I'm going to use two acronyms in this thread: my car is a 92 Auto 140K hg has been replaced prior to me at some point. Everything is stock except a Bosh blow-of valve (installed 2 years before this problem started), external tranny fluid cooler and fluidyne rad.
PIC = Poor idle condition
GIC = Good idle condition
The Problem Description: PIC at warm start up only and brief lack of power if I start driving during the PIC. This started over 2 years ago and it has basically not changed except for the frequency of occurrence, currently every time at warm start up. Has never occurred when engine is cold and never while I'm driving/stopped at idle. I've driven from cold start-up all day long and the PIC will not happen until engine is off for a short period of time. I've never timed it but I can guess it takes anywhere from 10-20minutes being off, then the PIC will occur upon engine start.
Additionally, it can be as much as 2-3 hours with engine off and PIC will still occur upon start up, even though the engine temp is warm but not at operating temp.
The engine has never stalled during PIC. During PIC, idle will bounce between 500 and 650 for approx 30-45 seconds, then idle quickly increases to @ 900-1000, followed by a gradual decrease in idle to the target of 650, but now in GIC. I can start driving at this point without any lack of power and not see the PIC until another shut down/warm start up.
When in PIC and parked, if I increase idle by opening throttle to... say 1000 rpm, there is still a noticeable mis-fire vibration. If I close throttle at this point the engine will remain in PIC. If I hold the engine above idle, then in about 30-45 seconds (just like when I leave the engine to idle), there will be a noticeable and sudden increase in rpm's (above the 1000 I'm holing it at without me opening the throttle more) AND the rough idling cease. Release throttle at this time, and then GIC at target 650 rpm...and good to drive.
When in PIC and parked and I give the throttle a quick sharp increase to 3000 rpm, (flooring the pedal) engine will leave PIC and enter GIC. Sometime I only need to floor the pedal once, sometimes twice, sometimes three times, but by the third flooring, engine will enter GIC...good to drive.
If I start driving while still in PIC, there is a lack of power and I feel a mis-fire. If I gradually depress the pedal before any turbo boost, car will increase in speed, but not at full power for several seconds, then, suddenly have full power. At this point, if I come to a stop engine is in GIC.
The change from PIC to GIC occurs instantly, like someone turning a switch.
If I start driving in PIC and immediately go to WOT, there is a very brief delay in engine response compared to normal, but then it kicks in and engine is at full power, come to stop, and engine is in GIC. This scenario is the quickest way to stop the PIC compared to other methods/descriptions previously stated.
Here is the history of work I've done on the engine AFTER the problem started. Note: this work was not done specifically for this problem (I have not thrown parts at this problem either), but I had always hoped that it might be resolved while doing other work...it has not.
Intake side:
removed and hot tanked plenum and upper intake runners. I did not remove the lower intake runners from the head, just cleaned them out.
Removed injectors, but did NOT service them.
Removed ISCV, cleaned it, bench tested per TSRM,
cleaned throttle and ports
installed all parts with new gaskets
knock sensor wires: the front wire was almost broken off the connector when I removed the intake, I disassembled the wire clip from the connector, re-striped the wire and soldered it to the metal connector and re-installed into the plastic connector, used shrinking tube to cover the bare wire, and a bit of ultra grey to give some support to the wire and connector together. The rear sensor wire was still well connected, but just had some cracks on the outer wire shielding, so I just added some ultra gray for support and covered the wire with shrink tubing.
Head/engine work:
installed new valve stem seals, valve cover gaskets, plug valley gasket, new plugs.
checked coolant for combustion gases on several occasions- none indicated
Exhaust:
new exhaust manifold gasket, rebuilt turbo,replaced all turbo/exhaust gaskets
Never have any smoke out the exhaust, checked plugs and look normal deposits.
Turbo: insured there are no leaks in the turbo intercooler or hoses/piping
Additionally,
AFM measured within specs (resistance).
Tried a different, newer and cleaner CPS - no effect
Ohm'd the coils packs, plug wires (plug wire are dated 2001 and probably have 40 K on them.
Performed the igniter grounding mod, O2 sensor ground mod, and replaced the ground wire from the coil pack - no effect
checked using my digi-fluke voltmeter the operation of 02 sensor = Good.
what else....have checked over and over, while the engine was apart and back together for vacuum leaks. I don't believe I have any and all of my hoses are replaced and or new. Used propane to hunt for leaks during the PIC to see if idle changes - found nothing Also used soapy water everywhere - non found
If you are going to say the fuel pressure up vsv, it is new and connected correctly. Also, I have on many occasions, jumpered the fuel pump on prior to start up in case pressure was not held - no effect, still PIC, so I don't think I have a fuel related problem. However, i have not check pressure with a gage, but I think with what I've checked and the problem does not indicate a fuel pressure issue.
changed the fuel pressure regulator - no effect.
If I remove the vacuum to the FPR while in PIC, idle increases but still mis-fires. If I pull... say the brake booster hose, idle drops, put some propane at the opening and idle increases.
EGR system functioning normally, and I give the EGR valve a tap with a hammer and stick during PIC thinking maybe its stuck open slightly. -no effect
Removed the ECU temp sensor connector when in PIC and no effect (other than getting the error code for no temp signal). Note: I ended up replacing the sensor anyway with a new oem one, as the connector part broke apart on me, so there is a new senor installed.
Checked the position of the throttle sensor and set to spec. Note: before I turn on ignition, I depress the pedal many times, thinking maybe the potentiometer in the throttle sensor has a bad idle position point (think dirty pot).- no effect
As stated above, cleaned the ISCV, and put in a different smoother working bearing. ISCV clicks when shut down engine. In looking for the ISCV to be related to the problem, I clamped shut the Air hose from ISCV to the hard line over the engine while in PIC. I would expect the idle to drop (as I cut off the main source of air to the engine) and this is what happens. Engine will just about stall while I clamp shut the ISCV hose, then when I release clamp the engine rpm's increase above idle (to be expected because the ISCV has opened trying to allow more air ), then decreases (as ISCV returns to correct position), but engine will still in be in PIC.
Timing is set to 10 BTDC while ECU in error check mode....oh and no codes have ever been thrown due to the PIC.
PIC occurs even when ECU is in diagnostic mode and,
I've checked for bad wiring harness/connectors, but don't think it is that.
I'll be checking the Vf voltage shortly to see what the TCCS is doing while in PIC and post when I have the numbers...
Rick
PIC = Poor idle condition
GIC = Good idle condition
The Problem Description: PIC at warm start up only and brief lack of power if I start driving during the PIC. This started over 2 years ago and it has basically not changed except for the frequency of occurrence, currently every time at warm start up. Has never occurred when engine is cold and never while I'm driving/stopped at idle. I've driven from cold start-up all day long and the PIC will not happen until engine is off for a short period of time. I've never timed it but I can guess it takes anywhere from 10-20minutes being off, then the PIC will occur upon engine start.
Additionally, it can be as much as 2-3 hours with engine off and PIC will still occur upon start up, even though the engine temp is warm but not at operating temp.
The engine has never stalled during PIC. During PIC, idle will bounce between 500 and 650 for approx 30-45 seconds, then idle quickly increases to @ 900-1000, followed by a gradual decrease in idle to the target of 650, but now in GIC. I can start driving at this point without any lack of power and not see the PIC until another shut down/warm start up.
When in PIC and parked, if I increase idle by opening throttle to... say 1000 rpm, there is still a noticeable mis-fire vibration. If I close throttle at this point the engine will remain in PIC. If I hold the engine above idle, then in about 30-45 seconds (just like when I leave the engine to idle), there will be a noticeable and sudden increase in rpm's (above the 1000 I'm holing it at without me opening the throttle more) AND the rough idling cease. Release throttle at this time, and then GIC at target 650 rpm...and good to drive.
When in PIC and parked and I give the throttle a quick sharp increase to 3000 rpm, (flooring the pedal) engine will leave PIC and enter GIC. Sometime I only need to floor the pedal once, sometimes twice, sometimes three times, but by the third flooring, engine will enter GIC...good to drive.
If I start driving while still in PIC, there is a lack of power and I feel a mis-fire. If I gradually depress the pedal before any turbo boost, car will increase in speed, but not at full power for several seconds, then, suddenly have full power. At this point, if I come to a stop engine is in GIC.
The change from PIC to GIC occurs instantly, like someone turning a switch.
If I start driving in PIC and immediately go to WOT, there is a very brief delay in engine response compared to normal, but then it kicks in and engine is at full power, come to stop, and engine is in GIC. This scenario is the quickest way to stop the PIC compared to other methods/descriptions previously stated.
Here is the history of work I've done on the engine AFTER the problem started. Note: this work was not done specifically for this problem (I have not thrown parts at this problem either), but I had always hoped that it might be resolved while doing other work...it has not.
Intake side:
removed and hot tanked plenum and upper intake runners. I did not remove the lower intake runners from the head, just cleaned them out.
Removed injectors, but did NOT service them.
Removed ISCV, cleaned it, bench tested per TSRM,
cleaned throttle and ports
installed all parts with new gaskets
knock sensor wires: the front wire was almost broken off the connector when I removed the intake, I disassembled the wire clip from the connector, re-striped the wire and soldered it to the metal connector and re-installed into the plastic connector, used shrinking tube to cover the bare wire, and a bit of ultra grey to give some support to the wire and connector together. The rear sensor wire was still well connected, but just had some cracks on the outer wire shielding, so I just added some ultra gray for support and covered the wire with shrink tubing.
Head/engine work:
installed new valve stem seals, valve cover gaskets, plug valley gasket, new plugs.
checked coolant for combustion gases on several occasions- none indicated
Exhaust:
new exhaust manifold gasket, rebuilt turbo,replaced all turbo/exhaust gaskets
Never have any smoke out the exhaust, checked plugs and look normal deposits.
Turbo: insured there are no leaks in the turbo intercooler or hoses/piping
Additionally,
AFM measured within specs (resistance).
Tried a different, newer and cleaner CPS - no effect
Ohm'd the coils packs, plug wires (plug wire are dated 2001 and probably have 40 K on them.
Performed the igniter grounding mod, O2 sensor ground mod, and replaced the ground wire from the coil pack - no effect
checked using my digi-fluke voltmeter the operation of 02 sensor = Good.
what else....have checked over and over, while the engine was apart and back together for vacuum leaks. I don't believe I have any and all of my hoses are replaced and or new. Used propane to hunt for leaks during the PIC to see if idle changes - found nothing Also used soapy water everywhere - non found
If you are going to say the fuel pressure up vsv, it is new and connected correctly. Also, I have on many occasions, jumpered the fuel pump on prior to start up in case pressure was not held - no effect, still PIC, so I don't think I have a fuel related problem. However, i have not check pressure with a gage, but I think with what I've checked and the problem does not indicate a fuel pressure issue.
changed the fuel pressure regulator - no effect.
If I remove the vacuum to the FPR while in PIC, idle increases but still mis-fires. If I pull... say the brake booster hose, idle drops, put some propane at the opening and idle increases.
EGR system functioning normally, and I give the EGR valve a tap with a hammer and stick during PIC thinking maybe its stuck open slightly. -no effect
Removed the ECU temp sensor connector when in PIC and no effect (other than getting the error code for no temp signal). Note: I ended up replacing the sensor anyway with a new oem one, as the connector part broke apart on me, so there is a new senor installed.
Checked the position of the throttle sensor and set to spec. Note: before I turn on ignition, I depress the pedal many times, thinking maybe the potentiometer in the throttle sensor has a bad idle position point (think dirty pot).- no effect
As stated above, cleaned the ISCV, and put in a different smoother working bearing. ISCV clicks when shut down engine. In looking for the ISCV to be related to the problem, I clamped shut the Air hose from ISCV to the hard line over the engine while in PIC. I would expect the idle to drop (as I cut off the main source of air to the engine) and this is what happens. Engine will just about stall while I clamp shut the ISCV hose, then when I release clamp the engine rpm's increase above idle (to be expected because the ISCV has opened trying to allow more air ), then decreases (as ISCV returns to correct position), but engine will still in be in PIC.
Timing is set to 10 BTDC while ECU in error check mode....oh and no codes have ever been thrown due to the PIC.
PIC occurs even when ECU is in diagnostic mode and,
I've checked for bad wiring harness/connectors, but don't think it is that.
I'll be checking the Vf voltage shortly to see what the TCCS is doing while in PIC and post when I have the numbers...
Rick
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. I would work from the ECU testing every voltage (start with +B/(+B1) to E1) and continuity check at the ECU wiring connectors until you stumble across something that is off of the required range. Turned out to be my ignitor, I had an extra, replaced it and it went away.