In gear car revs to 1300rpm fine then after a few seconds start to sputter

[kjsbomb]

As stated in the title, I've noticed that the car has either a missfire or stutter issue. I have no clue what else it could be. Things I have already done to the car, due to the milage and maintenance, I have replaced the coil pack, spark plug wires, spark plugs, put in new valve lifters and push rods, new catalytic converter, new exhaust manifolds, new mufflers, replaced the fuel filter, put in a cold air intake... i think thats it. The car is a 2000 3.8L with about 155,000 miles on it. It idles fine, and when I rev it it rev's fine. But when I put it in gear and hold the brake down and then rev it to about 1300rpm it revs up fine for about 3 seconds and then starts to sputter BAD! It doesn't kill the engine, but the whole car shakes bad! I'm at a loss of what else could cause this. I've put so much money into the car already and can't figure it out.

PLEASE HELP!!!

Thanks!

 

[kjsbomb]

Also, just a side note, I've worked on lots of cars and am not a newb lol. But this has me and everyone I show it to stumped! Just on here to see if anyone else has had this issue and/or got it fixed! Oh and I did notice when I changed out the cat's that the O2 sensors were covered in black soot, so I cleaned them off. I am down to 2 things, replacing the O2 sensor's or the throttle position sensor. I've checked the vacuum lines and all seems fine. Oh, and I changed the PVC valve too.

 

[briannova]

Also, just a side note, I've worked on lots of cars and am not a newb lol. But this has me and everyone I show it to stumped! Just on here to see if anyone else has had this issue and/or got it fixed! Oh and I did notice when I changed out the cat's that the O2 sensors were covered in black soot, so I cleaned them off. I am down to 2 things, replacing the O2 sensor's or the throttle position sensor. I've checked the vacuum lines and all seems fine. Oh, and I changed the PVC valve too.

I had issues with my wife's car as well, and though you probably checked this already, I'll mention it anyhow. I had a mechanic at my place today, working on an impala, which had about the same issues. Revs fine with no load, but put it in gear (load), try to rev it, and it runs rough, sputters, no power, etc,,,. The first thing he did was check for vacuum leaks, thinking the brake booster could be part of the reason it happens with my foot on the brake. No leaks, so he then removed the MAF sensor, cleaned it, and the car runs fine now, but he said to check the engine light issue (O2 sensors), as they may be full of soot from running it too long with the sensor dumping in too much fuel.

Good luck

 

[kjsbomb]

Well I've pulled the MAF and sprayed some MAF cleaner on it, let it dry and then put it back on. I was told not to actually wipe it or anything like that in case of damaging it. If I'm wrong please let me know! As for the O2 sensors, I think I'm going to replace them as well, they aren't too pricey. Only thing is there are 4 of them, lol. So it could get a little up there. I would just like to get this engine running smooth again. I can feel it when I'm driving too. The car will kinda surge/sputter when the RPM's are low, but then when I give it a little gas or get the RPM's up its fine. Just weird! Thanks for the response and I'll take a closer look at those O2's!

 

[kjsbomb]

Oh and the engine light is off. Which makes this even harder to trace!

 

[briannova]

Oh and the engine light is off. Which makes this even harder to trace!

My 99 3.8L Stang, and my Kia, both needed new MAF's in the past year. One in the stang just quit, started dumping way too much fuel, ran terrible, and the kia MAF, after taking a closer look, had a missing piece of 'foil' on the air flow sensor (which is also incorperated into the MAF). That's 3 vehicles in 1 year, 3 MAF related issues, all of which made the engine do some strange stuff. The kia was so bad, I had to unplug the MAF just to get home one day. I was told never to unplug them while the key is 'on', or engine running, they burn out super quick, and have very sensitive electronics inside. Have you tried seeing if it runs any different with it unplugged?

 

[kjsbomb]

I'll try to unplug the MAF tonight and post what happens! Another thing I noticed last night (while the engine was cold) it didn't do the sputtering. I put it in gear and reved it up to about 1100RPM (which would cause it to sputter) and it seemed fine. But then when I got to work today, after driving it and getting it hot, I put it in gear, reved it, and sputter is back! So now its down to it only does it when the engine is hot. Now the question is if the MAF is bad, when I unplug it, there should be no change correct?

 

[kjsbomb]

Also the good thing is, I found a new MAF on RockAuto for only $44! I've seen those things go up in the hundreds, so that's a relief too!

 

[briannova]

Also the good thing is, I found a new MAF on RockAuto for only $44! I've seen those things go up in the hundreds, so that's a relief too!

If it runs fine when cold, worse when hot, could be the MAF or IAT sensor. The IAT signals the intake temp prior to the MAF and controls the percentage of air to fuel. If the engine is hot, and you are using an air filter (like K&N), which is taking air from the hot engine area, or if the sensor is faulty, could also be the cause. Check these links for info and test proceedures for sensors. http://easyautodiagnostics.com/ford_maf_mustang/maf_test_mustang_2.php

http://easyautodiagnostics.com/index_ford_3.0L_3.8L/index_of_articles_1.php

 

[wmburns]

This is a great example of what can happen once trouble shooting reverts to "parts changing" mode.

Confirm this is an automatic or Manual. I'm going to assume it's an automatic.

Question. Has the cooling system been drained and re-filled? If so, were the V6 coolant refilling procedures followed? Could there be air trapped inside the motor? If so, this will cause the ECT to read low. The PCM will think the motor is cold when it's actually overheating.

http://www.allfordmustangs.com/foru...stang-irregular-rpms-showing-hot.html#2604913

This is also would be a great thread to show the power of an ODB2 scanner. If you knew for example what the PCM thinks the following values are when the problem is happening:

• engine coolant temperature (ECT)
• Input air temperature (IAT)
• air flow (MAF)
• fuel pressure
• timing advance
• PCM mode (open/closed loop).
• LTFT at idle and under load.

This would almost certainly provide the eureka moment needed. I also suspect that a good scanner could have already been bought and paid for with the $$ already spent replacing what may turn out to good parts.

Regarding the O2 sensors, only the front O2's control motor function. Don't change the rears unless a DTC specifically calling out the rears is seen.