When I’m chasing a running issue I always start with pinching closed all vacuum lines. Then start using carb cleaner. In that order.
CK5
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**FIXED!!**DEFINITELY***Super HIGH idle after multiple parts replacement - TBI 1990 K1500 350engine
- Thread starter ZombieK5
- Start date
the booster could be leaking when not applied. Pinching the hose would make a difference if this is the case. It definitely sound like it leaks when applied. Need 2 people to test that, one to press brake pedal and one to pinch hose.
Is there a video on how to fix the rod and bore vacuum leak?
gmbellew
Registered Member
if it surges at idle only when in closed loop,, but not in open loop, it could be the valve train is getting worn out and it needs a valve job. if you have a scanner of some sort, there could be clues in the O2 data. also, put a vac gauge on it and see what the vacuum is at idle. if it is rapidly fluttering, it may be a valve issue.
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I have some hose clamps that would work to shut down any passage in the hose.
I don’t think there is. I learned to do it literally over 35 years ago working for a small mom and pop outfit that had a huge word of mouth clientele. Because of their great work.
The hard part is getting the screws out of the butterfly plates. I’ve had to grind off the “swaged” end of the threaded end of the screws, then use a. Map gas torch to heat the rod around the screws to get the screws to turn out. Take the plates out, then tap the horizontal rod out toward the linkage side.
You need to find a Holley double-pumper rebuild kits that has the teflon strips.
Dig the old teflon out of the throttle-body
The teflon strips need to be trimmed to length, making it just long enough to completely surround the rod’s diameter to make the seal.
Gently tap the rod back through the throttle-body. New butterfly plates screws must be used with a bit of red loctite and the threaded end protruding through the rod must be peened over to prevent it from ever coming out.
I’ve done it many times, many years ago.
I haven’t seen any one else do it. It is many times just easier to replace the throttle-body
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I pulled off the tbi. I wanted to inspect the gasket which was brand new when I installed it. The attached photos are below. It seemed a little wet. Not sure what would cause that. It was torqued down to spec. Let me know your thoughts on the condition of the gasket.
I do not have an identical backup gasket. The other gasket I have has a open space between the throttle body bores. Is it possible I had a gasket? Will this other gasket work?
You need to lay a straight edge across the bottom of that throttle-body.
Being loose allowed it to get wet, more than usual. The gasket is a common failure area. Could be gas soaking in has always been the cause.
My memory say one style is small and one big block tbi, but i do not recell which is which
My memory say one style is small and one big block tbi, but i do not recell which is which
I put the new gasket in and it runs like total dog s*** now. It won't start and stay running.
The one w/o the center section ? I was thinking that is the big block one.
RockAuto sells that gasket for the 5.7 as well as the one without the gap between the bores.
I'm going to go get another one that doesn't have the space between the bores.
I have literally changed every hose on that throttle body and tightened every screw except for the ones that can't be reached for the regulator. I remove the IAC and checked it. It seems fine. I checked the bore for the IAC and it was clean. I put blue thread sealant on the brake booster line going into the intake. No leaks there. At this point it will start but it won't run.
I checked all the wires for any Nicks or cracks or brakes but there were none. At least there were none that I could easily see near the pigtails.
IAC clicks every time I turn on the ignition so it seems to function fine. The injectors are putting out nice spray without drips or anything else to suggest they're not functioning. The PCV valve is new and the hose from the valve to the throttle body is new.
I disconnected the brake booster hose and put a plug in it. I tried to start the truck and it really wouldn't start. I didn't think that would happen.
I disconnected the map sensor and it starts right up and runs at 600 RPM with no surging. What does that telling us? Bad map sensor? I replaced it with a AC Delco new one.
Actually it idles like a new truck.
It idle perfectly for about 10 minutes then just died but started right up again. It has settled into a 800 RPM when fully warmed up
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well when the ecm can't trust a sensors reading or is well outside parameters it will fall back on a fail safe set of tables. This will allow it to run, not efficient as if the sensors are working and correct.
Does this mean the map is bad, or the comp is just falling back on fail safe tables ? Not sure. It certainly know the Map is not changing while being disconnected.
Do you have the old parts ? Time to start swapping 1 at a time to see. After new gasket under TBI.
I just went through a bunch diagnosis, because I had 2 new fan clutches(different brands even) not working as they should. I was looking at other components, when the cause was my 1st go to. I knew it was an air flow issue. But same symptoms with 2 new parts had me second guessing
Does this mean the map is bad, or the comp is just falling back on fail safe tables ? Not sure. It certainly know the Map is not changing while being disconnected.
Do you have the old parts ? Time to start swapping 1 at a time to see. After new gasket under TBI.
I just went through a bunch diagnosis, because I had 2 new fan clutches(different brands even) not working as they should. I was looking at other components, when the cause was my 1st go to. I knew it was an air flow issue. But same symptoms with 2 new parts had me second guessing
Kicking myself... Possibly.
I thought I had the old parts. Only found my old throttle sensor. I'll keep looking thought.
I'm gonna contact RockAuto and see if they'll swap out the part
Btw, the exhaust smells a little rich
Did you reset the IAC after you changed it.
It sounds like after you changed it it went to crap
Yes, I reset it. Actually did that a few times whenever I changed anything.
he did at least once early. prob should do minimum air relearn after every change.
New MAP sensor on the way
So, New MAP Sensor. It idles a whole lot better however it goes into another surging cycle. I can get it to stop by turning off the engine and turning it on again but it will eventually go into a surging cycle.
I got surgical with the carb cleaner. I got up and close to the very very back of the TBI where the fuel injection and fuel regulator assembly bolts down. If I spray the carb cleaner where the fuel injector assembly bolts to the unit I get a definite RPM change. (see yellow arrow) I sprayed all around that TBI but didn't get any RPM changes until I did that. Now I have to wait for the engine to cool so I can unbolt the fuel lines and pull the injector assembly body off of the TBI, replace the gasket and tighten it all down again. I guess it could be worse. Any thoughts?
