bamaboy0323

iTrader: (1)

Sorry for the long post.


1992 Camaro with a 350 TPI, ZZ4 cam, vortec heads .600 lift, edlebrock headers with 3” exhaust. I have a surging/hunting idle that I’ve been trying to figure out for months now and I’m at my wits end. It’s not constant and sometimes the idle is pretty smooth and other times shakes the car.


Car idle is around 700-750 as it fluctuates a bit. Sometimes the car idles nice and sometimes it’s rough. I have the car idle for a few minutes then die and had it idle for 10 minutes and die. Sometimes it will run for 20 minutes or so and not die. I’ve only driven it around a ¼ mile or so and it feels like it has good power and pulls pretty well.


I’ve reset the IAC and minimum idle numerous times. I’ve made sure the TPS is reading .54 volts. I’ve tried 3 different IAC’s, TPS’s and TB’s with no luck. Idle is set to 700rpms in the chip. I’ve ran the stock chip and it runs rougher but does pretty much the same thing. I’ve checked for vacuum leaks and none were found. I just replaced the fuel injectors with #22 Bosche3’s from Southbay since I had a couple with leaking O-rings and it still didn’t help the issue. I’ve set timing anywhere from 3, 6, 8, and 10 degrees BTDC with no luck (same results). The car is a little hard to start no matter where I set the timing (like 3 seconds or so). I’ve also swapped out the ECM’s with no luck. I have new knock sensor, new CTS, new IAC.


I’ve datalogged multiple times. I have 1 or 2 knocks at startup but doesn’t increase while the car is idling or under load and there is no knock retard. 02 sensor seem pretty steady except when the car goes into closed loop then the O2 readings are all over the place. Car does the same thing with the O2 sensor unplugged. What else should I look at in the data logs that could maybe point me in the right direction?


Can someone please tell me what to do? Is there a way to know if maybe I need another chip and that’s causing my issues? I really don’t want to take it to a mechanic to have it diagnosed as I would rather keep my money and do it myself but I’m not sure what else to do.


Thanks.

86IROC112

Not an expert here but check your compression. My heads were toast and had poor compression. Fixed the heads, fixed the problem..

bamaboy0323

iTrader: (1)

Thanks 86. I bought the vortec heads and there were sent off to a machine shop and set up for higher lift. I looked at all the paper work the guy had and it seemed legit. Could these heads have went bad?

86IROC112

Probably not. My PO rebuilt the bottom end and just put the old heads back on. A compression test is free and one more thing to eliminate..

bamaboy0323

iTrader: (1)

Bump....

bamaboy0323

iTrader: (1)

Does this need to be moved to a different section?

FalconZ28

Right now I'm having the same issue.

I've got a 383 HSR with vortec heads, and mine hunts idle as well. I don't have an O2 sensor hooked up right now, and was hoping having it hooked up might solve some of the issues.

I don't have a custom chip or any data logging yet.

cardo0

Well it really reads like the IAC but you have given that good effort to. The IAC is used for idle control when small loads occur but is to slow for like AC or trans moved to drive occur. The timing is selected with surplus timing for small load adj as the timing can respond much faster then the IAC. IAC does this but is much slower to respond and i think of it as a course adj where timing adv would fine and fast adj. U should watch your timing in your scan log and see if thats what jumping around and the IAC is just chasing it.

Dont worry 'bout the O2 reading during closed loop as its supposed to vary - but it needs to vary between 100mV and 900mV so if its more (>900mV) or less (<100mV) then there is an O2 problem or O2 control problem.

Last is u may have mechanical problem causing this. Usual diagnose is the compression and leakdown test for cyl wear and cyl sealing. If u have burnt vlv its gonna be hard to get a steady idle. Simple vacuum gauge will show a burnt vlv by an erratic needle.

Thats enough for now and post a data log/scan if u can.

bamaboy0323

iTrader: (1)

The surging/hunting idle doesn't happen all of the time. Sometimes it idles a little rough and sometimes idles pretty smooth. It will idle good for lets say 10 seconds then shutter a little and go back and forth. Would compression still cause this?

cardo0

Compression would indicate cylinder wear and cyl leakage. Enough wear in 1 or more cylinders or a burnt vlv could affect idle speed. But i would expect it would be a consistent problem rather than intermittent like yours. But i really dont know how your ECM will react to low(er) compression. At a minimum i would get a vacuum gauge and look at idle vacuum - should be steady and with a ZZ4 cam and 0.600" lift at least 12"Hg vacuum. BTW how do u get 0.600" lift with a ZZ4 cam? ZZ4 is only 0.474"/0.510" Intk/exh lift. Unless u used 1.6 rocker arms then it would be 0.506"/0.544" intk/exh. I think u mean the heads have springs that can handle 0.600" lift.

First of all a vacuum test/reading will tell u if a vlv is being held open - u should have erratic vacuum if vlv held open. Or a low vacuum if major vac leak. How would a vlv be held open with 0.600" available? Well the vlv spring retainer to the vlv seal or guide boss distance really isnt 0.600" and the vlv spring retainer is hitting the guide boss/vlv seal. Or else the lifter preload was adj wrong and the vlv is being held open. A lot of owner are in complete denial they cant adj the lifters correctly but reality can be painful and expensive as the wrong preload will wipe the cam and send metal particles throughout the engine.

So before we go looking in the wrong place lets check the idle vacuum. I think u verified most of the engine controls now u should look at the mechanicals.

bamaboy0323

iTrader: (1)

Correct Cardo0, the heads are capable of .600 lift. I am running the stock 1.5 stamped rockers. I tested the compression and all cylinders have 165-180psi compression. As far as the lifter preload, I have done the procedure 4 different times. Could I have done it wrong, HELL YES . I have the headers off and plugs out right now so maybe I'll call someone in to reset my valve lash. I will get to work on the vacuum test. Thanks

cardo0

Well 165-180 compression press is pretty darn good and almost where i would want it using iron heads. I dont think u would get that on all cyl if a vlv was held open. Im not so worried bout the lifter preload holding a vlv open now that i read your compression results. So now it looks more like something else and if its mechanical i would think a large vacuum leak. So the vac test becomes more important now. But if your headers are off im sure it will be a while be for your ready.

I would like to see a data log though to look at how the timing is behaving with rpm and see if that IAC is shifting around. And did u drive the car at all before u put the new heads on? If u did was the same problem with idle there? A little more history here would help to.

bamaboy0323

iTrader: (1)

Pulled the engine and tranny out of an Iroc. I drove the other car maybe 3 miles and it didn't seem to have this issue while it was in the Iroc. I swapped the cam and put on vortec heads. I put it into my car and first was battling a huge vacuum leak. Got that figured out and now it idles around 720-730 with the occasional surging and rough idle. I looked in TunerPro and if you are referring to the Spark advance then it's all over the place but with the IAC staying consistent. Eventually the IAC gets down to around 5. It has died on me before a couple of times while it was surging but then can run for 10 minutes without surging. It does the same surging idle when i barely open the throttle blades at very low rpms but doesn't surge if I open it up a little faster or open it up more. I've been at this for about 4 months now and in the beginning I could reset the IAC and minimum air but now for some reason everytime I attempt to reset it, it doesn't reset and i have to take the IAC out and wiggle the pintle back down. This is a new IAC and my old IAC was doing the same thing.
I should have a datalog by wednesday if not tonight. I've taken this thing apart so many times it doesn't take me long anymore lol.

cardo0

Yea dont know what to make of the IAC u have. Slow open of throttles initiates a stall while fast open doesnt. I really sounds like a a control problem. I was going to mention a clogged fuel filter. I cant tell from your post if u mixed fuel injectors. FYI u have to change the FI constants for different injectors. And i dont think u drove it long enough to see any problems or the PO knew how to mask them. Whos ECM are u using? Did u swap out your ECM and/or wiring?

Your engine/car history is still kinda mystery my friend. Cant help u with what i dont know u have now or maybe even had before.

bamaboy0323

iTrader: (1)

I am using a 730 ecm with a custom chip and a harness from a 91 tpi. I don't know much about the engine except for what i've done to it. I am running all 8 Bosche 3's for fuel injectors. The engine was stock before I replaced the cam and heads. I took a vacuum reading last night and it was a fairly steady reading at 18. The needle floated very little just past the 18 line back and forth but never go to 18.5 or 17.5. Like i said, it moved very little. I'm running the same distributor and coil that was on the engine before I upgraded cam and heads. Not sure what else I can give you to let you know more about my engine, sorry.

cardo0

Ahh, so we have great vac. Well the small wandering would be the idle wandering but could also indicate something like the A/C or trans is loading the engine. I have a vac gauge installed right on my dash (where most install their tachs) and i can see the slightest load changes.

Dude i have to google 730 ecm to find out what it is. It reads like u changed from mass flow to speed density sys. So now did u swap this and was the swap done before the new engine install? Did u drive that car before the head/cam swap? If so any surging before head/cam swap? This is big animal to wrestle so lets go do easy stuff before it gets tough or at least aggravating. I will say something bout "custom chips" or custom tunes is they do take a short time for the PCM to learn. But on my OBD 1.5 PCM is was like and hour of driving and several starts. But it was definitely scary on first start.

Something we should have looked at would have been the spark plugs. Sorry i should have said this while u had them out and can only apologize. But ya know the new heads may need a hotter plug - at least for daily driving. I know this sounds backwards as when u increase performance usually with higher VE u need a colder plug. But if yours were black at all (and possibly wet) then u need a hotter plug. And your symptoms are a too cold plug rather than too hot. Too hot plug wont stall the motor but rather cause pre-ignition and burn holes in the piston tops. This is indicated by silver flakes on the plug insulator and tip. But if u look i dont think u will find any silver flakes but more likely black and wet plugs.

Something else we can try is just disconnect the knock sensor and see how it runs. U may have some low rpm detonation (i doubt this but it is possible) that pulls ignition timing enough at idle to kill it.

Thats enough for now.

bamaboy0323

iTrader: (1)

Yes. The engine was MAF and since i have a 92 i wanted to swap to SD. The 730 is just the model ECM that the SD's use. I don't not have the ac on although the blower moter is not installed in the car. I only drove the 87 Iroc(donor car) for a couple of miles so i can't really remember if it had issues. While I had the engine out of the car is when i swapped the cam and heads. I replaced all of the sensors with new ones(knock sensor, coolant temp sender, CTS, oil pressure switch, sensor above the knock sensor, IAC, O2). I can post a pic of what the plugs look like since i took them out the other day. They didn't appear to be wet but sooty on 6 of them. Can't remember what the other 2 plugs looked like. I can disconnect the knock sensor but when i datalog i only show 2 or 3 knocks at initial startup and then none while the car is running. I will also datalog tonight and show the car at idle and take it for a short drive. I had AC Delco r45ts but realized that these were for the l98 heads and i have vortec heads so i bought autolite 605's and gapped them to .040. Really confused on the spark plugs dealing with the different spark plug reach.Thanks for your time with trying to help me with my car. I really appreciate it.

bamaboy0323

iTrader: (1)

A few pics of my spark plugs.

bamaboy0323

iTrader: (1)

Not sure how to upload the tuner logs. Can someone please tell me how. Thanks

cardo0

Well ive seen worse plugs but those are definitely black. I would try at least the next step hotter plug. And if plugs are still black (but i doubt this) try the next step hotter. If u still have the old R45TS plugs no reason why u couldnt give them a try - maybe clean and gap them first though.

Im still thinkn bout the knock sensor as it may need to be grounded rather than disconnected. Im thinkn maybe if u get a trouble code it wont work disconnected unless u have a spare knk sensor to connect to that is grounded but not where it will hear a knock.

Ok i think u replaced the heads and cam and engine and EFI swap all together at the same time. Not to pick on u but that does multiply the chance of a problem. But if thats true it helps to know that as anything is fair game and nothing really known to work prior to installation.

I think u need a file hosting service like File Dropper to put the file where anyone can get it. Ive downloaded from FD before and no issues. Unless u leave your computer on line all the time and its set up as "server" where it acts as its own w/s u need a file hosting service.

cardo0

Ok, i couldnt post a reply with the File Dropper link in it. U will have to google File Dropper for the link.

cardo0

Injector constants? Are your bosche 3s what came with the 87 TPI? If not u need the correct injector constants for the bosche injectors. Did they include those in your tune? Also is there a difference between the 87 and 92 fuel pressure? U need to run the fuel press for your current system which to me reads like an 87 system. Maybe able to change this with just a adjustable fuel press regulator.

So when u upgraded to vortec heads how did u get the TPI intake base to match up to the runners of vortec heads? Vortec heads dont have a exh crossover to feed your EGR. Dont know how that will affect idle surging as i dont expect the EGR vlv to open at idle. But something else that may throw a trouble code though im not sure how.

bamaboy0323

iTrader: (1)

I just changed the injectors and no a new tune was not done. The bosche 3's are 22's just like the original multecs. I used the Scoggin Dickey intake. I have adjusted the fuel pressure to 43.5 with vacuum unhooked.

bamaboy0323

iTrader: (1)

Hopefully this works. I've zipped the files. There should 3.
82615-idle
3 mile run-driving
9115-7 mile drive

cardo0

Sorry due but u need to convert those data logs to a Excel spreadsheet format. I dont have Turnerpro software so a Tunerpro file wont do me any good.

bamaboy0323

iTrader: (1)

Sorry man, I thought you did. I will and put them on here. thanks.