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misfire problems when cold

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xkeithx

New CEG'er
Joined
Feb 28, 2006
Messages
7
first off i have a 99 contour 2.5L dohc manual trans. im getting codes p0171, p0174, p1151, p0156, p0302, p0300, and p0305 (from what i can remember). i live in southern california so the temps aren't that bad, it probably gets to 60 degrees at the lowest.

when i start the car in the mornings the idle is rough and i have to give it gas to keep the car from dying. i live right by the freeway and take it to school every morning so i'm not in much stop and go traffic. the check engine light blinks every day on the freeway, and once the car is warmed up the misfire goes away.

ive changed the plugs, wires, coil, iac, replaced all the vacuum lines, cleaned the maf, and nothing seems to help. the only thing ive done that improved the condition of the idle with the engine cold is i unplugged the MAF. when i did this it kept the idle more constant, at around 750 rpm. but with it plugged in it surges constantly between 250 and 750 rpm, usually hovering around 250 to 500, and occasionally dying. also, when i'm coming to a stop, the idle will just drop to zero and kill the engine (unless i give it gas).

i havent touched the o2 sensors yet because i don't believe they can cause an engine to misfire. i had a scan tool hooked up that read the live sensor data, and saw that all 4 sensors were switching between 0 and .1 volts, so i know they work, but they might just be slow. also, i have been scanning the car every day for the past 3 weeks and ive only seen the o2 sensor code twice, but the p0171, p0174, and p0302 codes show up just about every time.

once the engine is warm, its a totally different story. the idle still "searches" but i can drive the car without the check engine light flashing, and can tell that all 6 cylinders are firing. it usually also doesn't die every time i come to a stop. if the engine ran this way all the time (not just when warmed up), i wouldn't think there was anything wrong with it.

i bought some upper and lower intake gaskets yesterday and if i can get the fuel line disconnect tool i'll install them later today, and see if that helps any. other than that are there any suggestions to fix this condition?
 
You have a massive vacuum leak. The UIM/LIM rebuild is in the correct direction. In addition, make sure none of the tubings and clamps are loose or broken.
 
ive checked and rechecked the hoses and clamps about a thousand times, and havent found anything out of the ordinary. are there any other vacuum lines besides the 5 or so colored ones that are all bunched together next to the iac valve?

im planning on doing the manifold gaskets tomorrow afternoon, i didnt have time tonight to get it done. so lets hope that fixes everything.

just curious though- why do i only get the misfires when the engine is cold?
 
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My SVT is basically doing the same thing, except I'm not getting all the corresponding codes. If I let it sit for a day in the cold, if I try to start it, it'll either try to start and die or it'll not even attempt to run. If I push the gas when I turn the car on, it'll run fine as long as I keep the RPMS up. As soon as I let off the gas though, it dies right out. I notice though when it warms up a bit it'll stay running but idle very very rough and you can hear the misfire by listening to the exhaust.

For what it's worth, I didn't have this problem until I went to the car wash though. It did the under carriage wash...and I completely forgot my battery was relocated to the trunk. So I have that huge gaping opening. I'm guessing water got on top of the engine and got something important wet? This started about two weeks ago.
 
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Pen_Two said:
....For what it's worth, I didn't have this problem until I went to the car wash though. It did the under carriage wash...and I completely forgot my battery was relocated to the trunk. So I have that huge gaping opening. I'm guessing water got on top of the engine and got something important wet? ....
Click to expand...
Yes.......
 
ok i just finished replacing the upper and lower gaskets. cleaned both intakes for hours, and its still running like crap. i replaced the egr tube because it had some cracking on it, and checked the spark plug gap, they were a little too small so i fixed the gap, but all the plugs had the right color to them.

the engine is still running lean. i have a k&n cone filter and i dont have the stock airbox anymore. i can hear air rushing into the intake, and it is pretty loud.. so i think that the "vacuum leak" is actually coming from the intake to the engine. there are no leaks. maybe the iac is stuck? i had replaced it and used it for about a week but it didnt make any difference, so i returned it and put my old one back on. i cleaned it out and it seems to be working fine, so i don't really think thats whats wrong, just throwing it out..

i had a scan tool hooked up to the engine while it was running and got the live sensor data, and it seems like the engine coolant sensor is reading the correct value. i didnt see the voltages but the scan tool showed me the engine temperature, and it seemed about right.

pen_two: check the plug to the iac valve. maybe the contacts got water in them or something.. when the iac is unplugged the car won't idle; it will just die.
 
heres some of the live sensor data. i tried to approximate as best i could, but some of the numbers kept jumping around so much that it was hard to even record a range of numbers. the main ones that kept jumping around were the short term fuel trims, the long term ones stayed right about at 25% while idling. also the o2 sensor voltages were very inconsistent. they would all sit at zero for a bit, then there would be some activity, then they'd all get stuck at .1, then they would work again, it was very strange. anyways here is the sensor data and below that is a freeze frame:

calc. load: 32-40
ect: 201 deg. F
RPM 400-900
STFT B1 4-32%
LTFT B1 25.0%
STFT B2 20-32%
LTFT B2 25.0%
spark adv. 5-16
IAT 82 deg. F
MAF 0.25-0.31
TPS 16.8
STFT B1 S1 32.8%

and now the freeze frame:

calc load 34.1
ect 194 deg. F
stft b1 7.8%
ltft b1 25%
stft b2 14.0%
ltft b2 25%
rpm 708

there were more numbers but i didnt write them all down, i'll try to get a scan tool and get some more live data but the one i used was borrowed. i can always do it again if this data isnt sufficient.. i have no idea what most of it means. i do remember seeing the intake air temp being at around 70 to 80 when idling and reaching 130 or so when warmed up, my air filter is in the same location as the stock air box would be so im assuming it gets pretty hot in the engine compartment and the values for the intake air are accurate.

today i unplugged the intake air temp sensor and it didnt seem to have any effect on the engine performance. also the mil was flashing (indicating a misfire) on my commute to and from school today. once it got warmed up however, the misfire went away and the car seemed more powerful than it had before, probably due to all the scrubbing i did to the intake manifolds! so at least all that work wasn't for nothing.

i'm thinking that maybe there's a sensor that is fooling the engine into thinking that it's warmed up already, which causes it to run like crap when cold but run good when warm..? just a thought. i noticed one of the coolant temp. sensors is all green and looks old.. i took a picture of it, let me know what you guys think.
 

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In your picture, if you are talking about the thingamajig in the middle, that is the Coolant Temperature Gauge Sender. It should not have any effect on the engine or PCM (unless the wires are chaffed and touching some other sensor wire).

I just reread your original post. The O2 sensor values should be between 0 and 0.9 Volts.

Edit. Your MAF sensor readings are out of spec. If you can borrow someone else's MAF sensor, put it in and see if it helps. It should run from 0.6 to 0.9 V.

Don't mess with the O2 sensors until you get the MAF sensor checked out (unless the O2 sensors are more than 75K miles old. Then it might be a good idea to change them too.)

Also recheck the TPS reading and repost. It is way off the charts.

xkeithx said:
..... the only thing ive done that improved the condition of the idle with the engine cold is i unplugged the MAF. when i did this it kept the idle more constant, at around 750 rpm. but with it plugged in it surges constantly between 250 and 750 rpm, usually hovering around 250 to 500, and occasionally dying. also, when i'm coming to a stop, the idle will just drop to zero and kill the engine (unless i give it gas).

i havent touched the o2 sensors yet because i don't believe they can cause an engine to misfire. i had a scan tool hooked up that read the live sensor data, and saw that all 4 sensors were switching between 0 and .1 volts, so i know they work, but they might just be slow....
Click to expand...
 
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yeah i was talking about the coolant temp sensor. i was just concerned because it was all green and didn't look right.. and there is only one wire going to it, not two. about the o2 sensors, thats what i meant.. it varies between 0 and 0.9 volts, not 0 to 0.1 volts.

the maf reading was in cubic feet per second i think, it wasn't giving me a voltage reading. as i gave the engine gas, the maf value went up, but at idle it was around .25 to .3 feet per second or whatever the units were. i dont remember exactly, but it was the mass flow rate, not voltage.

i am pretty certain that the tps was at 16.8. one of my mechanic friends scanned it and said that the tps was supposed to be at that value.. but maybe he was wrong, what should it be at?
 
xkeithx said:
... about the o2 sensors, thats what i meant.. it varies between 0 and 0.9 volts, not 0 to 0.1 volts.

the maf reading was in cubic feet per second i think, it wasn't giving me a voltage reading. as i gave the engine gas, the maf value went up, but at idle it was around .25 to .3 feet per second or whatever the units were. i dont remember exactly, but it was the mass flow rate, not voltage.

i am pretty certain that the tps was at 16.8. one of my mechanic friends scanned it and said that the tps was supposed to be at that value.. but maybe he was wrong, what should it be at?
Click to expand...
If the O2 sensor is bouncing from 0 to 0.9 every second or so, then, there is a problem. It might not be the O2 sensors but it could be something else causing it to go berserk.

As for the MAF sensor readings, the 0.6 to 0.9 V value was for hot idle and yes, it is supposed to go up when the engine is revved but it should not go above 5.1 V. If you can get the dimensions of the readings, that would help greatly.

The TPS should be about 0.5 to 0.9 V at hot idle too. And the it should also go up when revved. And once again, it should not go above 5.1 V and if you can get the dimensions of the readings, that would help greatly too. I will check other sources (Autozone, etc.) for these ranges and edit this post later.
 
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