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Cherokee XJ RENIX 1990 - low power, bad mpg, problem with ignition and timing

8Mud said:
A couple of things to look at, the oxygen sensor, knock sensor and engine temp sensor harness runs up the front of the engine. If routed wrong it can cook on the exhaust manifold.
Click to expand...
I'll check that.
8Mud said:
Two holes in the throttle body for the MAP sensor vacuum line. Only one home goes all the way through to vacuum.
Click to expand...
Not sure if i understand correct. Vacum for map sensor is on the manifold. I have a renix, 1990. Not sure how it's done in newer models.

8Mud said:
The vacuum tube for the MAP is prone to rub through or crack, it only takes a tiny flaw to cause issues.
Click to expand...
I checked that, its ok.
8Mud said:
Do an ohm test on the TPS ground. That ground circuit has many splices any of which can cause issues.
Click to expand...
Ill check, but i did not have any problems with setting a correct position of TPS.

8Mud said:
Jump the ballast resistor.
Click to expand...
I'll try but i see no point. As i said before i have an LPG system and it's the same on LPG and on gasoline.

I also checked the vaccum fuel pressure regulator today, its fine.

Do you really guys, bad ground on one or few sensors can make such a difference in power and MPG? As i have seen on youtube and on the other forums i should make 0-60 in like 10 seconds? (im on 31 inch tires, silverstorne mt-117 sport, and i do it in about 16.... MPG should be no less than 12mpg i think, and it's 6? Im not driving 'pedal to the metal'.
 
"I bought it that way".
Many new daily revelations on this thread. Since the harmonic balancer has slipped, where TDC is not where it's supposed to be, everything in your XJ is now suspect.

If the previous owner installed a camshaft and degreed it ,when the harmonic balancer was only off slightly, the valve timing would be off and power could be down. Likewise, a stretched timing chain or a cam-sprocket off one chain-link can throw off the valve timing.

I'd suggest the following, since you "bought it that way":
1. Replace the harmonic balancer.
2. Replace the timing chain.
3. Check the camshaft lobe wear. If excessive, replace the camshaft.
4. Degree/time the unworn/or new camshaft so that the valve timing is in specifications. If you can't degree/time a camshaft, find a qualified mechanic who can.
5. Install the distributor per Cruiser54's instructions.

Best regards,

CJR
 
My jeep was a something like 'barn find'. Previous owner had if for few years, he mostly was just carrying wood from the forrest and for the last 3 years he kept him in barn, he just started it from time to time. When i bought it, jeep wasnt even starting, fuel was leaking but i wanted to fix this jeep and keep him. (Love on first sight ;))


When i started the engine, i made like 300km and started to work with a chasis.
This is how it looks now:


So it's not easy to track everything that previous owners changed, im learing it all the time with you guys.

Timing chain and sprockets are brand new, marks on the sprockets were correct. Old one wasn't that bad.

I think ill take of valves cover and timing cover and check camshaft and other valves stuff.
 
"Timing chain and sprockets are brand new, marks on the sprockets were correct. Old one wasn't that bad."

Your comments are very informative.
1. YOU, replaced the timing chain and sprockets.
2. YOU, only lined up the "marks" on the chain sprockets. That is not properly degreeing a camshaft. "Marks" on camshaft sprockets can be off or in-error. You need to forget the "marks" on the sprockets and first have your camshaft inspected for wear/damage and that ALL cam lobe degree openings/closings are correct for EACH piston. An unworn or new camshaft, with proper lobe degree openings/closings, should then be degreed properly without using the "marks" on the camshaft sprockets. You need to know that "the cam is properly phased with the pistons" and "NOT phased by where the marks are on the camshaft sprockets". Find a qualified mechanic to do that for you.
3.Your comment, "Old one wasn't that bad",indicates YOU swapped out the the chain and sprockets. In my view, your camshaft timing is suspect and it needs to be checked by a qualified mechanic other than yourself.

Best regards,

CJR
 
Didn't see it mentioned( unless is missed it), but you might check ALL your vacuum lines after checking the MAP line. Poor pressure through mutliple cracked lines could cause some issues but doubtful that much of a power loss issue.
I know egr was mentioned but is it disconnected or blocked off?
Have you verified fuel ballast is functioning and fuel pump is good?
I'll leave it to the smarter mechanics to discuss your timing.
 
90XJ_Seth said:
Didn't see it mentioned( unless is missed it), but you might check ALL your vacuum lines after checking the MAP line.
Click to expand...
I checked most of them, and as i said before i have duel fuel system, and the LPG ECU shows your vaccum pressure in real time so i can see them map of it and i know if i have a problem with vaccum or not.


90XJ_Seth said:
I know egr was mentioned but is it disconnected or blocked off?
Click to expand...
It's disconnected and vaccum lines are 'sealed'. No vaccum leak.

90XJ_Seth said:
Have you verified fuel ballast is functioning and fuel pump is good?
I'll leave it to the smarter mechanics to discuss your timing.
Click to expand...
Yes, it works, fuel pump is new, and problem is the same on both types of fuel.


I didn't do much progress with jeep as i am a bit sick, but i spoke with one jeep guy, and he told me to check exhaust manifold for cracks. And if no this maybe ECU.
And i think exhaust manifold may be correct way, because AFR looks good, and my spark plugs are totaly black when i unplug them. And they have like two weeks?
 
My problem on my 89 with bad gas mileage and low power was a mix of problems. A bad Map sensor, the Fuel Pressure Regulator went bad, allowing to much fuel in the motor, ruined the o2 sensor, which made the problem worse, and clogged my Catalytic converter. All of this reduced power and fuel efficiency. I had to get a engine computer reader to diagnose these problems.


Sent from my iPhone using Tapatalk
 
REM is 200$ + shipping to poland will br another 50-100$ probably. It's a bit too expensive for me. All the things you mentioned i have replaced.
 
szachmat said:
It's disconnected and vaccum lines are 'sealed'. No vaccum leak.
Click to expand...
If the EGR valve is stuck partially open, which I've seen before, it won't matter if the vacuum lines are plugged. It could be introducing exhaust gasses into the engine when it shouldn't. If you have a drill and a flat piece of metal, make a quick block off plate and give it a shot. Can't hurt to rule that out too.

Can you take a spark plug out and post a picture? I'm interested to see if it's burning too rich or lean.
 
Hello,


A little update:
- tips 1, 3, 4 done
I forgot about TIP 5 but i changed ground cables for new (the one on the firewall, and from the battery to then engine)
- i replaced knock sensor (had it for free from my friend)
- checked the ECU (its like brand new, give it to check for a guy who works with car electronic(don't know how to call him in english :X) and he told me that everything is fine with it.
- also i tried to check exhaust manifold for cracks, didn't see any
- i replaced whole distributor for remanufactured one


And all of it gave me nothing.
Need to check EGR, forgot about it.
 
I'm checking one more time things i've already done and I have a question about TPS adjusting.


According to instructions i've been using, i adjusted the voltage on SQUARE connectro (ABCD)
But When i now checked few videos on youtube, and this instruction (http://cruiser54.com/?p=54) I should adjust voltage on FLAST 3 pin connector (ABC), and THEN on square connectro (ABCD).
I don't understand it. It's connected into same TPS. If i adjust it first on flat connector with 3 pins, then do the same on square connector it's like i would not adjust on flat connector at all. 2nd adjusting cancels the 1st one.
Please explain if i'm right.


My Jeep is shifting up at about 4400rpm. I think it should go higher.




https://photos.app.goo.gl/VECMqnXx9RXtWY468
https://photos.app.goo.gl/qU1jX5S1V8PZ8cRV8
https://photos.app.goo.gl/Kxry7ZficNwSjSwC8


These are few videos from acceleration tests...
 
I adjusted TPS according to flat connector + i have checked EGR valve.
The EGR valve seems to be working, and it was pretty clear when i plugged it out.
SO i just plugged it back and reconnected vaccum line - it's working.
BUT after those 2 adjustments, jeeps runs, bad, gear shifting is bad so i need to adjust tps back as it was according to square connector.


What about changing gears? Should it bet at the begginng of the red marks on

I tried to do TIP5, but the info says "resistance should be near 0".
How much near? When i will know it's bad? For example TPS had 12 ohms.


Also ignition system is completly new and it has some small missfires while iddling. No problems with open throttle. Except that, no other bad noises from the engine.


And what about transmission shift point? Isn't ~4500 too low? TPS regulates that?
I'm really thinking about buying R.E.M+
 
I checked today ground on square connector, as i wqs re adjusting TPS. Almost 600 ohms... I made new ground connection for both, square and flat connectors, now it's 0 ohms. No improvement in power ofc :p and still shifts gears at 4300-4500 rpm.
 
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