Still need help with LT1

[94Form]

OK, I got my hands on a Tech 2 Scanner and these are the numbers I came up with. I still have a problem with a rough idle and also found my water pump leaking from the weep hole right onto the optispark. Additionally, I can smell strong gas fumes coming from the rear of the car after I turn the car off. If someone can read this and tell me what is wrong I would be forever in their debt.....

Engine Speed Bouncing (650-690)
Desired Idle Speed 650 RPM
ECT 181 – 185 F
IAT 82
MAP 34 – 35 KPa
MAP 1.20 – 1.34 Volts
BARO 102 KPa
BARO 4.96 Volts
Throttle Position .66 Volts
Throttle Angle 0%
Left HO2S Bank 1 Bouncing and alternating 60 – 900
Left HO2S Bank 2 Bouncing and alternating 60 – 900
Loop Status Open (when started)Closed (after running)
Short Term FT Bank 1 125
Long Term FT Bank 1 125
Short Term FT Bank 2 125
Long Term FT Bank 2 114
Fuel Trim Cell 16
Fuel Trim Enable Yes
Spark Advance 20
MAF Sensor Bouncing 6.20 – 7.20
Knock Retard 0
KS Activity 18 Counts
Knock Sensor OK
Low Resolution Signal Bouncing 2.2 – 2.3
High Resolution Signal Yes
Injector PWM Bank 1 3.0 ms
Injector PWM Bank 2 2.8 ms
IAC Position 2 Counts
Learned IAC 10 Counts
EGR Duty Cycle 0%
System Voltage 12.8 Volts
Air Control Off
EVAP Canister Purge 0%
Injector Fault No
TC/ASR Active No
Fan CTRL PCM A10 (if eq Off
Fan Control PCM A11 Off
A/C Request No
A/C Clutch Off
A/C Status Off
A/C Refrigerant Pressure 111 Psi
A/C Refrigerant 1.26 Volts
A/C EVAP. Temperature 86
Vehicle Speed 0 MPH
Transmission Range Switch Park/Neutral
Park/Neutral Position P-N--
TCC Brake Switch Closed
TCC Solenoid Off
1-2 Sol. On
2-3 Sol. On
Trans Range A Off
Trans Range B On
Trans Range C Off
Performance Mode Switch Open
Engine or Transmission No
Engine Run Time 00:23:30

[Joe 1320]

What I see is a slight imbalance in your injector pulse width from one bank to another. 3.0 vs 2.8

The injector pulse width should vary with the oxgen sensor cross counts. Your computer will be constantly readjusting the fuel mixture in both banks to give maximum economy while not at WOT, so your 02 counts will vary widely. Your injector pulse width is a real time display of the length of time the injectors are open in response to the 02 sensor reading and what is being read by the PCM. In the case of the pulse width, bank 1 appears to be getting more fuel than bank 2 based on pulse width. The short term corrections don't indicate this(125/125), but the long term corrections(125/114) point to the different rates of fuel from one bank to another.

The fuel imbalance, the rough idle, the smell of gas and the water pump leaking onto the optispark point to a partial ignition failure. The computer reads the 02 readings from both banks and when partially unburned fuel hits your bank #2 02 sensor, it is seen as a rich mixture, and the computer tries to pull fuel out of the offending bank of injectors to stabilize the mixture. The problem is that pulling fuel out makes the engine leaner than optimum and the mixture gets even harder to fire and you get a more pronounced miss. There is a slight possibility that an 02 sensor might not be 100%, but a typical indicator of that would be low cross counts for 1 or both 02 sensors, which doesn't appear to be the case.

IMHO, time to troubleshoot the ignition system. Most likely the optispark is contaminated, your plugs and wires may as well be changed while you are at it.

[Injuneer]

Re: Still need help with LT1

(NORMAL)Engine Speed Bouncing (650-690)

(NORMAL variation)Desired Idle Speed 650 RPM

(NORMAL)ECT 181 – 185 F

(NORMAL)IAT 82

(NORMAL)MAP 34 – 35 KPa

(NORMAL)MAP 1.20 – 1.34 Volts

(NORMAL)BARO 102 KPa

(NORMAL)BARO 4.96 Volts

(NORMAL)Throttle Position .66 Volts

(NORMAL)Throttle Angle 0%

(NORMAL)Left HO2S Bank 1 Bouncing and alternating 60 – 900

(NORMAL)Left HO2S Bank 2 Bouncing and alternating 60 – 900

(NORMAL)Loop Status Open (when started)Closed (after running)

(NORMAL)Short Term FT Bank 1 125

(NORMAL)Long Term FT Bank 1 125

(NORMAL)Short Term FT Bank 2 125

(Low, split range compared to Bank 1)Long Term FT Bank 2 114

(NORMAL if engine was idling)Fuel Trim Cell 16

(NORMAL)Fuel Trim Enable Yes

(NORMAL)Spark Advance 20

(NORMAL)MAF Sensor Bouncing 6.20 – 7.20

(NORMAL)Knock Retard 0

(NORMAL)KS Activity 18 Counts

(NORMAL)Knock Sensor OK

(I think this is NORMAL... indicated difference in pulse slot widths for each cylinder - that's how the PCM identifies the cylinder)Low Resolution Signal Bouncing 2.2 – 2.3

(NORMAL)High Resolution Signal Yes

(Seems a little high)Injector PWM Bank 1 3.0 ms

(A very slight difference from Bank 1, accounted for by 114 BLM, as Joe points out)Injector PWM Bank 2 2.8 ms

(LOW... should be in range of 20-40 counts. Air may be leaking into the system... vacuum leak??)IAC Position 2 Counts

(LOW, see above)Learned IAC 10 Counts

(NORMAL)EGR Duty Cycle 0%

(NORMAL)System Voltage 12.8 Volts

(NORMAL)Air Control Off

(NORMAL)EVAP Canister Purge 0%

(NORMAL)Injector Fault No

(NORMAL)TC/ASR Active No

(NORMAL coolant temp looks good for no fans running. Do you have 160degF t'stat?))Fan CTRL PCM A10 (if eq Off

(Ditto, on above)Fan Control PCM A11 Off

(NORMAL)A/C Request No

(NORMAL)A/C Clutch Off

(NORMAL)A/C Status Off

(NORMAL)A/C Refrigerant Pressure 111 Psi

(NORMAL)A/C Refrigerant 1.26 Volts

(NORMAL)A/C EVAP. Temperature 86

(NORMAL, assuming the vehicle isn't moving)Vehicle Speed 0 MPH

Ignore the tranny related stuff... not relevant.

===========
After looking at all this, I would take a slightly different view than Joe. Weak ignition, Opti problems mean misfires. Misfires mean unburned fuel and air go out the exhaust. The O2 sensors can ONLY see air, not fuel. They interpret a misfire as "lean" and start to add fuel (raise BLM's above 128). Your BLM's are dropping on the problem side (Bank 2). That condition can be caused by a leaky injector(s). In that case, the cylinder is very rich, the air is consumed by part of the fuel, and the excess fuel goes out the exhaust. In the exhaust, it consumes some of the O2 that was residual in the other 3 cylinders in that Bank, making it look "rich"... PCM cuts fuel by lowering the BLM on Bank 2.

Also concerned by the low IAC counts. Another possibility here... the EEC canister purge could be stuck open, allowing air and fuel vapors to be pulled into the intake manifold. The excess air can be offset by the lowered IAC counts, but the excess fuel goes through the system. But that would affect both sides of the engine roughly the same. But... might be a stuck EEC solenoid and a saturated EEC canister.

The smell of gas at the rear of the car also might indicate a saturated EEC canister, and some leaking hoses back there. Not unusual at all for the canister to get filled with fuel over time, and for the hoses to rot on a 9-year old car.

Another possibility, but this would affect both side of the engine would be a leaky EGR valve.

My first guess would be a leaky injector. If you swapped the injectors from side-to-side, it would be interesting to see if the problem moved with the injectors, or stayed where it was. Might reduce it to a problem with the O2 sensors. But, you swap them side-to-side and see if the problem follows the sensor.

[Joe 1320]

Re: Re: Still need help with LT1

Originally posted by Injuneer
[BThey interpret a misfire as "lean" and start to add fuel [/B]

DOH! major brain fart on my part...... sorry. As always, you are correct.

One other issue could also be a leaking exhaust manifold. Any leaks, even the smallest ones will introduce extra air in the manifold and it will get picked up by the 02 sensor as being rich.

[M3EATER - GG '00 WS6 T/A]

Hey... Joe & Fred.....

Do you have any recommendations on books that teach the logic & full operation on these late model OBD II EFI systems?

Gordon

[Joe 1320]

I don't know of one. I hope Fred does....it would be nice to have such thing. Fred?

[94Form]

Thanks guys. Here are some more things to think about that may change your thoughts about this problem. Hopefully you will read this.

I changed the plugs to NGK Iridium a day or two before the test. The old ones (Delco Platinum) came out black and dry (all 8) and the gap looks large but I didn't check. The wires were changed about 10K miles ago to 8mm Taylor Spiro pro. Yes 160 therm. IAT was moved to the airbox years ago as well as the screen taken from the MAF.

Also, I don't have a clue how to use the Tech 2 but there was an option to check injector balance and I did. If I did it right they each were showing the same thing on the graph.

I did check for gas in the line from the EEC solenoid to the Throttle body and it was dry with carbon coating (no gas). But I thought I heard an odd noise from the rear after I shut it off and then smell gas. I will look into replacing the canister or can it be repaired?

I have a new water pump but I'm still searching for the best price on the Opti. before I plan a weekend under her.

Is there anything else you guys can think of before I take the dive?

[Joe 1320]

For parts, here are two great GM venders:

Dal Slabaugh: 877-448-5451
email: lockitup@bright.net
VanDevere Buick/Pontiac/Olds Akron, OH

Jason Cromer: 877-726-8295 or 850-243-8826 (direct parts dept ph #)
email: gmparts@samtaylor.com
Sam Taylor Buick/Cadillac Ft. Walton Beach, FL

Last time I checked, jason was a little less $$$. I also heard Autozone now sells a complete plug and play opti..... might want to check on that.

As far as the noise, if you hear a hissing, it could be the gas cap. It is supposed to be sealed. When you open the cap, you should hear the pressure equalizing, but not on it's own when you shut down. That may also be a source of the gas smell as well. Ain't this stuff fun?

Since you replaced the plugs and wires, just make sure there are solid connections and no wires had touched the manifolds.

Fred had a great idea about swapping the injectors from one side to the other and see if the imbalance switches banks.

Rough idle? How rough is it? Could be the lack of a screen in the MAF. Some cars don't like this mod, some do.

[94Form]

The idle problem was that once the car had warmed up it would start to get real rough almost stalling then trying to launch sporadically when stopped at a light or corner. After that would begin, if I try to take off at the same light it felt like some power loss and bucking while accelerating and no great response to WOT (automatic trans).

The idle isn't as bad as it was before the plugs were replaced but the look of the old ones leads makes me think I'm about to ruin $70 worth of plugs. And I need to fix what is going wrong because I can feel the problem isn't gone. its just better because the plugs can handle a little more right now.

Also, I forgot to mention that I replaced the Coil with the plugs and cleaned the throttle body which brought back the deep throaty sound she once had.

As for the screen, that was taken out sometime in '99 and hasn't been a problem.

[Joe 1320]

The only additional "quick" tests I can think of is the tap test. Take the handle of a screwdriver and while the engine is running, tap the MAF, TPS and PCM. if there is any stumble, you've found a potential problem. You might also check the flat connector to the coil driver module. I've seen misfires due to poor connections. You may even need to adjust the pins to get a good contact. Also run the engine with the hood up to see if there is any blue glow around any of the plugs/wires or arcing of the coil to the block.

[Formulaboy95]

94Form Sounds similar to my problem

Curious.... did u replace the plug wires? Visually my wires looked fine, but under closer inspection.... No spark on #4. I could smell the gas leaking out the exhaust. Plugs looked pretty darn good for 60,000 mi! Take a look at the pic. Every thing looks excellent except for #4. I got absolutely no trouble codes! This might be due to a small leak from the WP since it is directly underneath it (and seems to be the only one affected)