Hey all,

So I have been driving my jeep around as a daily driver when I noticed that when I stomp on the peddle to open her up it putted, stuttered and all out sounded like it wanted to die. it idles just fine, holds good fuel psi(33) and no dead spots in the TPS it drives ok as long as you don't gun it. any ideas?

 

Any Renix problem and I would start checking the CPS as it only takes literally a minute or two. That said, what about regular tune up? Plugs been gapped lately?

That popping and doggin could mean it's lean. After checking the CPS I might consider checking the 02 sensor and changing the fuel filter if its time anyway.

Cruiser is the real Renix pro, (wrote the below V), but the intake air and coolant temp sensors may also be suspect if your lean. OK, and the MAP. Of course trying to sort that out if you don't know the condition of your wiring & sensor grounds....

Btw, curious, have you tried really floor-boarding it? I know on the surface that doesn't make sense, but if it takes off past 70 or 80* throttle that might tell us something.


　
　
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　

 

good fuel pressure ,what about volume last fuel filter change was ?

 

Plugs, wires, cap and rotor? Could be an issue in the secondary igniton system which points to the tuneup hardware. Fuel filter like freegdr suggests? Could be.

Make sure you've got a multimeter and are familiar with it.

 

X2^, & visually inspect the wiring to the 02 and the other lower sensors. Make sure nothing is melting on the exhaust manifold.

 

plugs and wires are all new and O2 sensor is only about 300mls old. the fuel filter was replaced about 2weeks ago but I will start there and test out the CPS(just replaced about a month ago) thanks again guys

 

i would even check the mass airflow sensor. might have a back vacuum leak and even be unplugged.
and even seafoam the rig after the tune up

 

i have an intermittent problem very similar to yours im 95% sure its the fuel filter and its probably not a bad time to change it any way

 

If you have a meter and you've done it once or twice, you'll find checking the CPS is barely tougher than simply checking battery voltage. (90 and earlier Renix Jeeps only) It's like the hart-beat for the system. Not much sense trying to administer help to a patient without checking for a pulse first!

Also you want to see a good strong snapping blue spark. I would use the coil wire, (and get zapped 1/2 the time!), or pull a plug, (and the fuel pump relay or a wire on the ceramic ballast resistor, by the air cleaner so the fuel pump won't run). Hold the body of the plug on a good ground.

If my CPS checked good, and my spark didn't, I'd consider checking my coil/ICU contacts;

C/O Cruiser-
　
　The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.
The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner.
Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and bolt the coil back on to the ICU.
While you’re right there unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier. Apply dielectric grease to the connectors and plug them back in.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.
　
Revised 11-29-2011


Then also the Renix ECU will ignore a number of sensors when you floorboard it, but not the MAP sensor

 

I think you're referring to the MAP sensor that's on the firewall and connected to the throttle body by a hose/plastic pipe that's prone to cracking, melting, plugging?

 

That was LeRoy Cruiser. I was wondering as well. OK, with the line cracked or plugged we know it would dump fuel and run rich. I wonder if the map itself fails to the lean side. I suppose a very restricted MAP tube might not let vacuum drop quickly at the MAP resulting in a momentary lean condition.

This link (has the link) to the Lunghd article on sensor testing; (has MAP testing) https://www.cherokeeforum.com/f51/he...ix-links-1397/

And here is more info on the 02 sensor; http://www.naxja.org/forum/showthrea...ht=sensor+test

 

lol.

 

I guess the Manifold Absolute Pressure sensor in our Jeeps, (& Chrysler?), ends up solving the same issues as a Mass Airflow Sensor (MAF), does, just comes at it a different way.

Guess it takes a stab at the fuel/air mix, then the 02 sensor refines it from there. Or tries to!

 

Yes I was referring to the map sensor, nice catch. Thanks.

 

Who is LeRoy Cruiser? LOL. OOOOPS!. Wrong quote.