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95LS 24v 3.0L Sudden Rough Idle?

Posted By: MrJeebs

95LS 24v 3.0L Sudden Rough Idle? - 05/29/13 02:13 AM

Hey Gang,

Well, my LS made the trip from CT to TX with no trouble at all. I was able to find work within 4 days of arriving, now working full time in the Beaumont area.

Now that I am not traversing huge hills and whatnot, my mileage is the best it's ever been, having gotten nearly 150 miles from a 1/4 tank of gas:-) The truck is running really well, but a day or 2 ago, I noticed the idle getting rough. Now it is all kinds of stumbly at idle. Not to the point where I can see it in the tach, but I can certainly feel it.

I searched the forums but wasn't able to find much pertaining to my vehicle model.

I am guessing a vacuum leak, but have no way to check it, as I have no tools or anything.

Anyone have any suggestions on what it might be, and a good place to take it that wont fleece me?

As always, thank you in advance for any advice/suggestions.

<img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: WigWiggy

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/29/13 09:48 PM

Might be the IAC motor. Should be able to find lots of posts on that if you do a search. It's a little motor that goes into the throttle body and allows a controlled amount of air in while you're at idle. It can get gunked up or just wear out to the point that you'll eventually stall at every stoplight. You can pull it out and wipe it with a dry rag but don't spray anything on it. Could also just be a dirty throttle body. Pull off the air tube and have a look. Even a small amount of gunk around the edges of the throttle plate can cause idle problems.
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 03:47 AM

Thanks for the reply, Wiggy <img src="/forums/images/graemlins/patriot.gif" alt="" />

I cleaned the throttle body per your suggestion, but it did not solve the rough idle, so I guess it's on to the IAC next. Will search for previous posts and see if I can get it done myself.

Thanks again <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: off-roader

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 04:53 AM

Quote
Thanks for the reply, Wiggy <img src="/forums/images/graemlins/patriot.gif" alt="" />

I cleaned the throttle body per your suggestion, but it did not solve the rough idle, so I guess it's on to the IAC next. Will search for previous posts and see if I can get it done myself.

Thanks again <img src="/forums/images/graemlins/cheers.gif" alt="" />

There's a test procedure to check if the ISC/IAC is good or bad in the FSM. You'll need a multimeter and more specifically an ohmmeter.
Posted By: DuCal

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 02:59 PM

This is the exact same problem I had on my 90 LS. First pull the ECU under the right hand dash and look to make sure it is not cooked (upper right hand corner of the circuit board)you will be able to see it. If it is burned then you need to get a new one or have it repaired. The next thing is to replace the IAC (idle air control) 25 bucks or so. The IAC can burn up the ECU so make sure it is replaced quickly. If you replace the IAC and the ECU is burned the car will still not run correctly. Good luck!
1. ECU check
2. Replace IAC (25$ and 5 mins)
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 06:48 PM

Thanks off roader and DuCal for the advice. Unfortunately my ecu is cooked. I went ahead a replaced the IAC anyway, so I should be all set once I replace the ecu.

Next question is, anyone know where to get a new one cheaply? I have no other means of transport down here in TX, so I can't send this one out for repair unless I can replace it. I will repair it regardless so I have a spare in case of future issues.

Thanks again guys. I only wish I had known earlier so that I might have caught it before it fried my ecu:-(
Posted By: off-roader

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 07:01 PM

Quote
Thanks off roader and DuCal for the advice. Unfortunately my ecu is cooked. I went ahead a replaced the IAC anyway, so I should be all set once I replace the ecu.

Next question is, anyone know where to get a new one cheaply?

For a used one try car-part.com or your local pull it yourself parts yard.

New one cheap? <img src="/forums/images/graemlins/lol.gif" alt="" /> <img src="/forums/images/graemlins/wink.gif" alt="" /> Seriously, I doubt you'll find a new one cheap.
Posted By: Canyonero

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 07:35 PM

Or try here.
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 11:21 PM

The very nice and knowledgeable gentleman at avproecm spent a good 10 minutes talking to me. He swears up and down that he has never seen, or worked on, a Mitsubishi MD306933 ECU. He says they simply do not go bad, ever. He wouldn't even agree to look at mine. Just told me to troubleshoot.

I am looking at one on ebay, will buy it then send this one to him so he can see a bad one for himself.
Posted By: off-roader

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 11:42 PM

Which brings up some good questions...

Is there visible damage on your ECU? How did you determine it's bad? <img src="/forums/images/graemlins/confused.gif" alt="" />
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 05/31/13 11:54 PM

Quote
Which brings up some good questions...

Is there visible damage on your ECU? How did you determine it's bad? <img src="/forums/images/graemlins/confused.gif" alt="" />


By the burnt area in the upper right corner as suggested by Ducal. I also found out that my ECU has been worked on before, or is a replacement, as there is all kinds of sloppy yellow writing on it.
Posted By: KrzyDav

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/01/13 06:07 AM

like sloppy yellow junk yard paint pin writing?
There's also a place in Houston that's been around a long time,( ?maybe-"ECUforcars"?).
.
Glad you had a good move,,, and esp. that it didn't fry on you when you were halfway to TX.
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/02/13 12:13 AM

Quote
like sloppy yellow junk yard paint pin writing?
There's also a place in Houston that's been around a long time,( ?maybe-"ECUforcars"?).
.
Glad you had a good move,,, and esp. that it didn't fry on you when you were halfway to TX.


Why yes, sloppy yellow junk yard paint pen writing is exactly what is is <img src="/forums/images/graemlins/barf.gif" alt="" />

Thanks, I appreciate the well wishes. The truck is running really well aside from the idle. I put the ecu back in, as I need the truck to get to work. I did order the one on ebay for $109 shipped. Hope to have it next week. Once I get them swapped, I am going to send the burnt one to the nice gentleman who told me they never go bad.I am very curious to hear what he has to say. He seemed incredibly smart and knowledgeable, Just like the crowd in here <img src="/forums/images/graemlins/kewl.gif" alt="" />
Posted By: fasteddy

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/02/13 05:00 AM

Quote
incredibly smart and knowledgeable, Just like the crowd in here



This will get you nowhere. We will still give you crappy advice and a load of sh*t when you do something dumb...
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/02/13 05:11 AM

LOL fasteddy, I meant every word! I have yet to receive a single bit of crappy advice from any of the members of this forum. In fact, you yourself would make a good intellectual match for the gentleman I spoke with. He was way above my skill level. I have said it before, and I'll say it again, this is the best online forum I have ever been a part of!

<img src="/forums/images/graemlins/smile.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/06/13 04:04 AM

Ok, so... Truck continued to run well except for at idle. It seemed to have improved ever so slightly once I fitted the new IAC, but that is likely just wishful thinking on my part. Anyway, I went out to grab a bite to eat last night, and when I left the restaurant, she was idling really rough, as in almost stalling. This was the first time it had been that bad.

But she ran fine as long as it wasn't idling. Got her home and shut her off, and went to bed.

I get up this morning, late for work, and she wont start. She tries to start, but stumbles and sputters and simply will not start.

I get home from work, and figure Ill try her one more time, only this time it doesnt even try to fire. It sounds like shes just spinning the crank, No indicatiojn of the slightest want to fire up. If Had to guess, there was no spark.

So I guess at this point, I am thinking the ecu has totally kicked the bucket. I am still waiting on the replacement I ordered.

It has been a very sad day for me today, as this is the very first time my LS has ever let me down and not started. <img src="/forums/images/graemlins/barf.gif" alt="" />

Do you all agree that it's likely the ecu? I suppose I should be grateful for the week or so I did manage to get out of it once it first exhibited the rough idle.
Posted By: KrzyDav

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/07/13 05:08 AM

on your disributorless 24 valve 3.0 you also have a cam sensor and crank sensor...they'd send a code.
When was the last Timing belt job? This isn't too likely but could belt be off by a tooth from bad belt or tensioner? (24 valve is an "interference engine" so you don't want a belt off the mark).
Posted By: DuCal

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/07/13 02:24 PM

I got mine new on EBAY for like 200.... I don't even want to know where he got it from for that price. I felt really bad about it for like two mins, then my monty ran perfectly and has never looked back. so I am better now. I'll PM you the link to him, he mite even have another.
Posted By: DuCal

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/07/13 02:29 PM

Ok, sent you a link to the sale, he has a few left as of this second.
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/07/13 11:41 PM

Quote
on your disributorless 24 valve 3.0 you also have a cam sensor and crank sensor...they'd send a code.
When was the last Timing belt job? This isn't too likely but could belt be off by a tooth from bad belt or tensioner? (24 valve is an "interference engine" so you don't want a belt off the mark).


The timing belt was done 4 weeks ago or about 1600 miles ago, when the oil pump was replaced due to a severe leak. It is a mitsubishi belt. I opted to replace it when the oil pooled in the cover under the crank pulley and contaminated the belt, which only had about 10,000 miles on it, which was done by Old Colt when he did a full front and top of engine service on her about a year or so ago. He did every pulley, seal, water pump, timing belt and tensioner, plugs, wires... you name it, he did it.

So I got the new used ecu in today, and it did not fix the problem. The truck acts like it wants to start now, but it sputters and pops and will not start. I tried pedal to the floor, light pedal, no pedal, all with no joy. It does make a bit of difference when a small amount of pedal is applied.

I am really distressed at this point. I am in a strange city with no transport. I have called a tow truck with a flatbed to take it to the local Meineke. The Meineke in my old town did the oil pump, so they should be able to share whatever records they have with the shop down here.

DuCal,

The ecus you linked me to are for a different truck, but thank you anyway. I appreciate the effort very much.
Posted By: off-roader

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/07/13 11:57 PM

Quote
The timing belt was done 4 weeks ago or about 1600 miles ago, when the oil pump was replaced due to a severe leak. It is a mitsubishi belt. I opted to replace it when the oil pooled in the cover under the crank pulley and contaminated the belt, which only had about 10,000 miles on it, which was done by Old Colt when he did a full front and top of engine service on her about a year or so ago. He did every pulley, seal, water pump, timing belt and tensioner, plugs, wires... you name it, he did it.

So I got the new used ecu in today, and it did not fix the problem. The truck acts like it wants to start now, but it sputters and pops and will not start. I tried pedal to the floor, light pedal, no pedal, all with no joy. It does make a bit of difference when a small amount of pedal is applied.

I am really distressed at this point. I am in a strange city with no transport. I have called a tow truck with a flatbed to take it to the local Meineke. The Meineke in my old town did the oil pump, so they should be able to share whatever records they have with the shop down here.

DuCal,

The ecus you linked me to are for a different truck, but thank you anyway. I appreciate the effort very much.


I recall new ECU's take time to learn the correct idle but I don't think it should run that poorly. You confirmed the new isc is still good right? the ecu and isc can make each other go bad. <img src="/forums/images/graemlins/frown.gif" alt="" />
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/08/13 03:38 AM

[/quote] I recall new ECU's take time to learn the correct idle but I don't think it should run that poorly. You confirmed the new isc is still good right? the ecu and isc can make each other go bad. <img src="/forums/images/graemlins/frown.gif" alt="" /> [/quote]

No I didn't Offroader. I do not have any tools or place to check it. But the one I bought was from Autozone, and it came with a lifetime warranty, so I called them and told them the one I just bought was bad, and they will have a new one in the store at 8 am. I asked if she would refund me once I brought the "bad one" back, and she said she would. I rented a car, so I will go there first thing and get it, put it in the truck and see if that is indeed the problem. New IAC and new used ECU. I sure hope this does the trick. I was not aware they could make each other go bad, I thought only the IAC could ruin the ECU. Thank you for the heads up. It is much appreciated, as always, sir.

<img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: off-roader

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/08/13 06:29 AM

Quote
[/quote] I recall new ECU's take time to learn the correct idle but I don't think it should run that poorly. You confirmed the new isc is still good right? the ecu and isc can make each other go bad. <img src="/forums/images/graemlins/frown.gif" alt="" />


No I didn't Offroader. I do not have any tools or place to check it. But the one I bought was from Autozone, and it came with a lifetime warranty, so I called them and told them the one I just bought was bad, and they will have a new one in the store at 8 am. I asked if she would refund me once I brought the "bad one" back, and she said she would. I rented a car, so I will go there first thing and get it, put it in the truck and see if that is indeed the problem. New IAC and new used ECU. I sure hope this does the trick. I was not aware they could make each other go bad, I thought only the IAC could ruin the ECU. Thank you for the heads up. It is much appreciated, as always, sir.

<img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> [/quote]

No problem. One of the ecu rebuilders told me that.
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/08/13 03:50 PM

I got another IAC and installed it this morning. The truck started, but is missing very badly. It does idle, but again it is sputering and popping.

I let it run for a good 20 mins to let the new ecu learn what it needs to.

There is not, nor has there been, any CEL.

Is there anyway to tell the timing belt has jumped a tooth without tearing off the front of the motor, again? I am WO deri g if all of the popping and sputtering might have caused the belt to jump?

Sorry for typos and grammer, typing this on my phone.

Anything else you all can suggest before I get slapped with a repair bill I can't afford?
Posted By: fasteddy

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/08/13 05:27 PM

Not likely timing belt. The simple stuff first. Spark, fuel - likely spark...
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/08/13 08:39 PM

Quote
Not likely timing belt. The simple stuff first. Spark, fuel - likely spark...


I was thinking spark as well, as it did run, which means it's getting fuel.

I am not able to find the exact method for clearing the ECU. I have read to remove power from it over night, hold the + and - cables together for 10 seconds then reconnect to battery... Anyone know the right way to clear the 306993?

Old colt did wires and plugs, as well as new coil pack about a year ago. If you were to hazard a guess, what could have happened to the ignition system from all the cranking/sputtering and misfiring?

Any ideas I could give the tech at Meineke would sure be much appreciated, before he spends hours diagnosing and whacking me with a huge bill.

<img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: DuCal

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/09/13 05:23 AM

Sorry brother I linked you to the 90 not the 95. I owe you one.
Posted By: KrzyDav

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/10/13 02:06 AM

I was just grasping when I suggested slipped T belt. I didn't recall any of your previous post on what you've done,,,gettin senile I recon.
I hope Rockauto sent you the right Distributor. With the wrong one it probably wouldn't run at all. Harness coming out the bottom and it's an '89.
Yours being OBD2 I think your stuck with having codes read.
That's probably the only way to see if it's cam or crank sensor.
You have 3 coils , maybe as seperate packs,,,were all replaced? I don't know much about them, I don't know if each one has an igniter or if those are inside the ECU.
.
On gen 1 the ECU and ICS are reset after the battery cable has been disconted to clear codes and then reset by starting and ildling 5 min. , shut off restatr and ildle 5 more. Each time idle will drop about 100rpm till it gets to 700rpm. Keep in mind the Gen 1 is a hundred time more primative an ECU.
I would never touch the 2 cables together incase some juice was left in a capacitor somewhere.
Posted By: MrJeebs

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/10/13 05:04 AM

No Worries, DuCal. I appreciate the effort very much.

Dave, my truck has a 1 piece coil set of 3 coils. They were replaced by Old Colt when he did the service on her a year or so ago.

The tech at Meineke told me Saturday that after much hassle and he got a code 41, which is Crank position sensor I believe. He said all kinds of numbers were way off, and that the timing was all fubar. All this is according to his Snap On Modus. Fuel pressure is good. He said he is going to diagnose it further before committing to tearing off the front of the engine, yet again. It has been taken down to the crank sensor 4 times in the last 2 years, most recently about 4 weeks ago before I made the trip down here. The sensor itself was replaced about 2 years ago, when a tech pinched the wires and ruined the sensor putting it back together.

As for OBD, my truck is 1.5, not 2, so it is still fairly primitive.

So I gfuess if the Snap On scanner can read the code, then the ECU must be ok? Or am i mistaken in that as well? LOL

As always gents, thanks ever so much for the replies.

Oh, I almost forgot, can anyone tell me the name of the stealer in TX that everyone orders from?



<img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: KrzyDav

Re: 95LS 24v 3.0L Sudden Rough Idle? - 06/10/13 05:09 AM

as I recall the dealer is called Southwest.
Maybe you still have some damage in the wires or connector on the cam sensor.
I think your codes are all a mess with everthing that's happened, unplugging stuff and such so your getting codes that are cause by secondary stuff and your problem is that cam sensor.
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