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Discussion Starter · #1 ·
I have read tons of postings on here about this problem, only thing is when they get close to fixing the problem, they quit posting:banghead: My car runs great when cold for about 20 minutes. I can drive to work, work 5-8 hrs., and drive home which is about a twenty minute drive. Once I get close to home, she starts running rich, stuttering, and bogging, and also idling very low. The SES light comes on and it smoothes out like nothing is wrong:werd: The car is pretty much stock, K&N cold air, cat delete, shift kit switch, thats pretty much all. I have already unhooked the smog pump, did the throttle body bypass, checked the plugs and wires(which were only 6 months old), replaced the plugs.....driver side was covered with black somewhat gummy soot, it gummed up the sandpaper I was using to try and clean them off a little. The passenger side was all but fouled and the porcelein on top was slightly burned. All the plug wires checked out..none burned or arching, routed away from manifold.
Didn't want to, but had a service tech from Goodyear Gemini scan my car with datalog...called LAUNCH...only code was Bank 1 HO2S Lean Exhaust. Which was why I unplugged the smog pump, I could drive a little further but not much. He said he thought I might have an intake leak so he smoked out my intake....we found nothing:banghead: The guy then rode in my car with me while doing the datalog to watch the results when it happened. Still nothing to be majorly concerned with...O2 sensors running little out of whack, but came back to what they needed to be at. I have checked every sensor, changed the fuel filter, checked fuel pressure; can't remember exact readings on pressure but I know it was where it needed to be.
I don't want to jump on the optispark bandwagon just yet...I know if that doesn't work drastic measures will be taken whether it involves a lake, bridge, brick wall, or JUNKYARD!!!:mad: If anyone has any insight on what I am experiencing please feel free to chime in. I can use all the help I can get right now. I really do love my car and just want to drive it more than 20 minutes at a time!! Thanks in advance:LS1LT1flag:
 

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Discussion Starter · #2 ·
I am new to posting on this forum, I read the before you post stuff, sorry if I posted in the wrong place!
 

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If you're getting an 1 HO2S Lean Exhaust, something is causing that when she's warmed up, making her go rich.....

My guess is the O2's. They're not too expensive off of ebay amongst other places. I was advised not to use the bosch brands and try the delco's if you can.

If your O2's are old, I'd start there.

I have heard of the EGR's going bad and causing a rough idle. If you've already removed the smog pump, it might not be a bad idea to get rid of all the smog stuff. It'll clean up the look under the hood too.

You're right, no one has posted what they found to be the fix. Losers...

EGR / AIR removal write-up with pics LT1 Z28 1993 - LS1TECH

1994 LT1 Running rich, possible causes? - Firebird Nation

my lt1 running so rich it dies - LS1TECH

94 z28 o2 | eBay
 

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Discussion Starter · #4 ·
Thanks for quick response! Haven't changed o2's since I got the car, pulled driver side out today, covered in carbon. Cleaned it with electronics cleaner and let dry for couple hours while removing rest of smog pump bs! Couldn't get passenger side o2 out, really rusted!! I'm kinda hoping that since it didn't throw a code on that side, maybe it's still ok?!?
I will post my results after I finish smog removal
 

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Also get a cable that hooks your car's dlc to usb port of laptop or notebook. Cable at ALDL OBD1 OBD cable OBDI OBD2 engine codes

Then get a scan program. Our member GaryDoug wrote an obd1 scan program especially for 94 & 95 f-bodies. Find it in sticky threads of 4th gen section. This program scans for regular codes, abs codes and sir codes. Also does running sensor scans.

While your at the link to download scan 94-95, also download the trial version of DataMaster. This scan program captures your real time sensor data to a file that can be played back in real time on DataMaster. If your having trouble pinpointing the problem, you can post .uni file to file sharing site and link it to our forum so members can run it on their DataMaster program.

Trial version good for 20 free scans and unlimited data playback.

GaryDoug plans on making his scan94-95 program do the same as DataMaster, eventually, but for now, DataMaster is king of that area.
 

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Discussion Starter · #6 ·
I was actually looking into getting a cable and tuner program after reading the posts in here about them, thanks for the advice on where to go and what to get! I finished the smog delete, luckily I do HVAC and had a bunch of black steel plugs laying around for the manifold, doesn't look the greatest but they are factory and don't look great either way!! Part store has to order my o2's to get the ACDelco's and I have to drive to work in the morning so I replaced the cleaned o2. I unfortunately didn't test the car, did make sure it would start and run just didn't drive it. I know it will get me to work in the morning and on the way back home if it's going to act up it will do it then. more tomorrow
 

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I'm savin up for the cable and program myself! Good for you, mine has a hesitation / stumble at idle to 2000rpm and I've read lots of posts that don't have an answer. It's good to have and tune for the future.
 

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Discussion Starter · #8 ·
Just got home from work and driving around for about 30-40 mins. This is the longest I have been able to drive since my issue. Don't know if all is good for sure yet, didn't want to drive endlessly on 93 octane and just burn it up, that s**t is expensive and I only run my car with 93, no lower ever. Also I swapped out the icm with a used one that a buddy had, not sure if this made a difference or not, it didn't hurt it so to speak. Seemed to idle a little smoother after I stopped for gas on the way home, which normally it would have idled a little low after my first stop.?. Gonna order my o2's off ebay, little longer to get them, but cheaper!!
 

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Discussion Starter · #10 ·
Got home from work today and driving around a little before coming home. It did it again:( seemed to run fine until I stopped at the store, shut it off, then cranked it back up? Seems to only do it when I run it for a while then stop somewhere, shut it off, and then crank it back up and go. It's almost as if something is holding it back while stuttering. While it is stuttering, I can pop it into neutral with my foot still on throttle and it clears up, but then I put it back in Drive and right away it's back again??!?? Really not sure what step to take next. Can't afford to keep throwing money at it, rally don't need a money pit! Any suggestions will be greatly appreciated.
 

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Discussion Starter · #11 ·
Just a quick thought, what would happen if I run it with the o2's disconnected? I have read numerous thoughts on this as some say it will run rich, others say the computer will revert to a pre[programmed fuel map. What do you guys think, haven't done this yet, but thinking about trying it to see if it makes a difference. I'll wait for a little feedback first!
 

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Your car is beginning to sound like you have old fashioned vapor lock. Cars from the past that had carburetors got this problem because thay had much heat under hood and no fuel return to tank to keep fuel cooler.

Our 4th gens have even more heat under hood but our fi cars have fuel that should return to tank and keep it cool.

So when you shut off your car, the heat soak is causing fuel to vaporize and interfering with fuel flowing through the injectors. The pcm is seeing a lean condition and adding much more fuel.

Not to say you actually have vapor lock, but since your chasing the problem, it is worth looking into.
 

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Discussion Starter · #13 ·
Okay so I checked my fuel pressure again just for kicks and after it was warm, say above 150*, when I turned the key on I only had around 34psi. I made sure that I had no leaks from my gauge or connector and all was good. I cranked the car and only had around 37-39psi. idling, and at first only 41psi at wot, I then disconnected the vac. from regulator and it only went up to around 45psi.?. I'm thinking fuel pump? Had a similar issue before but it seemed to fix when I replaced tps. coco, I also thought maybe vapor lock when I was talking to my father about it. I got a cheap gas cap, drilled a small hole through the vent and used it for a while, didn't seem to help or hurt so I switched back to the closed cap. Any suggestions as far as fuel pump?
 

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Discussion Starter · #14 ·
Also when I shut it off the pressure seems to climb back up, I'll post what it rises to here in a few hours.
 

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Okay so I checked my fuel pressure again just for kicks and after it was warm, say above 150*, when I turned the key on I only had around 34psi. I made sure that I had no leaks from my gauge or connector and all was good. I cranked the car and only had around 37-39psi. idling, and at first only 41psi at wot, I then disconnected the vac. from regulator and it only went up to around 45psi.?. I'm thinking fuel pump? Had a similar issue before but it seemed to fix when I replaced tps. coco, I also thought maybe vapor lock when I was talking to my father about it. I got a cheap gas cap, drilled a small hole through the vent and used it for a while, didn't seem to help or hurt so I switched back to the closed cap. Any suggestions as far as fuel pump?
your fuel pressure is within acceptable specs. keep looking.

the stock tank venting system has an inlet vent for letting air in, and a seperate evap tank and check valve for letting fumes out. you dont have vapor lock, and vapor lock is unrelated to your fuel tank

a vented cap (as i found out the hard way) is a stupid idea these cars, due to the angle of the fill neck, it will puke gas out on a full tank up a hill.
 

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Discussion Starter · #16 ·
Every forum or testing procedure I read it says these are low readings, that the pump may not be able to handle wot? I'm kinda leaning toward the pump as it didn't rise back up but to 39 and stayed there. Seems to be holding pressure fine but just not quite enough. As far as the vented gas cap, when I used it I had a wire threaded through the hole I drilled and knotted on both sides, that kept the gas from spilling out on me!
 

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Discussion Starter · #17 ·
Just a quick note of useful information, I used a quick connect fitting and hose from an old set of HVAC gauges that I had for my pressure tester. Just cut off one end of the hose and plug the pressure gauge into it with a hose clamp. The other end goes on the quick connect then the quick connect on the fuel rail. Very little gas escapes the connector when putting it on or taking it off. In order to bleed the hose after removing it, you have to use a rag or old shirt and unscrew the fitting as to not spray yourself with gas.
 

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Discussion Starter · #18 ·
Ordered fuel pump off ebay, just waiting for it to get here. I was off work yesterday, so I didn't go anywhere until my daughter go home and we ran to the store. My car ran like total s**t! This was the first I took it out and normally it would do fine for the first trip, not this time. Limped it back home, re-checked fuel pressure. It was lower than the other day barely reaching 36-37psi running at around 1500-2000rpm. While holding the throttle at this rpm the pressure would slowly drop to around 29psi then jump back to 36 and start slowly dropping again. Can't wait for fuel pump to get here, really hope this is my problem.?.
 

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Discussion Starter · #19 ·
So I got my new fuel pump today, finished installing it, followed directions to the point. Fuel pressure is up around 40-42 at idle, shut it off and the fuel pressure dropped? Just a scare I believe cause I cranked it back up, let it run for a few, then shut off again and it held steady then. BUT, unfortunately did not fix my problem!?! :( It will only run for a short time now before it starts messing up again, when it first runs, the idle is great but it seems kinda choppy. Wouldn't be surprised to find my plugs fouled again at this point. I am really lost on this one, debating between a new opti. and a Craigslist post. Like I said before I really do love my car, but I guess the feeling is not mutual.
 

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Discussion Starter · #20 ·
Just came in from running my car at dark to check for arcing across my wires or at my manifolds. As soon as I started the car, the coil was arcing all over itself! After it ran for a few and warmed up the wires started to arc across each other and at the plug boots. I just thought about it, just a month ago I had to exchange a set of wires that I bought for my 4runner because of the same thing! Going to exchange my wires tomorrow and get a new coil. Keep your fingers crossed:dontknow: I'll post results for anyone that may need it.
 
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