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TBI issues

oh yeah, I did check the injectors, cone shaped spray, no drops or anything.

I know for a fact that with the 02 sensor, the wire that is attatched is ok. Ill check the wire in the main harness.
 
79rustyk10 said:
.....I shortend the K5 sending unit to the same length as the old carb sending unit. I have 16 gallon shortbed TBI tank. .....
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Explain this please. You used the original K5 in tank pump/sending unit assembly? What did you modify on it?


My 88 k5 and burb both call for 0 degrees timing.

You discarded the vapor canister so of course you plugged the timed vacuum port it connected to on the throttle body, yes? How does the current tank vent? Did you keep the egr?


The FSM lists the following items to check for hesitation, sag & stumble:
Fuel pressure
Water contaminated fuel
Ignition timing
Fuel pump cycle system (wtf?)
TPS for binding or sticking
Generator output voltage (if less than 9 or more than 16 volts)
Open HEI ground CKT 453
Canister purge system
EGR valve operation

lak2004 said:
dont think so. post up in the region forum and see if someone can loan you that stuff or if someone with a set up would be willing to help you out.
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X2 use a scanner that lets you monitor what is happening in real time, it will save you lots of headache. My K5 flooded and ran like crap the other day. No check engine light. Plug in the autoxray and saw the coolant sensor was reading like -15 degrees F when it was 60 degrees out. Problem solved.
 
When I shortened it, I cut about 1 inch, if I remember correctly of the feed line, then use a compression union to pu them back together. I have been thinking of replacing the sending unit with the correct one for a pickup tank.

Yes I still have the EGR

unless I have gotten bad gas somewhere there is no water in the fuel, the tank was bone dry and the tractors and mowers all are running ok.

I will check to see if I have a vented gas cap on it. could that cause this?
 
I think you should just get a scanner on it and find out what the problem is. Find an ALDL cable and a laptop and check it out.
 
Vented gas cap isn't likely. Leaking compression fitting I could maybe see, do a search and see if you can find other posts where the fuel line in the tank has split to see if any had similar symptoms.

Not sure what cannister is being discussed, unless it's one of those "vacuum balls" that helps keep vacuum for things like AC vent operation. Either way, shouldn't affect anything, engine operation under load is based on LACK of vacuum, as that's what the MAP sensor is looking at.

EVAP has nothing to do with this problem unless the feed line is open and is a vacuum leak at times, which is unlikely, but probably possible if it's a switched feed and is open to atmosphere.
 
lak2004 said:
Really? How come?:confused:
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If it's the canister I'm assuming it is, then it stores vacuum.... which can help a motor especially if you have a aftermarket cam with less vaccum.

I do know that the map sensor runs off vacuum which could cause a problem if the computer isn't getting the vacuum it should be getting... it's been a very long time since I've had an aldl cable hooked up but I seem to remember that if the vacuum gets too low it goes into a "mode" that messes up the way your motor runs.

In my case my map senser was reading upwards of 90kpa at times which caused it to run in that mode... and it ran pretty much the way you described.... ran like ape **** at 2000 and was fine as long as you didn't hammer on it... but when you did it would just plain stumble or die.
 
The Evap canister stores fuel vapors from the fuel tank in a charcoal bed and is open to atmosphere. It stores no vacuum or pressure. The canister is connected to a timed vacuum port (open only when the throttle is opened) and whenever the throttle is open engine vacuum sucks fresh air through the charcoal bed in the canister, drawing the stored fuel vapors out to be burnt in the engine. It is not to be confused with the ball shaped vacuum reservoir. I’d have to look it up, but I’d bet the ball is to keep a vacuum source for the hvac blend doors, not for engine performance reasons.

If you are unable or unwilling to beg, borrow or buy a scanner then you'll have to go through and test each and every sensor and system that could be causing the problem. Just replacing parts without knowing if they are bad can get expensive.

Do you have any known good spare parts laying around that you can swap out to see if what you have now is bad?

Also check the grounds because loose or missing grounds can cause all sorts of weird stuff to happen.
 
Im working on finding a scanner. I tried the one the parts store lends out but that is only a code reader:mad:. the one we had when I worked there was an actual scan tool.
 
So today I was testing sensors, and my tps sensor I noticed wasnt working right. my GM factory service manual states .5 volts throttle closed, and about 5 volts WFO. well mine read nothing until about 1/4 throttle was about 1.6 volts, and at WOT was 3.6 volts. I am by no means a mechanic but this would mean my tps is bad right?
 
Is yours adjustable? I *think* some of them are on TBI, but I'm not an expert on them. My TPI setup is.

Does sound wrong, you are reading the voltage right? I'd have to look at the service manual, but I bet there are TPS error codes for too high or too low voltage, which you SHOULD be seeing (if that's how the code is triggered) if your voltage is non-existent at idle.
 
I don't know about the sensor it'self being adjustable but there should be a idle screw that will open/close your throttle blades which will change your voltage. If your 100% pausitive that your WFO when your testing then I'd say go ahead and swap the sensor.
 
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