'87 Xj 4.0l - Oscillating Rpm / Usually When Warm - Page 2

talentjeep · 11-15-2009, 09:48 PM

Last tank figured out 15 mpg. But that is with 45 minutes of idle and the Jeep is usually on the freeway before it's warm. Working on another full tank now and will take to same pump to compare. So far the gauge is halfway between 1/8 & 1/4 down and I have 77 miles on the trip odometer.

Fir3Chi3f · 11-16-2009, 12:34 PM

I did want to add that your temp fix has what I could tell completely stopped my dieseling problem. I'll have a more accurate mileage to post after my 3hr ride home for thanksgiving.

talentjeep · 11-16-2009, 10:19 PM

I just found an interesting article on 4x4 offroad. It's about a '94, but is has the 4.0L.

Project XJ Cheap Cherokee - - Jeep at Off-Road.com

They posture that a dirty air filter is blow by from faulty rear CCV. Much cheaper than EGR, I'd guess!

Fir3Chi3f · 11-17-2009, 12:23 AM

Here are some links on the subject of blow by:

Cherokee America - My Jeep is Blowing Oil onto the Air Filter!! - - Jeep at Off-Road.com

oil blowby fix

I didn't even think of sending you those links. I had read about it earlier but I don't have oil on my filter and just assumed that you had the same problem as me.

On my jeep- I actually think that my idle has become more erratic since removing that tube. But doesn't want to die as much as well as the fixing of the dieseling problem.

I remember trying to adjust my tps sensor a while back and it didn't matter where I set it, so maybe I will actually have to adjust or replace the bugger.

Anyone know if Jeep is making them more reliable? I read an article that said they go out whenever someone spits on the sidewalk and I usually try to only buy sensors from the dealer.

talentjeep · 11-17-2009, 02:42 AM

I'm sure you've seen this...

Jeep Cherokee Engines - RENIX (non-HO) Engine Sensor Diagnostics

I'm wondering if I can just take off all of the emissions crud from my valve cover and put a couple of regular ccv valves on there. I used to have a 455 Rocket and it just had little mushroom capped valves for crankcase ventilation...I wonder if I could just switch to those?

talentjeep · 11-17-2009, 02:48 AM

Quote:

Originally Posted by Fir3Chi3f

Here are some links on the subject of blow by:

Cherokee America - My Jeep is Blowing Oil onto the Air Filter!! - - Jeep at Off-Road.com

oil blowby fix

I didn't even think of sending you those links. I had read about it earlier but I don't have oil on my filter and just assumed that you had the same problem as me.

On my jeep- I actually think that my idle has become more erratic since removing that tube. But doesn't want to die as much as well as the fixing of the dieseling problem.

I remember trying to adjust my tps sensor a while back and it didn't matter where I set it, so maybe I will actually have to adjust or replace the bugger.

Anyone know if Jeep is making them more reliable? I read an article that said they go out whenever someone spits on the sidewalk and I usually try to only buy sensors from the dealer.

Thanks for the links.

What's weird is the oil in my air filter photo was at the front of the airbox. Not by the lines running from the engine (at the rear) so why was oil at the front? Does bad crank case ventilation mean oil in exhaust?

Fir3Chi3f · 11-17-2009, 12:14 PM

Maybe the PO did fix the blow by and just flipped the air filter around instead of replacing it. I actually filled the hole in the airbox that allows the oil in with epoxy and just have a vent filter on the valve cover. I keep those links around in case I ever get around to replacing the other tubes.

Fir3Chi3f · 11-20-2009, 12:38 PM

Bad news is that the engine was dieseling again last night. Good news is that I'm going to be driving home today for thanksgiving break and see how my mileage is doing without that tube on.

I'm also going to try adjusting my throttle positioning sensor before I go. Sometimes it likes to idle around 1k-2k rpm, going to look into a new tps while I'm home.

talentjeep · 11-22-2009, 04:59 PM

So now I've been told that the hose I disco'd only connects to the header to pull hot air off of it?

I'm not sure why it worked.

But my MPG is 16. Drove 257 miles, When I refilled at the same pump it was 16 gallons. This isn't too bad given this time of year. I have to start the Jeep cold and hit the freeway within 5 minutes, cruise for 10-15 minutes at 70 in fifth and then another five minutes of street driving.

So it is a mixed city/hwy and it is also an '87. I think I'm just going to count myself lucky since a huge number of threads on here are titled "HORRIBLE GAS MILEAGE"

I'm just going to leave the hose off permanently but when I have the cash and I rebuild my intake I'll replace the O2 sensor just to make sure.

I would like to replace my TPS too but those suckers are expensive at $120+! Most of the JY ones are either fubar'd or gone.

Fir3Chi3f · 11-24-2009, 01:06 AM

Agreed with those TPSs man, but $120 isn't too bad since I only have 176k miles on it. I still got 124k to go before I worry about anything really expensive

I plan on completely replacing my intake for one off a newer jeep. They bolt right up and are good for some ponies

Swapping to a 2000 Inlet Manifold

I remain sceptical over what anyone else says about my jeep. Some time in the future I really want a factory service manual, I hear it is a holy grail of information about these things.

talentjeep · 11-24-2009, 08:36 AM

Quote:

Originally Posted by Fir3Chi3f

Agreed with those TPSs man, but $120 isn't too bad since I only have 176k miles on it. I still got 124k to go before I worry about anything really expensive

I plan on completely replacing my intake for one off a newer jeep. They bolt right up and are good for some ponies

Swapping to a 2000 Inlet Manifold

I remain sceptical over what anyone else says about my jeep. Some time in the future I really want a factory service manual, I hear it is a holy grail of information about these things.

That intake swap looks awesome. Thanks for the link.

A factory service manual would be a godsend. I've seen a few links here and there you can order from but the sites don't look all that reputable. I'm surprised no one has digitized them yet. Too bad, a PDF would be better than nothing!

Fir3Chi3f · 11-30-2009, 01:34 PM

Well from my calc. I got about 17.88 mpg, mostly highway. Sounds good to me

That is without the tube, you said that you actually seen less mpg with it removed?

I also have heard from a mechanic that it is probably a heater hose. My new thoughts are that (at least mine) is putting out heat after the car is warmed up. And, because of the additional power from the removal of the heat, I could get it into 5th gear and still hold position with the other cars on the highway.

Have you traced where this hose goes?

talentjeep · 11-30-2009, 01:56 PM

Quote:

Originally Posted by Fir3Chi3f

That is without the tube, you said that you actually seen less mpg with it removed?

Have you traced where this hose goes?

I used to get 18-20, now I get about 16.

I haven't traced the tube yet. I've been too busy lifting it and trying to find tires.

Topgun514 · 12-02-2009, 11:16 PM

disconnecting that tube will not ruin gas mileage that bad...it will actually increase. I cut that entire front piece off and disconnected the vacuum tube from the back point. The only purpose for the front piece is to just pull warm air in the engine when the engine is cold, then it flips back when the engine is warm to pull in colder air.

Cutting the whole piece off just increases more air intake and colder air only at start up.

talentjeep · 12-18-2009, 07:02 PM

So I was under the Jeep today poking around with a flashlight trying to solve my shaking/wobbling issues and I noticed a few things:

My exhaust is cracked (red)! What also interests me is that the metal piece (green) is where the hose connects to the airbox! This means I was pulling exhaust air into my airbox after all which explains the fouling on the filter.

What I don't understand are the two objects mounted near the flange (blue and yellow). I thought Renix didn't have downstream O2 so what are these?