Help Diagnosing-Rough Idle, less reponsive, CEL codes 25 and 26 (1 Viewer)

[rainbow94]

Evening,

Over the past few weeks I have been trying to fix my 1994 FZJ80. It first started with a CEL. I took it in to have codes read and pulled codes 25 and 26 (air-fuel ratio lean and air-fuel ratio rich). I replaced the O2 sensor and it drove fine for about 500 miles then the CEL came back on. I just replaced the MAF sensor but the CEL is still on. The vehicle drives very rough. It idles much lower than usual at about 300 RPM and shakes vigorously. It is far less responsive than it normally is and frequently "jumps" rpms.

I have also recently replaced:
-distributor cap
-spark plugs
-air filter
-all fluids

I was planning on driving back home for the holidays in a few days (1500 miles round trip) but don't think the LC can make it in its current condition.

Any help or ideas as to what might be the issue is appreciated! I hoping to get the LC back on the road ASAP.

 

[ppc]

Have you checked the air intake tube for cracks?

 

[rainbow94]

yes, replaced it last year

 

[rc51kid]

this might be over simple. But clean the O2 sensor plugs. The ones on the O2s are new, but the ones on the wiring harness are still 20 years old. In the 94 they get wet and muddy being behind the wheel. Clean the contacts REALLY well then use some dielectric grease to help seal the plug.

 

[rc51kid]

PS other people have said that you can end up with those codes anytime that the truck is running that poorly. So you could also focus more on what is making it run that badly and not just the code. For me the truck ran GREAT but gave me those codes. For me it was needing those plugs cleaned. But again, my truck ran great. Yours is running badly.

When did it start running badly? After the MAF?
few things i thought of. Check the wiring harness near the EGR/cylinder 6. It gets hot and can melt or crack from heat. Also check to make sure all the plugs on the fuel injectors are making good contact and clipped on to the injectors well. Just wiggle them a little when it is running. One of mine would not clip on securely, the clips break. It slipped loose and i was running 5 cylinders until i pushed it on better. Also clean all the grounds and battery contacts for the electrical system.

 

[rainbow94]

It ran fine when the CEL first came on. I read the codes and replaced the original O2 sensors first. The CEL then turned off and ran fine until 500 miles later. Then it had a rough idle, lack of response (sluggish on the gas) and jumped RPMs. So i replaced the distributor cap, and the jumping RPMs stopped. I then replaced the MAF and the CEL went off for 25 miles, running rough. Now the CEL is back on and the LC still has a lack of reponse on the gas along with low RPMs and shaking at idle.

 

[rainbow94]

I just went turned the vehicle on. It does sound like it might not be firing on all cylinders. I will have to investigate tomorrow when it isn't dark and raining.

 

[rc51kid]

If it ran fine after replacing dist cap, also look for things in that area that you might have bumped. I know it sounds strange. But it might have had nothing to do with the dist cap and everything to do with a plug, short or loose ground that you bumped while working in the engine compartment. Basically you are going to check all the stupid easy stuff first. Grounds, plugs, and wire harnesses. Then start with the basics and check for basic motor "health" with stuff like compression test.

Again, just my opinion. There are people MUCH smarter than me around here. They should be around soon enough.