I have a 97 Tahoe 4WD with the 5.7 engine. 138,000 miles on it now. About 3 years ago, dealer replaced the intake manifold gaskets because of a coolant loss. Plugs replaced 2 years ago with AC Delco. During the last 2 months, it has developed a rough idle which exists when the transmission is in gear, neutral or park. I do not notice a problem driving or towing. Code reader only shows P0300.

After reading several of the old posts on this forum, I replaced the plug wires, cap and rotor (I know that they have not been replaced since I purchased the truck with approximately 60,000 miles on it). Problem has not gone away. I have also run about 3 bottles of Techtron fuel treatment through it. Still rough idle.

Truck passed local emissions tests (Nashville, TN) 2 weeks ago.

Suggestions on where to go from here other than to the dealer?

When mine (same year, engine, symptoms) did this, it turned out to be the fuel pressure regulator. You may try cleaning the throttle plate first.

After a lot of looking, it turned out to be a failing fuel pump.

After a lot of looking, it turned out to be a failing fuel pump.

Well, that repair lasted about 6 months and it returned, but this time worse. After a fuel pump and replacing most of the ignition system, I had it checked by a GM factory mechanic. He told me that the computers indicated it was a problem with the fuel injectors. He indicated that there was a TSB out from GM on this issue and that the 97 vintage fuel "spider" was known for going bad (I guess the same idiot designed it that designed the flawed intake VORTEC intake system that leaks). Anyhow, after a $300 "cleaning" the problem was better but not solved. I then spent another $1200 to replace the original fuel injection "spider" with an GM upgraded unit. Idles real nice now.

If the problem returns, I think I will replace the transmission and tires to see if that helps.... that is about all that is left.:banghead:

Well, that repair lasted about 6 months and it returned, but this time worse. After a fuel pump and replacing most of the ignition system, I had it checked by a GM factory mechanic. He told me that the computers indicated it was a problem with the fuel injectors. He indicated that there was a TSB out from GM on this issue and that the 97 vintage fuel "spider" was known for going bad (I guess the same idiot designed it that designed the flawed intake VORTEC intake system that leaks). Anyhow, after a $300 "cleaning" the problem was better but not solved. I then spent another $1200 to replace the original fuel injection "spider" with an GM upgraded unit. Idles real nice now.

If the problem returns, I think I will replace the transmission and tires to see if that helps.... that is about all that is left.:banghead:
Ha,Ha ,Ha..had to see the dealer or his factory trained tech to get it fixed,,

The new "spider" assembly is an upgraded unit that no longer has poppet valves. the system now has the actual injectors that spray into the intake runners.
You should not have any problems with that system. I have installed many of those with a 100% sucess rate.
A bottle of Techron every 3000 miles will keep the fuel system clean.

Ha,Ha ,Ha..had to see the dealer or his factory trained tech to get it fixed,,

The new "spider" assembly is an upgraded unit that no longer has poppet valves. the system now has the actual injectors that spray into the intake runners.
You should not have any problems with that system. I have installed many of those with a 100% sucess rate.
A bottle of Techron every 3000 miles will keep the fuel system clean.

One of my friends works for a dealership - but he does not work on GM's. He is a great mechanic on my Dodge Ram however. If place a lot of faith in factory trained mechanics - I just don't like the markup that dealerships put on the mechanic's labor and the parts.

Ha,Ha ,Ha..had to see the dealer or his factory trained tech to get it fixed,,

The new "spider" assembly is an upgraded unit that no longer has poppet valves. the system now has the actual injectors that spray into the intake runners.
You should not have any problems with that system. I have installed many of those with a 100% sucess rate.
A bottle of Techron every 3000 miles will keep the fuel system clean.

I just replaced the Intake gaskets on my '99 and it was getting P0300 and P0304. I had replaced an injector a while back and figured I'd save myself some time and just replace the whole spider while I had it apart. It runs much better. The spider was about $550 (much less than 1/4 the old poppets and fule pressure regulator). You can just tell it is a much better design.

My wife said she felt it stumble a couple of days later under load on the highway but it didn't set off the SES.

I'm going to put a trailer on it this weekend and see if it still has issues because that was when the truck would really feel like it was falling apart.

Great site and GMMerlin - thanks for all the great info you share w/everyone

I got this tahoe with 157,000 in June 06 and have had a few problems since. First the fuel pump went out, and was replaced with a new pump from napa. Then i changed the oil,plugs,wires,cap and rotor,flushed the old dexcool and refilled, and changed the tranny fluid and filter. I since have had the P1345 code and the distributor was off a bit after the new rotor(aftermarket) and a worn distributor gear. Got that fixed and then tranny issues. I saw some fine metal particles on the bottom of the pan and on the magnet when I serviced the tranny. No shavings or clutch material so I thought it was ok. Wrong, 164,000 and the tranny lost reverse. Got it rebuilt with a new beefier aftermarket reaction sunshell. It seems ok now. Well now, after all that, I have a random misfire code p0300 and once came up as p0304. It only does this after driving it for a while and when pulling a steep grade. Park for a while and the start it up and it purrs like a kitten. At first I thought, ignition coil. Well I picked one up at napa and installed it because I was in a bind and had no multimeter or scanner to get a better idea. Not a fix! Do you suggest anything? I am going to get a fuel pressure test kit and check for 60-66 psi with the key off. Then check it with the miss occurring if I can get it to act up. Checked spark and it was ok at all cylinders but couldn't get it to start missing again. It sat all night and for some reason it works! Any other suggestions?

I have a 96 Hoe with 200K, and had similar problems with the injectors, codes, and miss with hesitation at around 180k. Plus the intake manifold gasket leak. If you have fixed that leak already you are ahead of the game. Try this: Change your fuel filter, check your fuel pressure, should be around 65 psi. Here is the problem, the top half of the intake is a dry system with the spider in the middle. Eight little plastic hoses go to each injector which clip in at the intake port. The PCV dumps all the blowby and gook here also. This is most of the problem, it cokes up and hardens on everything, blocking up the end of the injector. Amsoil Power Foam works great at breaking this stuff up, spray it on thick and let it set up till clean! Block the intake ports off with sponges and Shop Vac and scrape it all out. Get 3 cans along with Carb Cleaner. Pay special attention to the ends of the injectors, use a small screw driver with care and clean away any residue. While you have the spider out replace the fuel pressure regulator. Add Chevron Techron fuel Additive Often. GoodLuck!

Fuel pressure is 58 to 60 at all times when running fine and even with the horrible miss. Changed the fuel filter just the other day. I guess it is possible that random injectors are clogging and the fuel pressure stays constant because of the regulator. Fuel pressure holds at 58 after like 10 minutes too. I looked into the upper intake and man was it dirty. Looks like an 1/8in of carbon over everything in there. Didn't have a scope to explore it much more. I plan to remove the upper intake and clean that up. I may put the new injector setup in while I have it torn apart. One question, could the cam position sensor be heating up (or the wiring to it) and intermittently dropping its signal without tripping any codes for it. I say this because while the engine was running I jiggled the wires to the sensor and the engine would stumble. The connector is not loose and the pins inside are in good shape. Maybe I was just interrupting the signal when I bent the wires around but no code for this sensor has ever shown up. IF the injectors aren't clogging, I think I am stumped!!

I did a little work on the tahoe last night. I got it warmed up to where it started missing then I unplugged the cam position sensor, and the miss went away. This definitely is making me think that there is an electrical issue. I know that the VCM will go to a default fueling strategy if the cam signal is lost, and I don't know if that is what cured my miss or the fact that the cam sensor no longer sent the VCM erratic signals. I would use my multimeter and check the signal for the sensor when it is missing but it is really hard to get to. I guess I will have to do something to determine if it is the sensor shorting out or the wiring. I will post back when I find out!!