Blue96z28

I'll keep it short and sweet, we've all had the hidden misses, hesitations, whatever. As of now, out of no where, the car seems to surge, not to bad, but very noticeable. Does not have any noticeable miss on free rev'ing or holding it at any RPM in neutral, but under load(driving) at any rpm when held there it will surge/miss. But when I get it on it, 3/4 or more throttle and run it through the gears, its VERY smooth. I've taken the usual steps, checked for burnt wires, etc, just changed the fuel filter, plugs/wires/opti are 10-15k/maybe 20k max on GM o2's or less, new MAF is clean, TB clean, IAC/IAT clean, new GM EGR, no codes at all after 50-100mi of missing, just happened out of no where, was driving down the road, and then it just started, been getting worse since really, not a long term deal where it happened over time deal. Any ideas appreciated, I'm running out

OBE1 95Z28

Wires are the biggest culprit. I know you stated that you checked for burnt wires; did the check include running it in the dark and looking under the hood for arcing? I've been fooling into thinking my wires were fine only to find out later that I did have a wire arcing in a hard to see area.

Blue96z28

Actually no I havn't tried that, I'll give it a shot though, thnx for the idea, I just unplugged every wire from the plug and visually/feel inspected for weather cracking/burns as much as I could of it without taking to much off the car(alternator, etc) - so the driver's side ones are pretty much 100% checked, but passengers side may be a little weak.

gixxer92

Might also look at what the ECM is reading for IAC counts, IAC should read around 40 at an idle, if possible

Blue96z28

We'll I checked in a dark area, no arc/sparks anywhere, pitch dark, nothing. I pulled off all the wires today and check them for cracking/burns, all are perfect, I know its not a wire as this just happened out of nowhere, just driving along, and then night/day difference as soon as it started missing, like someone threw a switch. Also I didn't do any recent maintenance on any parts of the car that would have touched or moved the wires from where they've been the past 15k or so when I put them on there. The coil is also only around 15k old, new GM one, not aftermarket.

I don't really have a way to do this, but I doubt its IAC related, the car idles well. The car seems to do it the worst when fully warmed up, I've seen the 2 million threads about the heat related missing and surging, maybe this is the ICM, as thats the only part of the ignition really that hasn't been replaced.

96SilverZ

Kinda sounds like my problem. Surging/missing/rough running at low speeds and when holding a steady cruising speed on the road. I thought I had it fixed. I've also checked/changed all but the module. Is there a way to test it?
Matt

Blue96z28

No way to test the module that I know of, people say autozone, PB, etc, but they have all turned me down. They test them, just can't do this one....I just swapped on one from my 95' formula parts car, exact same symptoms. So far I have visually inspected the wires, checked IAT, checked IAC, checked ECT in w/p housing, checked MAF, and swapped ICM, and swaped to a different coil all to no avail, absolutely no change on the symptoms, neither for the better or worse, which is surprizing. I'm thinking its the opti again, does not feel fuel related, and all the ignition **** is fairly new is what pisses me off. But it happens. I'm tempted to slap new wires on it, but its alot of work to get nowhere, this problem happened instantly, not like it got worse over time or developed after I heated on it, or ran it hard, etc, I was crusing at 65 and the BOOM, light switch, starts missing.

96SilverZ

Mine just started doing it one day leaving the gas station. If it gets bad enough the SES light starts to flash...I give it a couple revs and the light stops flashing and it seems ok for a while

Blue96z28

I just noticed that with the clutch in and rolling, it will vary its idle up and down, in a pattern, not randomly, seems to go from700-850 ish rpm just up/down up/down costantly, it does do this when at a stop, except for it only varies like 50 rpm, this is all stock tach. Does this give anyone any ideas? Plz chime in if you have anything....

Blue96z28

It seems to be doing it worse now, when rolling in neutral at like 60, when you first push in the clutch and it goes back to idle, it will go down to like 450, then to 900 abruptly, then it kinda gains control and starts varying only 600-750, then lose control for a second again, and dip down to 450, then back up to 900ish for a second, then continues with the 600-750 pattern. Is this the IAC or MAF maybe? No SES codes, and I don't have acess to a scanner, and I did the IAC resistance test, on shoebox's site, came back fine, then I did the MAF test, all the voltages were good, but the frequency response was only about 6.5khz instead of 7khz, here are my values:

http://web.camaross.com/forums/showthread.php?t=469802

any ideas would be appreciated....

Guest47904

You have got to get a scanner that can read realtime sensor values. Once you know what is occuring, you can devise a strategy to investigate it without just throwing parts at it. If you can't afford a scanner, have a shop scan it in both open and closed loop to see what is occuring. Which brings up another point.

Try disconnecting one of the O2s and see how it runs in open loop.