Stock and it does not seem right

[Wurf]

When I shift from 2nd to 3rd driving aggressively, as soon as I lift, grab third, then mash the throttle, there is a hesitation followed by what sounds like a muted backfire or thump before the motor recovers. Almost like a rich or lean stumble. The motor is completely bone stock and the ECU was reset about 2K miles ago.

It doesn't do this all the time either. Sometimes it runs fine under these conditions but it's probably 60/40 normal/hesitation + pop.

I paid extra attention in getting the PCV connection at the elbow into the factory connector completely.

I run Shell 93 almost exclusively.

Any ideas guys?

It ran better when I had my PG SRI on it and I'm thinking of putting it back on. I took it off for the winter now that I'm running snows and it's colder outside. I figured there would be little point in more power pretty soon when the snow flies but that was about a month ago now.

Nice winter we're having so far. 50's for highs almost every day is pretty crazy for mid November around here. El Nino rocks.

 

[hectik1]

When I shift from 2nd to 3rd driving aggressively, as soon as I lift, grab third, then mash the throttle, there is a hesitation followed by what sounds like a muted backfire or thump before the motor recovers. Almost like a rich or lean stumble. The motor is completely bone stock and the ECU was reset about 2K miles ago.

It doesn't do this all the time either. Sometimes it runs fine under these conditions but it's probably 60/40 normal/hesitation + pop.

I paid extra attention in getting the PCV connection at the elbow into the factory connector completely.

I run Shell 93 almost exclusively.

Any ideas guys?

It ran better when I had my PG SRI on it and I'm thinking of putting it back on. I took it off for the winter now that I'm running snows and it's colder outside. I figured there would be little point in more power pretty soon when the snow flies but that was about a month ago now.

Nice winter we're having so far. 50's for highs almost every day is pretty crazy for mid November around here. El Nino rocks.

Is the the traction control on? I noticed the same thing with my car....turned off the traction control and the problem was fixed.

 

[Wurf]

DOH!
I feel pretty stupid now...never even thought of that.
Those snows are soft and that HAS to be what's going on. I just never look at the dash to see.

Guess I'll try that for a few days and see what happens.

Nice call Hectik1.

Thanks!

 

[hectik1]

DOH!
I feel pretty stupid now...never even thought of that.
Those snows are soft and that HAS to be what's going on. I just never look at the dash to see.

Guess I'll try that for a few days and see what happens.

Nice call Hectik1.

Thanks!

No prob! The traction control can be very deceiving on this car especially when switching gears.

 

[Wurf]

Just returned from driving the car. DSC was left ON. Wound up 2nd gear, grabbed third and mashed the gas. No lights on the dash at all and same thing....hesitation car sort of noses over - THUMP from the exhaust...then it takes off. The traction control light never illuminated.

Turned off the DSC and let the car coast and tried again. No hesitation or thump.

I will be trying to remember to disable the DSC and see if I can reproduce this a few more times, but I thought it important to point out the traction control light never illuminates when the hesitation and thump occur.

 

[hectik1]

Just returned from driving the car. DSC was left ON. Wound up 2nd gear, grabbed third and mashed the gas. No lights on the dash at all and same thing....hesitation car sort of noses over - THUMP from the exhaust...then it takes off. The traction control light never illuminated.

Turned off the DSC and let the car coast and tried again. No hesitation or thump.

I will be trying to remember to disable the DSC and see if I can reproduce this a few more times, but I thought it important to point out the traction control light never illuminates when the hesitation and thump occur.

Light never goes on with mine either.(squinty)

 

[bykeryder4life]

I'd check the plugs over and check the gap, then go log fuel pressure during a run. I bet its one of the two. The whole time this is done the dsc and tcs must be off!

 

[08cosmic3]

The crappy stock BPV leaks badly, won't hold boost between shifts and when you get back into boost it will jerk badly. Get a Forge BPV.

 

[RUMBLEFISH]

Also check motor mounts.

 

[Wurf]

Car only has about 7500 miles on it so plugs are not on the suspect list for me. The hesitation followed by the thump.......I wonder if the pig rich mixture at the top of 2nd is leaving fuel in the exhaust which is igniting between shifts?

Come spring, I'm putting the PG SRI and PG TIP on the car and I'm going shopping for a test pipe.

The BPV.....I've been thinking about either the Forge or the new TS.

 

[MSMS3]

The crappy stock BPV leaks badly, won't hold boost between shifts and when you get back into boost it will jerk badly. Get a Forge BPV.

Very few factory BPV's leak. I'm running 13.4's @106. 0-100 is in the 11.6 second range. I have 25,000 miles on the car. My boost gauge shows -22 at idle and under full load boost spikes sometimes to 21 and always settles and holds very steady at 17-18 psi with mods below. The bpv would be the very last thing I would suspect given his symptoms. Yes, they can leak. Forge or any other brand can also malfunction. If his is the problem, I'd be very surprised.

To OP: what is outside temp? You may be running into some fuel cut coming up on boost in third gear if it is cold outside.

 

[Wurf]

Outside temps are in the 40's with highs around 50 here.
So what you're saying is the turbo is spooled up at the top of 2nd, I grab third and engine speed drops, I go WOT and there's possibly too much boost for the amount of fuel needed. Hmmm.......

Sure seems strange for a stock car, but I have to admit I don't encounter this problem in the summer. Warmer air = less oxygen so less fuel is needed for proper mixture however less power is generated.

That's an interesting idea but wow....hitting the fuel cut just because it's cold outside makes me wonder how far mods can take this car without FP internals.

 

[08cosmic3]

I was commenting from experience. My stock BPV would not hold boost between gear shifts and would come back in abruptly cause bucking, which caused the engine to rock causing the thumping sound.

Borrow a Forge from someone and put it on. I bet I'm right.

 

[mazdaspeed32007]

IMHO i think its exactly what mine was doing....

i would slam a gear and it would hesitate, pop, and flume of smoke out the back and then she would fly. not all the time, just sometimes. and other times it would stutter all the way through a gear!

i would change your plugs to a better plug. go with the denso's. try this first if your looking for a solution. i can almost guess this is what it is.