Rough idle after 411 swap

[Tparkhill]

Give us an update on what you've tried/results bud. I see from your sig that you've installed the upgraded MPFI spider. That should've also helped idle smoothness.

Thing that's stumping me is you only developed this issue after you swapped to the 0411,....leads me to think it's linked to wiring or PCM/tune issue.
Before doing the OS/tune swap in the PCM,.....check to assure a pin/wire connection at the PCM Didnt work loose during your 0411 swap. Check all your ignition related wires for any looseness,....with an ohm meter (if you can). Pull both connectors off the PCM and look at each pin (on the "connection to PCM" side) and assure one of your pins didn't get pushed back up into the connector,....you should be able to see the silver pins butted flush up with the end of the connector (all equal).
Do this test with the meter set on the "ohms setting", not the "continuity" setting.
I'm sure you already know how to do this,...if all looks good at the PCM connector end (all butted up/none pushed back up in the connector) disconnect the wiring/pin from the PCM connector, then pull the corresponding sensor/end connector and slap a meter between them,...while slightly wiggling the pin on the PCM end (do same on sensor/end connector),.....that'll test if the pin has worked loose/not making best contact,....your meter reading will jump all over the place if it's a bad/loose connection,...or show higher reading if there's any corrosion (per below).
When testing on a good wire/pin/connector, the "ohms setting" will show a steady/close to zero ohms (may show 1-3 ohms, which is ok),...but anything more than this would show a possible corrosion issue in the wire itself (hole in the wire insulation somewhere), or corrosion at the PCM pin or sensor end connector. If meter reading jumps all over the place, while your wiggling the wires/pins/connector,...it's showing you have a loose connection. And, of course, if no ohms reading during testing,...... sum-ting-Wong (broke).

Let us know how you faired out.

Thanks Hutch, I'll give what you suggested a try.

Sense you're like me with that 96-97 similarities what did you do with all your evap stuff? the 411 doesn't support our EGR and evap.

What about the black box jumper wire? I tried to dig down the harness far enough to pull it out but it kept going so I snipped the wires. maybe that doesnt mean anything I dunno...

Heres what I've tried since the 411 swap:
-Crank relearn (which took about a dozen tries on multiple different occasions) I was able to get it down as mentioned in a previous post
-scan for lean conditions or otherwise
-change plugs,wires, rotor, cap, MPFI, EGR block off
-vacuum test
-check timing advance @ 1200rpm or above
-check fuel pressure
-check PCM at least a hundred times
-cry at night

I haven't done a compression test yet but I can if you guys think I should, I just have a hard time believing that's a problem because i had no issues before. but we all know how it is to be a car guy.

Hutch, did you take a look at my log by chance? I know you're probably a busy dude, I appreciate every bit of help

[Hutchinson]

I'd do the compression check just for piece of mind/to know what my variance is between cylinders,....but, your right, you shouldn't need to do this given your current situation. Your list of what you've done so far looks like what I did,...no issues there. OleBlu, Fast4.7, and several other guys on here have done this swap too,....and they like to help.

I used LexTech's (man, he's a good dude) pinout sheet to do my swap a year ago. I just looked at my copy,....On his pinout, for the EVAP stuff, he shows:
- EVAP Canister Purge Solenoid Control - Dark green/white strip wire - moves from 96PCM C1-12 to 0411 C2-34
- EVAP Canister Vacuum Switch - Brown wire - 96PCM C3-15 - 0411 doesn't support this switch, tape it back up into wire loom.

I mounted all the EVAP stuff back in their original places on intake manifold and connected all the wiring connectors back into their corresponding connections (on engine end) and did the PCM wire connections per above LexTech's pinout.

As far as that jumper - if your talking about the Old 96PCM C5 connector,...which is simply a jumper wire,....mine went back into the harness bout 8" or so, and I was able to get it out. But, that shouldn't harm you if you simply cut it off,....if this is the same jumper your referencing.

One other thing got me thinking,...I didn't have any issues with my IAC (I installed a new one on new crate engine) and I don't know much about it,....but maybe do some research and check the operation/testing/scanner counts for the IAC. I haven't researched the IAC/how it works/how tested,....I just have basic knowledge on how it keeps engine idling smooth.
There are 4 wire/pins for the IAC on the 0411:
- IAC High Coil B > pin C2-76
- IAC Low Coil B > pin C2-77
- IAC Low Coil A > pin C2-78
- IAC High Coil A > pin C2-79

No Sir, I haven't looked at your last log yet,.....man, I was hungover as hell yesterday,,...didn't do shit. Birthday was Friday, so my two brothers/family took me out for dinner/drinks Friday night,....which ended up back at my place and didn't end till 6am Saturday morning,....yeah, I was useless all day Saturday. Better today, but, man I can tell I'm getting old,....can't take those hangover asswhippin's like I used to.

[Tparkhill]

As far as that jumper - if your talking about the Old 96PCM C5 connector,...which is simply a jumper wire,....mine went back into the harness bout 8" or so, and I was able to get it out. But, that shouldn't harm you if you simply cut it off,....if this is the same jumper your referencing.

Yes the C5 is what I was referencing.

No Sir, I haven't looked at your last log yet,.....man, I was hungover as hell yesterday,,...didn't do shit. Birthday was Friday, so my two brothers/family took me out for dinner/drinks Friday night,....which ended up back at my place and didn't end till 6am Saturday morning,....yeah, I was useless all day Saturday. Better today, but, man I can tell I'm getting old,....can't take those hangover asswhippin's like I used to.

Hahahahaha I know that feeling, But I'm 22 yrs old and can handle my alcohol pretty well

Hutch, I had an idea. what would you think if I took your bin from the repository and wrote the OS/VIN into my current PCM? My current PCM is a P01 out of a 2001 Blazer.

I'm starting to just accept that my engine will probably just run a little rough for the rest of time

[Hutchinson]

Apologies man,....I don't know enough about OS/Different PCM compatibility to answer that one for you. Maybe one of our more experienced guys will chime in and help. Sorry man, I don't wanna steer you wrong bud.

Your good on snipping that C5 jumper. Might wanna check that IAC though,,,,,you may learn something along the way, plus, it may solve your issue cheaply. Not saying the IAC is your issue, but wouldn't hurt to check it out on the scanner compared to what it should be doing,.....then you can teach me

[Hutchinson]

Simply thinking IAC (Idle Air Control),..and you've got an idle issue, yet, goes away when you put some gas to it,....be good to cross it off the list as a potential. Again, not saying this is the issue, but it could be a potential candidate,...maybe your existing PCM/OS doesn't talk well with the IAC? Just stabbing in the dark here man,.....trying to help.

[Tparkhill]

Simply thinking IAC (Idle Air Control),..and you've got an idle issue, yet, goes away when you put some gas to it,....be good to cross it off the list as a potential. Again, not saying this is the issue, but it could be a potential candidate,...maybe your existing PCM/OS doesn't talk well with the IAC? Just stabbing in the dark here man,.....trying to help.

Any help is appreciated! I will take all the help I can get, lol

[Fast4.7]

On my 1997 Express van the C5 jumper was about a 12" loop of wire that fell out when I started untaping the old harness to clean up the wire runs.

[Fast4.7]

My rough idle is more like a shudder than a misfire. Like the air/fuel mixture goes to lean for a split second. That engine has never run as smooth as my old TBi or Carb engines. I tried both adding and removing timing at idle and it was still there.

[Fast4.7]

It has ALWYS been there in my case. Even before the 0411 swap. After the marine intake. Even after the coil per cylinder swap. Its still there with the cam but atleast with the cam it is nowhere near as noticeable. I put the GM 357 HP 350 HO crate engine cam into it. 215/223 @ .050 and .474/.474 lift. Runs smooth as butter once it is above idle. I mostly notice tue shudder with a warm engine, in Park and its more pronounced with the A/C off.

[Hutchinson]

Same here Fast4.7,....I had that same shudder on the old 5.7L vortec/black box (everything stock),....same,...warm engine, in park, no AC on. Lasted for a split second, and would happen roughly every five-ten seconds or so. Just a slight/slight engine bobble,...wouldn't even see the rpm's drop,...but, it was noticeable. You described it perfectly.

On the new HT383e/0411/MPFI combo,...it's gone,...engine idles so smooth that, if you didn't hear it running, you wouldn't think the engine was turning. Only thing I have now,...new 383 has that clack-clack sounds like a deisel truck,.....they say it's because of the upgraded piston/skirts the HT383e uses,..causes slap/noise. It's not load, but noticeable.

Tparkhill,....does yours do the shudder thing,...or is it a constant stumble/bumble/misfire idle?

[Tparkhill]

Tparkhill,....does yours do the shudder thing,...or is it a constant stumble/bumble/misfire idle?

Its constant. I REALLY want to try a different PCM with your OS but I don't want to spend all my credits and come out with a bricked PCM.

Does anyone have a 2002 express PCM 12212156 OS they can send me so I know its right and then I can tune it to my needs? I'm about out of options here....

[Hutchinson]

Sorry bud, I don't have one of those. I know LexTech will sell you a 0411 PCM with a complete stock tune already set up in it (VATS off, alt codes off, etc) that'll match your existing drivetrain,.....you just tell him what you have, he sets it all up,....and ships you the PCM ready to go. I think last I heard, he sells them for $180.

LexTech, more-or-less pioneered the 0411 swap into 96-99 trucks, thus he has them nailed down and knows exactly what you need. Good dude to boot. For ease of application (plus, I didn't know shit bout tuning back then,....still don't), I simply bought my 0411 from him all ready set up,....did the pinout swap per his sheets and didn't have any issues. He shipped mine the next day and I had it a couple days later.

Maybe an easy way to go,....or, maybe one of the guys on here has one laying around that already has the base tune on it,....either way, it'll cost you two credits once you install a new PCM/initially download the new tune from it. If you have state inspections (Florida doesn't), your VIN not matching between vehicle/PCM could be an issue. I think, but don't quote me, LexTech can put the right VIN in too (we can't change it with HPTuners).

[Hutchinson]

By the way, when you did your 0411 swap, did you install the additional wires from trans (or instrument cluster) up to your PCM? LexTech does some finagling in the background that eliminates the need to install those additional trans wires,.... somehow (ancient Swahili to me).

[Tparkhill]

Huh... yeah unfortunately I do have inspections here (Washington) So maybe ill just hit him up. I do have his pinout and I agree he is da bomb

Im going to get a PCM from him asap

AND I'm going to get my money back from the guy I bought mine from - I just know something is wrong with it

[Oleblu]

Another option is the junkyard. Thats where I pulled mine from. I'm not sure what price lextech will charge for pcm only, but I paid 75 bucks for mine at the local junkyard, Before I knew he was shipping them with NEW connectors for 180 bucks. There were 4 credits used in my case. 2 to license my pcm first and then 2 more for the 02 express van tune found in the repository that we switched it to for a base tune. I did it all for a little over 200 in the end. So no doubt the lextech deal is legit. Priced for a gear head on a budget most definitely. There are a couple guys on the forum capible of correcting the vin. I'm in Texas with inspections and have a mismatched pcm/vehicle vin. In our po dunk town mines passed two years now running mismatched vin.

[Tparkhill]

Hey fellas been a long week. still haven't figured out whats up with the burb. I'm going to start fresh with a PCM from lextech and the right OS.

In the meantime I've been fiddling around with it to see if I can find anything abnormal.

Heres a video of the distributor play, maybe this is too much play? what do you guys think?

https://www.youtube.com/watch?v=3u6teEQ4Xm4

[Hutchinson]

Let us know how that LexTech PCM works out for you. LexTech is a good dude and will help you with any questions you have on your 0411 install.

As far as distributor play (per your video),...I don't remember how much play mine had when I restabbed it a year ago,...thus can't help much there bud. I wanna say it had less play than that (from memory) but, can't be sure,.....that was many moons and many cases of beer ago. Been raining here in Florida for the past two days straight, thus, ain't been able to go out and pull my distributor cap/check play.

[Tparkhill]

Let us know how that LexTech PCM works out for you. LexTech is a good dude and will help you with any questions you have on your 0411 install.

As far as distributor play (per your video),...I don't remember how much play mine had when I restabbed it a year ago,...thus can't help much there bud. I wanna say it had less play than that (from memory) but, can't be sure,.....that was many moons and many cases of beer ago. Been raining here in Florida for the past two days straight, thus, ain't been able to go out and pull my distributor cap/check play.

What?! I expect you to jump at every hint I give you!! haha nah that's alright man I'm gonna just got with the melonized one from Summit Racing and go from there. I have no idea if its ever been changed so might as well do it!

[GHuggins]

Can you get a video of the rough idle? Distributor play may be a bit much and pointing to a worn gear, but still should cause a super rough idle...

[Tparkhill]

Well guys the problem got worse by 100x today. My mom borrowed it to go into town and it lost all power and the engine shakes badly and back fires when you hit the pedal... I'm really thinking distributor now!