Jerks and pops when cold until full throttle is applied

[Z28This]

I have a 95 Gt 5 Speed and when the thing is cold or hasn't ran longer than 10 minutes it acts up aprox. 75% of the time. When driving and the accel. is mashed it starts jerking just a littl bit back and forth. You almost think its the road at first but you can feel a power loss. The further you mash it down the worse it gets until it starts popping inside the exhaust pipes. Doesn't crack like a backfire but just a low thud i guess you can call it. I have pulled codes and came up with 172, 173, and 543. Once the car is warm it runs pretty good but still doesn't idle to great. Didn't do this until i put an off road h-pipe on it a couple weeks ago. Car has 173K on the clock I looked up the codes and i was told the 543 is false if the car runs. I have added Motorcraft platinum plugs. Excl. 300+ race wires. MSC cap and rotor. Blaster coil. BBK Cold air intake all withing the past couple weeks (just got the car Can't really figure this one out unless the O2 sensors went bad as soon as i changed the h pipe. :BangHead:

 

[nrk]

O2 sensors.

 

[nrk]

Also might want to try cleaning/replacing the maf first. You could be throwing the code from having the o/r pipe too, and your o2 sensors might be fine, but don't quote me.

 

[CC'S95GT]

your computer doesn't know your cats are gone. (the o2's are before the cats on 5.0's).
clean the maf first. Then take out the platinium plugs. our cars don't like the platimium.

 

[reduceallpain]

I have the same exact problem with my car.......

 

[Z28This]

I have already cleaned the mass air flow sensor. In addition when i bought the BBK CAI it came with a mass airflow sensor and i used it for a while and put my old one back on and it didn't make any difference at all. The car ran this way before i changed to the platinum plugs. As for the cats being gone i didn't think your car knew they were even there because the cats where after the O2 sensors so by me cutting them off i wouldn't see that making a difference unless it would be that the exhaust is moving out faster now. Driving the car 200 miles out of state tommorow for thanksgiving.... HELP!!!!

 

[Christang95]

I had the same thing, For me it had something to do with the gas tank or fuel system. I think water and/or condensation got into the fuel system and created this effect. It happened more often when it rained and was very cold, usually dry gas helped.

 

[Z28This]

I had the same thing, For me it had something to do with the gas tank or fuel system. I think water and/or condensation got into the fuel system and created this effect. It happened more often when it rained and was very cold, usually dry gas helped.

Sweet. I will try some rubbing alcohol!! Used that on my quad once after i buried it in the river and it seemed to help.

 

[MustangChris]

bad fuel pressure regulator. Thats my $0.02.
also, since you just got the car, replace your fuel filter. it takes 30 minutes and is an easy maintance step. it will rule out a clogged filter as the problem.

 

[NXcoupe]

You swapped the pipe out and then it started doing this, and you are changing everything but what caused the problem. Your O2's are probably bad, when you remove them and move them around, pipe banging around as you are installing it, the little fragile piece in the sensor can break. I would start there, and what did you gap your plugs at? Please don't say they were pre gapped. Your BBK cai is also a culprit, your mass air is not designed to work with an elbow in front of it. It should be the first thing on the cai, with curves and such behind it. These cars are hard to get right when tuned for cold start driving, because they go too lean, yours sounds like that is the culprit.

 

[Z28This]

bad fuel pressure regulator. Thats my $0.02.
also, since you just got the car, replace your fuel filter. it takes 30 minutes and is an easy maintance step. it will rule out a clogged filter as the problem.

Just replaced the fuel filter less than 1k ago!

Yes NXCoupe Unfortuanately i was in a hurry and did not take the time to dig out my spark plug gapper and make sure they were right but the exact problem existed before the new plugs were installed.

 

[CC'S95GT]

I vote for o2's first. then fpr.
you don't really have time to troubleshoot so all you can do is throw money and parts at it.

 

[NXcoupe]

bad fuel pressure regulator. Thats my $0.02.
also, since you just got the car, replace your fuel filter. it takes 30 minutes and is an easy maintance step. it will rule out a clogged filter as the problem.

Just replaced the fuel filter less than 1k ago!

Yes NXCoupe Unfortuanately i was in a hurry and did not take the time to dig out my spark plug gapper and make sure they were right but the exact problem existed before the new plugs were installed.

Ok, so what about the O2's? You have codes, I don't have a manual on me to check what each one means, but probably the O2's are bad if it is showing a lean code or something to that effect. And not gapping your platinum plugs can make a problem worse. The gap is supposed to be .052, and gapping it closer with a lean mixture will make it run worse. Take or leave my advice, what do I know anyway? right?

 

[Z28This]

Alright just installed two new O2 Sensors! Heading to Ky in a few minutes so i will let ya know saturday what the verdict is! Thanks for all the help and have your thinking caps on saturday just in case. lol

When i get back and have some time i will pull the plugs and gap them also. Another reason why i didn't gap them was because i didn't know the gap.....now i do. Thanks NXCoupe

BTW One O2 sensor was definately bad becasue it rattled! So i have hope this will fix it!

 

[MeltedRubber]

O2's are not used by the computer to influence injector pulse width till warmed up. You run open loop for at least a few minutes during warm up and during that time O2 sensors are totally ignored.

Due a TPS voltage sweep during warmup, look for glitches and drop outs. Monitor MAF voltages during warmup at idle and accel, looks for glitches and dropouts. Start there before buying any parts.

 

[MustangChris]

You swapped the pipe out and then it started doing this, and you are changing everything but what caused the problem. Your O2's are probably bad, when you remove them and move them around, pipe banging around as you are installing it, the little fragile piece in the sensor can break. I would start there, and what did you gap your plugs at? Please don't say they were pre gapped. Your BBK cai is also a culprit, your mass air is not designed to work with an elbow in front of it. It should be the first thing on the cai, with curves and such behind it. These cars are hard to get right when tuned for cold start driving, because they go too lean, yours sounds like that is the culprit.

i thought this problem was remidied if you took the screen out from in front of your MAF. is that true?

 

[GREG@SN95]

bad fuel pressure regulator. Thats my $0.02.
also, since you just got the car, replace your fuel filter. it takes 30 minutes and is an easy maintance step. it will rule out a clogged filter as the problem.

Just replaced the fuel filter less than 1k ago!

Yes NXCoupe Unfortuanately i was in a hurry and did not take the time to dig out my spark plug gapper and make sure they were right but the exact problem existed before the new plugs were installed.

Ok, so what about the O2's? You have codes, I don't have a manual on me to check what each one means, but probably the O2's are bad if it is showing a lean code or something to that effect. And not gapping your platinum plugs can make a problem worse. The gap is supposed to be .052, and gapping it closer with a lean mixture will make it run worse. Take or leave my advice, what do I know anyway? right?

Here's all the codes...
http://sn95forums.com/index.php/topic,44796.0.html

172 - HEGO shows system always lean
173 - HEGO shows system always rich
543 - Fuel pump secondary circuit failure: Battery to PCM

 

[Z28This]

O2 Sensors Fixed the problem!! She runs great!! Thanks for all the help!!!!

 

[Addermk2]

O2 Sensors Fixed the problem!! She runs great!! Thanks for all the help!!!!

imagine that...