Bas Miss at WOT

TSWG00 · Oct 3, 2005

Big Miss at WOT

The past month I have noticed a Bad Miss at WOT, I notice that it does it alot when its cold, as for when its warmed up I haven't been able to test it yet, My CI has gone on and off but as of yet I haven't read the code lol (need a code reader). I'm thinking its either a MAF problem or Fuel problem. I guess the other option could be Sparkplugs. I guess its time for me to mess around with it to see what the problem is. I do notice its running Rich have not clue how to fix that problem. If anyone has any ideas let me know :-D.

matt_656 · Oct 3, 2005

if it is rich i would think it is mass air but that is just my $.02

TSWG00 · Oct 4, 2005

Yeah I have had problems in the past with the Mass Air, I guess I'll try and clean it. Does anyone know how and what to use to clean the Mass Air. It would make sense with the WOT problem. I guess I'll try and clean it when I have a chance. Lets hope that will solve my problem LOL.

TSWG00 · Oct 4, 2005

Next task is to do a compression test LOL

95opal · Oct 4, 2005

why dont you start by pulling the codes.you already said the cel came on so start their.also check your plugs,and wires they could be toast.you might also want to check your o2's if you have a rich condition.if its basically just a miss i would suspect something elect.(cap rotor,plugs and wires,they work wonders..) good luck

TSWG00 · Oct 4, 2005

Well the miss only happens when the engine is cold and at WOT once its warmed up I don't feel/notice it anymore. I'm working on buying a code reader since my stang always seems to throw codes my way LOL. I already know what the code is going to say its going to say one of the banks is running rich or its going to tell me one of my 02's is dead lol. Guess its time to buy that autoxray lol

HISSIN50 · Oct 4, 2005

Just as info you info you already know, O2's are not used when the motor is cold (for the first 30-120 seconds or so) and they are not directly used at WOT.

CManT1914 · Oct 4, 2005

HISSIN50 said:
Just as info you info you already know, O2's are not used when the motor is cold (for the first 30-120 seconds or so) and they are not directly used at WOT.

Yep. The MAF is used during warmup, because the O2's are not heated properly yet. However, once the engine is warmed up, during normal part throttle driving, the engine relies mainly on the O2's to adjust a/f ratio. But under WOT, it ignores them, and uses the MAF and the ACT sensors to calculate it. You saying it happens only when cold or WOT makes me think it's the MAF. Mine went south on me (3 times actually) and I got bad gas mileage, and horrible performance every time. But pull those codes before you do anything else.

TSWG00 · Oct 4, 2005

I know about the O2's not being use at WOT and at cold start. Yeah I had this problem before and the wire on the MAF needed cleaned but this time its only doing it when its cold, its kinda acting like its not getting enough fuel or its getting too much, Once its warmed up it still smells rich. Yeah I'm going to try and get a code reader. Thanks for the help guys. I'll let you know what the code reader says.

HISSIN50 · Oct 4, 2005

The O2's are used at WOT - just not directly.

mo_dingo · Oct 4, 2005

CManT1914 said:
Yep. The MAF is used during warmup, because the O2's are not heated properly yet. However, once the engine is warmed up....

But pull those codes before you do anything else.

The O2's start to be used way before the engine is hot. The heaters in the o2 sensors do the job in appx 120 seconds.

But you know you have codes to check, so pull them. Start with the basics.
Scott

DFG 5OH · Oct 4, 2005

have you checked the timing?

CManT1914 · Oct 4, 2005

mo_dingo said:
The O2's start to be used way before the engine is hot. The heaters in the o2 sensors do the job in appx 120 seconds.

But you know you have codes to check, so pull them. Start with the basics.
Scott

But they aren't used to calculate a/f ratio correct? That's what I meant. So technically, they still aren't heated up all the way for the first couple of minutes. Right?

CBZGT50 · Oct 5, 2005

I have the exact same miss problem at about 5000 rpm. I will be running it up and at 5K it just falls on its face at WOT. I took the TB off and cleaned it and it worked good for a while. I was able to get up to 6200K. Now it is crapping again, I cant get abouve 5100K and now I am looking at the TPS as being the culprit. That is the only thing I can think of on the TB that would cause something like that.

I know that if the MASS is pooped, it will not run for crap. Just my exp. I have been running rich 02's in my 95 Cobra and it just ran rich at high RPM and smoked like crap. It never effected the motor like a miss. Tomorrow, I am going to change out my TPS and see if I get a different effect. If not, I will do more research.

BTW, what does the small sensor (cant think of name) on the intake tube between the mass and the TB do? I have had it unplugged and seen little or no effect on the engine.

CManT1914 · Oct 5, 2005

CBZGT50 said:
BTW, what does the small sensor (cant think of name) on the intake tube between the mass and the TB do? I have had it unplugged and seen little or no effect on the engine.

That's the ACT (air charge temperature), or IAT (intake air temperature), whichever you prefer. It tells the computer hot hot/cold the incoming air is. It does have an effect on a/f ratio, but nothing like the MAF. Leave it plugged in, lol. Oh yea, the sensor itself needs to be indexed, to where the actual element is broadside to the incoming air. If you ever take it out and look at it, you'll know what I mean.

TSWG00 · Oct 5, 2005

Well I have notice when its cold and I try to get it going it will back fire and miss like crazy and want to die, even giving it WOT it does not like it. If I rev it up to like 3K and let out the clutch it kinda works but still wants to miss and back fire LOL. So I'm pretty sure its an A/F problem, I would like to get a A/F gauge but again I'll run the codes and see what they say. I'll probably do that this weekend. Its too bad you guys couldn't come and see what my car does LOL. I don't think its a timing issue cuz once its warmed up I don't feel or notice the Miss/studder

TSWG00 · Oct 5, 2005

CBZGT50 said:
I have the exact same miss problem at about 5000 rpm. I will be running it up and at 5K it just falls on its face at WOT. I took the TB off and cleaned it and it worked good for a while. I was able to get up to 6200K. Now it is crapping again, I cant get abouve 5100K and now I am looking at the TPS as being the culprit. That is the only thing I can think of on the TB that would cause something like that.

I know that if the MASS is pooped, it will not run for crap. Just my exp. I have been running rich 02's in my 95 Cobra and it just ran rich at high RPM and smoked like crap. It never effected the motor like a miss. Tomorrow, I am going to change out my TPS and see if I get a different effect. If not, I will do more research.

BTW, what does the small sensor (cant think of name) on the intake tube between the mass and the TB do? I have had it unplugged and seen little or no effect on the engine.

Yeah I would say the miss starts at about 5K and just gets worse as the RPM's climb, but once its warmed up I don't notice it. I wonder if Blocking off my EGR has anything to do with the problem LOL

TSWG00 · Oct 7, 2005

I really have a feeling its my MAF but I'll find out soon enough when I get the code read LOL

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