JustinJ94FSB
Newbie
1994 Blazer K1500 5.7 TBI. 138,500 miles.
The issue i am currently having:
Once vehicle is at operating temp, when i come to a stop sign the RPMs like to drop down and it catches itself before stalling but the RPMS sit way low. like the needle is down on the lowest possible mark on the tach. I have not checked digitally the RPMs. It also idles rough obviously cause the RPMs are so low. Also i notice a stinky sulfur smell from the exhaust.
This was happening before and after replacing the cat.(i have read that new cats can stink for a while which is why i say that) I used a IR thermometer to check temps going into and coming out of the cat and noticed it was almost 100+ degrees hotter going into the cat than coming out. I took the cat off and put a borescope cam in there and notice it was cracked in there, just decided to replace it. Didnt change any symptoms.
TLDR-
my truck has had issues with engine running that progressively got worse and eventually it left me stranded and had to be towed home. After poking around i discovered the heater hose fitting on the intake was leaking, and the coolant was somehow getting up under my distributor cap and had been corroding the contacts in there for probably a long time. I replaced the cap and rotor and the truck fired up no problem. But i still had something else going on. Idling problems, bogging, etc. Since it isnt my daily driver i have been just working out kinks as i have time. So i decided to address the leaky fitting which of course broke off the second i made eye contact with it. No specialty tools worked, had to pull the intake to get the fitting threads out.
During this intake manifold job i did the following:
Replaced oil pressure switch (gm genuine)
Replaced ignition coil (gm genuine)
Replaced spark plugs (ac delco oem)
Replaced ECT sensor (duralast)
Replaced MAP sensor (duralast)
Replaced IAC valve (gm genuine)
Replaced PCV valve 3 times (duralast, napa, and something else)
Replaced Thermostat/rubber seal (ac delco oem)
Replaced Air filter
Replaced Fuel Filter (gm genuine)
Replaced one-piece welded y-pipe/catalytic converter (walker)
Replaced O2 Sensor (gm genuine)
Replaced Harmonic Balancer/dampener whatever (gm genuine)
Cleaned Throttle Body thoroughly with throttle body cleaner and Replaced all gaskets with fel-pro
Replaced all other gaskets with fel-pro (intake, egr, throttle body to intake, etc etc)
Filled tank with new gas ~60 miles of driving ago.
Changed coolant, oil, filters, etc etc
Set the engine timing with the timing-correction connector disconnected, and got it dead on perfect, and then connected the plug back in.
Checked injector spray pattern several times, even recorded a 920 frames per second slow motion video of them, they have a very uniform and clean cone pattern. (i know that doesn't completely rule it out)
when i did the intake i tap/die all the bolts and holes and also used fine sand paper to scrub down all of the grounds for things like the ECT and whatnot. I used thread sealer on the bolts. I am doing research on symptoms of various parts and how they impact the vehicles operation when they are failing/failed. Each thing i feel like could be the next likely culprit, i replace it, and nothing changes.
The truck is running way better now than it has for a long time. It runs and drives like i put a whole new engine in or something.
sorry for very long post, ive been doing a ton of stuff trying to fix this before coming here for help, i like to learn but at this point im at a deadend. I literally dont know what could possibly be wrong anymore.
Its very possible i have done more and couldnt remember when writing this.
thanks for any guidance or advice on my next course of action!
The issue i am currently having:
Once vehicle is at operating temp, when i come to a stop sign the RPMs like to drop down and it catches itself before stalling but the RPMS sit way low. like the needle is down on the lowest possible mark on the tach. I have not checked digitally the RPMs. It also idles rough obviously cause the RPMs are so low. Also i notice a stinky sulfur smell from the exhaust.
This was happening before and after replacing the cat.(i have read that new cats can stink for a while which is why i say that) I used a IR thermometer to check temps going into and coming out of the cat and noticed it was almost 100+ degrees hotter going into the cat than coming out. I took the cat off and put a borescope cam in there and notice it was cracked in there, just decided to replace it. Didnt change any symptoms.
TLDR-
my truck has had issues with engine running that progressively got worse and eventually it left me stranded and had to be towed home. After poking around i discovered the heater hose fitting on the intake was leaking, and the coolant was somehow getting up under my distributor cap and had been corroding the contacts in there for probably a long time. I replaced the cap and rotor and the truck fired up no problem. But i still had something else going on. Idling problems, bogging, etc. Since it isnt my daily driver i have been just working out kinks as i have time. So i decided to address the leaky fitting which of course broke off the second i made eye contact with it. No specialty tools worked, had to pull the intake to get the fitting threads out.
During this intake manifold job i did the following:
Replaced oil pressure switch (gm genuine)
Replaced ignition coil (gm genuine)
Replaced spark plugs (ac delco oem)
Replaced ECT sensor (duralast)
Replaced MAP sensor (duralast)
Replaced IAC valve (gm genuine)
Replaced PCV valve 3 times (duralast, napa, and something else)
Replaced Thermostat/rubber seal (ac delco oem)
Replaced Air filter
Replaced Fuel Filter (gm genuine)
Replaced one-piece welded y-pipe/catalytic converter (walker)
Replaced O2 Sensor (gm genuine)
Replaced Harmonic Balancer/dampener whatever (gm genuine)
Cleaned Throttle Body thoroughly with throttle body cleaner and Replaced all gaskets with fel-pro
Replaced all other gaskets with fel-pro (intake, egr, throttle body to intake, etc etc)
Filled tank with new gas ~60 miles of driving ago.
Changed coolant, oil, filters, etc etc
Set the engine timing with the timing-correction connector disconnected, and got it dead on perfect, and then connected the plug back in.
Checked injector spray pattern several times, even recorded a 920 frames per second slow motion video of them, they have a very uniform and clean cone pattern. (i know that doesn't completely rule it out)
when i did the intake i tap/die all the bolts and holes and also used fine sand paper to scrub down all of the grounds for things like the ECT and whatnot. I used thread sealer on the bolts. I am doing research on symptoms of various parts and how they impact the vehicles operation when they are failing/failed. Each thing i feel like could be the next likely culprit, i replace it, and nothing changes.
The truck is running way better now than it has for a long time. It runs and drives like i put a whole new engine in or something.
sorry for very long post, ive been doing a ton of stuff trying to fix this before coming here for help, i like to learn but at this point im at a deadend. I literally dont know what could possibly be wrong anymore.
Its very possible i have done more and couldnt remember when writing this.
thanks for any guidance or advice on my next course of action!
