[quote=CCKen;2109624]While you're dealing with your O2S's, check mini fuse F17 in the PDC. It's the O2S heaters relays power fuse.


Ok, I'll take a look at that as well. Can you pull the relays for the O2 sensors to check for a non-working O2 sensor or is it better to just unplug the sensors one at a time?

Many thanks for the replies.

 

[quote=xKHANx;2109795]The relays control the heater in them, pulling them won't indicate anything readily unless your Jeep runs at 100% and isn't in warm-up mode.

 

Ok, thanks.

Installed the MAP and IAC, throttle response is definitely much better. I took a wire wheel to the tail pipe to clean it out to keep an eye out for any visible change.
I will install the O2 sensors on Sunday and post my results in a week or so after I have a chance to go a hundred miles or so.

 

Check that O2S heater fuse before you change the O2S's.

 

bought a 98 sport 4.0L auto with 225/75R15 and 263,000 km a few months back. first tank got me 340km(canada), changed plugs(champ), cap, rotor(BWD), wires(delco), air filter(it was clean but...changed it anyways) and did an oil change.
the next two tanks got me 420km and 450km. I feel I should be getting 500+
I notice it smells rich when idling, haven't looked at the tail pipe for black. Also, at stop lights I notice a slight miss, not much, but there is something going on.
yesterday I replaced the upstream O2 with an OEM from chrysler, filled up and going to see the next result. later today I will check the temp sensors with my snap-on scanner.
I have heard good results on replacing the coil pack, considering it has 260K + km om it, just because it's working, doesn't mean it is working well. I will be changing the coil after the next 2 tanks

so I ask this forum - what kind of distance should I be getting for mixed driving(30% hwy, 70% around town) to a tank(65L at fill up)?

sorry for hijacking the thread, but it's relevant.

conversion for non-metric
263,000 km = 163,421 Mi
340 km = 211 Mi
420 km = 261 Mi
450 km = 280 Mi
500 +km = 310+ Mi
65L = 17 Gal

after typing that out I see that I went from 12mpg to 16mpg, which is what xKHANx is hoping for, what tire size are you running?

 

I have checked the fuse, it is good. I also unplugged the downstream O2 and didn't see a difference in running but didn't get a CEL either. I haven't had the chance to do the upstream yet.

Running 235/75/15's

 

downstream O2 is used for monitoring catalytic converter efficiency and does not alter running performance, upstream O2 is for engine performance.
the computer uses the information from both O2 sensors to see how well the cat is working, it sees the change from upstream to downstream

 

I have a stock 97 with the 235/75/15's as well and I'm only getting about 15-16 MPG. Can't really hope for more unless you have any upgrades or a 5 speed

 

could it be possible that the rings have not seated yet? I had a 350 I rebuilt a few years ago, and the oil and gas mileage had the same problems you describe.

 

I dunno, I have 1400 miles on it, isn't that enough?

 

It took almost 2,000 miles before they seated on that 350. when I went to my machinest he said some take longer than others. mine finally seated going up a steep climb under heavy load in low range. after that quit running rich oil cleaned up quit burning oil gas mileage went up. I would run through the fuel system and do a compression test wet and dry to verify the rings. there will be about a 15 to 40lb difference in the test if the rings haven't seated.

 

another good way of getting rings to seat is to go down long steep hills having the engine braking for you.

 

WOW - guesses from sensors to rings.
How does going downhill, or uphill seat the rings? Did space aliens help?
Even chrome riings will seat in a few minutes IF the crosshatch was done right.

Do a compression check - last resort is the Bon Ami trick.

But I doubt it's the rings - you'd be getting A LOT OF BLOWBY!


Have a smog station verify the CO is too high - bet they'll also tell you the tailpipe O2 is too high due to the exhaust leak!

Do a smoke test on the exhaust - wet rag in the tailpipe to pressurize the exhaust, 3 or 4 squirts of oil in the TB to make it smoke, fix wherever the smoke comes out!

SIMPLE, EASY, FREE!

Let us know what you find!

 

placing a load on the rings is where the uphill downhill thing helps(that RPM gasses pressure stuff). if the rings haven't seated a smog test won't tell you anything except what you already know, and is he in a state where smog test are available? fix the exhaust leak. and I recall saying something about a compression test to verify the rings.

 

Don't have inspection or smog stations in Indiana nor do we have hills bigger than the hill a squirrel makes when burying an acorn...

I'll give the wet rag tip a try and see if I am smoking anywhere. Injectors came in today so I will do that swap tonight.