renix wont rev, rough idle, rich, backfires.

NightRieder · 01-11-2010, 08:38 PM

i need some help iv been back and forth with this. i bought this renix xj with a thrown rod threw the 4.0 block (#6cyl) sympoms inclued rough idle, engine shakes, im not to sure if it is miss firing or not. after the motor warms up a bit (about 45 sec. to a min. after starting) it back fires at an idle. it will not rev above the idle speed. it kinda sounds like it quiets down and if u try to floor it it backfires sometimes. according to the guy i bought it from it ran great before it blew. go figure. i reused all the sensors and the distributor and bought a 99 core (block, internals,head) so i just bolted the renix mani up. at first i thought the cps but the previuos owner said thats new. then i thought the knock sensor but then i was told it sounds like a tps problem. i need a direction cz im not getting anywhere.

=( i just wanna go wheelin again!!

thanks for the help!

that_1guy · 01-11-2010, 08:43 PM

could be your tps? or possibly something isnt plugged in. have you checked timing on it?

NightRieder · 01-11-2010, 08:46 PM

Quote:

Originally Posted by that_1guy

could be your tps? or possibly something isnt plugged in. have you checked timing on it?

i thought they have that self adjusting timing system. and i tried but when i had the timing light hooked up it seemed like it was missing spark every once in a while like not smooth. its ok for 2 cycles then misses one and so on.

jcjcherokee · 01-11-2010, 08:47 PM

I kinda had the same problem. If its an automatic i would buy a jeep tps and put on it. I bought the cheap ones and i got what i payed for. It was cheaper from the dealer than napa. Mine was popping in the intake. distributor installed right? coil. ignition module. just some thoughts

that_1guy · 01-11-2010, 09:07 PM

Quote:

Originally Posted by NightRieder

i thought they have that self adjusting timing system. and i tried but when i had the timing light hooked up it seemed like it was missing spark every once in a while like not smooth. its ok for 2 cycles then misses one and so on.

have you tried adjusting the tps, the renix tps's are adjustable. mine does the same thing with the timing, and i havent been able to figure it out i have a rough idle also, but mine isnt as bad as yours

NightRieder · 01-11-2010, 09:17 PM

Quote:

Originally Posted by that_1guy

have you tried adjusting the tps, the renix tps's are adjustable. mine does the same thing with the timing, and i havent been able to figure it out i have a rough idle also, but mine isnt as bad as yours

i havnt yet. but i will. ill try anything at this point. what have you tried so far?

that_1guy · 01-11-2010, 09:23 PM

i also tried to replace the fuel ballast resister thingy in the engine compartment on the driver side, made it idle much better, but when i was driving it, it didnt have enough power to the fuel pump so it wasnt supplying enough and it was cutting out so i went back to my original. also you could try and replace the fuel pressure regulator, you might be getting way to much fuel which is causing the backfire and such, try putting a fuel pressure tester on the fuel rail

**Mickey_D** · 01-12-2010, 12:51 AM

Mine is a 90 also and mine did much the same thing. Mine was the vacuum line from the manifold to the MAP sensor (mounted to the firewall directly behind the valve cover) was dangling down the back of the engine.

My suggestion is replace that vacuum line (cheap) and acquire a wrecking yard MAP sensor. $6 total to check if I'm right.

NightRieder · 01-12-2010, 01:33 PM

Quote:

Originally Posted by Mickey_D

Mine is a 90 also and mine did much the same thing. Mine was the vacuum line from the manifold to the MAP sensor (mounted to the firewall directly behind the valve cover) was dangling down the back of the engine.

My suggestion is replace that vacuum line (cheap) and acquire a wrecking yard MAP sensor. $6 total to check if I'm right.

i have been looking at that too. its plugged in there but it looks like its not on there all the way but i can push it anymore. im off today so unless it rains on me ill be out there testing everything all day and be back with an update.

dont stop with the replies though really helpfull thanks.

**Mickey_D** · 01-12-2010, 02:33 PM

The way to check the MAP sensor is to start the Jeep then unplug the vacuum line from the sensor.

If the Jeep doesn't really change much in how it's running, check to see if there's vacuum on the line. If there is, the sensor is dead. No vacuum means the sensor probably is working, but it can't do anything until you figure out why the lack of vacuum.

If the running of the engine changes drastically, then the sensor is operational and it's time to look elsewhere.

**webdog** · 01-12-2010, 03:47 PM

Quote:

Originally Posted by Mickey_D

Mine is a 90 also and mine did much the same thing. Mine was the vacuum line from the manifold to the MAP sensor (mounted to the firewall directly behind the valve cover) was dangling down the back of the engine.

My suggestion is replace that vacuum line (cheap) and acquire a wrecking yard MAP sensor. $6 total to check if I'm right.

I have had that issue before.

Another thing that helped my renix is cleaning and putting die electric grease on all the sensors under the hood, response is much faster and idles smoother.

NightRieder · 01-12-2010, 03:53 PM

ok. yeah i moved the vacuum line to the map from the top hole on the TB to the bottom one. got rid of the back firing as far as i can tell idles smoother. still wont climb rpms. seems to be running more stoich or atleast closer. i was thinking.. that hose thing that comes from the exh. mani to the air box..? if thats not on there would that make the o2 read lean then dump to much fuel causing misses?

jcjcherokee · 01-12-2010, 06:42 PM

that tube i believe is for when its cold and the engine is cold. i never run a jeep with it. i believe it was also for emissions during cold starts. I also would check the intake charge sensor (I believe thats the name) Its behind the throttle body towards the firewall.

1990JEEPXJ · 01-12-2010, 06:49 PM

Quote:

Originally Posted by NightRieder

ok. yeah i moved the vacuum line to the map from the top hole on the TB to the bottom one. got rid of the back firing as far as i can tell idles smoother. still wont climb rpms. seems to be running more stoich or atleast closer. i was thinking.. that hose thing that comes from the exh. mani to the air box..? if thats not on there would that make the o2 read lean then dump to much fuel causing misses?

if WA does smog checks and they see that hose is missing you wont pass... i know from experience.

NightRieder · 01-12-2010, 07:04 PM

Quote:

Originally Posted by 1990JEEPXJ

if WA does smog checks and they see that hose is missing you wont pass... i know from experience.

my county doesnt test all the ones around me do but not mine =) im good for another year or 2

01-12-2010, 03:53 PM	#12
NightRieder Registered User Join Date: Jan 2010 Location: Port Orchard WA Posts: 25 Profile Gallery Classifieds My Jeeps	ok. yeah i moved the vacuum line to the map from the top hole on the TB to the bottom one. got rid of the back firing as far as i can tell idles smoother. still wont climb rpms. seems to be running more stoich or atleast closer. i was thinking.. that hose thing that comes from the exh. mani to the air box..? if thats not on there would that make the o2 read lean then dump to much fuel causing misses?