question about oxygen sensors

[dug heath]

hi new limey here asking for advice from cousins across the pond.I have a 97 explorer with its engine warning light on, so I take it to local man with diagnostic apparatus .He tells me both oxygen sensors have failed, but its unlikley that both have failed at the same time so its probabley a wiring fault.he says it drives ok so not to worry about it. well i am,now as starting is ok but warming it up in cold weather, the revs are all over the place and i have to sit there for ten minutes with my foot on and off, what you call the gas pedel untill the engine is warm enough to idle on her own.After that she is fine and runs like a dream. any thoughts?anyone?

 

[2000StreetRod]

SOHC cold start problems

More than likely you have the SOHC which is notorious for lower intake manifold leaking gaskets. The DTCs reported were probably both banks too lean. You should obtain the actual codes before replacing anything. Often the codes can only indicate an engine symptom but not the cause. Many people replace O2 sensors when they are still functional. Then they have to determine the actual source of the problem. The only wiring fault that comes to mind that would affect both sensors at the same time would be the sensor heater wiring.

 

[scucci]

I agree with 2000StreetRod. That sounds like manifold gaskets. Usually starts out as surging/hunting in cold weather and can progress to requiring driver throttle control required to idle until the gaskets warm up and swell.

 

[dug heath]

thnks to 2000streetrod and scucci for the advice i shall investigate ta dug

 

[mplwcm]

ive got the same problem with mine. 4.0sohc i think i will be checking o-rings

 

[Amznwmn]

ive got the same problem with mine. 4.0sohc i think i will be checking o-rings

I've been having this problem for going on 2 years. Rough idle with RPMs up and down and up and down; sometimes it dies unless I keep it revved up to about 2500 RPMs until warms up a little bit. Even then I need to keep my foot on the gas at any red lights until its up to full operating temp.

At one point, I took it in and had a mechanic check it out. He said the codes indicated wore injector o-rings. Couldn't afford the $400 quote to fix it, so just been dealing with it since.

But I failed emission test last month, so I need to do something. Cleaned the MAF sensor, did tuneup, cleaned IAC. Took it over to AutoZone tonight and their printout said MAF, oxygen sensor or injector issue.

Will tackle oxygen sensors on Monday. Any other ideas?

 

[1998Exp]

The Autozone printout is intended to suggest to the sales guy what parts to sell you. The advice that has proven itself over and over again is not to buy any suggested parts and just ask them for the actual trouble codes (they look like Pxxxx). Post those here, along with the type of engine that you have (if you don't know, just get the 8th digit in the VIN). This will help the nice members on this site to advise you more specifically.

 

[janolsson]

Hi Dug
Welcome
Where are you in the uk? Come and say hi to the guys in the uk section UK section
As the guys have said the intake gaskets can give the symptons described. The engine monitors the air comming into the engine and adds fuel accordingly. If air is getting sucked in from leaky gaskets this will weaken the mixture.
If you are remotely handy with the spanners it is relatively easy to do. Do a search for oo12m kit installation.
You can buy the gaskets from a dealer but for not much more you can get the whole oom12kit which also includes new updated front tensioner and restrictor pencil. If you look under the throttle body on the inside side of the left (passenger side) head you will see a 27mm bolt. If this has a flat head you need the new one, if it has a 2" shaft on it you don't need to do the kit.
Whilst doing the job you could also clean the IAC which controls the air allowed in. BIGHVM has just done a thread on the IAC in the uk section but there are other how to's on here.
Regards

 

[jordan101]

im having same problem with the bank 2 sensor 1. thats what my code reader says then a lean code on same side goes on and off. In cold weather mine idles funny goes from 600 down to 300. Whats my problem. I think the o2 is causing it to run lean causing it to idle funny when cold. What do you guys think?