ENGINE POWER LOSS:   ( Bogging, Hesitation
, etc.)            
Page 4:   Bad Actuators.
Prerequisites  page 1 to 3 done.


Actuators are:
Fuel Injectors (all)

Vacuum Solenoid valves (EVAP, EGR(1 or 2), Dash pot)

EGR valve.
(94 to 98 Ecu commands this open cruising only) {prior to 94 , this opens off idle and never } Never idle and never W.O.T.

EVAP controls.  (Ecu commands this open cruising only)

Fuel pump activation relay.  ( only runs 3 seconds key on and full time cranking and running)

Main Power Relay (The ECU closes this relay any time the KEY is on) no exceptions.

CEL lamp , this lamp being bad will not hurt the ECU nor effect power loss , unless operator ignores it.

Ignition coil: the ECU (starting in 1991 only) creates spark by driving this coil.  If spark fails you my get DTC 41/42

ISC, if the ECU can not control the ISC the air supply may be too high and cause low RPM bogging.



The injectors must all fire.
Check there coils for 10 ohms resistance, if infinity? readings on  the coil, it is bad.  Burned open.
They all must have same coil resistance readings.
Listen to the injectors with a $5 mechancics stethoscope.  They must all click and SOUND the same.
If the injectors leak or dribble, Ignition key on , not running,  then the motor, will never run right and the O2 sensor  malfuncion due to rich misfiring (excess 02 in exhaust)
If the injector (s) is clogged the motor will lean misfire (P030x and newer and will let extra oxygen in to the Exhaust and  02 will go nuts and force motor RICH. causing Misfire on all cylinders due to rich and spark fouling condtions. ( this is not bogging this is MISFIRE)   Key point both lean and rich misfire , send illegal oxygen in to the exhaust stream.!
The ECU sees this illegal 02 and does the wrong thing, it goes rich .  Usually this causes all sparkplugs to  foul and all to misfire, compounding this issues.
The injectors must work perfectly or the EFI system will quite nuts.
Some confuse bogging with rich misfire, so I put this here only for those situtations.  SEE MORE HERE:

EGR must running at the proper regulated value and if you suspect the EGR as causing this ,just block it. and run road tests (off road , is legal).
If bogging stops , suspect a bad EGR circuit, causing it to open too far.

The Evap can flood  with raw fuel or the vacuum line fall off and leak or cracks can happen; that allow illegal air to enter the systems. ( lean at low rpm's)
Pull the EVAP vacuum hose from the plenum nipple (front of 16v plenum ) and on top of intake manifold on 8v.  then plug the hose so no air can enter this plenum nipple.
Run a road test to see if this cures the bog, if it does the EVAP system is faulty.
IF car bogs at  WOT ,the EVAP is not the reason.


Fuel pump acitivation is self explainitory , if the pump runs full time with engine running and pressure is at spec (fuel) then this is not an issues to bogging.

Dash pot ( 8v only part) only controls idle speed but if the intake manifold nipple to its VSV were to leak , it would act like the EVAP nipple leaking.

Some cars have  3 VSV vavles , any can crack at any point and leak and fail to respond to the ECUs commands !




rev 1 ,page 4




Privacy Policy