1994 with bad stumbling idle *** SOLVED = NEW O2 SENSORS... so far (5 Viewers)

[Driley]

Spent the last couple of days reading threads about the issue and most never provided an outcome. Here is my situation and I promise to provide a definitive fix if possible.

-1994 LC
-280,000 miles
-Wires, cap, rotor changed at 194,000 (way too long but impressive what OEM can do)
-Spark plugs changed at 260,000
-Intake hose replaced 9 months ago
-CEL 71 for the last 8 years (changed modulator twice and then put a business card in front of light)
-CEL 26 which just happened 3 days ago

Was running great 3 days ago (600 rpm at idle and smooth) but then it started stumbling at idle (in park, neutral and drive). Idle dropping to below 400 rpm, dancing around 200 rpm. I can put into neutral and rev about 1,000 rpm and the engine smooths out, mostly (still feel a hiccup/miss).

Took it to my son's shop (he works for a mechanic) last night and replaced inboard O2 sensor (NTK) but could not get the outboard sensor nuts off (rounded and corroded). The stumble has gotten worst to the point of shaking the vehicle horribly at idle. His boss is going to start the diagnosis this morning and it appears there a tons of suspects for this type of issue.

Stupid question...
Has anyone had a 1993/1994 LC (ODB1) that has had a really bad idle issue just start out of the blue that found a definitive reason?

The past threads have listed these items as potential causes and we will work through them all until the culprit is found:

-Recent battery/EFI fuse disconnection
-Cracked intake hose
-Throttle body needs cleaning
-Vacuum leaks
-Spark plugs, wires, cap, rotor and coil needs replacing
-Fusible links having issues
-O2 sensors spent
-Catalytic converter clogged
-Fuel filter clogged
-Fuel pump not working
-Injectors bad
-Wiring harnesses at fire wall and ECU issues
-EGR system issues

Have I forgotten or missed anything? Once we have a verdict I will advise for future victims.

With the amount of years and miles on this amazing vehicle, whenever my Land Cruiser has a problem I gratefully thank the spent/broken part and replace with OEM if at all possible. I just want to find the son of bitch so I can thank it and move on!

Any help greatly appreciated.

Cheers!

 

[GSTMike]

Essentially that code (26 rich condition) would infer the ecu has exceeded the maximum amount of fuel it's set to remove to maintain stoich. I would start with the simple stuff like hoses and lines as they age out and crack and then go from there. A very simple and effective way would be to smoke test the system however a simple PVC pipe end, shrader valve, air compressor and soapy water would also work and is handy to have around anyway

 

[Driley]

Essentially that code (26 rich condition) would infer the ecu has exceeded the maximum amount of fuel it's set to remove to maintain stoich. I would start with the simple stuff like hoses and lines as they age out and crack and then go from there. A very simple and effective way would be to smoke test the system however a simple PVC pipe end, shrader valve, air compressor and soapy water would also work and is handy to have around anyway

Thanks for the info! We have inspected all hoses but I will recommend a smoke test if son can't find anything.

Thanks again!

 

[GSTMike]

Here's something as well, I have a 94 with 228k I developed a 25 and 26 code however the 26 was first. Given how poor the mechanical condition of my truck was from the PO I went through and smoke tested it and found a couple of small leaks, I changed the PCV and a couple of near related hoses none of which made a difference (during this time the truck still actually ran fine just the codes would come and go mainly during short trip city stuff and never on long highway runs)

I looked at the 02 sensor which looked to still be the original ones so replaced those as well and after which I would no longer see the 26 code but would get the 25 almost daily during my short 3.3 mile commute to work, again no driveability concerns. I started to think along the lines that my AFM was perhaps suspect so started looking for a good one to purchase. I also changed the fuel pump and filter at the same time as I knew they'd never been done and given my code was for lean both of those made sense to me as an attempt in the right direction.

I got a wild hair up my ass one Friday after work and took a look at the O2 sensor wiring and found the one going over the transmission to the drivers side on the harness end had been butchered (I'm assuming by the PO or his mechanic Stevie Wonder) I took all their twisted together and electrical taped mess apart and carefully soldered the wires and heat shrunk then spiral wrapped everything. Thus far I'm a few tanks of gas in and no codes.

Probably not related but figured worth mentioning

 

[Red Merle]

Essentially that code (26 rich condition) would infer the ecu has exceeded the maximum amount of fuel it's set to remove to maintain stoich. I would start with the simple stuff like hoses and lines as they age out and crack and then go from there. A very simple and effective way would be to smoke test the system however a simple PVC pipe end, shrader valve, air compressor and soapy water would also work and is handy to have around anyway

I have a similar issue that just started a few weeks ago. I replaced the ECT sensor and cleaned up the connections for my O2 sensors. I will look again, but the full exhaust and O2 sensors have less than 15K miles on them since a full replacement.

Can you explain the pipe end valve tool you are describing more? I don't get it, but it sounds like it might be helpful to track down the issue I am having too.

 

[GSTMike]

I have a similar issue that just started a few weeks ago. I replaced the ECT sensor and cleaned up the connections for my O2 sensors. I will look again, but the full exhaust and O2 sensors have less than 15K miles on them since a full replacement.

Can you explain the pipe end valve tool you are describing more? I don't get it, but it sounds like it might be helpful to track down the issue I am having too.

Essentially if the hose leading to your throttle body is say 3" if you get a PVC end cap in 3" and install a shrader valve in it (tire valve) you can pump compressed air into the system and use soapy water to look for leaks (you'll see foamy bubbles) it's basically a poormans smoke tester.

Something else I didn't mention because it was something I addressed for no reason the first week I got my truck is to take a look at the wiring harness from the firewall that sits on the EGR pipe, it's known for the wiring inside to get cooked and cause any magnitude of issues. I relocated mine about an inch away after inspecting it and wrapping it with thermal wrap.

 

[Red Merle]

Ah, I get it now. I can do that, no sweat.

My wire harness should be fine. I deleted the EGR and wrapped the area in carbon tape when I did my HG job. I inspected the harness fairly thoroughly when I did that and wiggling the wires doesn't seem to change the idle issue.

It's also fairly sporadic and it doesn't throw a code most of the time. The main thing I notice other than the idle stumbling sometimes is a consistent "doggy" feeling when I am accelerating. It feels like the motor is running poorly and is lagging unless I give it more throttle than normal and then it will take right off. It's weird and none of my efforts have solved it yet.

 

[GSTMike]

Have you by chance taken a look at your throttle cable and kickdown? It might also be worth inspecting the harness side of your O2 sensors, like I said the PO on mine had done some really poor work on the side that goes over the top of the trans and I can only assume the work he did was because at some point 2-3 of the wires started to frey or wear on something.

 

[Red Merle]

My throttle cable is new. Is it possible for one to stretch? It was running like a dream for 15K miles until this.

I will take another look at the O2 sensors tomorrow. I did initially have the issue crop up after washing the truck so I thought I got water into something, but I have cleaned and blown out all the usual suspects but I think I did miss one of the O2 sensors, now that I think about it.

 

[Driley]

So last night my son and I were only able to get the inboard O2 sensor off as the outboard sensor nuts were rounded off (a sign the O2 sensors might have been changed before I got it in 2005 with 180,000 miles).

This morning his boss (the scoutmaster for the Boy Scout troop we are in) started with the basics. Did a compression test (all good there) and changed out the spark plugs. it still had the bad idle so he got under and was able to get the outboard O2 sensor off. Said that the wiring looked a little suspect as did the condition of the sensor.

After getting the second sensor on the stumbling idle went away. Spent the last hour driving around, stopping and starting and all appears good.

Paid him not nearly what he should have charged me and I am hopeful that is the cure. If not, I will be back on this thread again.

Cheers and thanks for the advice and info!

 

[Driley]

Also, he said that the connector for the outboard O2 sensor had green corrosion in it (have had heavy rains lately). Wanted to mention that since Red Merle posted about car wash...

 

[GSTMike]

A word to the wise with these older obd1 rigs (95+ guys are lucky here) get one of these TOYOCOM and a android phone or device, for me it gave me a massive jump start in where I was heading. For @Driley issue he'd likely be looking at one of the O2 sensors showing pegged rich at 20 and would have had an idea to start there!

Unfortunately the guy that makes them is out of stock but if you email him he'll keep you in the loop when he's building the next batch and he's very responsive on his Facebook group as well for tips and advice

 

[Driley]

Thanks for the info on the reader. I will track that down as the LC will remain in the family (my son gets it when I am done = dead).

 

[Driley]

The moral to this story is I have been putting off a ton of PM. The damn vehicle just keeps starting and taking me where I want to go... the proverbial "squeaky wheel" it has never been.

I plan to change that this year as most of the PM I have done is going on 12 years now.

As cruiserdan so eloquently put it... "That being said, my relationship with my 80 has been one of the most satisfying parts of my life". I completely agree!

Cheers to all!