I have an interesting problem with my FJ80. This is a long entry, but if you read it as if I'm a caller on Car Talk (that's 1-888-227-8255, hello you're on Car Talk), it makes the read more bearable.
I've searched on here, and haven't really found anyone with the exact problem. Seems like most just experience the first half of my issue, and not what's causing my confusion, and then never reply saying what the fix was. So here goes:
Background: Purchased a month ago for $3k, knowing it would be a "rolling project." Vacuum leaks galore, and an idle that would slowly cause the truck to stall. Fixed the vacuum leaks, and it idled high. PO had adjusted the throttle cable to make it idle as opposed to fixing vacuum leaks. I adjusted the throttle cable, and set in the correct idle speed. Ran great for a couple weeks. PO stated he recently replaced the fuel pump.
Description of recent PMs/baselining: 1991 FJ80, de-smogged (partially - I'm finishing up the PO's job), new plugs (gapped properly), fixed vacuum leaks around the air intake boot (next to MAF and TB), took off MAF cover to inspect, then resealed (did not touch the Two Screws), new O2 sensors/gaskets, new manifold to downpipe gaskets, new catalytic converter gaskets, coolant flush, and recent oil/filter change.
THE ISSUE: Went to the gym this morning real early. It's about a 7 minute drive. Truck started perfect and drove fine - no issues. I finish working out (~1 hour), and get in to head home. Truck again starts perfect. About 3 minutes down the road (35 mph zone, so not that far), the truck just bogs down. Idle speed slows to ~400 RPM. I pull off and put it in park. The truck is sputtering/hunting for idle at this point (sounds like I installed a huge cam). "Did you try turning it off and back on?" Well I'm glad you asked: yes I did. Issue persists. I feather the throttle - no real change. I floor the throttle - truck slowly climbs in RPMs, but very slowly, and it's still stumbling. I do this a few more times. Suddenly, with a roar, the truck comes back to life and settles in at a normal idle. I drive the remaining 4 minutes/2 miles home. I shower, eat, and get back in the truck to head to work. Starts fine, and then about 3 min into my drive, the issue once again rears its ugly head. I repeat the above procedure, and get the same result. Limp home and take my wife's car to work. This has been going on for about 1.5 weeks.
Here's another interesting piece, that may be entirely coincidental: This issue happens at the exact same spot every day when I leave work (the gym is on my way to/from work). I believe I'm overthinking it, but it seems strange. Maybe related to the warmup process?
Here are my thoughts/devil's advocate piece:
Fuel Issue: Fuel pump is not delivering fuel as it should, BUT why would the truck work, and then not, and then work again if the fuel pump is bad? How could a pump going bad be so consistently good and bad (happens at the same spot each day)? Fuel filter could also be clogged, and the blockage is somehow cleared at the same time each time the issue occurs (for some reason, this seems like the most viable option if it is a fuel delivery issue, only because it would be a wild coincidence that would definitely happen to me). Fuel injector(s) bad, but wouldn't they get worse over time? Again, how would they fail so consistently.
Vacuum Leak: Unmetered air is getting into the engine, BUT if there is a vacuum leak, why would symptoms not always be present? Again, how would it be so consistent in displaying symptoms?
Spark/Timing Issue: If timing is off and plugs aren't gapped correctly, it would cause it to run rough, BUT why would symptoms not always be present? It isn't misfiring, the idle just drops and it runs really rough, then runs normal again.
What I think it is, but want other owners' input: I think it's a fuel issue. Some sort of blockage in the tank, fuel line, or filter settles down overnight. This is why the truck starts just fine. As I drive, the blockage is shifted, and eventually makes its way to a fuel screen/filter opening. When I stop, as I sit there playing with the throttle, It again shifts/settles, and allows the truck to run fine again. The drive home does not cause enough movement to re-introduce the blockage to the system, which is why it drives fine.
That's what I've got for now. I'm trying to avoid throwing parts at a problem. I'm very new to these trucks, and new to the forum. And I could be totally wrong and I need a new MAF, intake boot, and whatever else expensive parts are out there. Please chime in if you've experienced this before. Thanks in advance!
I've searched on here, and haven't really found anyone with the exact problem. Seems like most just experience the first half of my issue, and not what's causing my confusion, and then never reply saying what the fix was. So here goes:
Background: Purchased a month ago for $3k, knowing it would be a "rolling project." Vacuum leaks galore, and an idle that would slowly cause the truck to stall. Fixed the vacuum leaks, and it idled high. PO had adjusted the throttle cable to make it idle as opposed to fixing vacuum leaks. I adjusted the throttle cable, and set in the correct idle speed. Ran great for a couple weeks. PO stated he recently replaced the fuel pump.
Description of recent PMs/baselining: 1991 FJ80, de-smogged (partially - I'm finishing up the PO's job), new plugs (gapped properly), fixed vacuum leaks around the air intake boot (next to MAF and TB), took off MAF cover to inspect, then resealed (did not touch the Two Screws), new O2 sensors/gaskets, new manifold to downpipe gaskets, new catalytic converter gaskets, coolant flush, and recent oil/filter change.
THE ISSUE: Went to the gym this morning real early. It's about a 7 minute drive. Truck started perfect and drove fine - no issues. I finish working out (~1 hour), and get in to head home. Truck again starts perfect. About 3 minutes down the road (35 mph zone, so not that far), the truck just bogs down. Idle speed slows to ~400 RPM. I pull off and put it in park. The truck is sputtering/hunting for idle at this point (sounds like I installed a huge cam). "Did you try turning it off and back on?" Well I'm glad you asked: yes I did. Issue persists. I feather the throttle - no real change. I floor the throttle - truck slowly climbs in RPMs, but very slowly, and it's still stumbling. I do this a few more times. Suddenly, with a roar, the truck comes back to life and settles in at a normal idle. I drive the remaining 4 minutes/2 miles home. I shower, eat, and get back in the truck to head to work. Starts fine, and then about 3 min into my drive, the issue once again rears its ugly head. I repeat the above procedure, and get the same result. Limp home and take my wife's car to work. This has been going on for about 1.5 weeks.
Here's another interesting piece, that may be entirely coincidental: This issue happens at the exact same spot every day when I leave work (the gym is on my way to/from work). I believe I'm overthinking it, but it seems strange. Maybe related to the warmup process?
Here are my thoughts/devil's advocate piece:
Fuel Issue: Fuel pump is not delivering fuel as it should, BUT why would the truck work, and then not, and then work again if the fuel pump is bad? How could a pump going bad be so consistently good and bad (happens at the same spot each day)? Fuel filter could also be clogged, and the blockage is somehow cleared at the same time each time the issue occurs (for some reason, this seems like the most viable option if it is a fuel delivery issue, only because it would be a wild coincidence that would definitely happen to me). Fuel injector(s) bad, but wouldn't they get worse over time? Again, how would they fail so consistently.
Vacuum Leak: Unmetered air is getting into the engine, BUT if there is a vacuum leak, why would symptoms not always be present? Again, how would it be so consistent in displaying symptoms?
Spark/Timing Issue: If timing is off and plugs aren't gapped correctly, it would cause it to run rough, BUT why would symptoms not always be present? It isn't misfiring, the idle just drops and it runs really rough, then runs normal again.
What I think it is, but want other owners' input: I think it's a fuel issue. Some sort of blockage in the tank, fuel line, or filter settles down overnight. This is why the truck starts just fine. As I drive, the blockage is shifted, and eventually makes its way to a fuel screen/filter opening. When I stop, as I sit there playing with the throttle, It again shifts/settles, and allows the truck to run fine again. The drive home does not cause enough movement to re-introduce the blockage to the system, which is why it drives fine.
That's what I've got for now. I'm trying to avoid throwing parts at a problem. I'm very new to these trucks, and new to the forum. And I could be totally wrong and I need a new MAF, intake boot, and whatever else expensive parts are out there. Please chime in if you've experienced this before. Thanks in advance!
