# 5.7 Vortec. No Power



## Racer593 (Aug 20, 2009)

OK everyone here we go. 99 Suburban K1500 4x4 5700 Vortec. 
This started while plowing at the end of the season last spring. 
When you start it, it starts, runs and idles well. after a short bit of driving(couple miles) it acts like it is starving for fuel if you give it more than about 1/2 throttle. I'm talking horrible here. Falls on it's face and starts to miss and loses speed. IF you pedal it it will gain speed but just at a slower pace. Basically you can't pass or gain speed in a hurry.
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Here's what has been replaced so far.
Fuel pump and filter
Air filter 
all 4 O2 sensors
Coolant temp sensor 
Crank pos sensor(Showed bad)
ECM(worked for someone on another site)
Cap, rotor, plugs and wires(AC Delco and Packard)
Exhaust gasket BEHIND convertors(Blew Out)
Not an electronic gas pedal.
((((((((((((((((((No SES Light at all))))))))))))))))))
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If you get mad and mat it and hold it on the floor, it smells very hot in the exhaust, I mean like you're welding it hot. 
I've run it with no O2 sensors in it, its not plugged convertors. If you shut it off while it's acting up and wait about 10-15 seconds and restart it, it goes away for a bit, like something resets. It has been scanned with a Tech II, top of the line Snap-On scanner, been to three different shops, INCLUDING GM Goodwrench, and while all have had suggestions(read:throw lots of money at it), no one has been able to fix it yet. 
Now I'm laid off, and I don't have the money for the truckside mount on my new truck, so I really need to get this thing figured out.
I've read hundreds of pages on here over the last month or so(laid off so I've got the time)and haven't found this type of problem for anyone else.
I know there are many VERY knowledgeable members on here. I just hope someone has an idea. Thanks in advance.
Sorry for the long post.

Chris :realmad:

P.S. It's also my wife's 'Burb now so I REALLY need to get it fixed now!! LOL


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## cubicinches (Oct 19, 2008)

Have any of the shops checked the mass air flow sensor? Have it scanned for erratic gm/sec MAF readings, or try a know good one. Typically, this would set a code, and you'd have a check engine light... but anything is possible.


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## Racer593 (Aug 20, 2009)

Yep. Replaced it also. Sorry, forgot that one. I've done so much over the past 9 months its hard to remember everything.
Thank you though.

Chris


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## Sydenstricker Landscaping (Dec 17, 2006)

did you do the fuel pressure regulator as well??


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## Luke_P (Sep 16, 2008)

google 1996-2000 vortec csfi recalls\service bulletins they are a known piece of crap(by gm) that will give you symptoms of all kinds similar to what you are describing. There is a updated gm part that gets rid of the poppet style injectors and replaces them with real ones. You can also get them aftermarket now from napa etc I put one in my 96 k2500 similar symptoms to what you are describing very frustrating. If you aren't seeing any codes and looking at what else you have done I would investigate this as well as weak fuel pressure (I know you did the pump but you did not say if they actually put a gauge on it)


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## Racer593 (Aug 20, 2009)

Thanks Sydenstricker & Luke P. Pump pressure was over 62psi while driving, under load. Seems like something else about injectors has sort of come up before in my travels. I'll have to check into the injectors and possibly the regulator. Any ideas are welcome!! LOL

Chris


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## Racer593 (Aug 20, 2009)

One thing I haven't tried is injector Cleaner. Reading around found a few that have done it and it cleared it up. A few bottles of injector cleaner is ALOT cheaper than the 500 dollar conversion right now. Thanks Luke for pointing me in that direction.

Chris


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## Luke_P (Sep 16, 2008)

If it is indeed your injectors and the cleaner works I would consider it borrowed time when GM first started cleaning them they found it pretty ineffective and moved to component replacment (I forget the exact timeline but at first they switched the bad poppets if they could then started using the updated part) and eventually went back to cleaning or poppet replacement because doing it right was costing to much. Check gm parts direct online I couldn't get it because I am 1 in canada and 2 nedded it yesterday my local stealership was $900 or so and napa around $600 (canadian). GM parts direct was like 300 for the gm part or something like that I looked on there the other day to find one for a friend and couldn't find it (forgot the #) but I am sure they will have it. May be worth looking into for down the road if the cleaning works.


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## brad96z28 (Aug 21, 2005)

Sounds like u may have a fuel volume issue U could have 62 psi and crap for volume. Was a volume test performed?


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## Racer593 (Aug 20, 2009)

brad96z28;814253 said:


> Sounds like u may have a fuel volume issue U could have 62 psi and crap for volume. Was a volume test performed?


Nout sure but probably just pressure. You know small town, small shops...AND a tight a$$ that just can't bear to take it to the stealership.(one of my guys IS a Goodwrench service manager with a Tech II at home though!!!!)

Chris


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## scottL (Dec 7, 2002)

MAP Sensor is all you really have left.

I had issues with the MAP sensor. It did stumble but, not too bad - mostly at cruising speed and throttle.

Your description sounds exactly like the injectors. The older design would get to a point and simply fail - no codes on mine. Replaced them with the new version and bingo!


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## ahoron (Jan 22, 2007)

Fuel pump wasn't from autozone or advanced was it? Had same problem replaced injectors and everything else. Then replaced the pump with ac delco problem solved.


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## Racer593 (Aug 20, 2009)

Nope AC Delco... I heard that before I changed it.
Thanks

Chris


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## NICHOLS LANDSCA (Sep 15, 2007)

Vac leak/intake gaskets?


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## brad96z28 (Aug 21, 2005)

Racer593;814266 said:


> Nout sure but probably just pressure. You know small town, small shops...AND a tight a$$ that just can't bear to take it to the stealership.(one of my guys IS a Goodwrench service manager with a Tech II at home though!!!!)
> 
> Chris


Even with a tech 2 It is only as good as the guy using it.


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## Racer593 (Aug 20, 2009)

He was actually born into a family owned Chevrolet dealership that was a staple here in town for years.Small town, dealer got bought up by bigger dealer from the city then they closed it about 2 yrs later. But he's had a wrench in his hand since day one!!! I do agree, though,you do have to have some knowledge to use it......
....Correctly.

Chris


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## scottL (Dec 7, 2002)

I was just thinking ....... 62psi seems low. I thought the fuel pressure test was to put the gauge on. Turn the key to build fuel line pressure. I believe 70-90 psi. Then turn the key and see where the pressure is at 1 minute. If it drops below 68 then your pump is bad. I remember going through 3 brand new GM pumps before finding a good one. It can happen.


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## 2COR517 (Oct 23, 2008)

brad96z28;814253 said:


> Sounds like u may have a fuel volume issue U could have 62 psi and crap for volume. Was a volume test performed?


It would seem to me if the pump can maintain 62 PSI while the engine is running, volume would have to be sufficient.


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## cubicinches (Oct 19, 2008)

60 - 65 psi is the correct fuel pressure. If it maintains 62 psi while running, the pump is fine.


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## Banger (Sep 12, 2008)

I have a few chevys in my fleet and I had simular issues as you descibed or DEAD ON!!!!

* It turned out to be the TPS (throttle Position Sensor) both times. *

Not sure if yours has a ICM (Ignition Control Modual) but simular issues may happen as well before full failure of that unit.

Also I had the exact same issue before on a older chevy I had years back It was a 92 K1500 with a 350 and throttle body injection.I had a *Spark leak *.. I had brand new plugs on the truck so I never thought of rechecking them. Just happened to open my hood at night and noticed the spark jumping ever so lightly on or near the exhaust manifold.The wires were all routed away from the exhaust but I guess when it got windy under the hood while driving or plowing ect... the wire in question touched the manifold and melted a section I couldnt even see. 
Probley not your issue but worth checking!

Not sure if you threw a code or not. Dont recall seeing you did but from what I know... *With no codes in the computer this is saying it is a mechanical problem and not an electrical problem.*

I'm banking on the TPS though. *It will forsure cause everything you said without doubt!*! However, you should have a code though. Might want to reset the PCM and see if it trips a code after some time.


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## Racer593 (Aug 20, 2009)

Thanks Banger. I have to check but I seem to think it's(TPS) been changed. So many sensors tested or changed its hard to remember. Makes sense though.

Chris


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## Banger (Sep 12, 2008)

Yea check it out FORSURE, Dont assume becuase it does sound 100% like what mine did. I had to replace it 2 times in 2 years on one truck. They are not expensive to buy. If I remember they under 20 bucks. 

I'm betting its the TPS but if its not just return the part. They give you a hard time returning it, tell them its not the right one and you already got the right one from another store  

Only thing that makes me wonder is why you dont have Codes? Do you have them or not and what numbers are they? I'm guessing your truck is OBD2 not OBD1 since its a Vortec.


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## Racer593 (Aug 20, 2009)

Finally threw a light and code today. Drivers side upper o2. watched the values reading out on the scanner and it read 7 with no change while the other upper was adjusting in the 120-150 or so range. goin out to put the new one in right now...let y'all know how it does.

Chris


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## Racer593 (Aug 20, 2009)

Changed the upper o2...still runs like crap. One more scan then Ill probably convert the injectors. Hate to spend the money, but it's gotta be fixed.
Again.

Chris


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## Nestech (Oct 6, 2006)

I garranty it is not an 02 sensor.

Still sounds like plugged conveter. Check the actual back pressure at an O2 sensor fitting.


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## Racer593 (Aug 20, 2009)

ran it with the upper o2's pulled and it did not make a difference. thing is, when it acts up, you shut it off for ten seconds and it runs fine for a bit. That seems electrical, something resetting...I just don't know.
Thanks Nestech. All ideas are respectfully considered.

Chris


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## Luke_P (Sep 16, 2008)

I have mentioned this in other posts but here's something to try take it out and run it untill it runs like a bag then keep it running like that for a bit. Pull over and take a temperature gun to the manifolds, if its injectors one or two cylinders should show colder then the rest. Then seeing as your laid off if your comfortable doing it pull the upper intake and check the injectors out if the corresponding cylinders poppets look like crap you have pretty much nailed down your problem. then its time to replace the poppets (cheaper but throwing good money onto crap in my opinion) or beg borrow\steal and do the conversion.


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## Luke_P (Sep 16, 2008)

nestech has a real good point about the cats if the back pressure at the 02 bungs seems high at all and you can't find a weak cylinder as mentioned above I would consider unbolting the Y pipe at the manifolds(depending on the studs condition of course) or the cat and run it open exhaust somewhere you aren't going to get a ticket if it livens right up you have your culprit also a plugged cat gets the exhaust crazy hot which would explain the burning smell you mentioned.....and the runs fine for a bit(like a reset) thing... I've seen Y pipes red hot before from plugged cats


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## jb1390 (Sep 23, 2008)

*Another Way to test the cats*

I just found plugged cats on my 98 350 yesterday. See my post about 98 vortec with no power. I also tried taking the oxygen sensors out with no noticable difference. The holes are only about an inch across, compared to two 3" pipes on my truck, so they don't make much of a difference. What I did to find it was to put a vacuum gage on it-start it, and it should have 20 inches or so of vacuum. Then run the tube up and hold the gage under one of your wipers, so you can see it while driving. You should have some vacuum all the time, except wide open throttle. I took mine for a drive, touched the gas pedal leaving the driveway, and the gage fell right to 0-no vacuum at all until I let off of the throttle. I cut the cats out, and sure enough, looks like someone melted the front of them all together. Put the straight pipes in until I get new cats, and it made a world of difference. I have vacuum while driving now too!


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## jb1390 (Sep 23, 2008)

*I really think its the cats*

One other note: I also noticed a difference when it was cold-it did a bit better. Not great, but better. The symptoms sound identical, I also had a friend look at it with a scanner. Do the vacuum gage test-I think you will find that is your issue.


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## jb1390 (Sep 23, 2008)

Racer, any updates??


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## Racer593 (Aug 20, 2009)

First off, thank you Nestech, luke and jb. I have thought from the start that it seems like a cat problem, but everyone has kinda led me away from it. I like the vac gage idea, and the thermal gun. I was out of town this weekend and have actually been working around the house for the last few days. get back to you when I try these things.
Again, thanks all.

Chris


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## Nestech (Oct 6, 2006)

What was the final verdict????


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## Racer593 (Aug 20, 2009)

OK everyone. First, I want to thank everyonr for all of their suggestions. All were considered or had already been tried.
Second, I made a mistake. I put the AC Delco pump on my pickup, not the Suburban. I mixed the two up. 
So, It is a pump assembly from Advance Auto Parts. Shop was driving it the other day(different shop) and he had a fuel pressure gauge on it. Well guess what? Lo and behold the pressure was at 50 psi when he stopped at my house to show me the gauge. We let it sit and idle for about 10 minutes and when it was around 43 psi it stalled. Shut the key off for maybe 15 seconds then restarted. Guess what? 59 psi. Then it gradually started to drop, while at the same time the computer started showing a very lean condition.
So I apologize about the fuel pump mix-up. I think we have finally figured out the problem. Thanks to everyone who helped out on this.

Chris


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## 2COR517 (Oct 23, 2008)

Don't pull the pump yet. It could be the fuel pressure regulator. Hopefully the pressure will drop while you're watching it again. When the pressure starts to drop, pinch off the return line. If the pressure goes up, it's the regulator. If it doesn't change, the pump is done.


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## B&B (Nov 4, 2006)

2COR517;850067 said:


> Don't pull the pump yet. It could be the fuel pressure regulator. Hopefully the pressure will drop while you're watching it again. When the pressure starts to drop, pinch off the return line. If the pressure goes up, it's the regulator. If it doesn't change, the pump is done.


Now where did you learn that little test from?


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## 2COR517 (Oct 23, 2008)

B&B;850107 said:


> Now where did you learn that little test from?


A little birdie told me......


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## Racer593 (Aug 20, 2009)

OK guys. I'll try it. 
Thanks

Chris


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## Racer593 (Aug 20, 2009)

It was the fuel pump. But I do have to thank everyone here for their help.Everything was appreciated.

Chris xysport


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## jb1390 (Sep 23, 2008)

Happy to hear you got it straightened out. Thanks for posting back with the update.


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## Racer593 (Aug 20, 2009)

no problem. I found a wealth of knowledge right here among new friends. thanks to everyone!!


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