New and need help

[crammit442]

I recently inherited my g'mother's '99 Tahoe. 2WD, 5.7 Vortec. It was rarely driven. I probably the last person to drive it roughly 9 months ago. When i went to pick it up I put a battery in it and it fired right up. Ran well as usual. Obviously, 9 month old fuel is OLD. At about an 1/8 tank I parked it overnight nose down on my very steep driveway. It was running very well when I turned it off. When I went to start it the next morning it didn't want to start. I could see the fuel gauge showed empty so I assume the fuel pickup is in the rear of the tank. Guessing that the pickup wasn't getting fuel, I let the truck roll down to the flat part of the driveway. It still wasn't very enthusiastic about starting. A quick shot of starting fluid and it fired right up. That's the good part of the story. It immediately had a very noticeable stumble/miss. So much so that in any other circumstance I would bet money on an ignition problem. I'm wondering/thinking that the old nasty part of what was in the tank was the first thing the fuel pick up sucked up. I went and filled it with fresh gas hoping that it would clean out anything I may have sucked up. No luck. A full can of Seafoam hasn't helped yet either. I normally drive a Toyota 4runner and am not very familiar with the 5.7 Vortec. The truck was running very well when I turned it off the night before. I'm guessing I need to change fuel filters, clean throttle body etc. I'm not sure, but I believe it's a throttle body injection system rather than port EFI. any help or suggestions would be greatly appreciated. I'm not even sure where the fuel filter is located. Thank very much in advance.
Charles

 

[bigfootchiro]

Welcome to the forum! There are lots of people on here that will be able to help. Is it able to start at all? You are probably right by changing fuel filter (probably should be done either way), it is located on the driver side frame rail below the driver door. Have you checked the fuel pressure? There's a schrader valve on the fuel line, driver side of motor, as it runs into the intake plenum. You can hook a gauge there, turn the key to ON (do not start), and see what your pressure is at. Then start (if possible), and read your pressures. They should read between 55-60 psi, if I recall correctly.

 

[crammit442]

It definitely starts and runs. It just misses badly. Like said, if it didn't start doing this under these circumstances I would be pretty confident that I was dropping one or more cylinders via ignition. I'll check fuel pressure and change the filter tonight. My gut feeling is that after being parked nose down w/the pickup out of the fuel, the first thing it picked up the next morning was whatever 9 month old gunk had settled to the bottom of the tank overnight and is not able to provide the correct amount of fuel. Thanks much I!
Charles

Welcome to the forum! There are lots of people on here that will be able to help. Is it able to start at all? You are probably right by changing fuel filter (probably should be done either way), it is located on the driver side frame rail below the driver door. Have you checked the fuel pressure? There's a schrader valve on the fuel line, driver side of motor, as it runs into the intake plenum. You can hook a gauge there, turn the key to ON (do not start), and see what your pressure is at. Then start (if possible), and read your pressures. They should read between 55-60 psi, if I recall correctly.

 

[bigfootchiro]

It definitely starts and runs. It just misses badly. Like said, if it didn't start doing this under these circumstances I would be pretty confident that I was dropping one or more cylinders via ignition. I'll check fuel pressure and change the filter tonight. My gut feeling is that after being parked nose down w/the pickup out of the fuel, the first thing it picked up the next morning was whatever 9 month old gunk had settled to the bottom of the tank overnight and is not able to provide the correct amount of fuel. Thanks much I!
Charles

Let us know what you find!

 

[crammit442]

Let us know what you find!

Well, it almost surely needed a fuel filter.......however.......still runs exactly the same. It certainly FEELS like an ignition problem. One thought, possibly far fetched, is that when I first picked it up I spent almost $10 in quarters at the DIY carwash cleaning nearly a year of pinestraw and mildew off of the whole truck. There was copious amounts of pinestraw at the grill between the hood and windshield. I sprayed a LOT of water there. While I'm sure it's solid state, it looks like this motor still has distributor. I wonder if there's any way that parking nose down on a steep hill allowed some moisture to get inside the cap. In our older Ski Nautiques, a bit of moisture in the distributor cap made the motor miss and stumble almost EXACTLY like this. A wipe and a shot of wd-40 fixed it every time. Any thoughts? I haven't checked the fuel pressure yet, but will. Thanks again.
Charles

 

[crammit442]

Bump for any brilliant ideas. It really does FEEL like an ignition problem. Its a very pronounced stumble/skip at all throttle positions. Sitting at redlight it misses so badly that it shakes like a motor w/too much cam for the street. Thanks in advance.
Charles

 

[east302]

1995 was the last year of the TBI, yours would have the central SFI.

Since it got doused with water, I'd pull the wires and check the rotor cap, see if it is cracked or if you have moisture in there. Assuming it is the original distributor, be careful with tightening the two screws that secure the cap to the distributor. The plastic tabs tend to crack or break.

A spark tester could help see if you have any ignition issues.

A fuel pressure test would be in order. There is a schrader valve on the driver side. Check the pressure with ignition on but engine off. Cycle the ignition a few times to get your maximum value, spec is 60-66 psi.

Is the check engine light on?


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[crammit442]

The "service engine soon" light is on. I'll try check the fuel pressure tomorrow. I'm sure the cap, rotor, plugs, and wires and maybe even the coil should all be replaced. I'll stop by O'Reilly's on the way into work and have them scan codes. We used my buddy at works code reader today and it came up with TPS, low voltage to MAF, and multiple misfires. It'll be interesting to see if they pull the same codes or not. Are codes pulled on these trucks reliable or are they subject throwing false codes like some systems are? I really appreciate all the suggestions. This truck is ideal for pulling my lawn trailer. I'm just concerned that I'm going to spend a bunch of money chasing a problem. The truck is mine if I want it. I would just like to avoid much spending to decide. Whatever's wrong with it happened between turning it off at 10:00 pm and starting it at 9:00 am the next morning. It was running great and whatever the issue is showed up the instant it started the next time. One other possible clue I haven't mentioned that might mean something to someone. Even when it ran great it was tricky to start. Turning the motor over for any length of time NEVER makes it start. It would only start with multiple short one or two second tries. Also, if it hadn't been driven for a day or so, it would frequently require a shot of starting fluid. Does that point to anything consistent with any particular known problem that my nose downhill parking may have made worse? Sorry for the dissertation. I just want to make sure I mention anything that could be useful. I hope that my descriptions make sense. Thanks so much!
Charles

 

[RED TAHOE LS]

When i went to pick it up I put a battery in it and it fired right up. Ran well as usual. Obviously, 9 month old fuel is OLD.


Charles, welcome to the forum. Can you start the Tahoe without touching the gas pedal ? If so, fuel pressure is probably acceptable. Two important things make the engine run, Ignition and Fuel. A fuel problem is erratic ( runs good and bad ) Ignition will run bad until you find the problem.
Give this a try, pull the spark plugs one @ a time and check for a small piece of carbon in the gap, my guess is one or more will have the same problem. Just take a small knife blade and clean out the gap. This often happens when a car sets and not driven.
Nice that Grand Ma is passing it to you. Is it 4wd and how many miles ? Post some pics when you have time, and let us know what fixed it. Good luck.
David g...................

 

[east302]

GM has troubleshooting procedures for each code, so once you get the actual codes that will help track down the issue.




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