Miss at idle. Any ideas?

[99FiveOh]

My car ran great, then after swapping in a T5 from my Tremec, I have a bad miss at idle. If I give it any throttle at all, it revs smooth and drives fine. It's only at idle. I can feel it through the seat when it does it.

When I installed my S/C I changed the cap, rotor, plugs and wires. My fuel pressure is set to 38 psi, I moved it around a little but no change. The MAF is stock but the wires are clean. I have a Pro M going in on Monday when I get my tune.

Is it possible that one of these old 19 lb injectors got damaged by the FMU? I haven't really seen any kind of REAL boost yet(anything over 5psi), but I did see around 60-70 psi on the gauge while in boost.


Like I said, either it didn't do this before the trans swap, or it did and I just feel it more now because I might have disturbed the motor mounts making them sit different and transfer more vibes through the body.

Should I just go have it tuned with the new injectors and MAF and see if it fixes it?

Also, I changed my TPS and there was no difference.

 

[HISSIN50]

Cylinder balance test is negative (sorry to repeat that - I think you've run one before the blower swap to isolate some issue)?

Could be it not a miss, per se, but rather a resonance issue?

 

[94TURBO5 O]

Check all of your vac lines.

 

[99FiveOh]

I'll go ahead and run another cylinder balance test.

 

[99FiveOh]

Ok, here are the results of a thorough engine code procedure.

Cylinder balance test: Well, the very first run, at temperature, revealed that #1 cylinder was acting up. So I ran the test 2 more times and I got code 9's for nothing wrong. Why did this happen?

KOEO: 334 = EVP Sensor was/is High.
564 = Fan Circuit Failure
My fan works just fine, why does it keep saying that there's a failure? I just installed a brand new fan motor today as a fire precaution so I know that's not the problem.

KOER: 314 = AIR Inopperative , Left or Front HO2S
311 = AIR system not working - Single, Right or Rear HO2S

Is it correct that since I have my smog removed completely that the above two codes are coming through?

when I go to get a tune on monday, what do I tell them to do to get rid of the smog codes? I'm suprised my EGR isn't malfuctioning, it's all rigged! I'll have that deleted from the EEC too. Also, what do I tell them to take out for the "tip-in retard"?

Thanks!

 

[99FiveOh]

nevermind on the EGR thing, I see now that EVP is EGR Valve Position sensor. I have it held about half way open with the home made plate between the EGR valve and the EGR spacer.

 

[HISSIN50]

Nice work. With the CBT, it should retrim the criteria with each iteration of the test. The criteria are based upon a percentage of the biggest drop observed IIRC. Basically, #1 is not contributing as much as it should, but it's not totally lame. I might pull that plug and have a looksie. You could tighten the gap up on that plug and see how it does after that (I've had luck doing this before myself). Might as well check compression while you have the plug out (if you can easily).

Good call turning off the EGR during the tune. Ditto the AIR stuff (you can use a resistor to fool the puter via the TAB/TAD as well, but a tune is the time to do it for real).

The tuning guys can tell ya the ins and outs of the Tip-in advice.
I might also ask them for specifics on having a checksum value input so you don't get a ROM code with the chip installed (it's something like a checksum 0 entry). They should know what to do.

Good luck.

 

[99FiveOh]

Thanks! Yeah, I gotta regap all my plugs anyway before the tune because I have them at 35 and I'm gonna go ahead and try 28. My car never had a miss before and it may be because of the 24's being in there now. Am I correct in thinking that higher heat range plugs kinda "Keep" themselves clean?

My car runs good through the RPM's with my fuel pressure set to 42, but idling suffers, it may be fouling out that one plug. When I backed it down to 38 psi, it idled alot better. I ran the CBT with it at 42 psi.

 

[99FiveOh]

Just took the car for a drive and it ran pretty good. It's pretty cool outside so I think maybe the ACT sensor being in the wrong place may have something to do with it. It does run like crap when it's warmer/more humid outside.

I'm gonna move the ACT into the discharge tube and go from there.

 

[mo_dingo]

Try running the CBT manually, yanking each plug wire until you find one that doesn't affect the idle as much as the others. Much easier.
Scott

 

[HISSIN50]

You're right-on - a hotter plug is less susceptable to fouling. That said, the 24's should be just about right for forced induction anyhow, should they not (I run 'em N/A and haven't noticed any issues).
If you have a new plug, try putting it in #1. It would rule out a damaged plug as a cuprit (I always get a headshake from the parts stores when I ask for 9 plugs; one spare is nice).

It would be curious to see if that one cylinder is loading up on fuel at idle (if you ever have access, switching that injector around with another and seeing if the issue follows the injector could be telling). Your FP observations might support that.

One more expensive to consider: With almost any forced induction, as you know an ignition box can really be helpful. It isnt needed but gives some room for fudge factor.

Good luck.

 

[99FiveOh]

Ignition box is in the works, but I'm gonna try to get by without one for now. I'll regap my plugs, install my new injectors and MAF and relocate the ACT sensor to the dishcharge pipe and get it tuned. I'll bet once that happens and the EGR and Smog stuff is turned off it'll run like a dream!