Another funky idle thread- with a twist (1 Viewer)

[terryjmatthew]

I'll start by saying I'm no noob when it comes to Toyota trucks and Land Cruisers, but this one has me stumped.
I bought a 94 FZJ two weeks ago tomorrow and when I went to pick it up it didn't want to start. I looked around and found that the intake hose was loose, reconnected it and it cranked and ran. After getting it home I took it for a test drive and noticed that it really didn't want to accelerate like I thought it should and it had a noticeable skip. Also found it to be pouring oil from the rear of the valve cover gasket so I decided to do a full tuneup on it while I was replacing the valve cover gasket.
So I replaced the plugs, wires, cap, rotor, valve cover gasket, cleaned the throttle body and it didn't "skip" anymore, but still didn't want to accelerate. It felt to me as if the TPS was malfunctioning because it would run out great at WOT, but didn't really want to accelerate anywhere between say 1/4 to 3/4 throttle.
So last Saturday I replaced the TPS with a known good used one and replaced the coil wire which I forgot to do when I was replacing the others. The truck ran like a top for a few minutes and then I noticed that when stopped the idle would start dropping slowly until the engine starting chugging and the RPMS would bounce until the engine finally stalled.

Fast forward to today. I have been searching possible causes here and have replaced parts until I am blue in the face and still have the same problems. Since the tuneup work I have replaced the TPS, AFM, IAC, ECM, fuel filter, checked and cleaned the engine grounds, replaced the battery terminals, and all the vacuum lines w/ the exception of the ones under the intake plenum. Jumping the diag terminals nets a constant flashing CEL which I understand to mean that there are no codes.

I am officially at wits end. If I can't figure it out in the next few days, I am going to drop it and my AMEX off at the Toyota dealer.

 

[little_joe]

Intake hose cracked? That's where I'd put my coin as this is a common problem on 15+ yr old trucks, esp if you are not careful removing/installing the intake tube.

 

[terryjmatthew]

Intake boot has been replaced as well.

Intake hose cracked? That's where I'd put my coin as this is a common problem on 15+ yr old trucks, esp if you are not careful removing/installing the intake tube.

 

[terryjmatthew]

Link to a video of it acting up.
http://www.facebook.com/v/10150251486272109

 

[kidglove13]

What about the fuel pump and the filter sock in the tank?
Sounds like a possible fuel problem.

 

[terryjmatthew]

What about the fuel pump and the filter sock in the tank?
Sounds like a possible fuel problem.

Just finished replacing them. No difference.

 

[kidglove13]

Sorry

Have your tried to check your fuel pressure?
MAybe partially clogged injector/injectors?

Have you tried dumping a bunch fuel injector cleaner in there and running it

 

[terryjmatthew]

Fuel injector cleaner is in the tank.
Replaced the FPR for s***s and giggles a few minutes ago. No change.

**edit**
I'm thinking the problem has to be electrical because it will idle fine sometimes and other times will only idle for a few seconds before it tries to cut out.
I will be pulling the throttle body(again) tonight to look at the EGR ports and clean them if they are stopped up.

 

[kidglove13]

How is your harness that runs by the EGR pipe?
Sometimes it looks ok but from the heat of the EGR the wires can get messed up on the inside of the wrap but look ok from the outside

 

[terryjmatthew]

Egr port in the intake was stopped up completely. Cleaned it out, but still no change.

 

[kidglove13]

Unwrap and check the harness by the EGR pipe

 

[terryjmatthew]

Haven't had a chance to open up the harness yet, but I was able to isolate the problem to the IAT sensor(which is part of the AFM) circuit. I cut the wire for the IAT for now and it idles fine and seems to have helped my lack of power as well.

Now I just need to track down a short somewhere or wire in a resistor to trick the ECM.

 

[terryjmatthew]

Following back up. Yesterday I took the time to unwrap the harness back around the EGR valve. Found one wire with a small bare spot in it. Taped that up and put it all back together. Managed to break a couple of the plastic connectors on the fuel injectors while I was in there monkeying around...

Still No change.

 

[lndcruz]

IIRC some people have found wires going into the interior to the ecu on the passengers side to be chafed by the body.

Not sure if its really a possibility, just throwing out ideas.

 

[Toyaddicted]

Do you have a cel on? It sounds like you may be time ahead to take it to a reputable shop and have them trouble shoot it. They have manuals and do this every day and that way you wont have to replace anymore parts that aren't the problem.

 

[Ebag333]

Here's Mr T's suggestions (from the FSM):

Low engine idle speed (Poor idling)
1. A/C signal circuit
2. Fuel pump control circuit

Rough idling (Poor idling)
1. Compression
2. Fuel pump control circuit

Hunting (Poor idling)
1. ECM power source circuit
2. Fuel pump control circuit

Hesitation/Poor acceleration (Poor driveability)
1. Fuel pump control circuit
2. A/T faulty

Surging (Poor driveability)
1. Fuel pump control circuit

Soon after starting (Engine stall)
1. Fuel pump control circuit

During A/C operation (Engine stall)
1. A/C signal circuit
2. Engine control module (ECM)

Have you tried disconnecting the A/C signal circuit (plug right in front of the battery)?

 

[terryjmatthew]

Worked on it a little more this afternoon. Set the timing at 3 degrees BTDC per the FSM, played with the TPS some more, replaced the PCV valve.
Still no change...

While I was looking around I noticed that the main relay was super hot so I decided to replace it with a known good one I had laying around. I also unplugged the o2 sensor while the truck was off just to see what it would do.

Cranked the truck up and it idles perfect!

Drove it home tonight with the 02 unplugged and it runs great. I'm gonna drive it another day or so and see what happens.

 

[HypocriticalHippie]

I was having idle issues, myself, after swapping in some new O2 sensors. When I unplugged them, I found that all of the trucks bad manners disappeared. It idled perfect, had good power, and to my surprise, got over 12 MPG around town. I re-installed the old 02 sensors as a temporary measure, thinking my MPGs might improve. The truck runs worse, and it doesn't throw codes.

I am half tempted to disconnect them and call it good...

Scott

 

[terryjmatthew]

Third day with both of the front o2's disconnected and it's still running like a top. Fuel mileage seems to have improved drastically and the weird pedal sensation/lack of power is all but gone.

Still has a slight loss of power when the engine is cold, but I can live with that for now.

 

[BlueCruiser84]

Does it throw a CEL with them unplugged? I have been dealing with a similar issue, but I am thinking mine might be fuel injector related. You didn't by chance feel it "shuddering" when you accelerated did you? I have fixed so many broken parts and hacked repairs on this thing, but it is still running a bit rough.

My wiring harness between the computer and the injectors is in rough shape. There are lots of places for wires to get pinched/burned along the way. I would take a closer look at that. You can test the wires at the ECM with a voltmeter and that will tell you if one is shorting out somewhere.

Hopefully, for you, it is just bad o2 sensors.