QWIKWS6

iTrader: (13)

I finally got around to installing a LE custom cam in my 97 Trans Am and sent the PCM out to Madz28 for a re-tune. Now its a cam-only car, stock injectors, TB, etc. I installed Crane Gold 1.6 SA rockers, Valve springs to match that cam, CSR EWP, new Delco o2 sensors with extensions, AC delete, changed every gasket including fuel injector o-rings and valve seals misc ****. Everything was done right and with help of a master mechanic. The idle was set at 750rpm from the tuner and the car sounds like its stumbling to stay near that idle. I plugged in the scanner and it read that I have random missfires in 3 cylinders and I have the Throttle screw all the way turned out which causes a IAC check engine light. Is there something im missing here? Everything is brand new plugs, wires, optis only a year old, I have a stock coil. What sensor tend to go bad on these cars because its driving me crazy not getting this car to run to its full potential after dumping 1k into it. I have a stock knock module hopefully desensitized in the tune. The car just sounds likes its missfiring at idle but runs like a raped ape to 6300rpm. Lmk if theres anything I can check with the scanner that I can relate back to you guys to see if somethings not up to par.

Thanks guys, I need to get this resolved its driving me up the wall
Btw anybody live in MI with tuning software for an OBD2 be willing to take a look at the car/tune lmk

96capricemgr

iTrader: (1)

Why would you even touch the throttle stop screw?

How was valvetrain preload set, specifically how was zero lash found?

bowtienut

iTrader: (1)

What are the cam specs? 750 rpm is pretty low to expect a smooth idle for a decent-sized cam.

RamAir95TA

iTrader: (2)

Plug wires in the correct order? Double check (run them one at a time instead of altogether).

Mystery Bird

iTrader: (7)

That's what I was thinking first but he says it runs "like a raped ape up to 6300."

moderate Z28

My 93 with Hotcam doesnt want to idle until its warmed up. Its been that way for years. I wonder if a dyno tune will help that. It has a mailorder tune. It runs like an old carburated car.

96capricemgr

iTrader: (1)

Dyno tune wont fix idle issues, but that is a tuning issue so a better tune would help. It could be spot on WOT and just need some cold start tweaks.

There is a dyno shop west of me a ways that doesn't want to dyno tune a car unless they can keep it overnight specifically so they can do coldstart tweaks the morning after.

QWIKWS6

iTrader: (13)

The cam is 226/230 .565/.565 111 lsa. I turned up the throttle screw to try and raise the idle a little bit. The plug wires are in the correct order I double and triple checked. Is it possible the ICM is bad?

96capricemgr

iTrader: (1)

By opening the throttle blades to try and raise idle you defeat the IAC distribution circuit which will compromise idle quality and low speed operation. I think the problem is bigger than that though.

If the IAC is not opening enough to maintain an idle the IAC bleed hole needs to be opened up a little.

Again how was the valvetrain preload set?

750 does sound a little low.
With the scanner what is the IAC position?

Far as ICM I haven't seen a bad one idle bad and work well up top, other way around yes where cars idle and drive fine but fail to perform under high load/rpm.

On plug wires I tend to keep a jar of multicolor zip ties around put matching ties on each end of the wires before you run them, that way you always have an easy check. Cheaper than buying numbers and this way if one falls off or the like it is easily replaced. A LOT of guys have spent a LOT of time chasing problems that were firing order related over the decades. Not saying your's are wrong, just this makes it so much easier to double check them.

QWIKWS6

iTrader: (13)

Ok so the readings I pulled are....
IAC 130cnt
A/F 14.7
B1S1 ranges 100-760mv
B1S2 443 stays right there
KR 1-2 deg
Learned IAC 32cnt
MAF 10-11
MAP ranges 51-58
Spark Adv 35-36deg
Short term bank 1 3.1-6.2
Short term bank 2 -0.1-2.3

Now from what I can see it looks like the B1S1 o2 gets reading all over the board and B1S2 o2 stays steady at 443 mv. Now there both brand new delco o2 sensors with 24" extensions. What gives?

The car isnt smooth till about 2700-3000rpm then after that it runs smoothly. Ill check the TPS voltage. I thought the idle was too low in my opinion but I let the tuner decide, it should still idle without misfires even at 750rpm, not exactly where I want it. I put NGK TR6 plugs in it gapped at .035 because I planned on spraying it, not that the plugs should have anything to do with the misfire issue but I thought id give as much info as possible to see if someone can turn me in the right direction.

Now before I installed the cam I had a slight issue with random missfires at idle, I changed everything opti, coil, wires, plugs and the problem never seemed to go away. The car always seemed rich to me and i turned the throttle screw up and it idled good enough for me not to mess with it anymore after spending all that money and the problem never really got solved. I have a feeling the same issue is causing the car to misfire now after the cam install, so im ruling out plugs, wires, coil, and opti. So whats the next common issue that causes random misfires on LT1s?

3 pedal SS

iTrader: (1)

Like Dwayne mentioned,try drilling out the IAC bleed hole. Bigger cams arent made to idle. It helped mine. What TB do you have?

trilkb

iTrader: (4)

The cam im running is a LE 1.5.

Its a 224/230 108lsa and im running .568/.565 lift with 1.5 rockers. (dropped from 1.6).

I am stock heads.

My idle was set at 800rpm from PCMforless. At stop lights when the car was up to temp it felt bad. I upped the idle to 950 and alot of it went away.

I didnt touch my stock throttle body at all, I didnt even do the IAC mod. When the idle was set to 800 it wanted to die when it was warm and I went from drive to reverse and back to drive (auto car). Upping the idle 150RPM got rid of most of it, but I dont know how it should act anyways lol, for all I know its still screwed up.

I dont know if what I did was the right way to fix it, but it made me think that alot of these mail order tuners dont know how cams act at idle. Picking 750rpm seems like a shot in the dark for a custom cam, especially when they cant even hear the thing run lol

edit: btw I adjusted my idle through the tune, not through the screw on the throttle body

96capricemgr

iTrader: (1)

A stock TB should let a cam idle decently though with maybe too high an IAC count as it does have a bleed hole, the aftermarket TBs all lack the bleed hole and many completely defeat the IAC distribution circuit by having it open to the plenum at the mounting surface to the intake.

sweetbmxrider

iTrader: (13)

Sounds like you have a bunch of little things wrong along with not fully addressing known issues. I'm sure one of our hardcore members can tell you exactly what to do but being its a cam only car, they may not want to waste their time.

96capricemgr

iTrader: (1)

The thing is it is very hard to help people who don't clearly answer questions or understand what they are doing in the first place.
You can ask 6 times how the preload was set and they come back with 1/2 turn or something like that and it is meaningless if they found zero the wrong way which is VERY common.

People have to WANT to be helped and that is rarely the case, they want a magic bullet or to be told whatever their suspicion is is blindly correct and that they did everything 100% correct.

Few years ago there was a guy on here with a car a few hours away from me who couldn't get it running right. They "checked everything" when I got there a few plug wires were wrong and the POS MSD distributor had a broken timing adjustment mechanism. A trip to AutoZone for a reman opti and straightening the plug wires out helped the engine a lot BUT he had trusted some local hack to build the 4L60 so once the engine was running right the tranny didn't work...........

It might be money well spent to offer a knowledgable local some cash, the OP lists Detroit, I am sure there is someone competent with an LT1 there.

QWIKWS6

iTrader: (13)

I can tell you I fully addressed every known issue what more can you do after replacing every common problem known with these motors? Spend more money trying to figure it out or ask people like yourselves what the problem may be. I think its funny how a "cam-only" car is wastings somebodys time to help diagnose a pretty common issue.

Sorry I do not know the answer to your preload question thats the one thing I had the mechanic set up and I am pretty sure thats not the issue here. And trust me I know what I am doing this is not my first go around with building a motor or installing a cam for that matter. I have a 440 big block Cuda that I built and race which is much simpler when you consider all this electronic BS that these new motors have which I know little about. Now with that said is there something else that you guru's may be able to come up with to help me further diagnose this problem?

trilkb

iTrader: (4)

I just noticed this..

"B1S1 ranges 100-760mv
B1S2 443 stays right there"

Is b1s2 the rear oxygen sensors with "simulators"? or is b1s1 bank 1 and b1s2 bank 2?

I know my car has 2 o2's and you can watch both of them. If your car had 4 o2's wouldnt you be able to watch all 4 of them?

If what i just assumed is true, why is there no b2s1 and b2s2 information?

EDIT: I just searched and yes there should be B2S1(2) information. The 443mv is for rear o2's. Are you using simulators or not?

You need to look at the b2s1 and b2s2 info as well to rule that out.


also
It seems like you never fixed this issue, and now its just alot more pronounced due to the bigger camshaft. So this is something totally unrelated to the cam or the tune.

I think you need to get the throttle body and IAC back to stock settings. Your car should be able to idle like that if mine can.

What opti did you use?

Did you get any codes?

Do you have EGR still?

And it did happen befor and after the cam swap right? according to your post that I quoted, or did I read that wrong?

EDIT AGAIN: Read up on spark plug gapping. Running to tight can cause misfires and surging idle. This info may be moot if you were at .050 befor the camshaft, but if you were spraying it and running .035, maybe thats where your misfire started?