Low throttle stumble and sputtering (video included)
#1
Low throttle stumble and sputtering (video included)
Hey everyone,
I have a 95 nearly stock Z28 (long tube headers with cat removed is all the mods it has) and I am running into an issue where the car stumbles when you give it about 5-10% throttle.
What is odd is that this occurs for about 10 seconds and then it clears up. Not until you let off the gas and apply it again can I get it to happen again. I am just digging into this issue but thought maybe I would ask the shade tree experts to get their opinions. For the record:
- New GM optispark about 20K miles ago
- Water pump was replaced at the same time
- New O2sensors about 20K ago
- New plugs
- Plug wires are fairly new
Car has 62K on the odometer and runs like a charm if I decide the get on the throttle.
I have a 95 nearly stock Z28 (long tube headers with cat removed is all the mods it has) and I am running into an issue where the car stumbles when you give it about 5-10% throttle.
What is odd is that this occurs for about 10 seconds and then it clears up. Not until you let off the gas and apply it again can I get it to happen again. I am just digging into this issue but thought maybe I would ask the shade tree experts to get their opinions. For the record:
- New GM optispark about 20K miles ago
- Water pump was replaced at the same time
- New O2sensors about 20K ago
- New plugs
- Plug wires are fairly new
Car has 62K on the odometer and runs like a charm if I decide the get on the throttle.
#4
11 Second Club
iTrader: (35)
I had a somewhat similar issue once which was the result of plug wire that was burnt by a header primary. Maybe check to see if any wires are close or resting on one of the primaries and may be burnt or cracked. Also would not hurt to clean the MAF with a MAF cleaner.
#5
Thanks for the replies guys. To answer your responses:
Does it have a tune for the headers? Good question. I've had the car for two weeks. Not sure if it does or not. I've ordered the OBD cable to run to my computer so once I get it I plan to log some data. I assume from that log we'll be able to tell perhaps what is going on and if this car has been tuned.
Clean the IAC? plan to do that Friday
Burnt plug wire? All the plug wires looked great when I changed out plugs over the weekend. I did notice that there was a heat shield on only one of the plugs. Probably a good idea to have heat shields on all of them right?
One other note of interest there was a code 13 stored in the computer when I had the local shop see if there was anything stored since I had never seen a SES light come on (aside from when you first start it) So I am going to go ahead and replace both O2 sensors this evening to see if I can nip this issue once and for all.
Does it have a tune for the headers? Good question. I've had the car for two weeks. Not sure if it does or not. I've ordered the OBD cable to run to my computer so once I get it I plan to log some data. I assume from that log we'll be able to tell perhaps what is going on and if this car has been tuned.
Clean the IAC? plan to do that Friday
Burnt plug wire? All the plug wires looked great when I changed out plugs over the weekend. I did notice that there was a heat shield on only one of the plugs. Probably a good idea to have heat shields on all of them right?
One other note of interest there was a code 13 stored in the computer when I had the local shop see if there was anything stored since I had never seen a SES light come on (aside from when you first start it) So I am going to go ahead and replace both O2 sensors this evening to see if I can nip this issue once and for all.
#7
TECH Resident
The car does not need to be tuned for headers. The tune is not a concern for this issue. Some people do have to tune out the EGR because some headers don't have enough back pressure to allow it to work properly. That issue will throw an EGR code.
That O2 code for sure is a concern.
You need to log some data on it to see what it's doing while the problem is occurring. Things like IAC counts, TPS data, O2 data, MAP data, MAF data, RPM data, etc.
I'm OBDII, so I'm not up on OBDI. However, if you get the right cable, there are a number of free software solutions you can used to log OBDI computer data(I think....). Will need for others to chime in on this.....
This is handy too...
https://ls1tech.com/forums/lt1-lt4-m...eshooting.html
That O2 code for sure is a concern.
You need to log some data on it to see what it's doing while the problem is occurring. Things like IAC counts, TPS data, O2 data, MAP data, MAF data, RPM data, etc.
I'm OBDII, so I'm not up on OBDI. However, if you get the right cable, there are a number of free software solutions you can used to log OBDI computer data(I think....). Will need for others to chime in on this.....
This is handy too...
https://ls1tech.com/forums/lt1-lt4-m...eshooting.html
Last edited by ACE1252; 05-19-2015 at 01:33 PM.