Really strange engine idling

[Hobz]

I've seen a lot of weird idle posts on this forum but none quite like this....

Everything's fine when cold. Then, when it is warm if I'm in gear, and ONLY if I'm in gear, the idle will jump madly about 1k up and down. I had to raise my idle or it would stall while driving around town. In neutral everything works great, UNLESS, I'm running low on coolant or running too hot, then it starts idling weird in neutral as well.

So, after reading around this forum I discovered that the coolant sensor might be to blame, and this made sense because of the behaviour when low on coolant. I replaced that (the one with the green connector on it) and I still have the problem!

Now, I'm guessing TPS or idle control valve, but those don't quite make sense either since I don't have the issue in neutral, even when I'm giving it gas :\

Anyone have any info to shed light on this?

[bubsy83]

I have the same problem. I just bought the car a few weeks ago and paid $1200 just to make the safety in repairs so I am kinda holding off on this. I have a list in the car of things I have learned form this board during a search about this problem specifically, so when I start rolling in some much needed cash I will tackle it. I will try to post my results in another post for ya later.
I will be watching this post as well to see where it goes with the more experienced MX-3ers on this forum adding their feedback.
I think this question has merit and good luck finding a solution. :D

[bubsy83]

Okay, here is what I found with my search on this issue, and by no means am I an expert on technical problems related to MX-3's. the list includes:
-temp sensors,
-intake hose,
-sensor connect ot ECU,
-EGR,
-faulty O2 sensor,
-faulty water thermo sensor,
-underpowered alternator, and
-grounding wires
From what I have read it could be anyone of these things or a combination of them. Does anyone have anything to add to this?? I am sure it would be a great help and also be much appreciated. Good luck...when I get mine figured out I will let you know. Thanks

[tehbrookzorz]

I used to have what seems like the same issue.

Now, I had several issues, each of which may have been contributing, but here's what I think you might want to check.

Shortly after I got the car, I had idling problems while stationary, while in gear, anytime.
This was due to the air intake tube. Check that.
At the same time, I adjusted the idle air control valve to compensate for the variable idle conditions.
I fixed the air tube leak.
I later noticed terrible idle issues and inconsistant stalling, which turned out to be the ignition module, but that's totally different from what you're describing.
When I fixed the distributor, I also decided to fix my faulty spark plug channel o-rings and valve cover gaskets, and while at it, the intake manifold gaskets and throttle body gaskets.
That's a job, don't do it until you know enough about it, though it's really not incredibly difficult.
I sealed up my vacuum leaks pretty good, but I was still having idle issues WHEN IN GEAR, but not when in neutral.
I asked about it on the forums, and nobody gave a concise answer.

Here is what fixed it:
Re-adjusting the idle air control valve.

I'd opened it up too much when I had the intake air tube leak, and when I sealed that leak, I hadn't readjusted it. Under normal operation, the engine will rev up a few hundred rpms from idle when you put it in gear to ease clutch engagement/prevent stalling. It seems if you have the screw too far open though, it throws off the metering and the computer struggles to maintain consistant in-gear idle. This is the first place I'd check, since I get the impression you've touched it before. Make sure there aren't any vacuum leaks while you're under the hood.

Hope that helps. If not, at least I got to practise my typing.

[fuxxy]

I used to have what seems like the same issue.

Shortly after I got the car, I had idling problems while stationary, while in gear, anytime.
This was due to the air intake tube. Check that.

I sealed up my vacuum leaks pretty good, but I was still having idle issues WHEN IN GEAR, but not when in neutral.

1. Can you post a pic of the "Air intake tube" ?

2. How do YOU find vaccum leaks?

My idle problems happen all the time (In Park, in Drive, randomly unless the A/C is on, then it feels like it goes away completely)

[Vanished]

yah defantly sounds like a vacume problem

The intake "TUBE" is located here:

See the throttle body? follow the black tube down the air box. Thats the one you shoudl be looking at. Its ripply, so it flexes with the engine. Its about 3 or so inches in diameter. It usually cracks between the ripples.

To fix it, get some shoe goo and put it were there are cracks.

[tehbrookzorz]

In this case, I would most likely blame your intake air tube.

You can test this theory by running the car, then looking under the hood while it's running. Try compressing the intake air tube a bit, pushing the ribs toward each other. If it seems to run a bit smoother, that's an indication of a leak. If you gently pull the ribs apart and it starts revving funny and/or dies, then again, you have an indication of a leak.

If you want, you can try spraying a bit of brake clean around the area of the suspected leak. If the engine revs up while you're doing this, you're obviously burning extra fuel (the brake clean). Water can be used for this test, but the engine will bog down if there's a leak.
My mechanic was just telling me that he used to work at a shop where they used to spray gasoline as a test of intake air leaks, but he had the misfortune of having old spark plug wires on an engine he was testing with this method, and a nice engine fire ensued. Don't use gas.

So if you have a leak, there are a couple of options. If you're short of cash, a temporary fix is possible by getting some black silicone from a parts store.
I took my intake air tube off to work on it. You loosen the clamps, pull the smaller tube that runs to both valve covers off where it connects to the intake, then pull the intake tube itself out, being careful not to damage it more.

Then seach the 'bellows' or 'ribs' for small cracks, and try to fill them in sufficiently with the black silicone, but give it lots of time in a well ventilated setting so that it can dry properly before putting the tube back in the engine bay. I wrapped my tube with duct tape for added security.

Then again, if you have a bit of money, I'd suggest fabricating a cold air intake of some sort. This entails putting a higher flow filter on the end of a metal intake, thus bypassing the possibility of more broken plastic ribs.
If you do this, you still need to use your volume air flow sensor. You can read up about this in the V6 FAQs.

Hope this helps.

[Hobz]

Awesome! I'll give that a shot. I do have cracking on the intake tube, and I did increase my idle before fixing the leaks there (lots of duct tape). I'll lower the idle and see if the problem persists. I might as well check for leaks while I'm at it, I still hear a hissing noise when I open the throttle making me think there is still a leak. Maybe it's CAI time after all

[Hobz]

That took care of it! Man it's nice to have a decent idle again

THANKS!!!!

[tehbrookzorz]

Good to hear man. Glad to be of help.

[alreadydefective]

yeah, i had the same problem, before i figured that out, i took it to a "mechanic", whom had the car for a week, didnt figure out what was doing it... so i got it back, got home and within 10 minutes, read this topic, and figured out that the mass air intake tube (i think thats what its called) was the problem... , looks like im goin to U-PULL-IT tomorrow to get a new one (car junk yard)... there are 2 MX-3's there (sadness i know) that probably still have them on it... mine is WAY too cracked, aka, i fixed 1 of em, and then found 2 more just now, fixed em so it should be good till i get the new one, but yeah... atleast i have that outta the way

[jschrauwen]

Aww come on guys. There's info already posted and I know I've posted debugging possibilities a number of times. Here we go again.
Like previously mentioned, too many take the easiest (read short-cut way) to try and solve idle problems. They'll adjust the Idle Air Screw and achieve a short term fix but what they've done is thrown the whole idle measuring process off base. Why, because they more than likely didn't put it into the Diagnostic mode when they did that. Then after messing around with it for so long they get fustrated and plead for help on the BB. There is an excellent diagnostic step by step block diagram on the online shop manual that is there specifically there for these situations.
As also mentioned previously, if the actual problem generator is found, all of the tweaking and adjusting of other components are now out of wack. Which means theings like doing a complete TPS adjust to get back to manufacturer specs.
Detecting vaccum leaks once again has been documented numerous times and tehbrookzorz has eluded to this. I personally found that if your searching for a vaccum leak, use the large butane refill bottles to spray along the entire lengthof all of the vaccum lines. Not sure which are vaccum lines??? Again posted pics and online shop manual covers that too. When the spray has encountered a vaccum leak the idle should shoot up substantially and quickly (quicker than other accellerants used or suggested). The butane has a way of pinpointing the leak quicker for me.
Conversely, looking for vaccum leaks using a water bottle mister will generate the reverse effects but not as easily or as accurately as the butane.
The water mister can also be used at night to spray along the lengths of plug wires in search for compromised cables which will be noticeably arcing and visable at night.
Other idle issues can be generated by numerous other problems, and in a lot of cases, it was through the owners own fault. How is this possible???? Perhaps they decided to do a mod like a CAI, and decided not to reconnect the FPR Sensor. Or, they don't keep up with regular maintenance and find that the thermostat needed changing many many thousands of km's earlier but didn't bother. Even when faced with numerous overheating problems, they continued to skirt the contributing factors until a point that the inital problem has escalated to other issues like head gasket fatigue. Perhaps doing regular maintenance would prevent these problems. It's also been doocumented that there are people who like to disconnect things like the TB coolant lines or something similar.
Anyone who picks up a used MX should plan to spend a bunch of money on maintenance needs unless there is documented proof of previous work. Things like doing a pressurized flush and fill of the coolant, engine oil, and tranny fluid would be the first things. Along with plug change, air filter change, PVC valve change. These should be automatic.
Were talking about a car that can be nearly 15 years old and been through 4, 5 or even 6 owners. Expecting to have a flawlessly running car without extra maintenance costs due to age, mileage and previous ownership would be unrealistic.
Back to the idle issue. I looked at the previous posts and for some I see no signature block info to tell me AT or MT, whether there are any mods, what has been done to present to remedy etc. I'm sorry gang, I'm not a mechanic those on this BB who are still need to have this info before commiting to making an assessment.
Idle that goes erratic may be caused by the shift of the engine on it's mounts (old car...of course the mounts can be quite weak). When that engine shifts or when shifting while driving and the problems surface concurrent to those shifts, it'sa usually a good bet that the ribbed intake rubber flex tube is cracked or worn. Most just look at the top but the majority of the engine heat will be transferred to the bottom of that tube. How many will take that tube off to fully inspect? Or, if using the butane trick, will you get completely around each pleat of that ribbed portion? If removing, remember that it's probably quite brittle and in doing so might just damage the tube even further. Best to find out then that it was that close to failing anyway.
Whan was the last time someone took the air fiter out of the airbox and cleaned out all of the sand and crap out of the bottom of it? When waas the last time someone cleaned out the inside of the intake tube that runs along the top of the rad to the air box? The less obstructive pathways for air to travel equates to a better running and more efficient engine. When was the last time someone cleaned out the inside of the TB with TB cleaner? All of these little things are not in any manual or how to. There common sense approaches to an old car.
Yes even the grounding wires from the engine might possibly create some running/idle issues if again, the engine mounts are so worn that a constant good connection may be compromised. A remote possibilty though. The running/driving with an engine overheating consisting is bound to create other failures if not tended to immediately.
Another common cause for poor engine running / poor idle is mods done cheaply (read ghetto) or done by cutting corners or not willing to do or spend what's necessary. It reminds me of an old muffler commercial - "Pay me now..... or pay me later". In other words, the causing factors aren't going to just dissappear and will eventually catch up with you.

[bubsy83]

Thanks Jschrauen for the in depth detail on the causes for this problem. Although I did not originally post this problem it caught my interest as it is my problem as well and I appreciate your insight.

I bought mine a month ago and yes, I am about the 6th owner and will followup with your advice on that aspect of owning the MX.

It's funny, 'cause I work at FRAM and their logo is "pay a little now, or a lot more later", same premise, and you'd think that I would know better especially with the benefits of getting free filters of all types for vehicles, so off I go.

I love cars and I am now just getting a clue on how to work with them...thanks, Barb

[tehbrookzorz]

We should almost sticky jschrauwen's response!

Thanks for the contribution. I hope mine helps. I am by no means an expert, but I'm constantly trying to pick up as much knowledge as I can, and even though some of these topics have been covered, I know it's difficult to access some of the previous posts. If I can be of some help, I'm happy.

By the way, I seem to remember delivering to EK Transmission in Cranbrook, and they had that sign up saying "Pay me now, or pay me later." It was a Fram ad, interestingly enough.

[ElectronBlue]

hey ya it was a common problem but another problem i came by was when my alternator was going to quit on me it was doing the same thing kind of since low range was not charging the batttery