Nate's 1998 Z28 Project

[Schuby87]

Can you get another scan on the scan tool?

[nascarnate326]

Here is a video I just took.

New plugs, new plug wires, new 02 sensors all today. Zero change. Appears to idle good but as soon as I back 10 feet out, and then try to pull forward its missing and shakes pretty bad. Let it idle again and it feels fairly normal.

Because of the exhaust being new its hard for me to tell anything based on sound.

[nascarnate326]

I think the negative fuel trims is what I need to solve. Something is making it compensate to keep the AFR where it should.

Verified all 8 cylinders are firing with heat gun.

[Fox Slaughter]

Well considering there is o2 before and after cats on the OBD2 models to monitor if the cats are working.
If you removed the cats and did not tune out the rear the o2s then its thinks the cats are messed up.

Open Loop is controlled by the tune for fueling.
Closed loop is when it warms up and now the o2s control the fueling.

[nascarnate326]

Rear 02's are removed, cats are removed, tuned for that.

[nascarnate326]

it also looks like drivers side headers are much cooler than passenger side headers

[Blue04ss]

Have you verified all the coils working properly?? I had a similar issue on my lightning where it would idle good and would rev good while in park but when in drive that's when it would act up. I know it's not GM but it's worth a shot. Sorry if you have already covered this.

[nascarnate326]

How do I verify if a coil is good?

I assumed they either work or they don't work.

With all four primaries being 30-40 degrees cooler than the passenger side just seems odd.

[Fox Slaughter]

Spark plug gaps correct?
Revving there is no load on the engine.
While driving there is load, possibly blowing the spark out?

[Lucky SOB]

Could be the coils. Check the resistance with an ohm meter. I'm sure somebody has the specs online.

Can't think of anything else causing them to run a different temps besides the other things you've replaced.

[Lucky SOB]

Could be the coils. Check the resistance with an ohm meter. I'm sure somebody has the specs online.

Can't think of anything else causing them to run a different temps besides the other things you've replaced. I guess it could be injectors?

[Fox Slaughter]

---

Ignition Coil Test

1. Disconnect the ignition coil output wire at the distributor cap.
2. Connect a spark plug to the end of the ignition coil output wire which you just disconnected.
3. Connect a ground wire to the threaded portion of the spark plug.
4. Disconnect the ignition coil ground wire from the negative terminal on the coil (Green Wire).
5. Connect one end of a ground wire to the ignition coil negative terminal.
6. Turn the ignition switch to the ON position.
7. Tap the other end of the ignition coil ground wire jumper on an good grounding point (for example the battery negative terminal) and look for sparks at the spark plug that correspond to the frequency of your tapping of the ground wire.
8. If you have a good spark at the spark plug, the ignition coil is good.
9. If you don't get a good spark, check for approximately 12 VDC from the coil positive terminal (black wire) to ground with the ignition switch in the ON position. You should also get approximately 12 VDC from the coil negative terminal (Green wire) to ground

Ignition Coil Resistance Check
In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.

1. Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
2. Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.

From LS1Tech.

[nascarnate326]

Michael is going to run out tonight and put my car on the laptop. Hopefully he can finally tell me whats wrong.

[hoogiesngrinderz]

Here are the logs. Log 1 is key on for a bit to check TPS and verifying sensors then engine start and idle. I cleared the fuel trims around frame 685. Log 2 is a short drive.

natez28_1.hpl
natez28_2.hpl

• Verified that the booster isn't leaking.
• Intake sealing well.
• Almost positive the issue lies with cylinder 7 as the header primary is much cooler than the rest.
• Unburned air/fuel is causing bank 1 o2 to read lean, PCM adding tons of fuel causing 1, 3, and 5 to burn way rich
• Injector 7 was swapped with injector 2 - no change.

Ran out of time and had to head back home. Still to check: Coil, compression, valve springs.

[nascarnate326]

Swapped the coil, no change.

Tomorrow ill ill take the valve cover off to inspect valve spring. Are comp 918's known to break?