Car started running rich and miss firing

[Darkness]

So the other day I took the car out at night for some go fast action with a few of my friends.

After running it hard for several minutes the car started running rough (as if it had a bad tune) and miss-firing. Also noted that the WB was showing about 10-11 AFR when it normally runs at about 15-16 at cruise with low load.

So now the car runs rough a very choppy and too rich. Every now and then I see that it smooths out a bit for a few seconds but still at a 12-13 AFR, then it goes back to running rough. I noticed at high loads and WOT seems to run good.

What could've happened? O2 sensor got burn in the highspeed run? Vac leak, headgasket?

What can I log to see whats going on, it has no trouble codes.

Thanks in advance.

[SSpdDmon]

You can scan and see if it's the O2's. If nothing turns up, check the plugs and wires. It might not be getting a spark somewhere.

[Darkness]

You can scan and see if it's the O2's. If nothing turns up, check the plugs and wires. It might not be getting a spark somewhere.
Funny thing, I reset the PCM and now it runs real smooth but the AFR is still too rich! :nixweiss:

[joecar]

Connect fuel pressure gauge to fuel rail;
Start engine, and check pressure, if it's too high, then regulator maybe stuck;
Turn off engine and watch pressure... it it's dropping then you may have leaky injectors which will cause running rich.

Check for restriction/obstruction/debris in air filter and/or air tract.

Check TPS correct range (0..100%) using scan tool.
Check ECT and IAT for correct temps using scan tool.

Check that the front NBO2 sensors switch at part throttle using scan tool.

Check for good spark (plugs/wires like SSpdDmon said).

Check all grounds including battery ground connection.

Some other things.

[Darkness]

Connect fuel pressure gauge to fuel rail;
Start engine, and check pressure, if it's too high, then regulator maybe stuck;
Turn off engine and watch pressure... it it's dropping then you may have leaky injectors which will cause running rich.

Check for restriction/obstruction/debris in air filter and/or air tract.

Check TPS correct range (0..100%) using scan tool.
Check ECT and IAT for correct temps using scan tool.

Check that the front NBO2 sensors switch at part throttle using scan tool.

Check for good spark (plugs/wires like SSpdDmon said).

Check all grounds including battery ground connection.

Some other things.
Hmmm sounds like a good idea to check the fuel pressure. I'll check that out tomorrow and will let you know. Thanks.

[Darkness]

Nope, all looks good, still doing it though. What could it be?

[SSpdDmon]

Might wanna pull the valve covers and take a peak inside then.

[Darkness]

Ok this issue is getting too old already. What should I log to see what going on? I pulled the valve covers already and everything looks good.

[TAQuickness]

have you replaced your O2's yet?

[Darkness]

have you replaced your O2's yet?
No, should I? Cant I just log them to see if they're working properly?

[TAQuickness]

you can log them, but if they are bad, how will you know what good ones look like (past logs maybe)?

i don't run NBO2's so I can't tell you what to look for, but I know they'll kick your ass if they're bad

[Darkness]

you can log them, but if they are bad, how will you know what good ones look like (past logs maybe)?

i don't run NBO2's so I can't tell you what to look for, but I know they'll kick your ass if they're bad
Damn, how much are they anyhow, not too expenssive I assume?

[TAQuickness]

not bad, Bosche 13111's are about 75 each in my neck of the woods.

[Darkness]

I just dont want to fork out 150 bux and not fix the problem

[TAQuickness]

compare your logs to old logs and see how it looks.

[Darkness]

compare your logs to old logs and see how it looks.
Thats what sucks, I never logged the O2 sensors :frown:

[bink]

No DTCs?
:cheers:
joel

[joecar]

Your WB says you're running rich;

Log the following:
LTFT1 or LONGFT1
LTFT2 or LONGFT2
HO2S11
HO2S21

If your NBO2 sensors appear to be working, the HO2S11/HO2S21 will:
at WOT: peg at something like 800+mV;
at PT: switch up/down (i.e. cross 450mV in each direction) [almost] repeatedly;

If they are doing this, then what do the LTFT's read...?
Does this correlate with the WB sensor...?
Are the LTFT's deviating from zero by more than 5% (say)...?
Rich or lean...?

Are you running a MAF...?
If so, log MAF and MAFFREQ and see that they correlate to TPS and RPM.

[Darkness]

Well this problem is still on-going... I dont know what else to do.
I've checked all of the following:
Injectors (not leaking)
Plugs (nice and brown)
Plug wires MSD (look to be working fine)
Vacum hoses (all fine)
Checked for broken valve springs (checked all fine)

Checked the header primary temperatures with an infrared thermometer and there was some differences off about 100F on a couple of cylinders. Need to check again tomorow to see if the readings are the same.

I appreciate all of you guy's help, but I'm still too new with EFILive to know what to and how to log certain parameters and know how to read the results. :help2:

[joecar]

Use the EFILive scan tool to do the Cylinder Balance test.

Then you may also want to do a compression/leakdown test.

[Darkness]

Use the EFILive scan tool to do the Cylinder Balance test.

Then you may also want to do a compression/leakdown test.
The cylinder balance test is not very consistent because the idle is bouncing up and down when rough. As for the compression test I'm doing it tomorrow.

[Darkness]

I got a code P0200 "Injector Circuit Malfunction"

Anybody know what this is?

[joecar]

P0200 = PCM detected incorrect voltage on injector driver circuit(s) for 5 seconds or longer.

[joecar]

Check the INJ fuse (and find the cause if it's popped);
Check for voltage at each injector connector;
Check for pulsing/"blinking" voltage with engine cranking,
if not, then check for short or open.

You have either:
a. one or more electrically open injector(s);
b. one or more injector circuit(s) that are open or shorted (to either ground, or to voltage, or to each other);
c. one or more bad injector connectors and/or harness connectors;
d. one or more failed injector driver(s) in the PCM;
e. a bad ground somewhere;
f. a bad connection to the INJ fuse, or the INJ fuse is blown (see "shorted" in b. above).

[Darkness]

Check the INJ fuse (and find the cause if it's popped);
Check for voltage at each injector connector;
Check for pulsing/"blinking" voltage with engine cranking,
if not, then check for short or open.

You have either:
a. one or more electrically open injector(s);
b. one or more injector circuit(s) that are open or shorted (to either ground, or to voltage, or to each other);
c. one or more bad injector connectors and/or harness connectors;
d. one or more failed injector driver(s) in the PCM;
e. a bad ground somewhere;
f. a bad connection to the INJ fuse, or the INJ fuse is blown (see "shorted" in b. above).
Thanks, I'll look it up. Would this be the cause for this whole problem? :Eyecrazy:

How do I check the blinking voltage? Sorry for the dumb questions :D

[joecar]

How do I check the blinking voltage? Sorry for the dumb questions :DDarkness,

Not dumb... it would be dumb to not know AND not ask... ;)

Can use a LED voltage probe (looks like a pointy screwdriver with red and green LEDs inside the handle, and a long wire lead off the handle to a crocodile clip... green lights up on positive voltage, red lights up on negative voltage; available at parts stores for $20), connect across injector harness connector, flashes as engine cranks...

Or can use injector connector test light (plugs into injector harness connector and flashes while engine is cranking; some parts stores have these, you need the GM variant, these are more expensive and less verstile than LED voltage probe)...

Or can borrow a scopemeter (will show a squarewave) if you know the right person...

May be able to use a DMM, but it's more difficult... you'll see a varying DC voltage while engine cranks, may be able to see an AC voltage... some DMM's have a Hz function, gives a reading matching RPM / 2.

You'll need a DMM to check for injector resistance and wire continuity anyway.

Goto www.ls2.com (http://www.ls2.com) and look at their forum's diagnostic sections (courtesy of Elmer, good job :cheers:)... they have diagnostic proceedures for just about any DTC... if you can't find it, I'll try to find it... it's sectioned by year/make/model, but most of these have the same exact diagnostic procedure.

Cheers
Joe
:)