- This topic has 8 replies, 6 voices, and was last updated 9 years, 1 month ago by
.
-
Topic
-
1998 Dodge Ram 5.9L 4X4 210,000km. Gas mileage took a dive this year, presently 9mpg. When new the vehicle got 14mpg, so it’s a change. Slightly rough idle but no performance issues. No codes. As routine maintenance I did plugs/wires/dist cap/rotor/air filter last month. Did injector cleaning on the vehicle with OTC canister technique. Planning on throttle body/IAC cleaning this weekend, and a closer look at the plenum. But peeking inside I’m not seeing oil pooling in the plenum and not losing oil, no pinging on acceleration. I did check for vacuum leaks with carb cleaner and I can’t find any.
Today I looked closely at the two original O2 sensors (with Autoenginuity and a generic oscilloscope). Upstream sensor reads about 0.08-0.12V, poor waveform with almost no readings above 0.6, lots of static, and blunted response (approx 0.5V) to propane challenge into a vacuum hose. I don’t get a sinusoidal wave from either sensor, more like a flat wave with occasional small hills (looked at with oscilloscope and autoenginuity program). Downstream sensor reads 0.16V, but it does rise to 0.8V with propane. LTFT -0.98, STFT starts out quite negative and eventually rises to variable after 20 minutes.
Removed both 4-wire sensors for bench testing. Can’t get the upstream sensor to generate more than about 0.2V when heating sensor with propane torch on the bench. Downstream sensor did better, and eventually reached 0.9V but when propane removed it slowly dropped down after about 60 seconds, not as fast a recovery as I would expect. I assume they are both zirconia sensors.
Would it be wise now to replace both O2 sensors? Do you advise that I go to the dealer for replacement or should I go for an aftermarket replacement. Any other thoughts?
-
Replies
-
What do your sensors cost to replace? I can replace both of mine for under $35. so I have a replacement set for it in the basement that I can use if needed. If they’re expensive then it might be a waste of money. I usually keep my vehicles for quite a while so I tend to look for the parts I might need in the future and if I see a good price on them I’ll pick ’em up so I’ll have ’em if I need ’em. Put 290,000 miles on my 1996 Neon and picked up a 1998 with only 128,000. Sold the 96 and most of the parts I had for the 96 will work on the 98. Planned it so it would work that way so now I’m covered for at least another couple years until the wife gets 300,000 miles on the 98. What the heck try new O2’s if they get you better gas mileage they’ll pay for themselves.
It sounds like the front o2 is lazy.If you spray carb
spray. the front o2 should spike. Call the dealer parts
dept to get a price.Forgot to ask, what kind of O’scope did you use? I’ve got a used Tektronix 2213 O’Scope that my brother gave me for some reason that I don’t know. I’ve been thinking of taking it out to play around with and using some t pins and doing some probing for the wave forms from some sensors just to see if it would work out should I need to use it. Probably try to take some reference picks of what they look like when the vehicle is running good so I’ll have something to compare it to if I suspect a problem with a sensor.
It’s a Rigol 1152E digital oscilloscope. Two channel, reasonable frequency and refresh rate, fairly sensitive, and very economical compared to what scopes cost in the past ($350). I can’t really afford more dedicated scopes like the picoscope or others.
I didn’t get a great tracing with the proximal sensor, but I think that was because the signal source was poor rather than a problem with the connection or artefact.
Today I’ll pick up an upstream OEM O2 sensor, but it was expensive — $150. I’ll try to record the results before and after.
On those old beasts the O2 sensors have to all but stop switching to set a fault code. They probably quite working optimal by the time it has 150.000 on it. For the cost of the replacement i wouldn’t think twice about replacing them.
Lazy O2 sensors are going to drop your mileage. Got the same problem with our Explorer. No codes, bad mileage, and 3 of the 4 sensors are lazy ( replaced the one that I can get to the connector without having to rip up the interior to get at the transmission tunnel access panel where the other 3 reside..it’s too tight to reach up there any other way ).
[quote=”EricTheCarGuy” post=146014]Chasing threads isn’t anymore difficult than running a fastener in. Just take your time, you’ll be fine.[/quote]
I have been video documenting all the relevant work I have basically done TODAY.. Promising. 🙂It is in that “D15Z1 Honda” thread I’ve been updating, whichever forum that ended up in.
Sent from my SAMSUNG-SM-G850A using Tapatalk
- You must be logged in to reply to this topic.