I have had a problem sometimes feeling a slight bog under aggressive acceleration (like a miss but no backfire) and recently heard that the C5 has a problem with the ignition coils. Sometimes I will also smell gas but have not when I have taken her in to be looked at (of course). Has anybody heard of this? Is MSD the way to go if a replacement coil is needed?

Thank you

 

When my car did the same thing it was the Magnecor plug wires I had installed. I took them all off and installed OEM plug wires and no problems. Your coils are excellent, much better than MSD or Accel, and should be fine. I would think you have a bad plug wire. You can either replace the set or take a volt meter and check for drop through the wire until you find the bad one.

Good luck.

 

700 ohms I believe

 

Hey, mine does the same thing. I notice it most when getting on it some when hitting the on ramp----sort of a dead spot. It's driving me nuts!

I recently bought the car. First thing I did was to replace the 99K mile plugs and wires. Went with Bosch plugs (0.060 gap) and GM Performance wires. Was thinking of putting back in the stockers and seeing if the dead spot is still there.

Next thing to check is fuel pressure I guess.

 

There are a couple of dozen things that can cause symptoms like you have. There's always too much information "NOT" provided to make a proper diagnosis of your problem.

Things that we need to know to properly help you:

-Year of your C5?
-Engine MODS/changes?
-Mileage?
-Any preventative maintenance that you have or have not performed.
-How do you normally drive the car?
-How frequently do you drive it (garage queen "during the weekends" or daily driver?
-What DTC Codes or CEL's do you have??
-Do you ever get a Check Engine light (CEL) or does it ever flash when the problem is present??
What is the Charging Voltage when car is running and age of battery?

If you do not know how to read the DTC's from the computer, here are some cool web sites that will provide you all the info on how to and what the codes mean:

This is the absolute best C5 Code web site!!!

http://www.corvettedoctor.com/Code_Main.html
http://www.corvettedoctor.com/index.html

[www.corvettedoctor.com

Go to “technical data base” and then to “Corvette ECM Computer Codes”. Then select your year car. Read the instructions and then scroll down to the "READ MORE" window to view the code definitions.\

Here is another very good site:

http://www.obd-codes.com/trouble_cod...d-ii-codes.php

Make sure to include the H or C suffix!!



As for the coils, your coils if they are operating properly work way better than a stock C5 HP level will ever need. Even if you mod your car, they still work very well!!! If you have tons of extra cash, we can all use a Christmas present. OEM coils are very good!

Some of the things that come to mind that can cause WOT issues are;

BAD WIRES. Good OEM wires should be clean, free of nicks, tears, burns and fit tight in to the plug and coil tower. They should also be inspected for corrosion and damage to the metal connectors inside the boot ends. Good OEM wires will OHM out at 250-750 Ohms. They are spiral wound metal core wires. If your reading some where in the 1000's or 10's of thousands of ohms,, the wires are TOAST! Up grading Spark Plug Wires (if the OEM wires are operating properly and not leaking voltage) will N O T net you any performance gains! PERIOD! Same for the coils. If you need to purchase new wires cause the old ones are bad, look for high quality wires with good material and ones that fit correctly! One of the very best wires that you can purchase for your C5 are the GM (red) performance wires! They work fantastic, fit excellent and last a long time! They are also very reasonably priced as compared to some of the aftermarket ones that will clean out a bank account for the same quality if not better OEM wire!

Clogged or restricted fuel filter:

Bad or low quality fuel:

Bad or worn spark plugs. (Excessive gap also)

Low or insufficient battery or B+ voltage:

Air/vacuum leak:

Dirty air filter:

Dirty MAF and or throttle body

Is it a cylinder mis or an engine bogg?? Makes a BIG difference in helping you with the diagnosis. Can you cause the problem to happen if you load the engine down at low RPM levels with a heavy throttle (i.e. 6th gear at 1200 rpm going up an incline?

There are more but you get the picture.


Bill Curlee

 

Not sure about KalEl but for me:


-Year of your C5?
98

-Engine MODS/changes?
Very very stock

-Mileage?
99K

-Any preventative maintenance that you have or have not performed.
Replaced fuel filter, trans filter, trans fluid, air filter, oil, oil filter, plugs, wires, oil sensor

-How do you normally drive the car?
Wick it up every once and a while--but normally like an old man

-How frequently do you drive it (garage queen "during the weekends" or daily driver?
Previous owner used it as a DD

-What DTC Codes or CEL's do you have??
No codes--no history codes

-Do you ever get a Check Engine light (CEL) or does it ever flash when the problem is present??
No and no

What is the Charging Voltage when car is running and age of battery?
Brand new Optima---Voltage within specs

Some of the things that come to mind that can cause WOT issues are;
For me it's not a WOT issue.

Good OEM wires will OHM out at 250-750 Ohms.
Mine measure at 400 Ohms

One of the very best wires that you can purchase for your C5 are the GM (red) performance wires!
That's what I've got

Clogged or restricted fuel filter:
New filter

Bad or low quality fuel:
Running premium---and a bottle of Techtron

Bad or worn spark plugs. (Excessive gap also)
New Bosch platinum gaped at 0.060

Air/vacuum leak:
I'll shoot things with starter fluid but it sure idles nice for any vacuum leak

Dirty air filter:
New

Dirty MAF and or throttle body
Inspected and clean

Is it a cylinder mis or an engine bogg??
No cylinder mis--more of a flatspot in the power delivery, almost non linear. Push the throttle more and it picks up. I did check the TPS and there are no gaps in the readout

Thanks for taking the time to reply Bill!

 

WOW! Excellent reply to the request for info! Check your Throttle body. Remove the tubing between the MAF & TB Have someone turn the key to on (engine not running) and have them depress the throttle. Watch the throttle blade. Make sure it operates smoothly and opens fully in one smooth clean sweep. It should shut smoothly also.

Check you fuel pressure at the times when the symptoms occur. Make sure your not loosing Fuel Pressure.

Turn OFF traction control and see if that makes a difference. You could be getting some false wheel spin info and causing the engine to pull fuel and spark.

When was the last time the engine was de-carboned??? Could be expierencing knock and the engine is expierencing Knock Retard (KN) Do a SEAFOAM treatment and see if that helps.

BC

Just some things to think about

 

I have a 2000 with about 110k on her. Only mod is airfilter (recently cleaned), headers and exhaust. I have changed the plugs, wires and alternator within the last three months to cure problem. I will check the ohms and the fuel filter for a leak.

Thanks for the help.

 

Also take a look at your accelerator pedal assembly. Mine did not give a code, but on the advice of another forum member, I replaced mine with one from Gene, and the flat spot is not only gone, but response is better and smoother, for what it's worth......

 

If you have access to an O Scope, you can read the output of the sensor. There are two sides. One reads high then goes low and the opposite for the other. Watching the throttle blade will also show you if there are issues with the signals from the peddle sensor or TB motor.

BC

 

Bill has got the list, codes were pulled?

 

Well a couple days ago I took the car out for an extended test drive---also wanted to test out the new valve body (Converter lockup issue---TSB out on it).

Anyhow I rigged a remote fuel pressure gauge up and taped it to the windshield. Also hooked up the scan tool----watching ignition advance and also state of front O2 sensors.

Drove and drove and drove---of course I could only make it do it a little. Ignition advance never dropped right off or backed down unexpectedly. The fuel pressure was constant and rock solid. And the O2 sensors never went into a lean state.

But like I say the problem never came up as bad as it has in the past. I have been disconnecting the battery for various things---wonder if the computer was somewhat relearning? I see some write ups about cam changes mention a relearn period. I never thought a relearn was something that these computers do.

Anyhow I guess I'll keep an eye on it and have the scan tool hooked up for the next few trips. And I think I'll check out the gas pedal too---thanks guys. Man I hate intermittents.

BTW I did check out the action of the throttle body--ran smooth and linear.

Good news is the valve body seems to be doing it's job now--fingers crossed.