View Full Version : 95 RRC 4.2 asking for help w/ diagnoseing an engine problem

11-23-2007, 08:31 PM

I have a 1995 LWB RRC, new problem started this week on a rainy day (dont know if that matters)

the engine started running really rough at a stoplight (almost stalling) and then when i tried to accelerate it had very very little power and made a couple of coughing / popping sounds. I pulled into a parking lot and it was at a really low rpm idle, almost stalling. Then the check engine light came on (45 - O2 sensor) and it ran smooth again.

I went to drive home and again really rough, low rpm idle and with no power on accelartion or even the slightest hill.

I know it could be many things, and not just the o2 sensor, but i dont have any idea how to diagnose the problem.

Any help would be great.


11-24-2007, 06:30 AM
check your catylitic convertors, the inner meterial deteriorates and turns to powder and plugs the screens,the easiest way to check is to remove the front o2 sensors and see if it regains the power.....

11-24-2007, 04:56 PM
Had the same problem with mine. Had a crack in the flange above the cat. Check the manifold for cracks. I replaced the Y pipe and O2 sensors and it ran fine for a while again. Had some other issues with the left bank fuel rail and poor spark. Do these symptoms sound familiar? If all else fails you can always use a can full of gas and a hand full of matches to fix it.

11-25-2007, 09:41 AM
Unplug the O2 sensors as was mentioned before and if they are the broblem the engine should run fine but with a slightly richer mix!

11-25-2007, 09:44 AM
ok so thanks for the advice
not sure if i was supposed to pull the o2 sensors or just unplug them
but i unscrewed the left one from the exhaust pipe and unplugged it from the wire so it is completely out.

The top 1/2 of the sensor is white, the bottom 1/2 is black and a bit greasy. I have no idea how they are supposed to look. Please let me know, and thanks again everyone.

11-25-2007, 10:15 AM
You can just unplug each one from there own female/male conectors so that when the computer senses them not there it will go into default mode. You moght want to put that one back in or it will get pretty noisy when you start it up. o2 sensors are very complicated pieces of engineering, your lucky you got a code! oh and they can just go when ever they feel like it too!

11-25-2007, 10:20 AM
ok here is a link (i hope) to a photo of the 02 seonsor

11-25-2007, 03:48 PM
ok so i screwed the o2 sensors back in and left the unconnected
i cleared the codes and let the rover idel for about 5 min in the driveway
everything seemed fine, smooth idel ect.

so i drove to the store about 15 min away and then let it idle in the parking lot as a test. right away the rpms started to fluxuate up and down. it went really far down (almost to 0) for a split second and then bounced back up and the check engine light came on again (45 - o2 sensor)

I drove home and it would idle low at stop lights but no bouncing around of the rpms.

The sluggishness is gone and no poping sounds.

Not sure what to test next.

11-25-2007, 06:34 PM
Ok sounds like the computer sensed the O2 sensors where not there, that was most likely when the check engine light came on. Every time you turn the truck on whithout the O2 sensors it will take a little bit until the computer recodnizes, that is most likly the reving up and down at idle. Now if it drives ok but it idles a bit rough I would get a few new 02 sensors and pop them in.
Pull the sparkplugs and see if the engine has been running rich, if it has it might be more evedence the O2 sensors are bad. At least with my experiance when the O2 sensor(s) go bad they have made my egines run to rich, sometimes almost enough so that the engine won't run!

11-25-2007, 06:45 PM
Dan, thanks for all of the help.

Can i tell by looking at the o2 sensor if it is rich or not? Also what do i look for on the plugs to tell if it was rich?

11-25-2007, 07:30 PM
I don't believe if the you can diagnose the condition of an o2 senser fron its looks because everything they do is inside. How many miles on the rig anyways, they like to go if there is any age on them. For the plugs, they will look oily black looking and they will smell bad. A good plug should be clean and should bairly smell at all, Take some pictures of the plugs and send them along i would like to take a look at them. Oh and believe it or replaicing the O2 sensors is actually part of doing a tune up! i would do them every 50k miles to keep up gas miliage and so that they don't quit at the wrong time!

I will post some pictures of my current project, 1990 range with bad bad carbon in the cylinders!

12-09-2007, 05:59 PM
Dan thanks for the advice, I ran into a bit of an emergency and didnt get to spend anytime with the rover these last couple of weeks. I'm back now and will pull the spark plugs and send photos.


92 classic
01-04-2008, 10:08 PM
I think u should get away from the o2 U have spent to much time their. you need to run a vaccum guage on ur motor and check for low vaccum this would tell u if u have a restriction in the exhaust or not.and a pulsating guage would tell u if u had a stuck valve ( a common problem) I would start their ..........

92 classic
01-04-2008, 10:14 PM
also what u are discribing could just be a bad part in ur secondary ignition (distributor plug wires ex) also u could check ignition module and ecu pin tension

post back id like to see ur findings

01-05-2008, 05:39 PM
ok well I pulled a spark plug and took photos and finally can get them online. here is photo. I'm gonna take it to a place to get it tested, i dont know how to do the vacume test and things have been so crazy as of late that i dont know when i will be able to get to it.



92 classic
01-09-2008, 07:52 PM
the pic of ur plug looks like its new usually the plug with some miles on it would have a whitish light brown electrod and the ring on the plug at the bottom of the threads would be black and kind of sutty go to advanced auto parts and look in a chiltons manual does not matter what car and they will have a color page somewhere in their that will show a spark plugs and how they look under diff. conditions

01-11-2008, 08:05 AM
yeah the plugs were replaced in feb of 07 and have about 30,000 miles on them. But i live in the city so almost all of my miles are long trips, I take the subway mostdays.

thanks for the sparkplug chat advice, i found this one that may help others