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I have a 1995 with 44,xxx miles on it. Engine started missing. I thought maybe bad gas replaced it. When that didnt work, I replaced the plugs yesterday. Left bank all four plugs looked decent and a light tan. Right bank however looked black and fouled maybe even moist. New plugs made no difference either. Any thoughts in the next step to diagnose this? Thanks ahead of time.
Does it do it cold and warmed up or only when warmed up?
Both, I might add it started out gradually like you wondered if it really just cut-out but by the time I finished the twenty miles home i assume i lost the all four cylinders on that side.
This seems like a good situation where a noid light would be useful to see if you're getting a signal to the injectors.
One thing sticks in my mind being it's all the injectors on one side of the engine, IIRC I think I read one time that the LT1 engine has 2 relays for the injectors, one for the left side and another for the right side injectors. Might be worth checking out the FSM to confirm if that's accurate and see what's listed for diagnostics assuming you're not getting a signal to the injectors on one side of the engin.
One thing sticks in my mind being it's all the injectors on one side of the engine, IIRC I think I read one time that the LT1 engine has 2 relays for the injectors, one for the left side and another for the right side injectors. Might be worth checking out the FSM to confirm if that's accurate and see what's listed for diagnostics assuming you're not getting a signal to the injectors on one side of the engin.
This seems like a good situation where a noid light would be useful to see if you're getting a signal to the injectors.
One thing sticks in my mind being it's all the injectors on one side of the engine, IIRC I think I read one time that the LT1 engine has 2 relays for the injectors, one for the left side and another for the right side injectors. Might be worth checking out the FSM to confirm if that's accurate and see what's listed for diagnostics assuming you're not getting a signal to the injectors on one side of the engin.
Thanks for the info I will look into that for sure, and post finding for future referance.
Double check that you have spark to all the plugs on that side. Assuming you do, then I agree with hcbph. If all four on one side are failing, that really helps narrow down the cause vs random misfires.
I think this thread is chock full of BAD information.
1995=Sequential fuel injection. Each fuel injector is individually fired by the ECM. They are NOT bank fired like the 92-93. They DO NOT use a relay. ALL fuel injectors are driven off a internal ECM transistor.
Its WAY more likely to be a NON-ignition issue. Ignition on only one bank having issues with a distributor. Not very likely unless someone pulled off ALL the plug wires on the Opti-Spark cap at the same time.
If one bank had normal looking plugs and the other had fuel fouled plugs....why do we need a noid lite? Unless the "normal looking bank" is NOT firing. Then again why on a sequential injection engine just one bank. Again NOT likely unless you have wiring damage on the one bank or NO power to them. Injectors have 12 constant with a ECM switched ground.
I think its much more likely you have a 02 sensor that is reading in error and causing one bank to run VERY rich.
Easy way to test WITHOUT a scan tool. Unplug your MAF sensor in your air duct after the air filter. This will put the car into open loop mode which ignores the 02 sensor and see how it runs.
A scan tool with data would make this MUCH easier, but you have to know what your looking at.
I think this thread is chock full of BAD information.
1995=Sequential fuel injection. Each fuel injector is individually fired by the ECM. They are NOT bank fired like the 92-93. They DO NOT use a relay. ALL fuel injectors are driven off a internal ECM transistor.
Its WAY more likely to be a NON-ignition issue. Ignition on only one bank having issues with a distributor. Not very likely unless someone pulled off ALL the plug wires on the Opti-Spark cap at the same time.
If one bank had normal looking plugs and the other had fuel fouled plugs....why do we need a noid lite? Unless the "normal looking bank" is NOT firing. Then again why on a sequential injection engine just one bank. Again NOT likely unless you have wiring damage on the one bank or NO power to them. Injectors have 12 constant with a ECM switched ground.
I think its much more likely you have a 02 sensor that is reading in error and causing one bank to run VERY rich.
Easy way to test WITHOUT a scan tool. Unplug your MAF sensor in your air duct after the air filter. This will put the car into open loop mode which ignores the 02 sensor and see how it runs.
A scan tool with data would make this MUCH easier, but you have to know what your looking at.
Does not hurt to check for codes either.
Sorry guys I have been out of town. I am back home now. There were no codes thrown. Tomorrow I am going to check for spark first because that is easiest. Then i will move on from there. Thanks for all the input so far.
I think this thread is chock full of BAD information.
1995=Sequential fuel injection. Each fuel injector is individually fired by the ECM. They are NOT bank fired like the 92-93. They DO NOT use a relay. ALL fuel injectors are driven off a internal ECM transistor.
Its WAY more likely to be a NON-ignition issue. Ignition on only one bank having issues with a distributor. Not very likely unless someone pulled off ALL the plug wires on the Opti-Spark cap at the same time.
If one bank had normal looking plugs and the other had fuel fouled plugs....why do we need a noid lite? Unless the "normal looking bank" is NOT firing. Then again why on a sequential injection engine just one bank. Again NOT likely unless you have wiring damage on the one bank or NO power to them. Injectors have 12 constant with a ECM switched ground.
I think its much more likely you have a 02 sensor that is reading in error and causing one bank to run VERY rich.
Easy way to test WITHOUT a scan tool. Unplug your MAF sensor in your air duct after the air filter. This will put the car into open loop mode which ignores the 02 sensor and see how it runs.
A scan tool with data would make this MUCH easier, but you have to know what your looking at.
Does not hurt to check for codes either.
When I unhook the MAF sensor what can I expect it to run like in a open loop situation? Thanks
Well the car has spark, and un-hooking the MAF sensor did not make a difference in run ability. I guess I will admit defeat and let a professional look at it
I belive you have two injector fuses one for each side I would check and clean. Also look for a melted o2 sensor wire on that side. Pull the vacuum line off the FPR and smell for fuel.
You are better off here chances are before you find a pro you will meet many a rapist.
Get the temp off each sides exaust with a temp laser.
How long has it been sitting might just be stuck injectors. Give them a tap.
Last edited by antfarmer2; 01-31-2017 at 05:51 PM.
Don't be too discouraged. These cars are old and it's hard to know how previous owners have maintained the car. First of all congratulations; 95 is one THE best years for the C4.
One thing to understand is that the C4 corvette is not a car that you want to throw parts at. The parts are not inexpensive.
If you plan to keep the car it would be wise to invest in the two volume (red cover) Factory Service Manual. The FSM is specific by individual year thus you want on for the 95 vette. You can often find these for sale in the parts for sale section of the forum or on fleebay for just under $100.
If you check in the regional section of the forum there will likely be folks who can recommend a vette specialty shop in your area. Remember that your's is a 22 year old car and the service techs at the local dealerships may not know anything about a corvette that's three generations old.
Well the car has spark, and un-hooking the MAF sensor did not make a difference in run ability. I guess I will admit defeat and let a professional look at it
That's unclear. Did you check that each plug is getting spark? An IR sensor might help find if the fouled side is working (as hot), compared to the other side.
Ruby has the best experience and input, so far, consistent with his many helpful posts. Reading the plugs, as you did, is a rare treat to read about, as most want to run to a scanner first. The old school methods still work and codes can be misleading. A vacuum leak is a good example. Unlike old school, one needs to add some basic electrical circuit knowledge, such as checking for good grounds and complete circuits. Learn the system workings and stay simple, at first.
You could try watching an accurate tack, perhaps on a tach-equipped timing light, to note RPM drop as each plug wire is removed. No drop = no power from that cylinder. Be advised, tho, that the ECM will attempt to maintain the programmed idle speed, so any drop is probably short-lived. Similarly, it will add fuel to adjust for unmetered air, such as from a vacuum leak, maybe on one side in this case, as it strives (closed loop) for the ideal air/fuel ratio (along the O2 sensor line).
Just think of all you'll learn by working this out, unlike just writing a check, or three.
BTW, too many shops know little more than you, but charge for their forays into unneeded 'fixes'. I found that true, especially at my selling dealership.
^^^^^^^^^^^^^ "BTW, too many shops know little more than you, but charge for their forays into unneeded 'fixes'. I found that true, especially at my selling dealership."
Very true. Many shops will have no problem at all spending YOUR money shotgunning the problem with parts until they hit on the right combination.
Just my $.02, I'd go with a bad O2 sensor or a bad connection to the O2 on that bank.
Once I did have a stuck injector that hosed down one side of the engine pretty bad. A shop had to find that one, but it was a good trusted shop that does Corvettes and deals in fuel injection.
You can use a cheap IR thermometer on each exhaust primary to make sure all four cylinders one side are firing and all four on the other side are not. I know you read the plugs, but this would just confirm things. There just aren't many things that would make one bank of injectors fail completely while the other half runs just fine. For example, it's way too coincidental that all four injectors on that side would clog so bad that they wouldn't fire at all.
Originally Posted by antfarmer2
I believe you have two injector fuses one for each side I would check and clean.
That's a good point. Here is a diagram from the Factory Service Manual for my 96:
Yours is probably similar (probably identical, seeing as how I can run a 95 PCM in my car with no other changes and it works perfectly). The "IP Fuse Block" is the panel on the passenger side of the instrument panel. That is, it's literally on the side, such that you only see it when you open the passenger door and pop the little panel off. On my 96, it's fuse numbers 22 and 23. If you have your owner's manual it should say which fuses are the two that protect the injector circuits on your car.
As you can see from the diagram, it's a very simple control circuit. Power flows from the fuses to the S132 and S102 splits, where each of the two lines splits into four for each individual injector. After each injector, it goes to the PCM, which controls each individual injector on/off cycle by grounding the circuit to let power flow through the circuit. In order for a whole bank of injectors to not get power, the circuit has to have a break or short somewhere from the fuse to the S132/S102. Any fault after the splits would only affect one injector. So it's basically either the fuses or the wire itself has a fault somewhere before or at the split.
Thank you guys I will check the fuses today. I have not checked with a IR thermometer but I did check by touching the manifolds and I still don't think the right bank is firing. I will update after I can check the fuses this afternoon.
Check the ohms on the injectors, there are many injector options from having oe's rebuilt, or many aftermarket ones at different prices (use the correct pressure injectors and don't be temped to upgrade if not needed).
Last edited by corvette95; 02-06-2017 at 05:17 AM.
01-25-2017, 07:05 AM
Newbie needs Diagnosis Help
