nbm00ss

iTrader: (9)

Hey guys, I have a 2000 Silverado with almost 200k on it. I've only had a couple minor issues until recently. Over the past couple of months I noticed that I started having issues with throttle response which is now to the point where I have to keep the MAF unplugged just to make the engine run. It runs like crap and I notice when the humidity picks up in the heat of the day it gets really bad. My friend suggested it sounds like a vacuum issue due to the problem becoming worse in time not just out of no where. I have to also shift the truck manually because it will shift on it's own way too early. When I run a diagnostics it throws a MAF code. I threw a new MAF on and it threw a MAP code. threw a new MAP on and it threw a MAF code again. As soon as I plug the MAF in, the engine bogs and dies. There is obviously a fuel/air ratio issue but I can't figure out where it's reading wrong. We checked all the vacuum lines and they all seem to be ok. We put a gauge on the MAF and it reads 0 vacuum but on the middle of the intake we get roughly 15 which still seems low. I have deleted the EGR on the truck but that was years ago and never been an issue. The truck is hard to start and idle's like it has a cam and you can feel the vacuum issue when you give it throttle from 900-2000 rpm it struggles to get going and will bog and die if I give it over 1/4 throttle. Once I'm up around 2500-3000 rpm it's a lot better but obviously it's still not good and I can only give it about 1/3 throttle or it will bog out. You guys have cured all my other problems pretty quickly so I'm hoping some of you have seen this before. Thanks!

Darkman

iTrader: (2)

Have you checked the compression on the engine itself?

nbm00ss

iTrader: (9)

negative. the engine only has roughly 40k on it. Forgot to mention that too. The problem will get worse when I plug the MAF in so that shows me it's not the engine itself but an electrical or vacuum issue

nbm00ss

iTrader: (9)

Nobody has seen this before??

99SSJarhead

iTrader: (2)

Check everything leading to the MAF. Air box, filter, the hose connecting them, everything right out the truck and look for a possible obstruction somewhere. If that is good check the pipes leading from the MAF to your throttle. If that is fine make sure the throttle is functioning properly.

If all of that is fine move on to the fuel lines. Check for proper pressure and replace the fuel filter. Inspect/clean the injectors.

Then move to the o2 sensors.

That would be the route I'd go with my f-body but I don't have a lot of experience with newer model trucks.

If you don't have access to one, I recommend an odb2 scanner (or even tuning software) that can read/record driving data like fuel trim, maf air flow, and some other key things that will let you know if you are running rich (too much fuel) or lean (not enough). That will help a lot more in diagnosing then just a trouble code

nbm00ss

iTrader: (9)

We have worked on the truck ALL day. Changed the fuel pressure regulator and gained better idle control and about 3 pounds of vacuum. Everything with the MAF seems to be ok, even threw a new one on to check and nothing different. We were just getting ready to move to fuel lines as it seems we have sealed any vacuum leaks and it looks like were getting spark. We changed the plugs bc the ones that were in it were shot bc truck was running very lean. Gonna investigate the fuel lines and injectors and hopefully find something.

lt1pwr1

iTrader: (1)

Well, here is what I"m thinking. You have 200K on the truck. Your car is designed to run with a MAF, however, it won't run right with the MAF plugged in. So, I bet your PCM is bad considering the high mileage on the truck. I'm assuming you have double checked your wiring and everything to the MAF?

Only other thing I can think of is if you have a bunch of unmetered air coming into the engine, like if there is a crack in the intake tube or something...?

One more thing, although based on your symptoms it doesn't sound like the issue but these trucks will commonly throw a MAF code when the cats go bad. They get clogged (pretty common) and the restriction causes a sort of turbulence to the MAF.

nbm00ss

iTrader: (9)

lt1pwr1- I had the pcm flashed when I installed this engine because it was tuned for a built 6.0L that was in it prior. We have tracked the wiring and haven't came across anything suspicious. Truck doesn't have cats so and I doubt even with O2 problems it would never create this big of a problem. I did change the fuel pump not too long ago and we were thinking it could possibly be faulty but I don't know I'm at a loss at this point I just wanna sell it how it sits and move on

nbm00ss

iTrader: (9)

Got it fixed! Turns out the fuel pump was going bad on top of all this but it wasn't showing as a problem at first because we had low vacuum too. Once the vacuum was corrected you could tell it wasn't getting fuel. I had replaced the pump in January and it was obviously faulty. Got it replaced for free and now she drives like new.

JoshuaGrooms83

iTrader: (2)

im having the same type of crap going on with my car. im about to check my map sensor vac tubes, replace plugs, replace o2 sensors, replace injectors, and replace fuel pump. on top of that i know my car was running a bit rich due to a PCM tune but what its doing now is rediculous. i havnt pulled any plugs yet to see if its running lean or rich yet. ill be doning that this weekend