96 Isuzu Rodeo Gas Mileage Problems

[spider1]

Ok, I moved to Iowa in April of this year. Since then I put some 18" chrome rims. These rims were really heavy and I realized that my mileage was going down. Well about a month ago, I took off the rims and put on the regualr ones wtih new tires. My mileage was good for about a day or two when I went to chicago and then it was bad again. I would say that I'm getting about 12.5 mpg on my rodeo.

I do know what I could do to make it better like it was before (15 city, 17 hwy). I hardly get on the hwy and use my car in city and I figured that was the reason why, but it still sucks.

Now I did change the timing belt In April, when I moved here, and I was getting crazy gas mileage from Texas to Iowa (21 mpg!), and I changed my spark plugs last June. so i wouldn't say they are the issue.

What should I check or do differently to make my car run better?

[highlandlake]

My suggestion would be oxygen sensors.

[spider1]

Ok, so how do the oxygen synsors work exactly? Do they need to be calibrated or replaced? How much would they cost me and I can I install in myself?

Thanks,

Ivan

[amigo-2k]

check the tire pressure

Also winter gas will give you lower MPG, and colder weather will too.

I went from about 18 mpg city this summer to about 14 city on my current tank due to the cold weather.

[surferfletch]

I was about to post on this topic. My rig has gone from 17-18 mpg down to 14-15 mpg. I thought maybe I'd swap the 2 upstream sensors...

[highlandlake]

Originally Posted by spider1

Ok, so how do the oxygen synsors work exactly? Do they need to be calibrated or replaced? How much would they cost me and I can I install in myself?

Thanks,

Ivan

To the best of my knowledge the O2's cannot be cleaned/repaired/calibrated/replaced with better used ones. They are purely a swap for new event. The cost varies from what you can find on E-Bay if you know what to look for - to the high cost of going to a dealer. The challenge to replacing them is that there are as many as four on your vehicle. They can be tested while in the vehicle using a high-end scan tool in the diagnostics port. But you have to know what to look for in voltage range. Also these sensors are a bi*ch to remove since they tend to get rusted in place, and are in hard to reach places sometimes. A special socket is available at parts stores. Put some penetrating lube on them in advance.
I just purchased one for my Chevy truck and it was only $20 with shipping - but I got lucky I think. Some sensors cost nearly $100 each plus labor if you take it to a shop.
Has anyone here had experience with whether the front or rear ones on a Rodeo are common to degrade?
Tom

[Gizmo42]

Its not uncommon on any vehicle for o2 sensors to start reading low without throwing a CEL. I had it happen on my mitsu before. Not sure how many the 96 has (my '99 has 4) but you would only need to change the ones before the cat converter. The ones after the cats really only tell the computer if the cat converter is working. I'm going to replace mine next spring simply to make sure the system is working right. As far as I know mine are all original and now have 96k miles on them.

[Ramblin Fever]

Same here, have the '97 Rodeo, 2 O2's went bad at around 150k; changed out all 4. Paid $45/each - installed myself.

Don't know how many the '96 year has, but they're not worth cleaning/recalibrating, at 100k+ miles they've done their job.

Definitely, on the 96 yr, bring your tire psi up to at least 34-35 on all 4's.

Agree to the change in gas mileage recently too; just a short 2-3 weeks ago, I was getting 18-19 city; I'm now down to 15 or so.

I actually cringed when winter comes around for this reason, find myself spending more $$ on gas alone.

Other then that, keep your breathers clean; i.e air, fuel filter, pvc, egr, etc.

[Ramblin Fever]

Originally Posted by highlandlake

Some sensors cost nearly $100 each plus labor if you take it to a shop.
Has anyone here had experience with whether the front or rear ones on a Rodeo are common to degrade?
Tom

My 4 sensors - Bosch brand, I paid $45/sensor; installed them myself. Fairly simple job, as long as you have small/medium-sized hands.

When you're removing the old sensors, start with a 1-2min idle on a cold engine, shut it off, then wiggle them out. Be careful to not allow the engine to run too long, exhaust/manifold get hot quick!

My 2 front ones were the ones that went.

[surferfletch]

Did you get those sensors at NAPA? I'm heading over there today...

[surferfletch]

Did you have to splice, or was it plug and play? Thanks!

[Ramblin Fever]

Got them at AutoZone - cheaper then Napa.

Plug and play; no splicing with the Bosch anyway.

[surferfletch]

Thanks!

[Ramblin Fever]

Anytime.

[surferfletch]

I know you guys in the rust belt don't want to hear this, but that was the easiest repair I've done on any vehicle. The old ones popped out with little effort with an adjustable wrench (supposed to be 7/8", I think, but I don't have one in the toolbox!) after disconnecting the connector. And the new ones plugged right in. The ones I took out were marked AC, like the fuel filter I swapped a couple of months ago, and the Bosch were a direct fit. I paid $52.99 each at AutoZone for these Bosch 4 wire precat sensors. They were "O.E. type" versus the "universal type," which were the same price. I got nearly 158K out of the first ones. I'll let you know if mileage improves. The truck ran great on the first trip around the neighborhood.