Cold Engine Stutter
01-20-2014, 04:24 PM
#1
Teching In
Thread Starter
Join Date: Feb 2012
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Cold Engine Stutter I have a 5.7 out of a 98 camaro with a 4L60e in my 68 chevelle. For a few months I have had an issue where it will cut (feels like a loss of fuel pressure) but only when the engine is cold. If I warm up the engine for several minutes it will not have this hesitation. Also, if the car is only off for an hour or two it will not happen.
I have checked the fuel pressure and its a little higher than normal at idle ~68psi. From what I have read here that's not too uncommon with the corvette filter which I used in the conversion. The pressure maintains at 55+ with the key on and not started. The racetronix pump I put in it is about a year old. The fuel pressure doesn't seem to move at all when the cutting out happens. If anything it may jump 1-2 psi and then recovers. While I was inspecting the car the other night I noticed a MAP wire was very loose and it affected the idle. I fixed the connection and it didn't solve the issue. The car has no mods with the exception of oil catch can. EGR has been deleted with block off plates in place.
The cutout is most noticeable at higher fuel consumption times such as uphill. Highway speeds seem to irritate it as well. However once the car is at normal operating temperature it goes away. I have used propane around the intake and vacuum lines with the IAC unplugged and couldn't find any vacuum leaks. I also purchased a new MAF, O2s, and TPS to see if it helped but it didn't change anything so I returned them. I put new NGK TR55s in it 2 weeks ago with no change either. I Ohm tested the wires and they were all identical resistances. They also all light up the timing light when I hook it up. The car doesn't throw any codes. Any ideas of where to look next?
I have checked the fuel pressure and its a little higher than normal at idle ~68psi. From what I have read here that's not too uncommon with the corvette filter which I used in the conversion. The pressure maintains at 55+ with the key on and not started. The racetronix pump I put in it is about a year old. The fuel pressure doesn't seem to move at all when the cutting out happens. If anything it may jump 1-2 psi and then recovers. While I was inspecting the car the other night I noticed a MAP wire was very loose and it affected the idle. I fixed the connection and it didn't solve the issue. The car has no mods with the exception of oil catch can. EGR has been deleted with block off plates in place.
The cutout is most noticeable at higher fuel consumption times such as uphill. Highway speeds seem to irritate it as well. However once the car is at normal operating temperature it goes away. I have used propane around the intake and vacuum lines with the IAC unplugged and couldn't find any vacuum leaks. I also purchased a new MAF, O2s, and TPS to see if it helped but it didn't change anything so I returned them. I put new NGK TR55s in it 2 weeks ago with no change either. I Ohm tested the wires and they were all identical resistances. They also all light up the timing light when I hook it up. The car doesn't throw any codes. Any ideas of where to look next?
01-21-2014, 04:15 PM
#3
Teching In
Thread Starter
Join Date: Feb 2012
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
The fuel lines are new and all straight. The only other mods I can think of are the rear O2s are deleted and tuner has accounted for them. The cats are also removed.
The car did something new today. I had been cruising for about 5 minutes <35. I had to wait for my wife so I left it in park and sat for a minute. She hopped in and I pulled out of the parking lot. Nothing extreme normal slow acceleration. Then I felt it start to chug a little like it would when I get up to 65+ and then BANG!! The car sounded almost like a back fire and died immediately. I coasted into a parking lot and took a look underneath. Nothing was obviously wrong externally. The bang didn't quite sound like a backfire. It felt more like metal on metal from the tranny. I could fell it really well in my feet.
The damn thing still didn't throw a code. Perhaps it may be my converter? The tranny goes through all the gears without an issue and has for a few years now. But highway speeds seem to bring this issue about more frequently than anything else. I may just take it to a tranny shop and have them check it out. Any thoughts?
The car did something new today. I had been cruising for about 5 minutes <35. I had to wait for my wife so I left it in park and sat for a minute. She hopped in and I pulled out of the parking lot. Nothing extreme normal slow acceleration. Then I felt it start to chug a little like it would when I get up to 65+ and then BANG!! The car sounded almost like a back fire and died immediately. I coasted into a parking lot and took a look underneath. Nothing was obviously wrong externally. The bang didn't quite sound like a backfire. It felt more like metal on metal from the tranny. I could fell it really well in my feet.
The damn thing still didn't throw a code. Perhaps it may be my converter? The tranny goes through all the gears without an issue and has for a few years now. But highway speeds seem to bring this issue about more frequently than anything else. I may just take it to a tranny shop and have them check it out. Any thoughts?
01-25-2014, 08:43 PM
#4
Teching In
Thread Starter
Join Date: Feb 2012
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Could a bad converter cause this type of stall? I am not sure if I should have it looked at by my tuner before I take it to the tranny shop. The car still hasn't thrown a code.