C4 Spontaneous horrible performance
Thread Starter
2nd Gear
Joined: May 2011
Posts: 2
Likes: 0
C4 Spontaneous horrible performance
I had to abruptly get off the peddle while under hard acceleration. Almost immediately my C4 began to sputter and dog under any attempt to accelerate. 25 was top mph. Prior to this, ran great.
Ran the obd and got code 13. Swapped out o2 sensor which cleared the fault code. Ran a little better for a few miles, and then went right back to horrible. Still no fault codes from obd. Belt tensioner is now chattering, and brakes feel like they are seizing. Does this sound like symptoms of anything to anyone? I've seen loads of great suggestions on other posts, and hope someone has any advice. Any help will be much appreciated.
Ran the obd and got code 13. Swapped out o2 sensor which cleared the fault code. Ran a little better for a few miles, and then went right back to horrible. Still no fault codes from obd. Belt tensioner is now chattering, and brakes feel like they are seizing. Does this sound like symptoms of anything to anyone? I've seen loads of great suggestions on other posts, and hope someone has any advice. Any help will be much appreciated.
Racer
Joined: Jul 2010
Posts: 308
Likes: 2
From: Kansas City MO
I'd check to be sure you didn't pop one of the big vacuum hoses off - PCV or breather - that would make it idle rough, have low vacuum (for brakes - makes pedal effort higher) and run poorly until you get it up in the RPM's.
Other than that you'll have to start looking underhood - spark plug wire fell off/burnt through, MAF and/or MAP sensor hose fell off/cracked, etc.
Other than that you'll have to start looking underhood - spark plug wire fell off/burnt through, MAF and/or MAP sensor hose fell off/cracked, etc.
Intermediate
Joined: Jul 2008
Posts: 30
Likes: 0
My Jeed does the same thing sometimes. It's usually accompanied with a breif loss of power steering and power brakes. Do you notice any other ill-effects or noises when it happens? My jeep has only done it while changing gears going uphill and the power goes once I start to turn. How about you?
Thread Starter
2nd Gear
Joined: May 2011
Posts: 2
Likes: 0
First, thanks to the great folks trying to help me. I haven't noticed any problems with PS or PB. I'll go over the plugs, wires, distributor, and any obvious vacuum hoses. Thanks for the hints, and I hope I can repay your kindness sometime.
Instructor
Joined: Jun 2008
Posts: 173
Likes: 0
From: Norman OK
Were you having any SES Code 13 problems before this event? If not, as Code 13 is an "open circuit" fault which went away with the sensor change, and it is now running like a dog and has other issues, did you break a left motor mount?
Also, as the O2 sensor wiring runs near the l/h gang grounds, did you stress the ground wiring in that area?
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
I had to abruptly get off the peddle while under hard acceleration. Almost immediately my C4 began to sputter and dog under any attempt to accelerate. 25 was top mph. Prior to this, ran great.
Ran the obd and got code 13. Swapped out o2 sensor which cleared the fault code. Ran a little better for a few miles, and then went right back to horrible. Still no fault codes from obd. Belt tensioner is now chattering, and brakes feel like they are seizing. Does this sound like symptoms of anything to anyone? I've seen loads of great suggestions on other posts, and hope someone has any advice. Any help will be much appreciated.
Ran the obd and got code 13. Swapped out o2 sensor which cleared the fault code. Ran a little better for a few miles, and then went right back to horrible. Still no fault codes from obd. Belt tensioner is now chattering, and brakes feel like they are seizing. Does this sound like symptoms of anything to anyone? I've seen loads of great suggestions on other posts, and hope someone has any advice. Any help will be much appreciated.
Why there is terrible performance now.
Check fuel pressure.
Check for a hot ignition spark( brilliant blue desired).
Check all injectors for correct impedance readings and near identical to one another.
If MAP sensor equipped make sure the vacuum line to the MAP is connected and not cracked anywhere.
Perform a fuel injector balance test if all possible.
Snap on & MATCO tools sold them black box injector balance tester in the past.
I own both and use them weekly along with a Snap On Fuel Pressure Gauge.
Injector balance test(s) performed correctly is 100 % foolproof at finding defective dynamic fuel flow rates of each electric solenoid type EFI fuel injectors at predetermined Ms/ Milli second pulse rates.
Kent Moore made same service tools for GM techs.
Have used it too.
Might have a weak or broken valvespring too if you have been driving your Vette hard & relentless pounding driving very fast if you are like myself.
BR
Last edited by 87 vette 81 big girl; May 15, 2011 at 02:37 PM.
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Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
May be my old mind is not working real good tonight or the meds have gotten to me. But I do not recall a way to balance test batch fire injectors on the car. Again maybe forgetting something.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
Very strange problem. Is the car backfiring or anything like that? You say the brakes feel like they are seizing explain more. You should be able to put into nutral can cost fairly well. give us more information on what is going on if you can
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
You have to disconnect all 8 batch fire injectors(electrical connectors) on a C4 and test them individually.
You " ignition key prime" every injector 5 seconds before testing.
Works great.
Snap On quit making their Version of a Fuel injector balance tester.
Matco tools still makes one.
The latest Snap On scanners with current 2010 -2011 has a fuel Injector built in Fuel Injector balance tester that works on several GM vehicles dating back to mid 1990's.
GM Tech 2 scanner updated has this Injector Balance test too within its operating software.
BR
Last edited by 87 vette 81 big girl; May 16, 2011 at 12:03 AM.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
falimer with that I though you were talking about under live running conditions. and yes after batch fire you should be able to watch and deactivate each injecor while live running. I was never a fan of the " black Box" deal. cause for the most part it is very easy to narrow down if it is injector or not at that point if it is injector I want to pull them and have spray patteren.leakage ect checked out. It always seemed like a waste of time to me.