Rough idle and error codes

[andypalmer]

Hi all,

I have been having problems with rough idling on my 98 SOHC for a few months now. When cold it is really rough, this gets better as it warms but it is also rough when warm and in gear (D, R, 1 etc). Once I put it into P or N it gets a lot better. Also the roughness coincides with a slight drop in revs. Normally it is idling around 600rpm, a little low? I have also had error codes relating to O2 sensors detecting both banks lean and system adaptive detecting both banks lean and the both rich. I have had the 00M12 mod performed (front timing chain tensionner and all intake manifold gaskets). It seemed to improve a little but not a lot. Also my X has been converted to run on LPG (liquified petroleum gas) which is introduced into the air pipe around the IAT sensor so I can rule out anything on the petrol delivery system (pump, injectors etc) as it does it on both fuels. I am leaning toward the MAF sensor but I am not sure and have already spent a lot on this truck so am reluctant to waste much more money on this problem.

Any ideas?

 

[marragtop]

You can try disconnecting the MAF sensor to see if that has any impact at all.

 

[andypalmer]

What would happen to indicate it was the MAF sensor? If it is that easy to tell it would be a lot quicker.

 

[timleedude]

It might run better without the MAF. If the MAF is defective, it's tell the computer wrong airflow information, so the computer will make the engine run rough or die. When you disconnect the MAF, there is no input from the MAF, so the computer will try to run the engine without the info from the MAF. If it runs better without the MAF, then the MAF is defective. Go out and get a new one. Don't drive the car without the MAF, can cause problems to the engine. The MAF (Mass Air Flow) Sensor, IAC (Idle Air Control) Valve and the TPS (Throttle Position Sensor) are common things to go bad when engine is running rough or dying. There are tests you can run to check the IAC and TPS. Check your service manuals.. Or you can post and someone from here will give you the procedures. Good Luck

-Tim

What would happen to indicate it was the MAF sensor? If it is that easy to tell it would be a lot quicker.

 

[andypalmer]

I removed the MAF sensor connector and there was only a slight difference. When I reconnected the connector the revs dropped by about 200 and it took 3-4 seconds for the revs to climb back to the 600ish mark. It appears that the engine is idling low because if you press the accelerator and force it up to around 700-750 (manual says should be 736) it is fine, no shudder and no noise. I'm not sure whether a sensor is at fault making it run lean or whether it is running lean and therefore idling low. I also tried tapping the IAC valve with a hammer but no change to the idle.

 

[timleedude]

Did you turn off the engine each time you connected/disconnected the MAF? It's bad to disconnect or connect while engine running.
It might be a defective MAF Sensor..but you should comfirm that the IAC and the TPS are good or bad.. There should be test procedure for those on the Service manuals. If not, post here and someone will hopefully give the procedures. If the IAC and TPS are tested good.. Then changing the MAF would be a "good bet"... Sometimes you have to gamble and hope it's the defective part.

-Tim

 

[andypalmer]

Tried the MAF again, this time turning the engine off between. No visible difference between connected and disconnected. Disconnected the IAC valve connector and idle steady at 450. I intend to get the multimeter out tomorrow and check the IAC valve and TPS as I'll have someone to rev the engine for me. Would the lack of change without the MAF rule it out or would it suggest the PCM is always getting a crap signal from the MAF?

 

[Turdle]

Honestly, from my extensive reading on this site--it sounds like leaky intake manifold o rings---both banks lean-cold rough idle---
Maybe they slipped during install???

 

[andypalmer]

I'll certainly be speaking to the garage that did it. I didn't do it myself as I didn't feel confident disassembling the engine that far. I was confident before they did it that it would sort the problem. By the way, my idle problem also appears when warm, just not as bad as when cold. Also the revs don't bob about as much as they did before.

 

[andypalmer]

Just checked everything with a multimeter and the MAF signal is way off what it should be. Also it reads open circuit when I check its resistance. I'll get a new one and see what happens. Thanks all.

 

[ma96782]

Also my X has been converted to run on LPG (liquified petroleum gas) which is introduced into the air pipe around the IAT sensor so I can rule out anything on the petrol delivery system (pump, injectors etc) as it does it on both fuels.

Enlighten me.....why???

Is the problem related??? You said, no.....so, was it running "perfectly" before and after the mod?

Aloha, Mark

PS....if you got some spare time:

Explorer Maintenance

http://www.explorerforum.com/forums/showthread.php?t=144066&page=1&pp=20

Explorer MAF cleaning

http://www.explorerforum.com/forums/showthread.php?t=154711&highlight=cleaning+mafs

IAC Cleaning:

http://www.explorerforum.com/forums/showthread.php?t=84220&highlight=iac

And, another IAC Cleaning thread:

http://www.moddedmustangs.com/cleaning-your-iac.html

Check for codes. Get a “base” to work off of.
_________________________________________________________________

 

[andypalmer]

In the UK LPG is about 2.5 times cheaper than petrol, 80cents a litre as opposed to $1.80 a litre. The mod was done 5 years ago and I have had the X for just over a year. It was running fine until around 3 months ago when I started looking into the problem. Also the problem occurs on both fuels. When it runs on petrol it is as standard ie the LPG system is completely disconnected and inactive so it cannot be the problem, it must be something common to both.

 

[ma96782]

Thx for the education.

So, you can get more miles per $ spent (LPG vs. un-leaded gas).......I assume? Not counting the cost of the conversion.

Aloha, Mark

PS....you might want to see Al Dive's thread.....he is also looking to smooth out his idle.....but, I suspect you got a bigger problem than his. Run a vacuume check and look for codes.

 

[andypalmer]

It gives the equivalent of a petrol doing around 40 mpg. Not too bad for such a large, heavy vehicle.

 

[ma96782]

If you get these error codes:

2nd Gen error codes 0171 and 0174:

http://www.explorerforum.com/forums/showthread.php?t=172289



And O rings on intakes:

http://www.explorerforum.com/forums/showthread.php?t=170707


http://www.explorerforum.com/forums/showthread.php?t=172451

Anyway, it may be time to do the intakes....AGAIN.

Aloha, Mark

 

[andypalmer]

I only had the gaskets done a month ago so unless they are misaligned or the manifold isn't tight I am confident it is not them. Also my low idle does not go away when the engine is warm, it improves but it is still obviously running lean. Even when I have driven 50 miles or so the engine still strains when put in gear which is why I think it must be something else.

 

[timleedude]

Andy,

Have you tried changing the MAF yet? How's the Truck running now?

-Tim

 

[andypalmer]

Found one on eBay for a 99-2004, mine is a 98 build. Just waiting for the seller to tell me if it will fit mine. Here is the item:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=006&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=160065878246&rd=1,1

Does anyone know if the 99 MAF is the same or near enough to work OK on a 98?

 

[andypalmer]

Tried a new MAF and a new TPS. Still no better, anyone got any ideas?