lt4 sputter
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lt4 sputter
She is a 96 CE lt4 (Lilith) with 120034k. A couple weeks ago I drove to the store and when I was done I started her up only to have her sputter out on me at idle like there was no fuel. I had just replaced the fpr and figured I would move on to the fuel filter. After that was swapped everything was kosher, a lil rough on idle but not like it was. Then today on my way home from work I stopped by walmart to pick up a few things. 45 mins or so later went to the car and where it normally takes a second or less to start took 3-5 seconds to start and then she tried to die on me at idle again, I have her some gas and as long as I was above 1500 or so I was good. While pulling out of the parking lot she tried it again just going into first. Then again same thing at the next red light, it felt like I had zero response from the throttle once I let off of the clutch. I was being robbed of all power between shifts at low speeds and absolutely miserable acceleration after that. I have a code reader to view the sensors but no clue on how to read them. Someone please help
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Oh yeah and after driving for a few mins I was able to sit at idle without having to hold her above 1500. Still idled rough but didn't try to die nor did she try to die while taking off from a stop. I still had that feeling of being robbed though.
Instructor
Joined: Nov 2013
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Sounds like a big vacuum leak check all your vac lines under the covers and to brake booster.
Pull vac line off fuel pressure regulator make sure it's not bad and pumping fuel I to the vac line( should be dry).
If no prob found with that try unplugging the MAF and then start it see if it clears up.
Fyi p0441 I believe is purge flow problem may need to replace the purge valve.
In very rare case I've seen valves like the purge valve go bad and short out causing computer failure hopefully that's not the case
If still no change then you need to get into checking fuel pressure/spark and a scanner that can read all the sensor data.
hope this helps.
Pull vac line off fuel pressure regulator make sure it's not bad and pumping fuel I to the vac line( should be dry).
If no prob found with that try unplugging the MAF and then start it see if it clears up.
Fyi p0441 I believe is purge flow problem may need to replace the purge valve.
In very rare case I've seen valves like the purge valve go bad and short out causing computer failure hopefully that's not the case
If still no change then you need to get into checking fuel pressure/spark and a scanner that can read all the sensor data.
hope this helps.
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The vacuum line to the fpr is fine, I checked all the others I could find and they did not appear to be leaking. I doubt the computer is fried song as it is only intermittent and not constant. The last time I had a big vacuum leak it was throwing up a lean condition code and I fixed that on the spot (it was the pcv elbow hose on the pass side) bit no codes like that now. And you are right about that code but I have replaced it 3 tones now and I think the canister itself is bad. Or the solenoid. As far as fuel pressure goes when I put a new fpr in the pressure was a couple psi below norm which is why I went to the filter next
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Instructor
Joined: Nov 2013
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The vacuum line to the fpr is fine, I checked all the others I could find and they did not appear to be leaking. I doubt the computer is fried song as it is only intermittent and not constant. The last time I had a big vacuum leak it was throwing up a lean condition code and I fixed that on the spot (it was the pcv elbow hose on the pass side) bit no codes like that now. And you are right about that code but I have replaced it 3 tones now and I think the canister itself is bad. Or the solenoid. As far as fuel pressure goes when I put a new fpr in the pressure was a couple psi below norm which is why I went to the filter next
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Just tried it, the maf read .89-.92 plugged in and .32 unplugged the fuel trim dropped to -1.6 - -.8 unplugged and .8-3.2 plugged in. What does that mean? No noticable difference but like I said it's am intermittent problem so is hard to replicate.
Le Mans Master
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Not sure, but the code is more likely an effect and not a cause issue. The first thing I would look at would be the fuel pump. When mine went out, looking back it was giving me warning cues, similar to what you were experiencing. Then on day, it ran great until I got almost home. Then it finally gave up the ghost two blocks from home.
Changing plug wires will help, but I would think if the no2 were arching that bad that it cut power would be getting a misfire code on that cylinder. Either way, if it's arching, change 'em.
But the best way to figure it out is diagnosis. Fuel pressure when symptom present, spark test and go from there.
Not sure, but the code is more likely an effect and not a cause issue. The first thing I would look at would be the fuel pump. When mine went out, looking back it was giving me warning cues, similar to what you were experiencing. Then on day, it ran great until I got almost home. Then it finally gave up the ghost two blocks from home.
Changing plug wires will help, but I would think if the no2 were arching that bad that it cut power would be getting a misfire code on that cylinder. Either way, if it's arching, change 'em.
But the best way to figure it out is diagnosis. Fuel pressure when symptom present, spark test and go from there.
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Another update: still had power loss and rough idle after the wire change. I went to the parts store and picked up MAF cleaner and TB cleaner and thoroughly cleaned both. She's running smooth as silk right now. As long as it holds up then I think that was the problem.
Max G’s
Joined: Nov 2008
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From: Monroe OH
NCM Sinkhole Donor
Hopefully it is fixed already, but if it does act up again take a look at the connector to the coolant temp sensor just below the throttle body. I had to change my connector on mine and fixed the issue. I would never have found it if we hadn't had put it on dyno and had all he parameters in front of us. We cod see the coolant temp drop to negative default number when it would loose contact.
Burning Brakes
Joined: Oct 2001
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From: TN
1996 Service manual
Hopefully it is fixed already, but if it does act up again take a look at the connector to the coolant temp sensor just below the throttle body. I had to change my connector on mine and fixed the issue. I would never have found it if we hadn't had put it on dyno and had all he parameters in front of us. We cod see the coolant temp drop to negative default number when it would loose contact.
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Update: She started acting up again so I changed the plugs from what I had to delco rapidfires and threw on MSD 8.5 wires and absolutely 0 issues. I decided to check the old plugs which were fine wires and about half of them were still at .050 gap and the others were at .070 and it was because that little nipple that sat on top of the puck was gone. My best guess is that they were not rated for my heat range and burnt off. The other reason I was thinking that is because the porcelain was covered in a white powder almost like the porcelain was breaking down due to the heat. But the delcos have no such nipple so I should be fine