The car starts fine and works great. it has oxygen sensor code which I have ordered online and would be replacing sometime this week

but for last couple days, the engine hesitates at 1500 rmp and upon pressing the gas paddle all the way, it accelerates.

Please let me know what could be the possible problem

 

bhavin, if the check engine light is flashing, DO NOT!!!!! drive the car. That is the car's way of saying that you are hurting it. Odds are, if you are lucky, you will only have to replace a catalytic converter. It could get worse. I would say to get the codes read to see what they are saying and to also replace the O2 sensor. It may be that simply the O2 sensor is your issue. But, if it isn't, this could get spendy really fast.

 

Thank you Thermo.
Since the issue started while I was driving, i had no choice but to drive abour 20-25 kms to reach home. The check engine light flashed few time and then was steady but this repeated few time till i reached home.
I will be taking the care to a workshop this week, if i receive O2 Sensor and hope nothing major. I will also be replacing all spark plugs with NGK iridium ones.

 

Hello Thermo,
Based on your experience would you be able to tell whether tell, to begin with, why this hesitation started, could it me electrical or mechanical?

 

Find out what DTCs are stored and correct the source(s) of the engine misfire(s). Misfires can be caused by oil finding it's way into the spark plug well and fouling the coil units and spark plugs causing them to short.

The stored DTCs will indicate which engine bank is having an issue. As stated above, DO NOT operate the vehicle under conditions that cause the MIL (Malfunction Indicator Lamp) to flash as catalyst damage is occurring.

 

bhavin, since your flashing condition is intermittent, then I would tell you to gently drive the car to a local auto parts store and have them read the codes for you. WRITE THEM DOWN!!!!! Once you have the codes, post them here and we can give you a pretty good idea of what is going on. Without atleast that information, we would be guessing. These cars suffer from a few common problems (vacuum leaks, bad plug on TPS, and oil in the plug wells are the big ones normally). But, it is possible that if your upstream O2 sensor is bad, it can lead to a rich condition in the engine and the flashing light.

 

Hello thermo
Thank you for your input. I have checked the plugs and there is no oil. However I am changing all 6 plugs today as well as cylinder 1 2 3 coils (previous owner have me extra coils from parts car). Will be picking oxygen sensors (2) and see if the work shop can replace them today. Will also get codes scanned and post here. Will update once these few things are done. Hope there is nothing major

 

I have changed upstream sensor (ones that can be easily reached from top). Drove the car and still the engine hesitates between 1500 - 2000 rpm. What I noticed is that if i keep the gas paddle steady, the engine then jumps to normal and the slowly drop the rpm. I got a local mechanic check the codes and this is what came up...P0300, random cylinder misfire detected and the second code is P1313 Misfire rate catalyst damage fault bank1.

He hooked up the scanner and we were doing live reading and found that the short term fuel was showing from -5 then goes up to -25 and that's where the engine vibrates, then the computer adjusts the fuel and the short term fuel drops to -5 / -6 range and this is when the engine stabilizes. He said it could be possible vacuum leak, or that the cat is backfiring causing engine to misfire.

I am just worried of spending too much money to fix one thing and the other starts. Please guide me to the next steps.

 

bhavin, before you get going too far, open up the hood of your car and lean in, resting your hands on the support over the radiator. If you look down at your left hand, it most likely will be just inboard of the headlight. If you go straight towards the engine from there, you should be at the end of the cylinder head (near the "front" of the engine). If you look there, you should see a few wires bolted there. Remove the bolt holding the wires in place and clean up the bolt, clean up the surface on the block, and clean up the surface of the terminals. Bolt everything back together and see what you have then. I bet you will find that the engine will run a lot better.

The other thing that I would tell you to do is to look at the tops of all the coils. See if you spot any with "white hairs" in the clear top. Normally they will be running around the outer edge of the coil (near the black plastic). If you see these "hairs", those are actually cracks that are allowing water to get into the coil and cause it to malfunction.

 

Hi Thermo, considering mine is a left hand drive, should i be leaning from drivers side or passenger side?

And no white hairs, no crack or leak over there.

 

bhavin, if you are standing in front of the car, it wouldbe behind the passenger headlight for you.

 

Hello Thermo,

I could not find the bunch of wires behind the passenger headlight. I will try this again in daylight. However, I spoke to one of the mechanic and he mentioned 3 things, 1) Coils, 2) EGR valve 3) Catalytic converter. He said try replacing one coil starting from cylinder one and drive and see if the misfire occurs and continue till cylinder 6. If the problem persists, then open the EGR valve and spray in WD40 to see if it is passing from one opening to the other. If it does, then it is EGR Valve.I opened all the plugs (cold engine) I had replaced and saw that plug # 3 had some oil (on the spark side) So I replaced the coil and drove for about 10 kms with no misfire. Will drive bit more and see how the car behaves. Will keep posted.

 

So I got my XJ6 scanned. Found exhaust leak and downstream sensor were not showing any signals. Fixed the leak. While removing the oxygen sensor, one of the thread got damaged so the mechanic spot welded the sensor and applied exhaust cement. Did not have much of a choice anyways except to cut the exhaust and replace. Drove the car in city and highway for sometime and no check engine light, no hesitation. Seems the problem is solved (touch wood). Enjoying my weekend ride yet again. Thank you guys.

 

Wait.....so you have an XJ6???? This is the X-TYPE forum. All the advice you were given was based on you having an X-Type. Either way, glad it worked out in the end.

 

ohoh. my bad......i see that i put this in wrong forum.
yes 97 XJ6 Vanden Plas.
is there anything that i need to clean to improve engine performance....like what Thermo mentioned above...bunch of wires below passenger headlight.

 

bhavin, this would be a question that you should ask in the other section. We would not necessarily know the little tricks to keep the kitty purring nicely, they would.