I have a '99 GT that has about 60k (mostly highway miles) on it. It has been sputtering and won't idle on cold starts, even though it's not cold and it gets ran every 2-3 days. It sputters and won't come close to idling until it's warm. I've seen this often in older, especially high compression cars, but this one is far too young and too well cared for to be doing this.

It has had two or three STP gas treatments over the life of the car. It has been suggested to me to use a gas treatment called "4 in 1" or "Sea Foam" both run between $6-8. To correct a clogged injector or something. Also it may need a new fuel filter (parts $10.) I don't know and I don't know how to check it. Are they simple to replace. If nothing else, would this improve MPG and are they better than STP? Thoughts plz. K, thx.


*Additionally, some mechs have told me that as of late fuel quality is down as in not refined and cleaned as much as normal due to the rush to get the pipes flowing again.

10/13/2005 1:37:47 PM

what grade oil are you using? if its not 5w-20 that is most likely the culprit, especially since it is geting cooler now, those stangs are finiky sometimes

10/13/2005 7:16:15 PM

is fuel pressure controlled by oil pressure on those finicky fords? serious question, maybe fordhack will chime in, he might actually know.

clogged injectors dont get unclogged after the engine warms, so thats out

fuel quality dosent either, im not gonna rule out bad gas, but it sounds like you have been having this problem a while maybe?

10/13/2005 7:39:54 PM

Any error codes flagged at all? MIL illuminating?

IAC not working properly or dirty as hell and hung up? How about the coolant temp sensor?

I don't really see where Sea Foam will really help this situation either. It seems like you've got some kind of cold start engine management malfunction...like Joel said, why's it doing okay warm if you've got a really dirty fuel system or filter? If anything, the system leans out when in closed loop at operating temperature, and fuel issues would most likely continue to manifest themselves even more so then.

10/13/2005 8:06:07 PM

Idle air control, goes bad on every 4.6 in it lifetime...get a new one at the dealer you should be fine, trust me I have seen it a ton, you can put fuel system cleaner through it til the cows come home it will not help

10/13/2005 8:53:27 PM

^ what he said

10/13/2005 11:25:15 PM

^^ happened on my 3000GT as well

[Edited on October 14, 2005 at 1:50 AM. Reason : pretty much the same symptoms]

10/14/2005 1:50:12 AM

^^^k, cost on that?

What about a new air filter or at least blowing out the one I have, it has been dry and dusty. I haven't looked at it and I don't expect it to fix the problem, but I but that certainly would not hurt MPG.

10/14/2005 9:53:57 AM

happened to my 00 GT as well. it's not too expensive. it's actually the only problem I've ever had with the car. actually, now that I think about it, I think it was my O2 sensor. eh, I can't remember. it was one of the two.

10/14/2005 10:01:13 AM

I think they usually run around 60 bucks at most parts places. I don't know what the dealer gets for one, though.

About 15 minutes to put it on.

10/14/2005 10:58:47 AM

^^That tends to happen to Fords (at least) if you ever fuel it while it's running. Even so, I've had that happen a couple of times to my '96 Ranger.

^What is involved in installing that? Would I be better off to just purchase the part and have my mech put it on? I'm in rural western NC, parts and labor are both cheap here, relative to Raleigh.

10/14/2005 12:25:43 PM

Two bolts, one plug. One gasket.

When in doubt, either get yourself a manual or get your mechanic to do it. It ain't much.

10/14/2005 12:43:25 PM

http://www.carsurvey.org/viewmorecomments_review_9027_1.html


Google says I'm not the only one.

10/14/2005 12:59:24 PM

Quote :

"To all whom experienced the stalling problem. I have some simple solutions to help solve the problem before you spend big bucks on the dealership fixing a 10 minute job try these tips. #1 Check your air filter and see if it needs to be replaced or cleaned if it is a K&N filter. #2 Next check your Mass Air Flow Meter to see if it has any carbon build up. If so, then use some carburetor cleaner and clean it out. Make sure you don't spray the electrical plug on this meter or you will ruin the sensor. After letting the carburetor cleaner sit on the part for about ten minute go ahead and rinse it off with slow running warm to hot water. Make sure that when you rinse this part you don't get the electrical plug wet because you will ruin the sensor. Then take a rag and wipe it down until it is completely dry. Now your ready to reinstall this part back on the car. #3 Then check your Idle Air Control Valve (IAC Valve) to see if there is any carbon build up. If so, just buy a new one from your trusted auto parts store. There is a small mesh screen on the inside that you won't be able to reach and it is more than likely clogged with carbon. Plus half of this part is an electric motor running the cylinder part on the inside and you might risk burning the motor out if it gets wet. The IAC Valve can range any where from $42.00-$55.00. Install the new part. #4 Finally check your Throttle Body for carbon build up. If you have carbon build up in your IAC Valve then you will have it in your Throttle Body. Take some carburetor cleaner and spay the inside of the Throttle Body and make sure you spray the flap real good. In case your wondering the flap is what opens and shuts in the throttle body that kind of looks like a lid. After letting the carburetor cleaner sit on the part for about ten minute go ahead and rinse it off with slow running warm to hot water. Then take a rag and wipe it down until it is completely dry. Now your ready to reinstall this part back on the car. If you follow these steps then you will resolve all your stalling problems. Don't make the mistake of just cleaning or replacing just one of this parts without checking all the other parts as well or you will still have problems. Do yourself a favor and follow my steps 1-4 in the order I have explained above and you will be a much happier camper. Let me know your results when completed. Thanks."

Sound advice?

10/14/2005 1:14:21 PM

try it and see what happens..

then you tell us.

[Edited on October 14, 2005 at 1:22 PM. Reason : yeah.. that sounds like good advice.]

10/14/2005 1:21:51 PM

Yes, that is sound advice

10/14/2005 3:35:35 PM

K, the Mech determined it was 99% likely that it is the Mass Air Flow Meter and ordered one. They usually run $100 but this particular one is $130. Even he was confused about that... He said if it was the idle air control or the O2 sensor that the check engine light would be on and it never has. He also said the MAFM would not show up on the comp but was easy to replace and that he'd put a thousand on Mustangs and similar vehicles. We're gonna try that and for good measure blow out/replace the air filter and run some good fuel treatment though it. He estimated that the car would gain several HP and MPG...

As to why the thing would run ok when it was warm... he said that there was a resistor in the MAFM that when warmed up, would make a more proper connection.

It's an expensive part, but it'll be worth the money and trouble if it corrects the problem and the efficiency of my car.

10/14/2005 4:11:05 PM

or you could have tried the $40 part first...

hopefully the mechanic is right

10/14/2005 5:11:03 PM

he just screwed you. Mass airs don't jsut go bad, especially on Mustangs, I have (or used to till e June) work with mustangs everyday...a idle air control will not throw a code...and mass air would and the only way it would go bad was if something physically damaged it...who did you take it to>?

10/14/2005 5:37:36 PM

yeah... i wouldn't change a maf unless i got bigger injectors

10/14/2005 5:39:16 PM

^^thats what I was thinking but have experience with on some other cars but wasn't sure on a mustang so i didn't want to sound like an ass and say that... oh well, I expect he'll clean the iac valve while installing the new maf and tell you it was indeed the maf. did he even look at the iac vale/motor, whatever it is on these things??



[Edited on October 14, 2005 at 5:42 PM. Reason : ^^]

10/14/2005 5:39:31 PM

Quote :

"yeah... i wouldn't change a maf unless i got bigger injectors"

what in the fuck are you talking about?

10/14/2005 5:39:58 PM

ignorance is bliss

10/14/2005 5:51:44 PM

apparently

10/15/2005 3:00:56 AM

i guess bigger injectors cause air to somehow flow different than the maf can sense it? from what i gather here

10/17/2005 7:19:25 PM

haha, WHAT GREAT LOGIC. i can't even actually comprehend what logic he was trying to use up there, oh well

10/17/2005 8:57:35 PM

man i wish IAC's for my car were $42.

i'd replace it every now and then.

fucker costs $150-200 and is tied into the coolant system so that you need to flush the damned thing to replace it or risk air bubbles.

damn honda.

10/17/2005 9:29:48 PM

well some of this has been covered but the mechanic you took your car to made some mistakes.
1. You can check the MAF, IAC, and most any other sensor on a 99 Ford with diagnostic software.
2. Lots of components go bad(including the IAC) and don't throw a code or throw a rich/lean code instead of a component based code which leads to many O2 sensors being replaced by mistake.
3. A maf wont cause a cold start problem because until the engine is warm the car runs in open loop and doesn't use the maf values to calculate fuel. A bad maf usually causes problems after the car has warmed up. You can check the values coming out of the maf and see if it is going bad
4. IAC's and DPFE's(unrelated to this driveability problem) are the absolute cheapest crappiest parts on damn near any Ford made in the past ten years.


Oh and don't blow compressed air thru an air filter. It will just tear the paper and gunk up your brand new maf and eventually dust the cylinders.

Optimus , no they don't use oil pressure to control fuel pressure on Fords gas motors. The diesel motors use oil pressure for fuel injection but thats a whole different ball of wax.

10/17/2005 9:31:07 PM

Quote :

"until the engine is warm the car runs in open loop and doesn't use the maf values to calculate fuel. A bad maf usually causes problems after the car has warmed up."

I am pretty sure that is not correct. The MAF is used to calculate fuel and spark requirements at all times. Closed loop means that the computer uses feedback from the O2 sensor to trim the mixture.

people get the MAF meters recalibrated to trick the computer into injecting less fuel than it would normally to keep from running rich on larger injectors. It's a dirty way to make larger injectors not run piss rich.

[Edited on October 17, 2005 at 11:19 PM. Reason : ]

10/17/2005 11:17:45 PM

It doesn't use the O2 sensors while in open loop, the maf is still used in all cars I've dealt with

[Edited on October 17, 2005 at 11:25 PM. Reason : which u said later in ur post nvm]

10/17/2005 11:24:58 PM

he is right on a msutang until it is warmed p the ECU ignores MAF sensor input. th eonly thin g the MAF sensor does during cold start is provide the transfer function(pre determoine value) that sort of sets up fueling, hence the reason ou can change the MAF on a mustang to compensate for larger injectors, because you change the transfer function.

10/18/2005 6:57:38 AM

If it is providing a transfer function as you say, then it is providing an airflow value to the computer. I don't understand how the computer can use the transfer function but not use the MAF when the MAF outputs the voltage for the transfer function.

10/18/2005 7:19:27 AM

theres not enough threads like this these days

10/18/2005 7:54:55 AM

the maf sends a barometric pressure reading during open loop but no airflow readings the barometric pressure reading makes a small adjustment to the fueling but most of that is set by long fuel trim readings from the last time it ran. I have seen mafs go bad but I doubt very highly that Beardawg61's problem is a maf. Its much more likely its the IAC starting to get carbon buildup. I hope he gets his car running right as quickly and painlessly as possible. Oh and since you are already having the maf replaced you have to do a few WOT runs to set the barometric pressure reading. Also if the mechanic has the capability you need to reset the KAM(Keep Alive Memory) on the PCM. Hope this helps.

10/18/2005 10:30:02 AM

How does a mass airflow sensor measure barometric pressure? Where have you gotten this information? None of the Ford fuel injection books I have mention anything like this.

I agree with you that the MAF doesn't sound like it is the problem here.

10/18/2005 10:47:41 AM

The map sensor is incorporated into the maf housing on the most late model Fords. The maf uses the map sensor readings and air flow to calculate the barometric pressure. I got this information from Crossroads Ford where I have worked as a technician for almost 5 years.

[Edited on October 18, 2005 at 12:03 PM. Reason : calculating baro. reading]

10/18/2005 11:55:08 AM

Cool, I didn't know that. But still it's the BAP sensor not the MAF that sends that reading. Do the computers still get the baro pressure from the MAP when at full throttle and when the key is first turned on?

[Edited on October 18, 2005 at 5:23 PM. Reason : another question.]

10/18/2005 5:22:31 PM

Ok there is no barometric sensor in lat model fords period, end of discussion there. The only other sensor incorperated into tlate model MAFs is intake air charge.

the transfer function from what I understand is just internal resistance....but the explaniation was from the late Jim Gonzalez founder of the now defunct Pro-M. By changing this transfer function you can fool the computer into running larger injectors without a re-tune.


trust me Idle Air control, the vic has eaten 3 in it's life...
and I have sold countless others when I work on Mustangs..

10/18/2005 5:51:37 PM

That is what I thought...

The transfer function may be an internal resistance because whatever they do to recalibrate the meters gives a different voltage output from the sensor. But again, if it is sending a signal, the computer is using it for fuel and spark calculations.

10/18/2005 6:43:36 PM

10/18/2005 6:50:24 PM

ok this is the only good thread that has happened in the garage in quite a while...so it has to get a ttt

10/18/2005 11:29:29 PM

^^ this is one of more technical discussion on this board lately..

I dont think it would be the MAF either.. unless someone took it out and fiddelled with the sensor.
But even then, like fordhack said it isnt really sensing air flow untill closed loop. I think the guy who mentioned going with bigger injectors is thinking of hotrodding or for the future mods..but in this case, I doubt he's thinking of supporting more hp. The IAC is a cheap part, but should defiently be one bought from ford. Hear you have to turn aftermarket ones wierd ways for it to read correctly. Shrug..the mech is trying to help, perhaps he is right, perhaps he's just eliminated a possibility. If not, get the IAC and do it yourself.

10/19/2005 8:04:43 AM

The IAC, idle air control, does not read anything. It is an electric solenoid controlled by the computer to vary the air that is bypassed around the throttle at idle. I still don't buy it that the MAF doesn't work in closed loop. That would mean that every time the engine was operated at full throttle, the computer would ignore the MAF signal. The older mustangs ('89-93) went to predefined tables at WOT for spark (maybe fuel too, I can't remember at the moment). The newer ones, '94-'95 at least, use the MAF signal to determine spark requirements, even at WOT. This is why the newer cars have so much trouble with recalibrated MAF meters when people do this to use larger injectors. The transfer function (the voltage output vs. the mass of air) changes, and with that change, it alters the points on the fuel and spark tables. The computer still has the MAF voltages it was programmed with from Ford, and now that it is seeing less voltage, it thinks there is less load on the engine, thus injecting less fuel. What most people don't think about is that it also changes the load point for the spark table as well, screwing up the ignition timing. Most people don't have problems, but recalibrating the air meter for larger injectors isn't the best solution. Even at cold start up, the computer uses the MAF to determine spark and fuel requirements. The only time it might not use the MAF input is at WOT, but I think that Ford changed that in the newer models.

10/19/2005 8:17:35 AM