Will PayPal Someone $25 If They Can Figure Out What's Wrong

[edwardzracing]

Alright... this is not exactly a Gen III problem, but there isn't a lot of activity in the Vortec forum, so I wanted to make the post here. I cannot for the life of me figure out what's wrong with my truck.

Truck is a 2000 S-10 with the 4.3L Vortec V6 and A4.

I've had an issue with the truck getting warm and running like royal ass. It misses HORRIBLY like it's running out of gas. I just put a new fuel pump in it, fuel pressure seems fine. When cold, the truck runs excellent... like nothing is wrong. Heats up, runs like shit. I replaced the o2 sensors and it seemed to fix it, but nope, problem is still there. I tried disabling the EGR to eliminate that, and that was no fix. Unplugged the MAF, still no fix. Unplugged IAT, still no fix.

Should I try unplugging the EGR rather than disabling it via the computer? I recorded some data... hopefully I recorded the right PIDs to help you guys. I didn't get a reading on injector duty cycle. Could one of those be somewhat plugged? I'd think it'd run like crap ALL THE TIME if that were the case... not just when it's hot. I'm going to post 2 logs. I started recording AFTER it began acting up... this was the worse it's ever ran. I parked the truck and worked on a friend's computer for a few hours... came back out and recorded a bit of data on my way back home after it cooled down.

Maybe someone can look these logs over and get an idea as to what might be going on. I'm running out of ideas. Should I try unplugging the o2's and see what happens? They're brand new so I don't know how they could be the problem. Anyways, like the title states... if someone can give me an idea that works and resolves the issue... I'll send 'em a quick $25.00 for their efforts in helping. No PayPal? Hell, I'll send you a money order. I know it's not much, but I'm desperate for some kind of help. The tune on the PCM was STOCK prior to my temporary effort at disabling the egr. I have not changed anything else.

Thanks for reading.

Brad

[GAMEOVER]

Post up the current tune

[mr.prick]

Post up the current tune

And the stock tune as well.

[waterbug1999]

To me, it sounds like a bad temp sensor, but its readion ECT. Not familiar with the vortecs, but my Trans Am did the exact same thing.

[edwardzracing]

Alright... posting up the current and stock tunes. I smoothed VE tables on the current tune, and I did a little tweaking to the transmission tables as well on my current tune; just to firm up the shifts a little, but it's definitely not transmission-related as I can put it in neutral after it's heated up, try to hit the throttle and rev it and it still misses like crazy. Here they are though. Remember, even after reloading the stock tune it still runs like ass after heating up. Willing to try just about anything at this point.

Thanks to everyone for their input. Glad to see there's some interest.

[Big Mike]

Does it idle smooth even when hot?

Any DTC codes? Does the CEL blink when it's running poorly?

Last time I had a Vortec 4.3 do what you're describing it was the ignition coil weakening when it got hot causing misfiring. Turns out this is NOT AT ALL UNCOMMON. Seem's there well know for it.

[edwardzracing]

Does it idle smooth even when hot?

Any DTC codes? Does the CEL blink when it's running poorly?

Last time I had a Vortec 4.3 do what you're describing it was the ignition coil weakening when it got hot causing misfiring. Turns out this is NOT AT ALL UNCOMMON. Seem's there well know for it.

Yeah, I'm wondering if I have a coil going bad myself. No DTC's or check engine light... check engine light never flashes or anything. It seems to idle just fine, even while hot, but once I get into the throttle... even really slowly... it bogs, and misses... doesn't backfire... just acts like it's out of gas. Even in park. GRRRR!! Thanks for responding :) Think it over.

[Lextech]

The distributor/cam sensor gears go bad also. They will get sharp edges on the teeth. Just a thought.

Jeff

[joecar]

Warm Log:
HO2Sx1 voltages:
- go to zero immediately when TP is opened and trims shoot up very high;
- show average cycle time 0.5s (seems too short);
MAF:
- stays low like RPM, but does not really mirror RPM;

There may be an air leak in the exhaust;
There may be a problem with the MAF sensor;
There may be some bad ground connections;


Cold Log:
HO2Sx1 voltages:
- go to zero some time after TP is opened;
- show average cycle time 1.5s (seems about right);
MAF:
- follows/mirrors RPM;



BTW (unrelated): HO2S22 is flatlined zero... bad connection...?

[edwardzracing]

Warm Log:
HO2Sx1 voltages:
- go to zero immediately when TP is opened and trims shoot up very high;
- show average cycle time 0.5s (seems too short);
MAF:
- stays low like RPM, but does not really mirror RPM;

There may be an air leak in the exhaust;
There may be a problem with the MAF sensor;
There may be some bad ground connections;

Would an air leak in the exhaust be something I could hear (exhaust leak)?? Wouldn't it have to be a pretty big exhaust leak to make it run that bad? I can take a video from inside the truck and let you both hear and see what's going on.

I tried running it without the maf, and the problem still exists. Could it still play a role in this problem even while unplugged?

No idea where to start with ground connections. Would it be a ground that has something to do with something that requires more voltage after the truck heats up? Wouldn't a bad/loose ground cause a poor condition regardless of temperature?


Cold Log:
HO2Sx1 voltages:
- go to zero some time after TP is opened;
- show average cycle time 1.5s (seems about right);
MAF:
- follows/mirrors RPM;

BTW (unrelated): HO2S22 is flatlined zero... bad connection...?

Is that the o2 behind the cat? I don't know if it's even working... I didn't think much of that sensor as I wasn't sure it had any effect on this problem. I tried disabling cat protection and that didn't change anything either. Would engine coolant temperature have anything to do with this issue?

[jetblast]

can you post an open loop log?. let the eng. sit overnight and do a 30% to 40% tps run all before the coolant temps go above 130f.

[hquick]

When you say you tried running it mafless....did you set the tune up to be in speed density? Or just unplug the MAF and try running it?
If it's not setup properly for SD (speed density - Mafless) and you unplug the MAF....it'll run like crap and have no acceleration.
MAF's are 'extremely' vulnerable to heat.

[edwardzracing]

UPDATE - Well it's definitely not ignition related... unless it's the distributor itself. I replaced ignition coil, ignition control module, rotor, and distributor cap... no fix. It's getting worse too. 25 miles of freeway cruising and then it really starts bucking, and missing. Any slight incline and it's really no good. Still seems to run fine when it's cooled all the way off. I had to park for 10-15 minutes today because after getting off the freeway, I was really holding up traffic. After parking for those 10-15 minutes... the truck ran better, but still acted up. Ugh.


When you say you tried running it mafless....did you set the tune up to be in speed density? Or just unplug the MAF and try running it?
If it's not setup properly for SD (speed density - Mafless) and you unplug the MAF....it'll run like crap and have no acceleration.
MAF's are 'extremely' vulnerable to heat.

I've ran the truck without the MAF in the past, and it ran just fine... I did this last summer when I got EFILive and was trying to learn how to tune in speed density... I never made any changes because I didn't have a wideband, but yeah, it ran fine without the MAF. Doing the same thing now (loading a "tune for speed density logging" tune and unplugging the MAF) changes nothing and the truck still runs absolutely horrid after getting hot.


can you post an open loop log?. let the eng. sit overnight and do a 30% to 40% tps run all before the coolant temps go above 130f.

I will do this tomorrow morning and post it up in the afternoon.

So, after dropping close to $200 for all this ignition stuff, I'm still up shit's creek. Any other thoughts before I light said truck on fire? Thanks to everyone for reading and sharing their thoughts and ideas.

[joecar]

How/where does it get it's crank sensor signal...? From the distributor...?

[sixltrbtr]

When did this all start? I would also like to know if you can make it go into open loop while it is hot and does it still run bad then?

[drdarthinvader]

something simple as a spark plug lead?

[chevy052500hd]

What is your fuel pressure? You should be in the 60psi range. Have you changed the fuel filter? What spider setup do you have? Is it the original or the new multi-tec 2 design. See if you can shut off individual injectors with efilive I am not sure if you can do that with dvt.. that way you can narrow down if it is an injector issue.

[onegonewild]

I have dealt a lot with these trucks in the past and i currently own 2 of them. The problem with fuel pressure is not evident here unless you are backfiring into the intake. These trucks have a very hard time starting if the fuel pressure is low and tend to backfire when mashing the gas whether driving or idling.

From your description, I would make sure the distibutor is almost dead on 0 degrees. you should get a code if it is off but the cam sensor is in this distributor and can cause late or early fuel. The crank sensor is on the front timing cover and hardly ever goes out. I would like to see a full log of STFT, crank, cam, HO2s, TPS, Timing and so on to better analyze this for ya.

I hate saying this, but i ran into a van the other day that was a 2000 model and had the v6 with the same issues. I had perfect data across the board on this van and replaced the pcm which resolved the problem. Van ran pretty decent when it was cold but literally would not rev past 3000rpm as it warmed up. To better describe it, it felt as if the van had a MSD box on it that was cutting out the ignition at 3000.

[edwardzracing]

How/where does it get it's crank sensor signal...? From the distributor...?

I guess the crank sensor signal is in the front of the motor. I believe the cam sensor is on the distributor.


When did this all start? I would also like to know if you can make it go into open loop while it is hot and does it still run bad then?

The problem was very minimal for quite some time... then the fuel pump died and I assumed that was what was wrong. I fixed that, and the problem still existed. It wasn't anywhere near as bad as it is now, but it definitely would show signs of a problem after heating up. So I then replaced the o2 sensors and the fuel filter... after that the truck ran damn good. I thought for sure I had fixed the problem, but not more than a week later the problem reappeared, and it's only gotten worse. Truck still runs damn hard for a truck with 150,000 miles... WHEN COOLED DOWN, lol. Heats up and it's a joke.


something simple as a spark plug lead?

I guess it's possible... plug wires are next on my list. I have to see what money I have left after paying my insurance. I really don't think it's spark-related. I'm beginning to wonder if the fuel pump is not adequate enough or something. It seriously feels like it's running out of fuel.


What is your fuel pressure? You should be in the 60psi range. Have you changed the fuel filter? What spider setup do you have? Is it the original or the new multi-tec 2 design. See if you can shut off individual injectors with efilive I am not sure if you can do that with dvt.. that way you can narrow down if it is an injector issue.

Not sure what the fuel pressure is... I assumed it was alright, but I honestly can't say for sure. I need to get a gauge on there and see what's going on, especially when it starts acting up. I wish there were a way to monitor it via EFILive, but apparently there isn't (at least not that I know of). I have no idea what the spider setup is, let alone a multi-tec 2 design. No DVT with these PCM's, so I can't disable injectors. I'm going to try and Sea Foam the truck via the method posted over at LS1tech and see if it helps at all... last time I did it, it worked great. That was a long time ago though.


I have dealt a lot with these trucks in the past and i currently own 2 of them. The problem with fuel pressure is not evident here unless you are backfiring into the intake. These trucks have a very hard time starting if the fuel pressure is low and tend to backfire when mashing the gas whether driving or idling.

From your description, I would make sure the distibutor is almost dead on 0 degrees. you should get a code if it is off but the cam sensor is in this distributor and can cause late or early fuel. The crank sensor is on the front timing cover and hardly ever goes out. I would like to see a full log of STFT, crank, cam, HO2s, TPS, Timing and so on to better analyze this for ya.

I hate saying this, but i ran into a van the other day that was a 2000 model and had the v6 with the same issues. I had perfect data across the board on this van and replaced the pcm which resolved the problem. Van ran pretty decent when it was cold but literally would not rev past 3000rpm as it warmed up. To better describe it, it felt as if the van had a MSD box on it that was cutting out the ignition at 3000.

I hope to hell it's not the computer, but at this point, who knows? Probably worth trying... they're really not that expensive (at least the ones I can find on eBay, hopefully they are what I need). Anyways. I'm pretty sure the distributor hasn't moved... no DTC's to say it has. I will try to get you a full log of the information you requested. Would you know what PID's I need to monitor for Crank and Cam?

Thanks for everyone's input and responses. Hopefully I can figure this out. I will post a log file I created from start up (cold) to fully warmed up when it started missing today. Expect that in about an hour. Doubt anything will stand out, but I guess we'll see.

Thanks again to everyone for reading.

[GAMEOVER]

I have an 98 s-10 and your describing something that happen to my truck after I put in a new fuel pump...On my truck it was the fuel pressure regulator inside the intake, next to the injector spider's... The 1998 & Up 4.3 Vortec's are notorious for leaking fuel inside the intake.

[Big Mike]

I was under the assumption that you've already checked the pressure with a gage. If you haven't monitored fuel pressure under driving conditions don't do anything else until you do. Fuel pumps new or old can and will cause issues such as this when they're defective. The pump gets warm, pressure drops down, and they run like s#%t. Been there many times myself.

No point in chasing your tail while throwing money at it.

[onegonewild]

I agree with the fuel pressure. Make sure it is perfect at idle and under a load if possible. Have a friend brake torque it while you stand to the side and watch the gauge. If distributor is dead on and the ignition system is not dragging ass at higher temperatures, check your data and see if the STFT is leaning out or if the computer is pulling timing.

What pcm are you using? The black one or the LS design with 2 big connectors?

[chevy052500hd]

I bought a fuel pump from advanced auto when my factory pump took a dump acted exactly like what you are describing, Replaced it, about 6 months later the truck started doing it again, check the fuel pressure and it was not where is should have been, ended up being the pump again, this time replaced it with a factory pump and have never looked back at it. Even though the pump from advanced had a lifetime warrenty, I don't want to be replacing it for a lifetime. just some food for thought.

[edwardzracing]

Damn, I should have monitored short term fuel trims on the log I did today. I'm going to post two screen shots... one from a log of the truck hot, and one from the truck mostly cooled down. The hot one is ugly.

HOT

http://www.haleracing.com/images/efilive_screenshots/2000_s10/heat_problem/HotTruck.jpg

COOL

http://www.haleracing.com/images/efilive_screenshots/2000_s10/heat_problem/CoolTruck.jpg

Does this tell anybody anything?? I'm starting to believe the pump may be trash. I'm going to make sure the grounds for it are good, clean and tight, check the pressure and then go from there. The screenshot definitely doesn't look pretty.


I agree with the fuel pressure. Make sure it is perfect at idle and under a load if possible. Have a friend brake torque it while you stand to the side and watch the gauge. If distributor is dead on and the ignition system is not dragging ass at higher temperatures, check your data and see if the STFT is leaning out or if the computer is pulling timing.

What pcm are you using? The black one or the LS design with 2 big connectors?

I'm pretty certain it's the black one, but I'd have to look and make sure.

Thanks again to all!

Brad

[chevy052500hd]

pump looks like it is trash, had the same stft values. verify the fuel pressure, should tell you all.

[chevy052500hd]

Here is a fuel system trouble shooting from gm's service manual. Should help point you in the right direction

[edwardzracing]

Here is a fuel system trouble shooting from gm's service manual. Should help point you in the right direction

Thank you!

[TAQuickness]

Take a look at the scan or tune help menu under tutorials. There is a write up in there for logging fuel pressure. It's LS1 specific, but covers enough ground that you should be able to implement on your vehicle.

[edwardzracing]

Verdict is in... fuel pump. Apparently the one I used to replace my original must have been crap. Luckily I paid under $50 for it via eBay... must not have been an OEM pump. Get what you pay for huh? Luckily I had an extra F-Body fuel pump sitting in my spare parts bucket. Jacked up the truck, lifted the bed (again, ugh) and pulled the pump. The F-Body pump was clearly a little bigger in width, but it was the same height so I figured I'd give it a shot. I had some pretty good fuel injection hose, so I went with it... sure enough it primed and fired up. Went for a drive... approximately an hour and a half, no issues... truck runs hard for a little 4.3 with 150,000 miles. Hopefully (knocks on wood) I haven't spoken too soon, but it definitely seems like things are normal again. I'll keep everyone posted if things change and go south again.

As for the reward, I guess it would go to Big Mike. He seemed to be the first to mention the fuel pump. I probably should have a done a better job at describing the problem. I kind of falsely claimed the fuel pressure was okay, but at the same time I claimed it felt like the truck was running out of gas when it got hot (which would obviously be a fuel pressure problem). I honestly didn't know there was a fuel pressure problem, I just know it FELT like one. Oh well, hopefully the problem is solved now. Big Mike, feel free to PM me if you'd like... I'll stand by my word and shoot you a quick $25 if you have a PayPal account. Thanks to everyone for their insight. Hopefully I won't have anymore posts regarding truck problems... only questions about the Camaro and tuning it, lol. Thanks again!

Brad

[98 tigershark]

Hello TAQuickness,

Do you mean LS1 PCMs right. I have used them on transplanted LS2,LS6,Ls3, LS7 and L92s into cars with the LS! PCM.
Let me know as the directions worked well for me and was a very good suggestion by you I thought.
98 tigershark


Take a look at the scan or tune help menu under tutorials. There is a write up in there for logging fuel pressure. It's LS1 specific, but covers enough ground that you should be able to implement on your vehicle.

[Big Mike]

Thank you for the offer Brad but theres certainly no need for payment. Like many here I'm only here for two reasons. First, to learn. And second, to help out with input whenever I can. Financial gain isn't amongst it anywhere. Simply hearing that the truck is working correctly again is more than enough "payment" for me and I'd like to think that if and when I had an issue the guys here would be just as happy to help me out. :wave:

Mike

[98 tigershark]

A bad fuel pump did the same thing and I had to use 3 pumps before I got a good one. That took me almost a year to fix as I also threw money at it. Fuel pressure is a problem for me again as this time the tank condensates and freezes water in the line in the winter and now I carry a bottle of stop fuel freeze, the yellow bottle and not the red. I always check the fuel pressure as a matter of maintenance now. Like checking the oil on all my cars.
98 tigershark

[sixltrbtr]

Glad to hear you got it fixed. Hopefully you used submersable fuel hose. If not the fuel could eat through the outer hose and the fuel pressure will burst the inner part of the hose.