92 Idles Very Rough | Ford Explorer Forums - Serious Explorations

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92 Idles Very Rough

darrendwilson

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February 23, 2010
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Year, Model & Trim Level
1992
1992 Explorer, 6 cyl, Four Wheel Drive, Manual Tranny, 207k miles

My '92 Explorer runs fairly smooth while accelerating and while driving down the road but it idles very rough. I bought a code reader and got the error code 172 - "Heated Exhaust Gas Oxygen Sensor Voltage Signal Indicates 'Lean' (Bank #1)". Would this sensor make the vehicle idle rough by going bad and just needs to be replaced, or is it more likely there is something more that is making this sensor give this error? I checked all the vacuum hoses and they are all attached and don't seem to be leaking. Any help is appreciated!
 



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mine 93 does that i did a copression test i have an bad head gasket so i am going to get a new motor from the jonk yard
 






Yes, a bad O2 sensor could give you those symptoms and the code, and, yes, it is certainly possible that something else is wrong triggering the O2 sensor code. That's what diagnosis is all about: determining the actual fault from the list of possible faults. In some ways, lean O2 sensor codes can be among the more difficult to diagnose properly.

Is your 172 from the KOER test, or is it only a CM code? Have you tried the KOER test, yet? Because KOER code represent "hard" faults, it might be easier to diagnose from the KOER test. If you haven't tried it, yet, that's probably the first thing I'd recommend.

If you were to look up the "circuit pinpoint test" in a proper manual for a KOER or CM 172, probably the 1st thing they'd have you do would be a fuel pressure test. If you're interested, you can often find proper diagnosis manuals in public libraries.

In addition to checking for vacuum leaks, don't forget to check the wiring between the O2 sensor and the PCM.

Some people like to think of O2 sensors as a maintenance item. One strategy I often see employed in diagnosing these if the O2 sensor has more than 50000 miles on it is to replace the sensor (as a maintenance item) and see if that fixes it. If it does, great. If not, then go through the more difficult task of tracking the real problem down.
 






My 93 dose the same thing. Fuel pressure is okay. Vac lines okay and as far as I can make out so is the wiring to the two O2 sensors. Mine will throw a CEL every now and then but only if I idle a lot as in city traffic or going down a long grade using 2nd gear and little to no brakes and no throttle. Once up to free way speed or were the motor can run for a mile or so if clears its self and turns off the CEL. Pulling codes I only get the 172 sensor fault/ lean this is KOEO and never any when check KOER. have changed the sensors out in the past but it only cleared things up for a bit tell it came back again and never has it help clear up the bad idle problem Right now its bad again and no codes at all new plugs and all as I had to have that dang Calif smog check again .I get the enhanced check were I live and as always I just make it in the nox part max is 501(PPM) avg 149PPM and mine meas at 491 (PPM) at the 15MPH test and at 25MPH it is MAx 745PPM and mine 626 PPM with avg at 144PPM.
now co2 I am right on the money but HC PPm I am 0 at 25 mph max is 52 and at 15 mph max is 87 and mine is 14 with avg at 14 so good there also . I know the NOX is also because I am a 49 state truck and have no EGR valve so the cat has to do all the work. This was two days after seafoaming it also. I want a good idle also some one help us!!
 






Check vacuum lines and fittings. I found a leak in the grommet to the brake booster and since fixing it my idle quality improved a bunch. ALso look for loose upper intake bolts. I had several that were finger tight and a fresh gasket and proper tightening also made a noticeable difference in overall drivability and idle quality was most noticeably improved.
 






When ours had a rough idle it was a leaking intake manifold gasket.
 






Check vacuum lines and fittings. I found a leak in the grommet to the brake booster and since fixing it my idle quality improved a bunch. ALso look for loose upper intake bolts. I had several that were finger tight and a fresh gasket and proper tightening also made a noticeable difference in overall drivability and idle quality was most noticeably improved.

can you tell how you fixed the grommet in the break booster?
 






Thought I would share with people that I had a severely cracked grommet on the brake booster valve and I got a replacement at NAPA for about $8.50. It came with a new valve and grommet, both are exactly the same. The valve is made in Mexico while the rubber is made in the USA. The part number for my 1991 was UP 89000 and can be seen here:
http://www.napaonline.com/Catalog/C...e-Booster-Check-Valve/_/R-UBP89000_0063321048

Here you can see my old one (bottom) and the new one (top):
https://dl.dropboxusercontent.com/u/464376/vehicles/1991 Explorer/Pictures/IMG_20131114_125741.jpg

Hopefully this helps someone out.
 






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