Engine Light, but no apparent issues - JeepForum.com
 
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post #1 of 8 Old 09-26-2017, 10:42 AM Thread Starter
zunami
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1999 XJ Cherokee 
 
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Xj Engine Light, but no apparent issues

Apart from a few common replacements, including fuel pump, clock-spring and fuel-injector - my '99 cherokee limited has never had any issues.
It has under 200k miles on it, and every mechanic who has taken a look at it have always said it is one of the best maintained and preserved engines they've seen in a '99.

That said, recently the check-engine light has come on for what seems like no apparent reason.
There was absolutely no problems driving it. Oil was changed just a week or two ago, and the jeep has hardly been driven since then.

Tank was over 2/3, oil levels read fine, battery read fine, temperatures were within normal range and the vehicle performed exactly like it always does.

It left me wondering exactly why that light came on.
I investigated for any leaks, and came back periodically to see if there was anything smelling in the engine or any leakage, but there has been no evidence of any of this.

As of late, the Jeep has been showing some issues when being started.
It normally starts right up, but sometimes it acts up a bit after being started up again right after the engine has been turned off.

For instance if I park the car to wait for someone and switch the engine off, the car will stall a bit when I try the ignition, and I have seen the "check engine light" come on in conjunction with that, where the car drove slightly strange for the first 5 or so seconds after it starts like this, but then went back to acting perfectly normal.

If I am to describe the event, it seemed like the car started somewhat slower than usual, and like the engine was running on reduced power.

I've been told that the jeep probably needs a new starter soon, and that this is fairly common around the 200k mile mark, but I don't actually have a lot of experience with Jeeps.

It is important to emphasize that these are two separate issues, at least according to my experience (I'm not denying that they very likely could be related).

To summarize

1) Occasionally after turning the jeep off, for instance to wait for someone, when started again briefly after, the engine will sometimes stall a little prior to coming on, and seems like it is running on "reduced power" (less noise and gas less responsive). When this happens, the check engine light comes on, but goes away after a brief moment, as soon as the car starts acting normal - which is usually after about, 2-3 seconds.
I've been told I probably need a new starter.

2) This morning, the check-engine light came on while driving. There were no apparent issues, the car performed with no noticeable problems, no leakage and all gauges showing fine levels.
I have not started the car back up since, to see if the light is still there or not.

Does anyone know what this could be?
Is it likely that the two problems are related?
Is it likely that my friend is correct in that we probably need a new starter?

In the past, we had an issue where the battery of the Jeep seemed to die on us far earlier than it ought to, and we've replaced the battery on it, just slightly more frequently than what people tell us to "expect".
We've been told there might be a minor malfunction with the actuator.
Could this be related?

If anyone has experienced something similar or has experience with this, feel free to chime in.


- ST
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post #2 of 8 Old 09-26-2017, 11:00 AM
Newtons3
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Shooting from the hip.....hot restart issues with stumbling from initial idle have often been the result of injectors leaking. Fuel pressure drops and can cause issues restarting. The fuel accumulates in the intake tract and it takes a few seconds to get all that sorted out when it refires. You never stated......what was the CIL for? What was the code?
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post #3 of 8 Old 09-26-2017, 01:09 PM Thread Starter
zunami
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Quote:
Originally Posted by Newtons3 View Post
Shooting from the hip.....hot restart issues with stumbling from initial idle have often been the result of injectors leaking. Fuel pressure drops and can cause issues restarting. The fuel accumulates in the intake tract and it takes a few seconds to get all that sorted out when it refires. You never stated......what was the CIL for? What was the code?
Sorry, I'm not too well-versed in the technical lingo.

What is a CIL?

I don't even know how to check a code! Unfortunately, my car-expertise begins and ends with the ability to change a wheel/tire and replacements of minor parts.

I imagine I could get the code from a mechanic with the right machinery to check for it, unless we're talking about two different things - I'm not aware of any code I can check on my own.

If the engine light is still on when I need to drive the car home later today, I'll take it down to the nearest mechanic and try to get him to get a read.

Your guess sounds pretty good, but discouraging considering the injectors were very recently replaced.
It is, of course possible that it wasn't done right.

Come to think of it, these issues didn't start until after we replaced the fuel-pump (we had previously replaced the injector), and the road-assistance tampered an awful lot with the injectors, to try and see if that was the issue.
It is possible something may have happened.

I might need to get this checked out.

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post #4 of 8 Old 09-26-2017, 02:12 PM
Newtons3
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AUTOCORRECT. Should have been CEL, not CIL. CEL= check engine light. With only the emerging history to go on, I'll stick with my original guess and throw in that with the injector replacement, the plugs should have been changed.
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post #5 of 8 Old 09-26-2017, 04:50 PM
tjwalker
It's the crank sensor!
 
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When you have a check engine light, job #1 is always to retrieve the code and let that code guide you to possible offenders that could be the root cause. Anything less is guesswork.

Caution: Retrieving codes is easy, but interpreting them and performing the correct repair is not always so straight forward. Usually, some testing is required to verify that the part you are replacing is the actual culprit. Never throw parts at it on a hunch. Terribly expensive and not efficient.

Either take it to a trusted shop and have them explain the code and repair to you or if you like, you can post the actual code here for comment. Some parts stores like Autozone will read the code for you for no charge. If you have them do that, write the exact code down and post it here, NOT just a description. With OBDII codes, the devil is definitely in the details!

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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post #6 of 8 Old 09-26-2017, 06:38 PM Thread Starter
zunami
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I appreciate the tips.

Naturally, it was always my intention to stop by a mechanic, but understand that this issue occurred in the early hours on my way to work, and that, by the time that I wrote this, I wasn't off yet and was not at liberty to take my car anywhere.
I intended to stop by my usual mechanic, who usually reads codes for free, but he is apparently on vacation, and there are no other mechanics in my immediate area.

With no means to read the code on my own, I have no real other choice than to guess what it could be for now, and right now, Newton's theory seems to hold up. I just took a look under the hood and gave the injection system a close examination. I noticed that 5/6 of the electrical connectors all looked fine, but the 6th was missing the red switch that you need to push to safely disconnect the... well, the connector.
I imagine this might be why the engine light has suddenly come on, because the connector is probably not properly attached. I wonder if this could also be the cause of my other issues - but honestly, I'm not too certain what the electrical connector actually does.
We just had the injector itself checked, not a month ago, and I almost refuse to believe that it isn't operating as it should - so I'm hoping I found my culprit.

Assuming it is the connector, is it safe enough for me to roll down to the mechanic tomorrow? I'll have to pick one in town where I work instead, so it is a bit of distance after all.

I wonder if I could apply some sort of quick-temporary fix to see if the engine light goes away, that might tide me over better until I get to the mechanic. Short of taping it though, I'm not really coming up with any ideas.

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post #7 of 8 Old 09-27-2017, 05:12 PM Thread Starter
zunami
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Update:

I got the code read, it's P0121.
The mechanic said that there's a discrepancy in voltage in the TPS sensor, but that it seems minor and irrelevant, other than that it keeps the check engine light on.

I didn't get anything else out of the mechanic, as he says I need to go see a different mechanic, and didn't charge me.

There's only a few mechanics around my area who deals with electric and computer issues, and apparently I'll need one of them.

The mechanic assured me it wasn't an important or particularly serious issue, and says I can fix it or not fix it, and it will not matter.

The electric connector to the fuel injector apparently holds tight despite the missing switch, and it will not need replacement until someone has a reason to disconnect it, because after that, it will likely not come back on.

I also noticed that the issue with my "hot start" stalling, has stopped, for now.

I'll be calling the place that does electric and computer fixes when I have time tomorrow.

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post #8 of 8 Old 09-28-2017, 05:43 AM
tjwalker
It's the crank sensor!
 
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If your mechanic isn't willing to dig into a basic P0121 code, then I do agree with him that you should try a different shop. This time, try to make it an ASE Technician, who are trained in how to diagnose and resolve engine codes with a testing based strategy.

All codes should be chased and resolved. The problem with letting them ride is this. Even if the code isn't giving you any current driveability symptoms, then when another problem comes along and sets another code and because your check engine light has been on for a while, you don't even know you have a new problem. And you now have an even more confusing situation with resolving the new problem and the old one. You've added complexity because you have to figure out if the old code is related to the new code or is it two sepearate issues? See what I'm getting at here?

The P0121 (throttle position sensor circuit) is generally a pretty easy one to resolve on the XJ. As you seek service for this, consider if there is anything else that needs to be done on your XJ at the same time you have it in the shop. What is the history for routine tuneup maintenance like spark plugs, wires, distributor cap, rotor? Any fluids need to be changed like coolant, (inspect hoses and how about thermostat) transmission, transfer case, differentials?

Take it to a reputable shop, good luck and keep us updated!

Here is more on that P0121 code:

https://www.obd-codes.com/p0121

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
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