C4 surging light throttle
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
C4 surging light throttle
Title says it all. Looking for thoughts on why my recently acquired c4 was driving perfectly fine on Wednesday. Sat outside in heavy rains on thurs/fri.
Which, side note, I found out the driver side window/door is leaking. The driver side carpet was wet. weatherstripping job is in my future.
but I go to drive it today, and it accelerates fine, but steady state light throttle cruising it’s surging. Idle is steady. It’s only when I’m cruising in higher gear.
if this was an old school small block, I would describe it as hitching, as in the timing was too advanced.
I would also appreciate anyone’s recommendation on a obd scanner.
Which, side note, I found out the driver side window/door is leaking. The driver side carpet was wet. weatherstripping job is in my future.
but I go to drive it today, and it accelerates fine, but steady state light throttle cruising it’s surging. Idle is steady. It’s only when I’m cruising in higher gear.
if this was an old school small block, I would describe it as hitching, as in the timing was too advanced.
I would also appreciate anyone’s recommendation on a obd scanner.
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
Melting Slicks
Joined: Jul 2005
Posts: 2,202
Likes: 302
Could just be in need of a general tune up. Plugs, wires, verify fuel pressure, change fuel filter, etc. Always good to start with the basics when acquiring a used car.
For scanners, I'd check ebay. Probably loads of them on there.
Or get an ALDL cable and download TunerproRT.
For scanners, I'd check ebay. Probably loads of them on there.
Or get an ALDL cable and download TunerproRT.
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
Could be. I changed the oil and air filter when I got it.
pulled a plug and it looked in decent shape.
ill get a fuel filter. Might as well. Although I think a fuel filter would pose more problems under heavier acceleration vice light cruising.
do all OBD1 scanners work the same? I’m very new to this idea of engines with computers. To be honest, I’m already not a fan. There’s nothing wrong with carburetored small blocks lol maybe I shoulda stayed in my lane.
pulled a plug and it looked in decent shape.
ill get a fuel filter. Might as well. Although I think a fuel filter would pose more problems under heavier acceleration vice light cruising.
do all OBD1 scanners work the same? I’m very new to this idea of engines with computers. To be honest, I’m already not a fan. There’s nothing wrong with carburetored small blocks lol maybe I shoulda stayed in my lane.
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
Can anyone explain the difference between an
ALDL cable, 16pin with tunerproRT
or a snap-on mt2500 off of eBay?
Is there a difference in capability? Doing some other searches, it seems the snap on can make changes to the ecm but the aldl cable is just for monitoring data?
Does the snap on monitor data as well?
thanks
ALDL cable, 16pin with tunerproRT
or a snap-on mt2500 off of eBay?
Is there a difference in capability? Doing some other searches, it seems the snap on can make changes to the ecm but the aldl cable is just for monitoring data?
Does the snap on monitor data as well?
thanks
Melting Slicks
Joined: May 2003
Posts: 2,076
Likes: 281
From: Dyersburg TN
The Snap on will just work. TunerPro RT (which I use) will take a little tinkering to get the settings right to take to your Corvette, but is really cool after that. Both are good options. I also have an older Auto Xray unit that does OBD 1 and 2.
The nice thing (to me) about TunerPro RT is the ability to make the display large so I can easily peek (not stare) at it while driving. Also software is free and cable is usually less cost than dedicated device. Either option will get you what you need and both will be among the lower amounts you will spend over the life of your Corvette.
The nice thing (to me) about TunerPro RT is the ability to make the display large so I can easily peek (not stare) at it while driving. Also software is free and cable is usually less cost than dedicated device. Either option will get you what you need and both will be among the lower amounts you will spend over the life of your Corvette.
Can anyone explain the difference between an
ALDL cable, 16pin with tunerproRT
or a snap-on mt2500 off of eBay?
Is there a difference in capability? Doing some other searches, it seems the snap on can make changes to the ecm but the aldl cable is just for monitoring data?
Does the snap on monitor data as well?
thanks
ALDL cable, 16pin with tunerproRT
or a snap-on mt2500 off of eBay?
Is there a difference in capability? Doing some other searches, it seems the snap on can make changes to the ecm but the aldl cable is just for monitoring data?
Does the snap on monitor data as well?
thanks
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
Thanks.
I think I’ll pursue getting a snap on.
I did some more elaboration today. There was no surging until the coolant warmed up.
makes me think it’s the coolant sensor or maybe the maf.
once it was warmed up it would randomly surge for a couple minutes, then act right for a few miles, then start surging again.
Ima disconnect the maf and try to clean it. Look around and try to identify any loose/intermittent connections.
I think I’ll pursue getting a snap on.
I did some more elaboration today. There was no surging until the coolant warmed up.
makes me think it’s the coolant sensor or maybe the maf.
once it was warmed up it would randomly surge for a couple minutes, then act right for a few miles, then start surging again.
Ima disconnect the maf and try to clean it. Look around and try to identify any loose/intermittent connections.
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Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
I cleaned the maf and throttle body, and the associated connectors.
it drives right now, no stumbling or surging. But now I have a check engine light lol.
stumbling and surging=no light
runs smoothly=check engine light.
im doing some more reading and I’m wondering if when it’s running open loop everything is fine, which it switches to closed loop it has a problem with one of the gazillion sensors.
it drives right now, no stumbling or surging. But now I have a check engine light lol.
stumbling and surging=no light
runs smoothly=check engine light.
im doing some more reading and I’m wondering if when it’s running open loop everything is fine, which it switches to closed loop it has a problem with one of the gazillion sensors.
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
I spent the better part of 45 mins looking for it. Contacted the PO. He said you have to remove the trim under the steering wheel, it’s up there.
do the CEL codes stay stored? When I restarted it I no longer had a code and it was stumbling some on light accel. I think cleaning the MAF was just coincidence with the intermittent fault
do the CEL codes stay stored? When I restarted it I no longer had a code and it was stumbling some on light accel. I think cleaning the MAF was just coincidence with the intermittent fault
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
Got the lower dash panel off, jumpered pins 4 and 12. Got the following codes
H44 H47 H50 H77 H78 h28
44 says driver O2, 47 is knock sensor. Hopefully those two are related.
50 says system voltage low. Not sure why that’s there, battery is in good health and charges. So I think.
77 and 78 is because the PO wired the fans to be on 100% of the time.
h28 is because, I’m assuming, the 1-4 shift lockout is disabled.
I guess that goes along with my theory, drives fine when cold, ie open loop. When it switches to closed loop it gets bad data from O2 sensor.
H44 H47 H50 H77 H78 h28
44 says driver O2, 47 is knock sensor. Hopefully those two are related.
50 says system voltage low. Not sure why that’s there, battery is in good health and charges. So I think.
77 and 78 is because the PO wired the fans to be on 100% of the time.
h28 is because, I’m assuming, the 1-4 shift lockout is disabled.
I guess that goes along with my theory, drives fine when cold, ie open loop. When it switches to closed loop it gets bad data from O2 sensor.
Burning Brakes
Joined: Aug 2023
Posts: 1,093
Likes: 35
From: San Diego
A battery needs to be above 12.5 to be "good". The charging system takes a long time to overcome a battery that hasnt been on a tender for a while.
Bad O2 will not make Knock Sensor bad. But, without actual live data you cant tell what either is doing. O2 sensors run off of .1 volts. Knock sensors, if they go bad are rare, but check wiring first, see if its loose, broken etc..
Bad O2 will not make Knock Sensor bad. But, without actual live data you cant tell what either is doing. O2 sensors run off of .1 volts. Knock sensors, if they go bad are rare, but check wiring first, see if its loose, broken etc..
Thread Starter
Burning Brakes
Joined: Dec 2017
Posts: 1,043
Likes: 414
2023 C3 of the Year Finalist - Modified
Can anyone share what tool they use to remove the driver side o2 sensor?
the o2 socket I have doesn’t work. The metal shielding around the cat prevents it from seating fully
the o2 socket I have doesn’t work. The metal shielding around the cat prevents it from seating fully