Misfire? But not really

[Talladega]

I put a set of Stainless Works long tube headers with high flow cats on this weekend. All went well but in my first two days driving it, it now feels like the car has a misfire. When I say that it gives a "chug" or a "pulse" when under throttle and below 3000 RPM. I put new NGK Iridium IX and Taylor 409 plug wires with thermal boots on them. The car is not throwing any check engine lights so I don't think it is really a misfire. Could it be that the exhaust does not create enough back pressure? I have QTP cutouts but they are after the cat and it doesn't seem to make a difference if they are open or closed. The exhaust is stock after the cutouts. I had DynoSteve do a remote tune but I loaded that a few days before installing the headers and didn't notice it then.

Any ideas what could be causing the pulsating?

Thanks in advance

[Sidecardog1]

From your description of the symptom, it sounds like your air fuel ratio is now out of calibration since your remote tune was done prior to the increase in the engines air flow by the addition of the headers and hi-flow cats. Talk to DynoSteve about your change and see if he agrees that you need the tune adjusted to get more fuel below 3000 rpm to cure the lean issue.

[Talladega]

Originally Posted by Sidecardog1

From your description of the symptom, it sounds like your air fuel ratio is now out of calibration since your remote tune was done prior to the increase in the engines air flow by the addition of the headers and hi-flow cats. Talk to DynoSteve about your change and see if he agrees that you need the tune adjusted to get more fuel below 3000 rpm to cure the lean issue.

Thanks, I e-mailed Steve to see his suggestions. He is always great about getting back, but in the mean time I am hoping for other minds suggestions.

[StingrayblueSS]

Did you check the plug wire connection. I have Taylor wires and when I first put them on I had a hard time with them slipping off the plugs. Now I check them intermittently.

[Talladega]

Originally Posted by StingrayblueSS

Did you check the plug wire connection. I have Taylor wires and when I first put them on I had a hard time with them slipping off the plugs. Now I check them intermittently.

No, I have not. Wouldn't that throw a check engine light if a plug wire was off or loose?

[PalmerGA]

Originally Posted by Talladega

No, I have not. Wouldn't that throw a check engine light if a plug wire was off or loose?

Not necessarily. These cars are a little unpredictable sometimes with the codes they show (and don't show).

Why would you load a custom tune BEFORE installing the headers? I suspect that is what's causing your issue. Let us know.

[StingrayblueSS]

Never got a code just had a thumping at idle. I could feel it not hear it

[Talladega]

Originally Posted by PalmerGA

Not necessarily. These cars are a little unpredictable sometimes with the codes they show (and don't show).

Why would you load a custom tune BEFORE installing the headers? I suspect that is what's causing your issue. Let us know.

I checked with DynoSteve and he said loading the tune prior to installing the headers would not hurt anything. The pulse was not there for the few days in between loading it and installing the headers. It only appeared after installing the headers, plugs, and plug wires.

[its a syn]

Running a throttle controller?

[Talladega]

Originally Posted by its a syn

Running a throttle controller?

No

[PalmerGA]

Originally Posted by Talladega

I checked with DynoSteve and he said loading the tune prior to installing the headers would not hurt anything. The pulse was not there for the few days in between loading it and installing the headers. It only appeared after installing the headers, plugs, and plug wires.

Interesting. I didn't think it would "hurt anything" - just thought the ECU might be confused with the tune without the upgrades. No question, if DynoSteve says it's okay... it's okay. He's the best.

[Olddudesrule]

I'd have to second double or triple checking the plug wire connections. Might even consider swapping back the OEM wires to see if the problem persists. No product is ever perfect, possibly you have a bad wire. Symptoms sure sound like a bad plug or plug wire connection.

[Talladega]

Originally Posted by Olddudesrule

I'd have to second double or triple checking the plug wire connections. Might even consider swapping back the OEM wires to see if the problem persists. No product is ever perfect, possibly you have a bad wire. Symptoms sure sound like a bad plug or plug wire connection.

That's what I am thinking.
How do I test if a plug wire is bad?

[christianchevell]

Replacing wires its usually the case to check if ones bad you use continuity and check for resistance I personally use Granatelli's , and like them and they do show how to test wires in their comparisons in videos. You could need a MAF cleaning, air tube loose, TB loose, MAF loose unsealed well, loose wire to one coil stretched out from installing headers making a terminal connection loose, bad ground,....The list goes on as to what it could be, Hopefully you double check and tighten things and it goes away with relearning its AFR over time.
I personally never thought much of Taylor wires myself, wires have to be low impedance and they don't make the best but they are thought of as tough. My headers I have to keep the front left of the engines plug ends coming out pointed right to help keep the spark plug wires from contacting the header surface. If it was not for everything being new you would be in the look for a cracked spark plug category of recommendation after a header install... I know the back ones are hard, you must be running tr6ix which I run but I am cammed, many use NGK 55s also of the NGK recommended from shops....with 7s for Forced induction. Hopefully you did not try to gap iridium plugs , and BTW most thermal boots have metal in the fabric so its not good they touch the headers either if they do. I would be checking the plugs install especially the ones hardest to do...