Random misfire, bad idle, terrible acceleration

[msrebecky]

Hello. I have a 1994 Land Cruiser that I recently bought. Close to 300k on 5he odometer and has been running fine until last week. Started to idle rough and accelerate poorly. Been going through the different threads to pinpoint the issue. What really has me stumped is while changing the spark plugs, i noticed a connector to the driver side of the back plug (under the egr modulator I believe) was unplugged and looped back into its self on the female side. Also the EGR modulator tubes connecting to the throttle body were disconnected and looped back as well. Both sides. The throttle body side and modulator side. Is there any particular reason for this? Could it be my problem for the idle and acceleration? Don't want to plug them back in and cause a bigger problem. I'll try to get pictures after work.
Thanks.

 

[Rusty Marlin]

The EGR vacuum system has been disabled, probably somebody chasing a P0401 code and chose to "fix" it by taking away the problem while preserving the stock look. What does the wiring for the EGR gas temp censor look like? Stock, or subtly modified? They might have slipped a resistor in the circuit to provide the proper feedback to the OBDII ECU.

I "fixed" mine by deleting the entire EGR system.

 

[msrebecky]

Everything looks stock. Have not seen a code since I changed the o2 sensors, spark plugs and "fixed" the MAF/VAF. Figured I should clean the sensor and removed the wrong part. You know the deal. Also, the problem gets worse once the engine heats up. Runs well at first and then starts missing. Randomly at first and progressively more.

 

[ZackR]

Sounds like the previous owner disabled the EGR, I did the same on mine. Have you checked fuel injector wiring harness near the EGR pipe? Search and there are a ton of threads about those wires being shorted and causing misfire issues that don't light up the CEL. I had this issue as well and it wasn't apparent externally, I had to pull the loom off and the heat foil to find it.

It was a night and day difference after the wires were repaired. No more hesitation or warm misfires.

 

[Rifleman]

They might have slipped a resistor in the circuit to provide the proper feedback to the OBDII ECU

Just as an FYI his truck is a 1994 so it's not OBD2, it's OBD1, the change over from OBD1, to OBD2 happened around the beginning of the 1995 model year on Land Cruisers.

I've read that during the change over from OBD1, to OBD2, that some early 1995's were still OBD1. Toyota did the change over to OBD2 early, even though being fully OBD2 compliant wasn't required by the feds until the start of the 1996 model year.

Because of this It was not until a little into the start of the 1995 model year before all the new Land Cruisers were fully OBD2 compliant.

Question for Msrebecky, have you checked to see if you have any stored trouble codes since you did those repairs?

 

[msrebecky]

Ok. The injector wiring harness is definitely touching the EGR pipe. There is not much moving room though. Also, any idea what this ground wire may go to? It was just hanging between the motor and the fire .

 

[msrebecky]

Question for Msrebecky, have you checked to see if you have any stored trouble codes since you did those repairs?

No. I have been waiting for the CEL to come back on. Driven maybe 25 miles with no light yet. Not burned out though. Comes on when key is turned to "ON".

 

[Rifleman]

If you've driven 25 miles, that should have been enough of a drive cycle to set any new codes if there was a problem.

 

[ZackR]

Here's where that ground wire goes. Let us know what you find in the wiring harness near the EGR.

 

[Rusty Marlin]

Just as an FYI his truck is a 1994 so it's not OBD2, it's OBD1, the change over from OBD1, to OBD2 happened around the beginning of the 1995 model year on Land Cruisers.

Thank you for correcting that, I should have known better.

 

[msrebecky]

It was a night and day difference after the wires were repaired. No more hesitation or warm misfires.

Were you able to repair them yourself?

 

[ZackR]

Were you able to repair them yourself?

Yes, in my case the wires were intact and just needed some electrical tape to cover up where the insulation rubbed off in a few places. I then re wrapped everything, replaced the loom, and zip tied the harness away from the EGR so it wouldn't touch (even though my EGR is disabled).

 

[msrebecky]

Can spark plug wires be a possibility when the engine starts to warm up? Seems like it would be a problem right off the bat.

 

[BILT4ME]

Can spark plug wires be a possibility when the engine starts to warm up? Seems like it would be a problem right off the bat.

They can be, particularly if they are a crappy off-brand. The Toyota ones are known to love you long time.

Spark plug wires do usually show their issues when hot, not cold. But I don't know as that i the issue here.

 

[fz1boxer]

heater hose leaking bit at the valve may want to replace soon.

 

[msrebecky]

Yes, in my case the wires were intact and just needed some electrical tape to cover up where the insulation rubbed off in a few places. I then re wrapped everything, replaced the loom, and zip tied the harness away from the EGR so it wouldn't touch (even though my EGR is disabled).

I cant seem to find the bracket that secures the harness away from the EGR pipe. Probly gonna make one out of some scrap from work.

They can be, particularly if they are a crappy off-brand. The Toyota ones are known to love you long time.

Spark plug wires do usually show their issues when hot, not cold. But I don't know as that i the issue here.

I think I'm gonna go ahead and replace the wires and try to eliminate that as a problem. Also gonna crack open the distributor again and try to dry up any moisture that may be in there. Friend seems to think that may be an issue. The distributor o ring is leaking but not bad so I may try and change that out. Do you have to remove the valve cover to align the gears or can it be done without.

heater hose leaking bit at the valve may want to replace soon.

I'll get on it as soon as I take care of the current issue. Been meaning to do so.

 

[ZackR]

The plastic bracket for the wiring harness is often broken or gone, I used zip ties to secure the harness away from the EGR pipe.

The distributor O ring is easy enough to replace but will require you to reset the ignition timing. Not a difficult procedure but the key thing is to follow the FSM and use a jumper (paperclip) between TE1 and E1 in the diagnostic port before doing so. Stock is 3° BTDC however many folks including myself bump this up a bit to around 8-9°.

 

[msrebecky]

Any idea where I can get a whole digital copy of the FSM.

 

[msrebecky]

So I have a feeling that this much oil in the distributor is a problem.

 

[BILT4ME]

I would install a new Toyota cap, rotor, and plug wires, based on what I see on the arced points in the distributor.

As far as the oil amount goes, it's not horrible, as in, not enough to cause misfiring YET.

But, most of the Distributor O-Ring is on the EXTERIOR of the distributor itself. Your oil issue is internal, which means replacing the distributor eventually. Not a rebuildable issue....yet.

As far as doing the Dizzy O-Ring without timing it? Absolutely possible. It's how I've done a couple of them, but you MUST be cognisan of what you're doing and you do NOT have to remove the valve cover to do it.

Remove battery and battery box
Remove cap only
Clean the area around the distributor base with wire brush / solvents, etc so no crud falls in when you remove it.
Using a sharp object (large pocket knife, scratch awl, nail), mark around the outside of the slotted portion of the distribuot into the head. The mark needs to be on the HEAD.
Make a SINGLE scratch mark perpendicular to the slot on the outside of the distrib against the head. This will be the prefect line that MUST line up after you place the distrib back in.
Take a picture of the exact location of the rotor so you can get it in the exact same location when you put it back in. It is important that you get the picture from as straight on as possible.
Once all marks are made, you can loosen the locking nut on the distrib and gently (while rotating) the distrib, pull it out.

DO NOT ROTATE THE ENGINE WITH THE DISTRIBUTOR OUT OF THE ENGINE.

Cut off / break off the old O-Ring, lube the new one and install it on the distrib.
Clean the hole in the head with a solvent soaked rag.
Oil the hole and the shaft of the distrib WELL.
Insert the distrib.
NOTE: the rotor will turn when you pull the distrib. Note which direction it turns, as it will turn opposite when you reinstall.
Align the rotor in the "removed" position in relationship to the distrib body and aling the body near the position it came out. and reinsert the distrib..
The FINAL alignment of the rotor, with the body in prefect alignment with the scratch mark means your timing will be exactly as it was when removed.

If you screw this up, you can fix it, but you have to take a whole lot of steps to get there.