensor, you can apply a vacuum to the FPR to change fuel pressure. As vacuum to the FPR goes up, fuel pressure goes down. At the same time, the O2 sensor should start indicating towards more lean.
If all of this checks out and you are absolutely certain that you do not have any intake or vacuum leaks, then the only other engine component that could be causing a rich mixture is the DME Temp Sensor II. This is the sensor at the front of the block with the Blue connector. You can test this sensor with a DVM. The sensor is an NTC, or Negative Temperature Coefficient device. All this means is that as the temperature goes up, the sensor's resistance goes down, and when temperature goes down, resistance goes up. If this sensor is not functiong properly, or if there is an open circuit to the DME, the DME will not see the correct coolant temperature, which will cause the fuel/air mixture to be "off".
07-16-2005, 05:25 PM
#32
Three Wheelin'
Thread Starter
I took the intercooler pipes off this morning to check the throttle plate. It is exactly where Danno said it should be and the TPS has been tested to operate correctly.
I've got the B&C pins jumpered and adjusted the idle. I had to screw the adjuster screw completely closed to get it to run at 850RPM. Does this mean I have a massive vac leak?
Why does it run rich if I've got a vacuum leak the size of Texas?
The stop plug is out of the AFM, so it looks to have been adjusted at some point, but I was able to pass emissions with making no changes other than a TPS since that time. I think this is something new, however the car has idled like this since I put the TPS in.
I've got the B&C pins jumpered and adjusted the idle. I had to screw the adjuster screw completely closed to get it to run at 850RPM. Does this mean I have a massive vac leak?
Why does it run rich if I've got a vacuum leak the size of Texas?
The stop plug is out of the AFM, so it looks to have been adjusted at some point, but I was able to pass emissions with making no changes other than a TPS since that time. I think this is something new, however the car has idled like this since I put the TPS in.
07-16-2005, 07:47 PM
#34
Race Director
"I've got the B&C pins jumpered and adjusted the idle. I had to screw the adjuster screw completely closed to get it to run at 850RPM. Does this mean I have a massive vac leak?"
Yeah, you've got a big intake leak somewhere between the throttle-body and intake-valves. Simplest method to troubleshoot is to disconnect the two large 1/2" hoses on the throttle-body, plug up the ports and hose-ends and see how it idles then.
Also contrary to popular belief, the "idle-adjustment" procedure with bridging the B&C terminals to disable the ISV is NOT to adjust the actual idle-speed itself! Idle speed is purely controlled by the DME. The ONLY thing you're doing with that procedure is setting the mechanical air-bypass at the throttle-body so that it provides 100% of air needed for idle-speed and 0% of air comes from the idle-stabilizer. That way, when the car's warmed up and operating correclty, the idle-stabilizer stays fully closed and 100% of the idle-air comes through the idle-screw. Then ONLY when the AC's running or when the car's cold, does the idle-stabilizer kick to maintain idle-speed against the higher load. With a properly working ISV and no intake leaks, you can adjust the idle-screw with the ISV connected and you'll notice that the DME adjusts to compensate and idle stays rock-steady at 850rpm... also dash tach tends to read high...
The only real idle-speed adjustment you can make is to INCREASE idle-speed above the spec 840rpm. You can do this by introducing more air into the engine than necessary, such as with a mis-adjusted throttle-plate, a mis-adjusted idle-screw, or vacuum leaks. In all three of these cases, the DME will completely close up the ISV in order to compensate, but once the ISV is fully closed, there's no way the DME can future shut off air-flow to reduce idle-speed, thus higher-than-desired idle-speed, which was the case with Nick's car.
"but 21 times the limit has to be some kind of record "
Yeah huh??? But HC emissions is only about 3x the limit. This super-rich mixture would tend to drive up CO levels. The cat may be dead too... or installed in reverse... The NOx stage comes first and the Ox that's stripped off is combined with CO to make CO2... if you install the cat in reverse, you'll reduce NOx, but not CO...
Get voltage readings on the AFM next. That data will be useful in troubleshooting and solving this problem.
Yeah, you've got a big intake leak somewhere between the throttle-body and intake-valves. Simplest method to troubleshoot is to disconnect the two large 1/2" hoses on the throttle-body, plug up the ports and hose-ends and see how it idles then.
Also contrary to popular belief, the "idle-adjustment" procedure with bridging the B&C terminals to disable the ISV is NOT to adjust the actual idle-speed itself! Idle speed is purely controlled by the DME. The ONLY thing you're doing with that procedure is setting the mechanical air-bypass at the throttle-body so that it provides 100% of air needed for idle-speed and 0% of air comes from the idle-stabilizer. That way, when the car's warmed up and operating correclty, the idle-stabilizer stays fully closed and 100% of the idle-air comes through the idle-screw. Then ONLY when the AC's running or when the car's cold, does the idle-stabilizer kick to maintain idle-speed against the higher load. With a properly working ISV and no intake leaks, you can adjust the idle-screw with the ISV connected and you'll notice that the DME adjusts to compensate and idle stays rock-steady at 850rpm... also dash tach tends to read high...
The only real idle-speed adjustment you can make is to INCREASE idle-speed above the spec 840rpm. You can do this by introducing more air into the engine than necessary, such as with a mis-adjusted throttle-plate, a mis-adjusted idle-screw, or vacuum leaks. In all three of these cases, the DME will completely close up the ISV in order to compensate, but once the ISV is fully closed, there's no way the DME can future shut off air-flow to reduce idle-speed, thus higher-than-desired idle-speed, which was the case with Nick's car.
"but 21 times the limit has to be some kind of record "
Yeah huh??? But HC emissions is only about 3x the limit. This super-rich mixture would tend to drive up CO levels. The cat may be dead too... or installed in reverse... The NOx stage comes first and the Ox that's stripped off is combined with CO to make CO2... if you install the cat in reverse, you'll reduce NOx, but not CO...
Get voltage readings on the AFM next. That data will be useful in troubleshooting and solving this problem.
07-17-2005, 05:47 PM
#35
Three Wheelin'
Thread Starter
I covered up the big 1/2" holes on the intake and it held a bit more vacuum while warmed up (16in hg). I had to open the idle adjuster screw a tad to get it to run. It still ran rich, but I'm trying to fix one thing at a time, right now I'll focus on the vacuum leak. So now I've got the intake manifold off but I can't find any vacuum leaks.
Does anyone have a guide for replacing all the vacuum lines on the car?
Is there any way for me to tell if the AFM has ever been adjusted? The plug has been pulled, but I don't know if the previous owner adjusted it to account for whatever I'm dealing with.
Does anyone have a guide for replacing all the vacuum lines on the car?
Is there any way for me to tell if the AFM has ever been adjusted? The plug has been pulled, but I don't know if the previous owner adjusted it to account for whatever I'm dealing with.
07-17-2005, 05:50 PM
#36
Three Wheelin'
Thread Starter
Also, I have a new TPS on the car and that seemed to be when the rich running condition started. I guess it's possible I could get a broken TPS from the dealer. Has anyone ever had a TPS that was new and broken?
