Driving me nuts

[DisturbinBurban96]

O.K. Here's my story. 1996 Suburban, 5.7 Vortec, 145,000 miles. I replaced the fuel pump and filter about two months ago because it was starting very hard when it was very cold (I live in Michigan) and I noticed the pump sounded "weak". It ran perfect for two months after replacing them. About two weeks ago I took the truck on a trip and after about two hours of driving it started to lose power on the highway, like if I tried to accelerate or climb even a slight hill it would just fall on it's face. I made it to a rest area, left it running and looked under the hood, everything looked fine. I tried to rev up the engine and it stalled. It started right back up and ran fine for the remaining 15 minute drive home. It seemed to run fine over the next couple of days because I only drove it on short trips. Then I discovered that after driving it for more than 20 minutes it would do the same thing. It's strange, because I could be rolling along at whatever speed, it would start to run bad, I could put it into nuetral, turn off the key, restart it, pull it back into gear, and be fine for a while longer. During this time there was no SES light that I was aware of, but I discovered the bulb was burnt out, so who knows how long it was on. I replaced the bulb and the light came on. I had it scanned and it showed multiple engine misfires, a bad EGR pintle reading, and bad O2 sensor. I replaced cap, rotor, wires, plugs, cleaned the EGR valve, and replaced the air filter. I waited on the O2 sensor because my mechanic said it may have gotten a bad reading from the misfires. The truck still did the same thing and the time it takes to act up has progressively gotten shorter. The SES light came back on (strangely when the engine was running good) , so I had it scanned again and the same O2 sensor showed up. I replaced that and the truck still acts up. So now I'm at the point where I've done all the things that needed to be done anyway, and from here on out it's a crapshoot. I'm thinking a coil and ignition module are my next step but would appreciate any suggestions before I just start throwing on parts I don't need. Thanks for taking the time to read this babble.....

[Vadar-Frank]

You may want to check for a vaccume leak at the intake manifold. I had the same problem on my 96, and after spending a lot of unnecessary money, discovered the leak near the distributor. would not have found it if I had not sprayed some carb cleaner around the area and caused the truck to sputter at idle. You may also want to have your cat. converter checked.

[dirty dan]

Sounds like Catalytic Converter loaded up. Any muffler shop should be able to check on it in about 10 minutes. There is also a vacuum test you can perform to look for clogged exhaust but I can't remember the procedure off the top of my head.

[vendpro]

Check you Fuel pump. It has an in tank pump with a filter screen on it. I would almost bet money that you have trash in there cloging it. Have it pressure tested and that should give you something to go on. Just had to put one on my 92 astro w/ sim. prob

[jimmydager]

Take your truck to your local auto parts store and have your ignition module tested. Mine was bad and caused the same sort of problems. It is an easy, free test and if it is bad, it can save you a lot of money instead of throwing random parts at it. I hope this helps

[localyokel]

Hi, I am wondering about your replacement fuel pump.Some replacements dont come w/ what I think may be called a pulsator? What ever it is called it's about a 1 1/2"to 2" piece of rubber that connects the pump to the lines.My 89 had one (assuming 97s do as well)when I replaced my pump w/ a napa cheapie it did'nt come w/ one.When my fuel pressure went away shortly after.I decided to go w/ an ac delco which comes w/ new rubber pulsator and wire connectors.When I took the old rubber off and sqeezed it I noticed about a 1/4 in dry rubber crack in it.(pump was probably fine)loosing pressure through the crack. Good luck!