Hello I'm mark

I recently purchased a 99' xj 4.0 i6 man. Last weekend i changed plugs, wires, air filter, oil filter, seafoam. It's got 218k on it and it's time things get replaced.

After seafoam I got a code that went away. After Irene I got the a code again and I'm now getting a hard idle and a loss/ hesitation of power right at the 2k line with a misfire then slight hesitation till 2300k and after till 2500k a surge of power. Everytime. It's also chugging at speed when I coast off the gas.

Took it to a local shop to scan the code.
Upstream o2
Downstream o2
Bank 1 lean

The lean throws me off cause it's running really rich. I get barely 100 miles to a half tank compaired to my recent 200. The exhaust smells super rich and is spitting what looks like sooty water not gas or oil. And no smoke. No antifreeze in oil. No vacuum leaks.

I read the TPS can can give a lot of similar symptoms.

I read that the o2 upstream can also.

Also the IAC which I will attempt to clean tomorrow along with TPS.

First time back to my tools after Irene. My road is blocked by trees, 6 power lines, and 18 different mud slides for 5 miles. No power till Saturday they say.

Spent the better part of today searching and reading, but would appreciate a little input.

 

It certainly does sound like you need new o2's. My downstream (bank 2) sensor was bad. Gotta recommend doing both, if ones bad, the other is probably not much better... Don't skimp on quality with these guys. I spent 110/ea. on mine, they have a warranty and are definitely worth it. The TPS and IAC valve are ok components to change as well if your lookin to do a more complete tune up.

 

you got ripped off if you paid 110 per o2 sensor... warranty or not

 

K..

 

Yea you def did. My local advance has both denso and Bosch OE direct fits for $65, so after I get outta work I'm picking up a new o2 and seeing how that works.

I'm gonna ask it here and I'll search when I'm not working but, is there a way I can reset my computer after I change my o2 to clear all codes so it's not running on the current ****ty fuel map?

 

hmmmm.....check MAP sensor too.....do you have a MASS air flow sensor?
clean that too....... how about fuel pressure check? you can attach gauge at fuel rail and vary RPM to see pressure change.....if no change then maybe regulator is on its way out too?

change out fuel filter, run some STP/GUNK fuel injector treatment..etc etc.

TPS & IAC is a good bet too, as well as the O2 sensors.....hows the backpressure at tailpipe? might be cat goin on you (unless its relatively new)....

just a few thoughts sir.....

cpnwrench

 

Changed out the upstream o2 and reset
The ecu.

Idle, stutter and code gone along with running rich. Cleaned the throttle body, don't see a MAF

 

I have been getting about 250 miloes per tank...seemed normal to me. about 12mpg..what should we be getting?

 

Before I was getting 200 to half a tank. Best I had it before sensor failed was 210 miles. I just filled the tank again and it seems back on track with 60 miles on this fill.

 

So you're saying that you get 400 miles to a tank? Im lucky to see 200 on my 97 with 31s.

 

In order to compute fuel mileage, you need to accurately measure miles traveled and actual gallons of fuel. Just judging "half a tank" won't tell you much. On the other hand if you mean 9.8 gallons, for instance, that's something else.

Also, keep in mind that tire size is important. If you have oversize tires or different from stock differential gears, odometer readings will not be accurate unless the speedo gears have been changed accordingly.