1992 LT1 Coupe: First time with scan tool

[Hib Halverson]

TunerPro is the most popular
TunerPro and TunerPro RT - Professional Automobile Tuning Software
Datamaster that I show the screenshot above from is free for the 1st 20 logs then you have to buy it.
Only put that up to display typical features because it has the most user friendly interface


ALDL OBD1 OBD cable OBDI OBD2 engine codes
There are others exactly the same but this is the cheapest I have come across.

Thank you VERY much for posting those links. The cable is something I'd been looking for.

 

[Hib Halverson]

After reading the latest post in this story, I think I'd pull the injectors and have them flow tested. If you find a problem, replace all of them. If you don't find a problem, replace both the O2Ses then see what happens.

 

[vetteoz]

Thank you VERY much for posting those links. The cable is something I'd been looking for.

I'm impressed.
Have read most of your very imformative articles online and in print over the years and didn't think you could teach a 'ol dog ,new tricks

 

[92BlackVette]

It's just GOTTA be an injector. They're 18 year old Multecs.

I'll be giving Jon at FIC a call in the Spring.

Mine are OEM too, but I won't replace them until I have too......155,000 miles ;squint:

 

[cpk1966]

Similar Problem here

It seems we both are struggling with similar problems. My 1992 has 20k miles on it. It ran fine on the way to work and on the way home like on 5 cylinders. Owner of Corvette shop locally told me it was definitely the opti-spark. It set the Left O2 sensor code so I replaced those first with no change. I replaced the opti spark and the water pump while I was there. The rotor and contacts were green with corrosion so I was pretty happy actually. Put it together and started it. A little rough at the start but after a couple of minutes it was perfect. Smooth idle and better performance than the last 10 years. It sat for a week and I started it last Sunday and back to the same. Horrible idle, no power and set the O2 sensor code again. Put it away and went out today to investigate and it idles reasonable, not perfect but much better. Still lacking on power. O2 sensor readings look good. I am confused as it seems you are. I will keep you updated and follow your progress as well. Good luck.

 

[gmjunkie]

It seems we both are struggling with similar problems. My 1992 has 20k miles on it. It ran fine on the way to work and on the way home like on 5 cylinders. Owner of Corvette shop locally told me it was definitely the opti-spark. It set the Left O2 sensor code so I replaced those first with no change. I replaced the opti spark and the water pump while I was there. The rotor and contacts were green with corrosion so I was pretty happy actually. Put it together and started it. A little rough at the start but after a couple of minutes it was perfect. Smooth idle and better performance than the last 10 years. It sat for a week and I started it last Sunday and back to the same. Horrible idle, no power and set the O2 sensor code again. Put it away and went out today to investigate and it idles reasonable, not perfect but much better. Still lacking on power. O2 sensor readings look good. I am confused as it seems you are. I will keep you updated and follow your progress as well. Good luck.

Better be checking the grounds,All of them!!
Been there done that!:L:L:L
The ones on the back of the engine really SUCK!!

 

[screamin_conure]

Better be checking the grounds,All of them!!
Been there done that!:L:L:L
The ones on the back of the engine really SUCK!!

Hey CPK,
Sorry to hear you're still having problems. There's no more dissappointing feeling than dropping a ton of money in your car to fix a problem only to have the symptoms continue.

I'd have to agree with Junkie. With only 20k on the clock, your car has done a lot of sitting. I'll bet that all of that sitting has allowed moisture or condensation to seep into places where it can do some damage (witness the corrosion you reported on your Opti's terminals). From the hit-or-miss nature of your problem, plus the fact that you're reporting the car is down on power, my gut feeling is you're battling something electrical in the ignition system. Was the ignition coil checked or replaced when they did the Opti? If not, I'd be starting with that. Unplug the connections to the coil and check for corrosion. Replacing the coil might be an option, but check your electrical connections first.

It seems a bit odd that it threw a code for the 02 sensor again after replacing it. Again, that kinda' point to an electrical/ground fault. Are you using a scan tool of some type to see the sensor readings? Also, do you have a set of factory service manuals for your year?

 

[cpk1966]

I do have a scan tool and the O2 readings look good. I did check the coil and both connectors coming off that were spotless. I also have the FSM and am going through the diagnostics. It is actually idling with just a slight miss right now but when you accelerate it vibrates under load. I am leaning towards ignition or fuel injection. When I unplug one injector at idle on the drivers side you cannot really notice a difference. On the passenger side you can absolutely notice. I need to get a fuel pressure gage and investigate further. I am going to remove the plugs and see if one of them is a lot different than the others but at least I may be narrowing in on something to look at here.

 

[screamin_conure]

I do have a scan tool and the O2 readings look good. I did check the coil and both connectors coming off that were spotless. I also have the FSM and am going through the diagnostics. It is actually idling with just a slight miss right now but when you accelerate it vibrates under load. I am leaning towards ignition or fuel injection. When I unplug one injector at idle on the drivers side you cannot really notice a difference. On the passenger side you can absolutely notice. I need to get a fuel pressure gage and investigate further. I am going to remove the plugs and see if one of them is a lot different than the others but at least I may be narrowing in on something to look at here.

I agree. I think you're right on the brink of getting it sorted out. Sounds like, at this point, the only difference between the issues with our two cars is that I'm not experiencing the loss of power under acceleration. Just a poor quality, rich smelling idle and a high right BLM during idle. By chance, do you know what your BLMs were during closed loop at idle?

 

[cpk1966]

I agree. I think you're right on the brink of getting it sorted out. Sounds like, at this point, the only difference between the issues with our two cars is that I'm not experiencing the loss of power under acceleration. Just a poor quality, rich smelling idle and a high right BLM during idle. By chance, do you know what your BLMs were during closed loop at idle?

I will start it up and let go to closed loop and reply back with all of the readings. If I recall I was around 140 on the left and a little lower on the right but I will check. From seeing your post it looks like you are running pretty high on your BLM.

 

[screamin_conure]

I will start it up and let go to closed loop and reply back with all of the readings. If I recall I was around 140 on the left and a little lower on the right but I will check. From seeing your post it looks like you are running pretty high on your BLM.

Thanks CPK! I appreciate it. ;worship

Yes, she's WAY rich on the right bank. I can see it on the scanner and smell it with my nose.

 

[cpk1966]

The Stats!

Thanks CPK! I appreciate it. ;worship

Yes, she's WAY rich on the right bank. I can see it on the scanner and smell it with my nose.

Okay, I made some progress tonight. before it is in closed loop and the fan comes on I think I can tell the cylinder which is not firing. Seems like I can tell when I unplug three of the injectors but the other one does not seem so much. Anyway, I let it go into closed loop and here are the readings:

A/C Pressure 48 psi
Coolant Temp 186.8F
MAP Sensor 1.31 Volts
Throttle Sensor 0.62 volts
Battery voltage 14.0 Volts
Manifold Air Temp 58.8 F
Left Oxy Sensor 580mv - Fluctuates between 180 and 800
Right Oxy Sensor 176mv - Same on the fluctuation
Left Block Learn 145 - This one fluctuates between 144 and 156
Right Block Learn 117 - Pretty stable 117 - 121
Blk Lrn Cell 16
Left Integrator Value 127
Right integrator value 125
CCP Duty Cycle 0%
Idle Air mtr pos 20 steps
Desired idle 662 RPM
Spark Advance 24 deg
Engine RPM 650
knock retard 0 deg
throttle angle 0 deg
egr duty cycle 0%
Learned idle position 16 steps
TCC not locked
CCP purge Off
Lear control enabled

As you can see, the data shows my left side is flaking out a little.
Hope it helps.

 

[screamin_conure]

Okay, I made some progress tonight. before it is in closed loop and the fan comes on I think I can tell the cylinder which is not firing. Seems like I can tell when I unplug three of the injectors but the other one does not seem so much. Anyway, I let it go into closed loop and here are the readings:

A/C Pressure 48 psi
Coolant Temp 186.8F
MAP Sensor 1.31 Volts
Throttle Sensor 0.62 volts
Battery voltage 14.0 Volts
Manifold Air Temp 58.8 F
Left Oxy Sensor 580mv - Fluctuates between 180 and 800
Right Oxy Sensor 176mv - Same on the fluctuation
Left Block Learn 145 - This one fluctuates between 144 and 156
Right Block Learn 117 - Pretty stable 117 - 121
Blk Lrn Cell 16
Left Integrator Value 127
Right integrator value 125
CCP Duty Cycle 0%
Idle Air mtr pos 20 steps
Desired idle 662 RPM
Spark Advance 24 deg
Engine RPM 650
knock retard 0 deg
throttle angle 0 deg
egr duty cycle 0%
Learned idle position 16 steps
TCC not locked
CCP purge Off
Lear control enabled

As you can see, the data shows my left side is flaking out a little.
Hope it helps.

Thanks CPK! Yeah, it looks like you're running fairly rich on the left bank and just a shade lean on the right. In comparing your idling numbers to mine, they're almost identical with the exception of BLMs. I'm feeling even more confident that I'm dealing with an injector or two that are on their way out. You had replaced your left 02 sensor previously in response to an 02 sensor code, correct? Are you still getting that code?

 

[screamin_conure]

Well, to follow through on my original post, I thought I would post an update and more or less put a period on it.

Over the last few days, I've gone ahead and had both O2 sensors replaced, the in-line fuel filter replaced, and just today I installed a set of Bosch III injectors from FIC (thanks Jon!).

I'm happy to say that for the short time that the weather allowed me to drive the car today, it ran GREAT! No more choppy/bouncy idle. Nice and smooth. The numbers from my Auto X-Ray now show the BLMs MUCH closer to the normal range of 128 (still a little high now on the left bank at around 136 - 140, whereas before it was the right bank that was pegged at 160). In all, a VERY nice improvement in driveability.

COME ON SPRING!!!

 

[pgtr]

ALDL OBD1 OBD cable OBDI OBD2 engine codes
There are others exactly the same but this is the cheapest I have come across.

Slightly off topic from the OBD1 discussion here...

I've also seen USB/OBDII (not ALDL/OBD1) cables cheap ($20ish maybe?) on a certain major auction site. These appear to be sourced from offshore - watch the shipping costs. Many seem to reference "VW/Audi" and others simply "CAN". I have no personal experience with these - don't know if they'd work ok on a PC and hooked to a GM...

 

[cpk1966]

Awsome to hear she is up and running. I have been out of the country for a while and since it was nice today I went back at it. Checked the resistance on the injectors and one of them is an open! Guess that answers my question. Pulled them off and they are sticky like glue is on them. I think I will follow you and replace the set. Keep you posted!

 

[cpk1966]

By the way, which injectors did you get? The original 22LB or the 32LB set from FIC?

 

[screamin_conure]

By the way, which injectors did you get? The original 22LB or the 32LB set from FIC?

I went with the Bosch III, 22LB set from FIC, which are identical to the original Multecs. They fit right in, no problems. I did have a small issue when I installed the very first injector, in not knowing when it was properly seated. After fiddling with it for a while, I figured out that as you're pushing the injector in (gently rocking it from side to side and NOT twisting), when it stops and won't go any further, it's seated. I was thinking that the bottom o-ring had to be completely seated inside the manifold, but that is not the case. When they stop, they're in. Also, be prepared for a good amount of gasoline to come out of the fuel rails as you're tipping them back, but especially as you're tipping them forward to re-install them, as the Bosch III injectors install into the intake manifold first with the "unplugged" fuel rails coming down on top of them. There will still be a fair amount of gas in the rails which will likely pour out as you're moving them in place over the injectors. Have LOTS of rags lying across the top of your engine to absorb as much as possible.

While I'm happy with the Bosch injectors in general, after having had some time to put some miles on the car with them in, I can say that they weren't the "magic bullet" I was hoping for. Overall, my car runs great, with the exception that I'm still having wonky idle issues, plus after putting the injectors in, the high BLM (was pegged at 160, now 128) that I had at idle on my right bank has now moved over to the left bank (was 130, now 140). It accelerates hard with no misses or bobbles and cruises just great, but for the life of me I can't get it to idle smoothly or consistantly. It either idles very low and rough, or, typically after a good amount of heat builds up in the engine, it SOMETIMES begins to idle too high. Other times, it will idle at the proper RPM without fail. When it's idling high, usually shutting it off for a few minutes will bring the idle back down, which tells me it's not a vacuum leak. It also has a slight stumble at idle. The IAC valve is new, and the TB has been cleaned out as well as it can be without completely removing it from the engine.

It's driving me nutty!

 

[Hib Halverson]

You've just spent money for a new set of injectors you may not have needed. I may have suggested this before but, if I did not...you need to stop guessing and get a copy of the Factory Service Manual and troubleshoot with that.

Keep in mind that with 160 on the right side long term fuel trim, the system is adding fuel...a lot of it. With 140 on the left, it's adding fuel, though not as much.

Gven the past symptoms, that new injectors, new IAC and a clean TB did nothing and current symptoms are lack of idle stability and high fuel trims, you need to get back to basics....look for a vacuum leak.

 

[gmjunkie]

You've just spent money for a new set of injectors you may not have needed. I may have suggested this before but, if I did not...you need to stop guessing and get a copy of the Factory Service Manual and troubleshoot with that.

Keep in mind that with 160 on the right side long term fuel trim, the system is adding fuel...a lot of it. With 140 on the left, it's adding fuel, though not as much.

Gven the past symptoms, that new injectors, new IAC and a clean TB did nothing and current symptoms are lack of idle stability and high fuel trims, you need to get back to basics....look for a vacuum leak.

Lots of little vacuum lines on these cars that Nobody hardly ever checks!:L