Possible ECU Problem?

[RidgwayCO]

Ok, This may be a long shot, but here goes.....Shortly after purchasing my 1994 FZJ80 I made the rookie mistake of trying to remove what I thought was the MAF from the VAF body. I was not aware of the damage I caused and attempted to start the truck numerus times after doing this. Since making that critical mistake I have been chasing a rough idle. I've replaced the VAF and a boat load of other parts. Is it possible the damaged VAF somehow damaged the ECU?
I'm down to looking at a valve adjustment and injectors otherwise. A rebuilt ECU is cheaper than either of those. Below is a list of items I've replaced or work performed chasing this rough idle. OEM parts were used when available.

SPARK PLUGS (Gap Checked)

IGNITION COIL

SPARK PLUG WIRES

DISTRIBUTOR CAP & SEAL

DISTRIBUTOR ROTOR

FUEL PRESSURE REGULATOR / O-RING

IDLE AIR CONTROL VALVE & O-RING

VAF REPLACED WITH REBUILT

INTAKE AIR HOSE

PCV VALVE

REPLACEMENT OF VACUUM HOSES

OXYGEN SENSORS REPLACED (2)

FUEL FILTER

OIL FILLER CAP

TROTTLE POSITION SENSOR

TIMING CHECKED (4 DEGREES) SMOKE TESTED VACUUM LINES AT INTAKE EGR VALVE CLEANED-TESTED IDLE AIR CONTROL VALVE PORT CLEANED EGR MANIFOLD PORT CLEANED

TIMING CHECKED (4 DEGREES)

SMOKE TESTED VACUUM LINES AT INTAKE

EGR VALVE CLEANED-TESTED

IDLE CONTROL VALVE PORT CLEANED

EGR MANIFOLD PORT CLEANED ENGINE COMPRESSION TESTED

 

[thatcabledude]

What part number is on the ECU?
There are 3 different part numbers for OBD1 FZJ80s. One for CA, 1 that is known to go bad, and 1 that is preferred. I think the one that goes bad might be specific to 1993 year model though.

 

[RidgwayCO]

What part number is on the ECU?
There are 3 different part numbers for OBD1 FZJ80s. One for CA, 1 that is known to go bad, and 1 that is preferred. I think the one that goes bad might be specific to 1993 year model though.

The ECU # 89661-60221 (211000-1081)

 

[BILT4ME]

What did you replace the VAF with? Another of like kind and known good?

It could still be poor signal / operation of the current VAF.

What symptoms are you still experiencing?

 

[RidgwayCO]

What did you replace the VAF with? Another of like kind and known good?

It could still be poor signal / operation of the current VAF.

What symptoms are you still experiencing?

Actually I have tried three "rebuilt" VAF's including my original (all from the same rebuilder). All are Toyota 22250-66010 units (Denso)

When left idling I get an OBD1 code 25 (running lean) that goes away once I am out driving at 50mph or so for a few minutes. When idling the engine has a discernable "miss" or stutter. When the miss or stutter occurs the engine RPM's drop just enough to be noticeable on the OEM tach but not a lot. At the tailpipe the miss almost sound like a "puff" of exhaust (if that makes any sense).

 

[BILT4ME]

Actually I have tried three "rebuilt" VAF's including my original (all from the same rebuilder). All are Toyota 22250-66010 units (Denso)

When left idling I get an OBD1 code 25 (running lean) that goes away once I am out driving at 50mph or so for a few minutes. When idling the engine has a discernable "miss" or stutter. When the miss or stutter occurs the engine RPM's drop just enough to be noticeable on the OEM tach but not a lot. At the tailpipe the miss almost sound like a "puff" of exhaust (if that makes any sense).

Is it possible you've got a random misfire on your injectors, possibly from a melted or poorly repaired wiring harness near the EGR?

 

[RidgwayCO]

Is it possible you've got a random misfire on your injectors, possibly from a melted or poorly repaired wiring harness near the EGR?

I suppose anything is possible. I am going to try and inspect the wiring harness near the EGR and see if anything is visible there. Then I suppose if I'm going to dig into checking the injectors it may be worth going ahead and replacing them while I have intake off as well as all of the goodies under the intake.

 

[SmokingRocks]

I don't think your ecu is bad. It sounds like a wiring issue.

 

[ppc]

What brand of O2 sensors did you purchase and how many miles ago? How long ago were they replaced?

 

[RidgwayCO]

What brand of O2 sensors did you purchase and how many miles ago? How long ago were they replaced?

I installed Denso units about 300 miles ago. These were installed in an attempt to correct the rough idle and intermittent code 25.
NTK were not available at the time.

 

[ppc]

My first suggestion would be to check out the wiring and make sure all the connectors are corrosion free. You may want to relocate the O2 sensors into the exhaust manifold after removing the PAIR system unless you live in an area that does extensive smog inspections. What is the condition of the exhaust as a leaking system or an aftermarket system may not have the O2 bungs positioned properly.? Other than that I would look for the NTK's if you are still getting codes generated.

 

[Cruiser Vic]

Chase down the lean code first. Monitor O2 sensors while adding propane to see if you could get a rich lean sweep. While idling remove oil cap on valve cover see if you can notice a difference in idle. Do you happen to have the Denso part numbers you installed. 93_94 have a different sensor than a 95 through 97.

 

[RidgwayCO]

Chase down the lean code first. Monitor O2 sensors while adding propane to see if you could get a rich lean sweep. While idling remove oil cap on valve cover see if you can notice a difference in idle. Do you happen to have the Denso part numbers you installed. 93_94 have a different sensor than a 95 through 97.

Hello, Yes the Denso O2 sensors were both 234-4520 units.

 

[RidgwayCO]

Hello, Yes the Denso O2 sensors were both 234-4520 units.

If I remove the oil cap while idling the engine almost dies, it bogs down and sputters dramatically.

 

[jonheld]

If I remove the oil cap while idling the engine almost dies, it bogs down and sputters dramatically.

That's supposed to happen. 100% normal.

 

[TrickyT]

The ECU # 89661-60221 (211000-1081)

That ECU is an “updated” (first used in May 1993 production vehicles) OBD-I with separate TCM and ECM units. It is known to be extremely reliable. Your problem is 99.99% something other than a bad ECU.

 

[Pericles]

Just to confirm: the truck was not idling rough prior to your disassembling the VAF, correct?

 

[RidgwayCO]

Just to confirm: the truck was not idling rough prior to your disassembling the VAF, correct?

That is correct.