piwo8

Greetings from Poland,
Patient: Cherokee 1988 4.0 renix, a.t.
Symptoms: low idle speed - 350 or less,
idle is not stable,
there is a slight hesitation when you push the acceleration pedal rapidly; it is just a piece of a second, but noticeable and very annoying; sometimes after pushing accelerator rpm goes down to almost 0 - for a little while, then goes up.
Yes Mr Cruiser, I follow pink link below.
Now I'm at cps testing. It gives 235 ohm resistance, and keeps jumping from 0.2 to 0.5 V while cranking.
The question is are these readings ok or should I change the sensor?
Can symptoms, listed above, be connected with cps failure?
TPS is adjusted properly.
Looking forward to hearing from you
Piwo

cruiser54

CPS failure is usually intermittent no-start or just no-start.

Your symptoms sound like a tune-up/sensor issue.

What have you completed in the pink link?

Have you ever replaced the plugs, wires, cap and rotor?

Made sure the intake manifold bolts are tight?

piwo8

Thank you for your reply
Cap, rotor, wires, plugs, air filter - brand new.
Tasks completed: 1-5, 8, 9, 11 - proceeding 7
Vacuum checked. Manifold has just been reinstalled (upgrade of lpg installation) with new gasket.
I have 746 injectors.

I have to crank about 2-3 seconds to start engine.

cruiser54

2 to 3 seconds is absolutely normal on a Renix.

Ever replaced the oxygen sensor?

You have the C101.....

I have a write-up that is pretty complete but without finishing touches if you would like to do that at some point.

piwo8

Oxygen sensor - I'll check it, I've seen a write up somewhere. It's quite expensive here - the mopar one. And I'm not sure about crown's quality... I'll write about results.
Thank you ones more.

piwo8

http://www.xj-jeep.pl/czerwonoskory-1988-vt1336.htm

How do you like the colour?

RusNorthID

I was just having the same issue on my new to me 88 mj and this was my problem haha make sure you check all your grounds

piwo8

I don't think I have any ground wires there...

Oxygen sensor checked. Resistance: 34000 ohm
It shows 5.0 v without flowing.
So I will change it and let you know.

DFlintstone

Not to distract from Cruiser, (who I learned loads from), but I watched my CPS go down below a .3, before it failed. In your shoes, I might try his idea on drilling it's mount holes a tad bigger, and installing it with downward pressure applied.

Yes, you SHOULD have that ground RunsNorth posted. It's a breaded cable from the rear of the valve cover, to the firewall on the drivers side. Pretty crucial that. You might scrape the paint off the firewall where it connects. It's the only engine to body ground. Alot of us have added a second one just to be sure. I just went from my AC compressor to a radiator mount bolt. Not ideal.

The CPS can be easy...

Change Your CPS. I found if you BACK the fronts onto ramps, you won't have anything in the way, where you need to lay. A stand under the left front frame would be in your way.

If CPS itself is putting out less than .35 Volts AC, unplugged, while it's cranking with a good battery, or the resistance is not 200 ohm's plus/minus 75, hot;

11mm socket > 3 inch extension > universal > long (18-24 inches of extension). Your feet are sticking out under the passenger side, you can reach up past the front drive-line with your left hand to hold the CPS from the front. Your right hand is on the ratchet way back by the tranny cross member. If you tie a long string on the old, you can use it to haul up the new. Toss that piece of plastic if it's still there, and do not drop the bolts in there! Echlin # CSS980, (from Napa, for 87-90), should be fine, but some prefer to go to Jeep. I wouldn't bother with anything else for that.

If your left forearm is bigger than a quart Mason jar, you might consider removing the front drive-line. Also you can cut your old CPS wires if they go through a deal on a bell housing bolt, then be sure your new are held somewhere safe.

The second one is REALLY easy!



Also I've seen posted instead of drilling the holes a tad bigger, some just smack it (the bracket I'd assume), with a hammer to bring it closer to the flywheel. Sounds dicy to me. I'd have a spare in hand it I tried that!

cruiser54

BTW, there's a new write-up in my tips. #27. C101 elimination.

DFlintstone

Ha! Beautiful! (btw CF, I'm big on ventilation while soldering). I think breathing only a little burning insulation is not good. (not to mention lead and flux). Yea,,,,A Nube will figure out soon enough a solder joint needs to cool, before you can side the shrink wrap over!

DFlintstone

piwo8

Hi there,
As suggested, I,ve changed oxygen sensor for Denso 234-3116 (of course sent from USA ). Ilde speed is still little low, but other negative behaviour has gone. Engine is running much better. Thanx for all the help!