Is anybody familiar with the throttle body injection and how the fuel flows through the manifold under various conditions?

[Backpacker]

More specifically;

How does the fuel flow to each cylinder under normal conditions?

 

If one injector is clogged, will the good injector deliver any fuel to the opposite bank without adjustments from the computer ie: limp mode?

 

I've read and experienced first hand that one injector can deliver enough fuel for both banks if one goes bad and the computer sees it. I'm curious how it compensates the flow of fuel through the manifold for one injector operation.

 

I believe I have a clogged injector, and before the computer realizes this and goes into limp, only one bank is getting combustion causing a very low and violent idle and almost non existent throttle response. Once it triggers limp the engine operates flawlessly but with the governed engine speed.

 

 

 

 

 

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Edited July 10, 2017 by Backpacker

[RCWD21]

It's basically just a large hole where the throttle body sits and then the fuel is pulled to the cylinder that has caused a vacuum on its short runner.

 

The TBI system is sorta smart but pretty dumb at the same time. At idle and "normal" driving only one injector is operating. Under WOT or heavy load the second injector kicks on and they both deliver fuel.

 

Which injector that is really depends on if they've ever been replaced before due to the 50/50 wiring. My 87 you can see fuel spraying out into the throat and hitting the throttle plate, with a bright enough light and blipping the throttle I can see much more fuel being delivered.

 

Have you tried removing and switching the injectors to see if one is indeed bad or if there's a build up on the tip? Mine were pretty bad when I did my throttle body rebuild.

Edited July 13, 2017 by RCWD21

[Backpacker]

It's basically just a large hole where the throttle body sits and then the fuel is pulled to the cylinder that has caused a vacuum on its short runner.

 

The TBI system is sorta smart but pretty dumb at the same time. At idle and "normal" driving only one injector is operating. Under WOT or heavy load the second injector kicks on and they both deliver fuel.

 

Which injector that is really depends on if they've ever been replaced before due to the 50/50 wiring. My 87 you can see fuel spraying out into the throat and hitting the throttle plate, with a bright enough light and blipping the throttle I can see much more fuel being delivered.

 

Have you tried removing and switching the injectors to see if one is indeed bad or if there's a build up on the tip? Mine were pretty bad when I did my throttle body rebuild.

Yeah I did the injector switch and discovered my injector is bad. The last two days I've been driving with the bad injector partially disconnected. When I bought it it had one bad injector and I replaced it. Now 8 months later the other old one finally went bad.

The coil went bad in the first one but I'm not sure why the second isn't working. After many trips to salvage yards I ended up buying new with the warranty. It should arrive at the parts store today, I wish they weren't so damn expensive. I'm gonna have my two bad ones rebuilt and kept in the tool box for the future because I feel like it will happen again someday.

 

 

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[RCWD21]

Well if you ever look for more used ones just remember that the throttle body on the v6 and the 4cyl engines are the same. But hopefully your new injector fixes your issues. When mine gives me problems it's MPFI time.

[Backpacker]

Well if you ever look for more used ones just remember that the throttle body on the v6 and the 4cyl engines are the same. But hopefully your new injector fixes your issues. When mine gives me problems it's MPFI time.

Yeah i noticed that they looked similar. I checked all 86-89 pathys and hardbodies. Every single throttle body was gone, I looked at like 10 vehicles.

 

 

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[RCWD21]

That sounds like here where I am. There's an 89 harbody and that was the last one I found. Luckily the manual lockers were on it still, I really wanted a spare TBI set up just in case

[Backpacker]

That sounds like here where I am. There's an 89 harbody and that was the last one I found. Luckily the manual lockers were on it still, I really wanted a spare TBI set up just in case

Dang that's the one thing I forgot to check for. I found a set on CL 120 miles from me for $40. Even with gas I think it would be worth the drive.

 

 

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[RCWD21]

That's not too bad of a drive. I couldn't wait to get the auto hubs off of my rig

[Backpacker]

That's not too bad of a drive. I couldn't wait to get the auto hubs off of my rig

I haven't had any problems yet but I've only used the 4x4 a handful of times so far.

 

 

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[RCWD21]

My big thing was when trying to rock myself out of a rut or hole. Constantly locking and unlocking got old real fast

[Backpacker]

My big thing was when trying to rock myself out of a rut or hole. Constantly locking and unlocking got old real fast

Last time I went wheeling I got stuck in some coarse sand and was doing this pretty hard and almost got out, makes me wonder if that's why I couldn't do it, i felt like I was so close to getting unstuck.

 

 

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[RCWD21]

My frustration always came when I was in a few feet of water, I've never been stuck in sand but a ton of people around me have. It's funny to see mall crawlers and pavement princesses try and follow a stock pathfinder through very simple stuff lol

[Backpacker]

My frustration always came when I was in a few feet of water, I've never been stuck in sand but a ton of people around me have. It's funny to see mall crawlers and pavement princesses try and follow a stock pathfinder through very simple stuff lol

That's funny. The only two times I've been stuck were in very dry rutted out river sand. Both times I didn't air down and I think most of it was operator error and being too paranoid because I was the only vehicle. I haven't hit any sand yet with my new 31x12.5 tires and I think that will make it a little easier next time.

 

 

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