Here We Go: Idle Problem, Searched, Tried Fixes, Details Inside
11-29-2005, 08:46 PM
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Here We Go: Idle Problem, Searched, Tried Fixes, Details Inside
Setup:
Engine:
B20z (2001)
sk2 manifold
hondata IM gasket
30k on engine
Car:
96 Civic DX w/ orig. engine harness (did the appropriate wiring for an OBD2 - OBD2 swap 2 yrs ago)
Throttle body: Original b20z TB minus the original FITV (installed block off plate), no coolant running to IACV.
ECU: used to run 98 LS (p75). Switched over to 95 LS (p75) w/ obd2-obd1 harness)
Problem:
With obd2 ECU:NO problem.
With OBD1 ECU:Cold starts, idle goes to 2k (fine), 10 seconds later, bounces 1200-2000 rapidly until warm. When warm, idles fine, engine strong whether warm or cold.
Attempted fixes:
Searched for vacuum leaks, none found.
Set base idle per Helms. Idle is 760rpm.
Adjusted TPS to .47V/4.85V.
Cleaned IACV (although wasn't dirty at all really).
Disconnected ALT-C line for charging issue. Worked great, didn't do anything for this problem.
Checked FITV port in TB, doesn't feel like there is a vacuum leak.
EVAP hooked and working
Alternator, and Distributor are OBD2, if it helps.
So what is the technical explanation, if the ECU move from OBD2 to OBD1, is causing this problem? Could the OBD1 ECU be looking for a FITV? Trying to compensate for airflow wth idle correction? Am I on the right track? LMK
Thanks...
Engine:
B20z (2001)
sk2 manifold
hondata IM gasket
30k on engine
Car:
96 Civic DX w/ orig. engine harness (did the appropriate wiring for an OBD2 - OBD2 swap 2 yrs ago)
Throttle body: Original b20z TB minus the original FITV (installed block off plate), no coolant running to IACV.
ECU: used to run 98 LS (p75). Switched over to 95 LS (p75) w/ obd2-obd1 harness)
Problem:
With obd2 ECU:NO problem.
With OBD1 ECU:Cold starts, idle goes to 2k (fine), 10 seconds later, bounces 1200-2000 rapidly until warm. When warm, idles fine, engine strong whether warm or cold.
Attempted fixes:
Searched for vacuum leaks, none found.
Set base idle per Helms. Idle is 760rpm.
Adjusted TPS to .47V/4.85V.
Cleaned IACV (although wasn't dirty at all really).
Disconnected ALT-C line for charging issue. Worked great, didn't do anything for this problem.
Checked FITV port in TB, doesn't feel like there is a vacuum leak.
EVAP hooked and working
Alternator, and Distributor are OBD2, if it helps.
So what is the technical explanation, if the ECU move from OBD2 to OBD1, is causing this problem? Could the OBD1 ECU be looking for a FITV? Trying to compensate for airflow wth idle correction? Am I on the right track? LMK
Thanks...
12-06-2005, 06:14 PM
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Re: Here We Go: Idle Problem, Searched, Tried Fixes, Details Inside (b20guy)
The OBD I evap. system is totally different.
The OBD I ECU is purging from a cold start until the coolant temp is 163F because the OBD II solenoid is normally closed, while the OBD I is normally open. The OBD I purge is connected to a ported vacuum source at the TB, while the OBD II is connected directly to the intake manifold and duty cycle controlled by the computer.
If you disconnect the evap. purge valve, this problem will go away. However, the canister will never purge, and it will eventually get saturated. You can just unhook it and let the vapors vent to atmoshere.
If you want the evap. system to work without chipping the ECU and doing some tricks in the software, then you have to change a few parts (TB, evap. solenoid, canister, vacuum lines).
The OBD I ECU is purging from a cold start until the coolant temp is 163F because the OBD II solenoid is normally closed, while the OBD I is normally open. The OBD I purge is connected to a ported vacuum source at the TB, while the OBD II is connected directly to the intake manifold and duty cycle controlled by the computer.
If you disconnect the evap. purge valve, this problem will go away. However, the canister will never purge, and it will eventually get saturated. You can just unhook it and let the vapors vent to atmoshere.
If you want the evap. system to work without chipping the ECU and doing some tricks in the software, then you have to change a few parts (TB, evap. solenoid, canister, vacuum lines).
12-07-2005, 09:12 AM
#5
Honda-Tech Member
Re: Here We Go: Idle Problem, Searched, Tried Fixes, Details Inside (b20guy)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b20guy »</TD></TR><TR><TD CLASS="quote">Set base idle per Helms. Idle is 760rpm.</TD></TR></TABLE>
Just checking, but are you sure this is the correct idle speed to adjust to? Usually you have to unhook the IACV, which allows the idle to drop down to the curb idle speed (usually 450-550rpm). So if you've set the curb idle to 760rpm and then plug the IACV back in, it won't have any room to do its job.
What kelly said is also very feasible.
Just checking, but are you sure this is the correct idle speed to adjust to? Usually you have to unhook the IACV, which allows the idle to drop down to the curb idle speed (usually 450-550rpm). So if you've set the curb idle to 760rpm and then plug the IACV back in, it won't have any room to do its job.
What kelly said is also very feasible.
12-11-2005, 06:55 PM
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Re: Here We Go: Idle Problem, Searched, Tried Fixes, Details Inside (EE_Chris)
No I st my base idle to 450-500, and ended up with a 750ish idle.
I tried what kelly said about the evap. Unhooked the evap connector and that did not fix the problem. Any other ideas welcome.
I tried what kelly said about the evap. Unhooked the evap connector and that did not fix the problem. Any other ideas welcome.
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