Myzz96Z28

Alright I have a problem with my '96 Z28 and need help and it seems ignition related but I'm not sure. My car runs 100% at start-up but once it's been within operating temp for about 10 minutes or so I have a misfire between 1500-1800 RPM's and the whole car shakes until it gets out of that range then it runs fine. I have the delteq set-up mounted on the top of the intake and a Dynaspark Gen 3 opti specifically made for the delteq and LTCC systems on my car. I had the ignition control module checked at advance auto and it worked fine (we checked it 3 times to make sure it wasn't heat that was making it falter and it was fine all 3 times) and when I put a spark tester between the coils and spark plug wires each tower misfired. My car is not throwing a SES light and I have an OBD2 pcm tuned by madZ28. What would make my car run messed up within a certain RPM range and after reaching operating temp? It seems like something is telling my ICM to misfire the coils almost. My alternator is the factory one and it reads about a 16th of an inch below the middle mark on my volt meter but that shouldn't cause the misfire should it? I also changed my MAF back to the screened and unported ends to just rule that out and it made no difference (said something about ported MAF's maybe causing a problem in the delteq manual so that's why I tried it). thanks

Myles


1996 Z28 M6
8 PSI Blown and Intercooled ATI kit, Strange 12 bolt w/ 4.11's, BMR suspension components, SLP subframe connectors, Dynatech 1 3/4" primary long tube headers, custom 2.5" Y-pipe made by me, McLeod Street Twin w/ steel flywheel, etc.

capper9631

swap the ICM out with a known good one and take it for a spin. they can test out ok at the auto parts store and still not work properly when on the car...

ulakovic22

I had a similar issue a little while ago and I changed plugs and it went away. I couldn't visiably tell anything was wrong with my AC Delco's, but when I changed them it cleared right up.

Swapping ICM's and spacing it off the head is a good idea too. I tried that first to see if it was an issue for me. 2 washers on the left stud and 3 on the right stuf IIRC.

Fei

I had the same issue. My O2 senors were shot. Completely. Both of them. Blown head gaskets do that apparently.

I tuned out closed loop to verify and sure enough, it cleaned right up.

Myzz96Z28

The ICM is on top of the intake since I have the delteq set-up which uses the V8 northstar ignition set-up so you're thinking of the stock set-up (they tell you to put it on the valve cover which I thought would be a lot worse as far as heat sinking goes so that's why I mounted it on top of the intake). ulakovic22, did your car run fine cold but misfired once it was warmed up? I would think spark plugs wouldn't work right off the bat if they were the case but I've heard of stranger things. I took out the O2 sensors and ran the car up to operating temp and even without them it still misfired in the same range which if they weren't even plugged in but they were the cause of this then that should've at least cleared that up I would think. Anyone know where I can get a ICM for a 1995 Cadillac Eldorado or equivalent cheap? They usually run $300-$400 which is why I can't just throw on another one to see if that's it. Any other ideas? Also how do MAP sensors act when they are on their way out, most of my sensors are still the factory ones, except for the O2's and MAF.

Myles

CreatiVe2

it could be the sparks plugs.... before you blame the system (nice setup btw) try and go from the source back. how many miles are on the plugs? pull them and compare their color to this chart
http://www.aa1car.com/library/reading_spark_plugs.jpg

if they all check out, test the wires and boots.

unless you have already done this :/

will.b.brown

ive got the delteq system and have had my car for 14 yrs. spark plugs wear and become less efficient and begin to effect hw your car runs. i guess you might could run them down till your car wont run anymore but that would just be rediculous. the ses light wont trip for this probably until somewhere around the rediculous stage. if your o2 sensors arent reading right then they sure wont when theyre pulled out. someone correct me if im wrong about that. and just because its based on the cadillac ignition doesnt mean you need the caddy computer. delteq designed the system to run with what you have. do the simple things first im sure it just needs fresh plugs and wires. distributorless ignitions have more juice than single coil ign and the wires and plugs dont always last as long. oh and the coils would have been fine on top of the valve cover.

1994 formula, black, 193k, m6, hardtop, factory oil cooler, cold air, 1.6 rr, power programmer tuned @ 160 degrees, slp headers, borla catback.

GreasyB

Sounds like o2 sensors to me.

Myzz96Z28

I didn't say I needed the cadillac computer, I said I needed the cadillac Ignition Control Module. Spark plugs are pretty new and I've never actually been able to drive the car since I've had this set-up on because I had an optispark with 16,000 miles on it and it **** the bed. I decided to go with this system because I was sick of replacing optis and when I put it on it wouldn't run because the opti was completely gone so I bought the dynaspark gen 3 opti and put that on and the car was finally running but started doing what it's doing now and I still haven't figured it out. Can someone answer me if the spark plugs aren't any good wouldn't the car be doing this right on start-up? thanks for the help

Myles

1quikZ

Not nessecarily, somtimes the failure will only be apparent under load.

Myzz96Z28

I'm not putting it under load and the car is still doing it, I'm just running the car in my garage and revving it in neutral. I replaced the oxygen sensors with new ones and it didn't change anything. Could this be a possible tuning problem? Maybe with my set-up something isn't coinciding with the tune for some reason. The car is backfiring out the exhaust also so it seems to be running rich. Do you think it would be worth it to get it dynotuned if I can and maybe what's causing the problem will present itself then? It would be nice if the SES light actually came on at a time like this. I scanned it and there were no stored codes or anything so I dunno.

Myles

Kaj

get it dynotuned. something with your tuning seems fishy.

Myzz96Z28

Well I found a brand new ICM on ebay for fairly cheap and some new coils too so when these come in I'll let everyone now if it works or not, hopefully it does.

Myles

GreasyB

Did you go out and take it for a drive with the new o2's in? Because just letting it sit under no load will not change the fuel trims enough to fix your problem.

Myzz96Z28

I pulled the PCM fuse before I started the car so that should've fixed it. I've had bad O2's before on this car and that always worked when it was the O2's.