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Does MAF sensor cause this? I am puzzled!!!

I

iskoos

CEG'er
Joined
May 23, 2008
Messages
245
Location
Orlando, FL
Hi guys,

I am fairly new to this forum but NOt new to world of Contours. I have owned one for 9 years. It is 95 Contour GL 2.0L 4cyl Automatic.
I am having a strange symptoms recently. All of a sudden my car started showing weak(low), erratic, sputtering idles.
This issue started all of a sudden. When car comes to a stop, idle becomes very unstable and if the engine is not warm, it will most likely die. When I see the idle gets erratic(I cannot tell the rpm; I don't have tach), I pump the accelerator couple of times and this helps.
When you accelerate, and/or when you drive at any criuse speed, the car is smooth and reliable. There is absolutely no signs of any problem.
The problem is only at idle.
When I start up the car in the mornings for example, it starts up and idles for couple seconds and then it sputters and dies because engine is cold. I need to keep the gas pedal depressed for a few seconds for the engine to warm up so it can hold the idle but even then idle is very unreliable...

What I did so far:

1. I started with cleaning the oil separator and changing the PCv valve thinking that PCV was clogged. The PCV was dirty but it wasn't clogged. I replaced it but it didn't help.

2. I removed and replaced the IAC valve thinking that it was the culprit and I was so sure of it. I was WRONG!.. It wasn't the problem either. I chekced the IAC valve and the original one was working but didn't want to take a chance and dropped in the new one just to make sure. Nothing changed unfortunately... So I know it is NOT IAC valve...

After driving and testing the car for couple of days, I decided to clean and put the original IAC valve back so I can return the new one since it wasn't going to help. I did it yesterady and when I put everything back and cranked the car up, It fired up immediately. I drove it, it was driving fine but all of a sudden check engine light came On and stayed on all the time. I opened the hood to realize that I forgot to plug back the MAF sensor connector!..
I did put it back and the idle became erratic immediately.
I unplugged it, it worked fine; put it back again; having the same issues.
I am really confused!.. This morning, I started the car with MAF sensor unplugged. It started fine, the idle was a bit high at first then it slowed down. I drove the car in the neighborhood for 5 minutes. it drove fine. But the CEL on all the time and when I stop I realized that idle was still a bit high. I guess due to MAF sensor being unplugged.

I had codes 181 and 157 when I unplugged the MAF sensor and I guess this is normal. I already had code 335 in the system before I unplugged the MAF. Code 335 (My car is OBD-I) is about DPFE sensor but I replaced that just two months ago. So I doubt that is my problem here...

So right now I am puzzled and asking you. Does a bad MAF sensor cause rough, sputtering erratic idles???

Thanks in advance...
 
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Well not to be smart aleck, but you just PROVED that the MAF sensor does cause your bad idle! At this point you are the expert.

Search these forums for how to clean the MAF, maybe that will do it.

Mike
 
Hey guys. Thank you for your help...

Yes it seems it is MAF sensor and I founf the problem but I have been working on my cars for years and never seen MAF sensor caused a problem like this.
There is only two things making me doubtful:
1.I never get any code in the ECU about the MAF sensor.
2.LIke I mentioned above, with MAF sensor connector unplugged, the idle increase a bit. I am guessing that ECU runs the engine with default setings or it freaks out since no signal coming from MAF. And when the idle is high, the problem doesn't shop up of course because the problem only shows up when the car is idling. So the actual problem may very well be hiding behind the high idle RPM making me think that if I cange the MAF sensor, the problem will be cured...

So that's why I asked if a bad MAF sensor cause this type of idle surges.

I will see if I can find a used MAF sensor at a junk yard but it will be difficult I can see...
 
If you have an oiled filter (K and N, etc) the oil may have contaminated the MAF. Is the EGR valve OK?
 
You could have a SMALL vacuum leak. Small enough to affect slow normal idle but once rpm raised a little (the higher idle speed mentioned) enough volume of mixture required that problem is now covered up.
 
FavoriteMystaque said:
If you have an oiled filter (K and N, etc) the oil may have contaminated the MAF. Is the EGR valve OK?
Click to expand...

No I never used K & N filter. I do have a regular one and it is pretty clean.
When I checked the MAF it was clean but I used CRC spray cleaner to clean it anyways.
I am not sure if EGR valve is okay. Is there an easy way to check it? I meant without removing it...
 
amc49 said:
You could have a SMALL vacuum leak. Small enough to affect slow normal idle but once rpm raised a little (the higher idle speed mentioned) enough volume of mixture required that problem is now covered up.
Click to expand...

You could have a point too. I visually inspected some of the vacuum lines past Saturday but didn't find anything.
Is there any effective way of determining vacuum leak?
 
other than spraying a little starter-spray around specific areas that could be leaking, no..

If you spray a minute amount in different areas, the idle should change because the vacuum leak sucked the starter spray in the intake and it reacted with the air/fuel already going in to the engine.

Of course, its easy to create false positives if you are spraying wildly or carelessly and the actual FILTER is what sucks it in... lol Either way, if there is a leak its after the MAF (closer to the engine) since anything "before" the MAF isn't a leak (the MAF is still seeing the air)

You could search the forums for the "suck test" for an EGR/DPFE test.

Tony2005 seems to always have that link on hand...
 
smoke test is most effective but costly. most people spray carb cleaner where they think a leak might exist to see if the engine runs differently.
 
What do you guys mean when say "Vacuum Leak?"

I do understand that a torn boot between MAF and intake is a vacuum leak and should be easy to determine. Those boots can be checked.

I will try starter spray test once I feel comfortable doing that. But my question is what other things are considered vacuum leak?
Asking this so I can start checking everything I can since lot of people focusing on vacuum leak issue.

So if there is a crack on the hose that is after PCV valve; would it be considered a vacuum leak? Or if there is a crack/torn on the little rubber hoses connected to DPFE sensor or EGR selenoid, would that be considered vacuum leak?
 
You're on the right track...

a vacuum leak would be ANYTHING that is allowing unmetered air in to the engine. when the engine is running it is pulling air in to the engine with every stroke of the pistons. The air runs through the MAF and is metered by mass. The mass of the air is what determines how much fuel the car dumps through the injectors in order to create an optimum air:fuel ratio.

If you have a leak ANYWHERE after (as in.. closer to the engine than) the MAF, it is considered a "vacuum leak" because it is allowing air to be pulled through the crack/leak via the vacuum the engine is making.

The places could be along the MAF (on the engine side), the throttle body where it mates to the MAF rubber, the other side of the throttle body where it mates to the engine, the UPPER intake manifold where it mates to the lower intake manifold, a cracked vacuum line/booster line (the two black vacuum lines that plug in to the top of the UIM), etc, etc.

Its hard to name EVERY place that can leak, because it could be ANYTHING that is between the MAF and the cylinders themselves.

Anything "after" the burn cycle is on the exhaust side, and thus isn't under vacuum, but is being pushed out instead.

edit: if you haven't rebuilt your Upper intake and lower intake in a while (or EVER) then I would HIGHLY suggest doing so... the reasons being that it cleans the tons of crap you are sure to have that rob efficiency/gas mileage and power from your car, as WELL as the fact that in a UIM/LIM rebuild you replace the UIM/LIM gaskets (or, at least, you get to SEE the gaskets and inspect them) and those are two main causes of vacuum leaks you can't SEE or get to while the car is together.

the how-to is in the Duratec Maintenance forum under the read-first thread (in the UIM section)
 
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Ray said:
edit: if you haven't rebuilt your Upper intake and lower intake in a while (or EVER) then I would HIGHLY suggest doing so... the reasons being that it cleans the tons of crap you are sure to have that rob efficiency/gas mileage and power from your car, as WELL as the fact that in a UIM/LIM rebuild you replace the UIM/LIM gaskets (or, at least, you get to SEE the gaskets and inspect them) and those are two main causes of vacuum leaks you can't SEE or get to while the car is together.

the how-to is in the Duratec Maintenance forum under the read-first thread (in the UIM section)
Click to expand...


Not to be hating on you Ray, but its kinda hard to clean the UIM and LIM when you dont have one. Its a Zetec!:laugh:

But you do have the right idea, cleaning the intake manifold on our cars would be time well spent.
 
you've obviously never owned a zetek, nor worked on one... there are THREE LIM'S and TWO UIM's on the Zetech..

DURR...
 
So is there a zetec walk thru for intake manifold disassembly and cleaning?
Checked the Zetec forum could not find...
 
Man, if you haven't done that type of work before it could be a real can of worms for you, no insult intended. Hard to get to all the intake bolts unless you have a bunch of tools. Also, standard plastic manifold can be easy to break if overtorqued. I'm curious about the response above about all the manifolds upper and lower Zetec has. I'm sure maybe somewhere some are 2 piece but the 3 Zetecs I have are all one piece manifolds. Better to just start searching for the leak by verifying that ALL hoses are not leaking before you rip the intake off. Start blocking off every vacuum hose off that intake that is not required for the motor to continue running, power brake booster, any hose going to heat/ac equipment, DPFE (EGR), PCV, evap canister, etc. Be careful, some of those quick on/off type connectors will break easy once they're old. I would weed out every one of the external leak possibilities before I yanked an intake.
 
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amc49 said:
I'm curious about the response above about all the manifolds upper and lower Zetec has. I'm sure maybe somewhere some are 2 piece but the 3 Zetecs I have are all one piece manifolds.
Click to expand...

....joke.... hence the misspelled words, and incorrect phrasing.

Of course, on CEG, you can't assume anything because of a misspelled word... :nonono: LOL
 
Not an expert here, but was experiencing similar issue a while back. Long and short of it was a vacuum leak. Turned out to be a crack in one of those "plastic" vacuum lines that runs along the back of the engine, along the firewall to the right of the DPFE sensor . Stick with looking for a vacuum leak. Don't be afraid to spray some starting fluid around the hoses to find it, just be careful and spray small amounts. I unloaded a whole can before I found mine. I also found a small crack in the 2" piece of rubber tubing between the PCV valve and the metal tube it connects to. Replaced the leaking hoses and all was well. Just for the hell of it, you might want to remove your throttle body and clean out the ports in the manifold. Alot of times those holes get sludged up as well. Just remember to replace the T.B. gasket, they're only a dollar or two. Goodluck!
 
Thank you guys since a lot of you focusing on vacuum leak, I will focus more on that before I taking the manifold apart. Believe me I am not fan of doing unnecessary tedious work if it is not needed.

I had many issues with this car in the past and everytime I am not exaggerate, EVERYTIME I was told a possibility of vacuum leak and EVRYTIME it turned out to be something else, like a sensor or a spark plug or spark plug cable...

I hate to hear the words "Vacuum Leak" because there is so much to look at and I don't know where to start...
I already checked some of those hoses behind the throttle body but will focus on some more...

Question: Some of the stuff like spraying around requires me to remove the air intake assembly. Is there any harm to run the engine for a few minutes with all air intake assembly (all the way to throttle body) taken off?
 
on a SMALL (almost imperceptible) level, TECHNICALLY you are getting unfiltered air in to the engine.. On a normal day, the amount is so minute that you'll never notice. would I do it in a dust storm in Iraq? No.. but in your driveway... sure.


Now, with the MAF unplugged, you'll be reverting to a set of programmed tables instead, so the erratic idle, etc, will go away as you stated in your first post... just listen for the idle to change when you spray it in different areas, taking care not to allow the mist/fumes to enter the TB or filter, etc... (false positives)
 
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