- Joined
- Oct 21, 2004
- Location
- BFE Desert east of Cali
Had a very slight misfire forever on my wagon (90 745T), but it has changed to a full blown stumble at idle now, almost stalling the motor sometimes, depending on load.
Conditions:
Engine warm, running closed loop. Worse after a 5-10 minutes of driving than just sitting in the driveway idling. Doesn't matter what gear the trans is in. Sometimes stumbles when the e-fan kicks OFF, not very often.
Idle is smooth until the ECU goes closed loop, then the misfire starts.
Backstory:
Been fighting knock enrichment issues for 8 years. About a month ago while driving to work I got a CEL for knock sensor. Cleared and it reset each time, first time it saw 2000rpm. This is on a chipped EZK with desensitized knock circuit. Installed a stock non-EGR EZK, no issues at all. Also NO issues with knock enrichment, so full boost, AFR's mid-upper 10's, pulls strong and clean. Hasn't done this in years. No other work done to the car for a few months prior.
Checked:
Grounds checked at ECU/EZK boxes, cleaned at intake.
New NGK plugs, old ones were slightly black from running rich in boost but looked good otherwise.
Wires ohm out, have around 30k on them, new Bosch cap and rotor.
Bypassed MSD6A, no change.
Power supply from RSR to injectors shows 6.3ohms including the ballast, on all 4 injectors. Injectors show 2.2ohms.
3 different AMM's, no change.
2 different O2's, no change.
ECT checked out at 3700ohms at 50*, 331ohms at 185* operating temp, checked at EZK and ECU.
2 different RPM sensors, no change.
Noticed the lights flicker at idle, despite steady 14.4v. Checked AC at the battery, .06-.22vac, need to check at the alternator. Fluke spec's .5vac max when checked at the alternator. Alternator is a 170A Mechman.
Haven't checked compression in a year, last check was 175 across the board.
Haven't checked valve clearances for a year, last check was .016-.018" warm. Vacuum is smooth and stable at around 18" in neutral with a warm engine.
Current EZK is a TLAO chipped 147 gold box, ECU is TLAO chipped 967.
AMM is 012", running stock airbox.
Injectors are #65 Delphi running 4-bar rail pressure with a Walbro 255 in-tank, straight 91* pump gas from a station I've been using for years, no issues on the wife's car.
I would consider fuel supply except the issue starts when the ECU goes CL. Same for secondary ignition.
Plan (when the rain stops) is to check ripple voltage at alternator, see if that's an issue given the lights flickering. Also need to check fuel pressure. Probably try swapping power stages as well as RSR.
Open to any other thoughts.
Conditions:
Engine warm, running closed loop. Worse after a 5-10 minutes of driving than just sitting in the driveway idling. Doesn't matter what gear the trans is in. Sometimes stumbles when the e-fan kicks OFF, not very often.
Idle is smooth until the ECU goes closed loop, then the misfire starts.
Backstory:
Been fighting knock enrichment issues for 8 years. About a month ago while driving to work I got a CEL for knock sensor. Cleared and it reset each time, first time it saw 2000rpm. This is on a chipped EZK with desensitized knock circuit. Installed a stock non-EGR EZK, no issues at all. Also NO issues with knock enrichment, so full boost, AFR's mid-upper 10's, pulls strong and clean. Hasn't done this in years. No other work done to the car for a few months prior.
Checked:
Grounds checked at ECU/EZK boxes, cleaned at intake.
New NGK plugs, old ones were slightly black from running rich in boost but looked good otherwise.
Wires ohm out, have around 30k on them, new Bosch cap and rotor.
Bypassed MSD6A, no change.
Power supply from RSR to injectors shows 6.3ohms including the ballast, on all 4 injectors. Injectors show 2.2ohms.
3 different AMM's, no change.
2 different O2's, no change.
ECT checked out at 3700ohms at 50*, 331ohms at 185* operating temp, checked at EZK and ECU.
2 different RPM sensors, no change.
Noticed the lights flicker at idle, despite steady 14.4v. Checked AC at the battery, .06-.22vac, need to check at the alternator. Fluke spec's .5vac max when checked at the alternator. Alternator is a 170A Mechman.
Haven't checked compression in a year, last check was 175 across the board.
Haven't checked valve clearances for a year, last check was .016-.018" warm. Vacuum is smooth and stable at around 18" in neutral with a warm engine.
Current EZK is a TLAO chipped 147 gold box, ECU is TLAO chipped 967.
AMM is 012", running stock airbox.
Injectors are #65 Delphi running 4-bar rail pressure with a Walbro 255 in-tank, straight 91* pump gas from a station I've been using for years, no issues on the wife's car.
I would consider fuel supply except the issue starts when the ECU goes CL. Same for secondary ignition.
Plan (when the rain stops) is to check ripple voltage at alternator, see if that's an issue given the lights flickering. Also need to check fuel pressure. Probably try swapping power stages as well as RSR.
Open to any other thoughts.