97 tahoe stalling
bowtie_fan
02-25-2021, 06:06 PM
warning- I'm definitely not a mechanic & I don't know how much of this is actually necessary to type out here... so please bear with me as I ramble.
My son took my 97 tahoe (5.7) a couple of weeks ago & it wouldn't start when he tried to come home. I went to see what I could do & it ended up starting, so he drove it home (about a block).
The engine light didn't come on, so I've got no codes to help me out. Knowing everything I've replaced the past few years, but not really knowing what to do next, I chose the simplest route. I cleaned the air filter (K&N lifetime) & tossed a bottle of fuel treatment in the tank... that didn't help.
since then it's gone from stalling after a few min of driving/running, to intermittently stalling after starting & cranking and not wanting to actually start. kinda acts like its flooded, but tbi and fuel injectors are not things I'm very familiar with. If I give it some gas, it'll run, but will stall a few sec after revving back down. Doesn't seem to be running rough when it does either.
pertinent history (?):
-Roughly 2 years ago, I had the spider injectors replaced @ a shop.
-I replaced the fuel pump + harness, as well as fuel filter about a year ago.
(Inside of gas tank was immaculate, so I'm thinking it's not likely to be a clog in the fuel system)
-Last spring, it threw a code leading to an 02 sensor & MAF being replaced.
I went ahead & replaced the MAF again today in case the oil from the filter had fouled it... still stalls out, so no luck there. Though when it started, I noticed a lot more smoke than usual from the exhaust... cranked it again, more smoke and even a small backfire. smoke is non dissipating, white/grey... but not blown head gasket-y if that makes sense.
last week I unhooked the neg cable when running and it kept on for a min so I'm thinking the alternator is ok. & I just replaced the battery last month.
Don't really know where to go from here.... I can def hear the fuel pump running when the key is turned... so I'm guessing that is ok?
idk... would an IAC valve maybe help... or pcv? I'm just taking stabs in the dark at this point.
While I'm not great with diagnosing issues, I'm not exactly a novice when it comes to wrenching. I used to have dad diagnose & then I'd replace what he told me to... but can't do that anymore. These days I tend to just throw parts at a prob till it works again, but my husband and bank account both dislike that lol. Really hoping someone can help me out here.
My son took my 97 tahoe (5.7) a couple of weeks ago & it wouldn't start when he tried to come home. I went to see what I could do & it ended up starting, so he drove it home (about a block).
The engine light didn't come on, so I've got no codes to help me out. Knowing everything I've replaced the past few years, but not really knowing what to do next, I chose the simplest route. I cleaned the air filter (K&N lifetime) & tossed a bottle of fuel treatment in the tank... that didn't help.
since then it's gone from stalling after a few min of driving/running, to intermittently stalling after starting & cranking and not wanting to actually start. kinda acts like its flooded, but tbi and fuel injectors are not things I'm very familiar with. If I give it some gas, it'll run, but will stall a few sec after revving back down. Doesn't seem to be running rough when it does either.
pertinent history (?):
-Roughly 2 years ago, I had the spider injectors replaced @ a shop.
-I replaced the fuel pump + harness, as well as fuel filter about a year ago.
(Inside of gas tank was immaculate, so I'm thinking it's not likely to be a clog in the fuel system)
-Last spring, it threw a code leading to an 02 sensor & MAF being replaced.
I went ahead & replaced the MAF again today in case the oil from the filter had fouled it... still stalls out, so no luck there. Though when it started, I noticed a lot more smoke than usual from the exhaust... cranked it again, more smoke and even a small backfire. smoke is non dissipating, white/grey... but not blown head gasket-y if that makes sense.
last week I unhooked the neg cable when running and it kept on for a min so I'm thinking the alternator is ok. & I just replaced the battery last month.
Don't really know where to go from here.... I can def hear the fuel pump running when the key is turned... so I'm guessing that is ok?
idk... would an IAC valve maybe help... or pcv? I'm just taking stabs in the dark at this point.
While I'm not great with diagnosing issues, I'm not exactly a novice when it comes to wrenching. I used to have dad diagnose & then I'd replace what he told me to... but can't do that anymore. These days I tend to just throw parts at a prob till it works again, but my husband and bank account both dislike that lol. Really hoping someone can help me out here.
j cAT
02-26-2021, 09:00 AM
YOU HAVE TO PUT ON A SCAN TOOL ... also put a fuel pressure gauge on the fuel rail on the intake manifold area.. pressure key on eng off 60-65PSI.. if the pressure is below 55psi hard start or no start.. replacing a fuel pump when it was failed then you should replace that fuel pump relay old truck electrical issues....REPLACE THE FUEL FILTER... your MAF has oil on it well the engine has sludge in it and the crankcase ventilation system is not working . spray MAF cleaner on it and inspect the hoses on the top of the engine ..replace the PCV VALVE.... IF THE GAS TANK DROPS BELOW 1/4 OF FUEL THEN FUEL PUMPS DIE.
Blue Bowtie
02-26-2021, 06:37 PM
That's mostly right, with a few variations.
Instead of replacing the PCV valve, clean your existing one and reinstall it. Aftermarket PCV valves are TERRIBLE for having incorrectly calibrated springs (both of them) and incorrectly contoured pintles. I previously worked in a Textron facility which maufactured the OEM pintles for Delco PCV valves. Each valve application had its own pintle design, and each run was SPC tested on an actual flow bench for proper form and operation at various flows and pressure differentials. One size does not fit all, and the aftermarket has awful control over this.
Second, the 1997 fuel pump is inside an in-tank fuel module which submerges the fuel pump with bypass/return flow until the tank is completely empty. It's not a good idea to run a tank near empty, but ¼ full is not a problem.
ACTUAL 1997 Sierra Module
http://www.wwdsltd.com/files/1997SierraFuelTankUnit.jpg
Instead of replacing the PCV valve, clean your existing one and reinstall it. Aftermarket PCV valves are TERRIBLE for having incorrectly calibrated springs (both of them) and incorrectly contoured pintles. I previously worked in a Textron facility which maufactured the OEM pintles for Delco PCV valves. Each valve application had its own pintle design, and each run was SPC tested on an actual flow bench for proper form and operation at various flows and pressure differentials. One size does not fit all, and the aftermarket has awful control over this.
Second, the 1997 fuel pump is inside an in-tank fuel module which submerges the fuel pump with bypass/return flow until the tank is completely empty. It's not a good idea to run a tank near empty, but ¼ full is not a problem.
ACTUAL 1997 Sierra Module
http://www.wwdsltd.com/files/1997SierraFuelTankUnit.jpg
brcidd
02-27-2021, 02:45 AM
Yeah, I learned that the hard way- about fuel pumps being flooded by return gas- in their own "bucket" to keep them cool and submerged. When I pulled out a pumped-down fuel tank fuel pump, it was full of fuel and I spilled fuel all over my sister-in-law's condo garage- and it smelled up the whole condo.
Automotive Network, Inc., Copyright ©2025