95 LT1 Rough (low) Idle on Start out of nowhere
06-04-2010, 03:09 AM
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95 LT1 Rough (low) Idle on Start out of nowhere The Story:
One day, I drive the car home and park it. The car ran perfectly fine when I parked it. I go to start it the next day, and it won't idle. The idle was so rough that the car would sputter and die or level out around 300rpm. I had to feather the pedal to keep idle. It also ran pig rich.
So I pulled it into the garage. I first checked for vacuum leaks. I had one small leak thinking that was the problem. No luck. I checked all fuses inside and under the hood. All were fine.
I figured I'd do a tune up on it either way, so I replaced the plugs and wires (no signs of wear on the old plugs or wires). Then started replacing parts...
- Swapped out the MAF to another I had laying around. No change.
- Replaced the coil. Nope.
- Replaced the ICM. Nada.
- Replaced the Opti Spark (but not the cap and rotor which looked fine).
- Bought a new PCM, had it properly flashed to my car. Nope.
- Changed the oil and oil filter. Ran a magnet through the oil to see if there was any signs of metal. The oil was clean.
- I even swapped out my alternator to the semi-new one off my last 95 LT1 TA.
Then I started to get desperate...
- Pulled everything off to check the timing chain. It was a little loose, so replaced it anyways.
- Checked, cleaned ALL grounds at hot wires from the battery to everything.
- Finally, I started went through all of the connectors related to ignition and Opti. I cut some off and replaced/soldered in new wire in the sections that seemed to be questionable.
Nope. To all my efforts, the car seems to have a serious timing issue that started one day out of the blue. And yes, I am getting fuel. I know because I'm smelling/seeing RAW fuel at the tailpipes.
I even rented a scan tool, which was outright stupid since this damn car is that oddball OBD 1.5 with the OBDII connector, but OBDI setup. I tried two different scanners and they don't connect.
So here I am with a car that is making my hair fall out. This is beyond frustrating, and all I want is my baby back and running to enjoy this summer.
One day, I drive the car home and park it. The car ran perfectly fine when I parked it. I go to start it the next day, and it won't idle. The idle was so rough that the car would sputter and die or level out around 300rpm. I had to feather the pedal to keep idle. It also ran pig rich.
So I pulled it into the garage. I first checked for vacuum leaks. I had one small leak thinking that was the problem. No luck. I checked all fuses inside and under the hood. All were fine.
I figured I'd do a tune up on it either way, so I replaced the plugs and wires (no signs of wear on the old plugs or wires). Then started replacing parts...
- Swapped out the MAF to another I had laying around. No change.
- Replaced the coil. Nope.
- Replaced the ICM. Nada.
- Replaced the Opti Spark (but not the cap and rotor which looked fine).
- Bought a new PCM, had it properly flashed to my car. Nope.
- Changed the oil and oil filter. Ran a magnet through the oil to see if there was any signs of metal. The oil was clean.
- I even swapped out my alternator to the semi-new one off my last 95 LT1 TA.
Then I started to get desperate...
- Pulled everything off to check the timing chain. It was a little loose, so replaced it anyways.
- Checked, cleaned ALL grounds at hot wires from the battery to everything.
- Finally, I started went through all of the connectors related to ignition and Opti. I cut some off and replaced/soldered in new wire in the sections that seemed to be questionable.
Nope. To all my efforts, the car seems to have a serious timing issue that started one day out of the blue. And yes, I am getting fuel. I know because I'm smelling/seeing RAW fuel at the tailpipes.
I even rented a scan tool, which was outright stupid since this damn car is that oddball OBD 1.5 with the OBDII connector, but OBDI setup. I tried two different scanners and they don't connect.
So here I am with a car that is making my hair fall out. This is beyond frustrating, and all I want is my baby back and running to enjoy this summer.
Last edited by Anarchology; 06-24-2010 at 04:36 PM.
06-24-2010, 08:48 PM
#4
Why didn't you change the cap? They are most notoriously the problem with stumbling. They can look fine, but you can't see the inside of the cap. There are many small contacts running through there. Moisture/oil can soak into the cap and begin to arc those contacts. Since you've already pretty much covered the rest of your possible problem areas, I'd start there.
06-24-2010, 10:05 PM
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Why didn't you change the cap? They are most notoriously the problem with stumbling. They can look fine, but you can't see the inside of the cap. There are many small contacts running through there. Moisture/oil can soak into the cap and begin to arc those contacts. Since you've already pretty much covered the rest of your possible problem areas, I'd start there.
I just went out and bought the cap and rotor. The good news is I now have another lifetime warranty on a car part. The bad news is my credit card bill is now $160 more.
Once I get this all done tonight, I'll post an update. I'd love for this to be the issue. I want my car back out on the road.
07-23-2013, 11:47 PM
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I believe a faulty fuel pressure regulator could cause this issue. There is a user on here that had a similar problem:
I should have had the car there last Thursday, but I got everything put back together to take it for a spin down the driveway... and it wouldn't start.
After a couple attempts it started up, but the idle quality was terrible. My first thought was: "hey, someone stuck a cam in here while I wasn't looking!
"
It started smelling of gas and smoking a little bit so I shut it down. I looked around underneath the car, and noticed that the heat shield on the passengers side was wet. It smelled like gas.. Dad suggested I check some of the spark plugs, so I went back out to jack up the car, now a stream of gas poured out the driver's side header!? I pulled all the plugs, and a couple on the left side were wet, the rest looked ok. Initially I was thinking an injector was stuck open... It had been about a month since the last time it ran.
I turned the engine over by hand, and a good amount of fuel came out of cylinder #5, and the rest were dry. I cycled the key to 'on' to prime the pump a couple times, and turned it over a few more times. Now I had gas coming out both sides of the engine! Time to pull the fuel rail & injectors... I got all of the injectors out of their holes, and put paper towels under them. Then I had my brother turn the key on so the fuel pump would run. We did this a few times for good measure, and no gas would ever come out of the injectors. I turned the engine over again, and got lots of fuel out of the cylinders. What is going on??
I was lost on how fuel was getting into the engine with no injectors installed....
Just for kicks, I pulled off the intake elbow, held open the throttle body and looked inside of the intake with a flashlight while he primed the pump again. A stream of gas shot out from the right side of the intake! Surprised the hell out of me lol. So now I know where it's coming from, but why? I found the vacuum hose it was coming from, and followed it around the back of the intake to the fuel pressure regulator. Apparently the regulator crapped out in the past month of sitting. Not a big deal since we have a disassembled LT1 down in the basement.. I took the fuel rail off my car, and swapped out the regulator with the spare one. Hooked the fuel lines back up and did a test run to make sure it was good before putting everything back together. I didn't get gas shooting out all over the place, so we're good to go! I got everything put back together, and changed the oil and filter since I know there had to be some gas in the oil now.. and it started up and idled perfect, on the first try! That's always a good feeling
After a couple attempts it started up, but the idle quality was terrible. My first thought was: "hey, someone stuck a cam in here while I wasn't looking!
"It started smelling of gas and smoking a little bit so I shut it down. I looked around underneath the car, and noticed that the heat shield on the passengers side was wet. It smelled like gas.. Dad suggested I check some of the spark plugs, so I went back out to jack up the car, now a stream of gas poured out the driver's side header!? I pulled all the plugs, and a couple on the left side were wet, the rest looked ok. Initially I was thinking an injector was stuck open... It had been about a month since the last time it ran.
I turned the engine over by hand, and a good amount of fuel came out of cylinder #5, and the rest were dry. I cycled the key to 'on' to prime the pump a couple times, and turned it over a few more times. Now I had gas coming out both sides of the engine! Time to pull the fuel rail & injectors... I got all of the injectors out of their holes, and put paper towels under them. Then I had my brother turn the key on so the fuel pump would run. We did this a few times for good measure, and no gas would ever come out of the injectors. I turned the engine over again, and got lots of fuel out of the cylinders. What is going on??
I was lost on how fuel was getting into the engine with no injectors installed....Just for kicks, I pulled off the intake elbow, held open the throttle body and looked inside of the intake with a flashlight while he primed the pump again. A stream of gas shot out from the right side of the intake! Surprised the hell out of me lol. So now I know where it's coming from, but why? I found the vacuum hose it was coming from, and followed it around the back of the intake to the fuel pressure regulator. Apparently the regulator crapped out in the past month of sitting. Not a big deal since we have a disassembled LT1 down in the basement.. I took the fuel rail off my car, and swapped out the regulator with the spare one. Hooked the fuel lines back up and did a test run to make sure it was good before putting everything back together. I didn't get gas shooting out all over the place, so we're good to go! I got everything put back together, and changed the oil and filter since I know there had to be some gas in the oil now.. and it started up and idled perfect, on the first try! That's always a good feeling
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07-24-2013, 11:25 AM
#8
Have you checked the fuel pressure regulator, ive gone through a couple on my LT1.
When they go bad they start leaking fuel into the intake, causing long starts, rough idle and strong gas smell. Pull the vacuum hose off and prime the key a few times to check for fuel leaking out of it.
When they go bad they start leaking fuel into the intake, causing long starts, rough idle and strong gas smell. Pull the vacuum hose off and prime the key a few times to check for fuel leaking out of it.
