so no surge in open loop when running on set program, but surge starts when in closed loop and computer starts controlling actuators and looking at sensors. Might need to do some learning esp if the surge is very minor
CK5
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**FIXED!!**DEFINITELY***Super HIGH idle after multiple parts replacement - TBI 1990 K1500 350engine
- Thread starter ZombieK5
- Start date
gmbellew
Registered Member
the only difference from open loop to closed loop is the feedback from the O2 sensor is used to fine tune fueling.
seems like there is still some sort of TBI gasket problem, or the MAP hose assembly that connects to the back of the TBI under the fuel regulator is an issue if the idle changes when you spray carb cleaner in that area.
seems like there is still some sort of TBI gasket problem, or the MAP hose assembly that connects to the back of the TBI under the fuel regulator is an issue if the idle changes when you spray carb cleaner in that area.
I guess it’s possible for the leak to be there. You need to be sure and isolate the throttle bores from the carb cleaner when spraying on the upper side of the throttle body.
Have you watched the voltage rate-of-change coming out of the O2 sensor?
It should oscillate from low to high and back to low to high fairly quickly. Like atleast once every two seconds if not faster.
It should oscillate from low to high and back to low to high fairly quickly. Like atleast once every two seconds if not faster.
OK.
Insert video of me screaming down my street with crazed look on my face.
I am waiting for the data cable to arrive so I can hook up my laptop (arriving Saturday)
LATEST ISSUE
For giggles I went to swap out the NEW throttle position sensor for the old one. One of the aluminum screws broke off and now I need to extract it. Which means I need to remove the TBI again. GRRRRRRRRR!!!!!
BEFORE that I cleared the computer and reset IAC. Issue remained after that. Truck was hard to start after reconnecting negative terminal but eventually it ran... But still surged.
Disconnected MAP and truck idled fine.
I believe there WAS NOT a gasket leak and the change in RPM was carb cleaner getting into the injector chamber.
Im ready to just go out and buy an entire aftermarket fuel system.
Any recommendations?? Basic OEM level performance.
****TOMORROW****
I had to walk away from it today. Didnt want to set the garage on fire.
Tomorrow I will extract broken screw and reinstall TBI.
Would the O2 Sensor be bad? It is a new BOSCH O2 sensor
I can't imagine TWO MAP sensors being bad.
This shouldn't be this hard.
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Waiting for my data cable to arrive so I can hook it up to my laptop. Cable will be here Saturday
The NEW fuel pump I put in was from Delphi. It was part of a new sending unit/pump assembly. The datasheet shows 12psi on the pump. I am not sure what OEM pump output is.
I HAVE NOT taken it out on the road. I am not familiar with how much driving this needs to "learn"
My Toyota need VERY little learning drive time. My Subaru takes ALOT of learning drive time. I had to drive over 50 miles for the Soob to "learn" so I could get it inspected. This is my first TBI Chevy. Always had older K5's with Quadrajets.
I HAVE NOT taken it out on the road. I am not familiar with how much driving this needs to "learn"
My Toyota need VERY little learning drive time. My Subaru takes ALOT of learning drive time. I had to drive over 50 miles for the Soob to "learn" so I could get it inspected. This is my first TBI Chevy. Always had older K5's with Quadrajets.
gmbellew
Registered Member
check the MAP vacuum line for cracks.
pull the EGR vacuum line off the TBI and put a vacuum gauge on it and see what it does at idle.
pull the EGR vacuum line off the TBI and put a vacuum gauge on it and see what it does at idle.
gmbellew
Registered Member
while the TBI is off, check the nipple on the back where the MAP hooks up. make sure it isn't cracked where it comes off the TBI unit.
Understood. I'll inspect once I have the TBI off the truck.
ECM re-learn is a very particular-to-each-vehicle, thing.
I own 2 ford escapes. An 03 and an 05.
Melinda wanted the 03, so I drive the 05. Very minor differences between them.
ECM’s are identical, though. Don’t ask me how I know
Anyway, we get them both registered and inspected together. So I go through them both about 3 weeks before they’re due and fix whatever needs repaired.
Ended up clearing the codes on both on a Saturday afternoon. Had Melinda drive hers, I drove mine. Once around the valley on the belt route. With a bit of city driving back to the house off the high way.
25 minutes and 17 miles of varied speeds the 05 is all re-learned and ready to be inspected.
The 03 took over 100 miles and several hours to get it back into the same condition. No codes, no odd running conditions. Just took a very long time for it to “re-learn” back to the ready condition for inspection (smog check)
Same ECM’s, you can swap them between the two cars, it doesn’t matter.
The O2 signals on both cars are similar. The short and long term fuel trim numbers are very similar. Hell, even the engine timing change counts are similar.
So, what gives?
You got me!
Damn ECM’s makes me insane.
I own 2 ford escapes. An 03 and an 05.
Melinda wanted the 03, so I drive the 05. Very minor differences between them.
ECM’s are identical, though. Don’t ask me how I know
Anyway, we get them both registered and inspected together. So I go through them both about 3 weeks before they’re due and fix whatever needs repaired.
Ended up clearing the codes on both on a Saturday afternoon. Had Melinda drive hers, I drove mine. Once around the valley on the belt route. With a bit of city driving back to the house off the high way.
25 minutes and 17 miles of varied speeds the 05 is all re-learned and ready to be inspected.
The 03 took over 100 miles and several hours to get it back into the same condition. No codes, no odd running conditions. Just took a very long time for it to “re-learn” back to the ready condition for inspection (smog check)
Same ECM’s, you can swap them between the two cars, it doesn’t matter.
The O2 signals on both cars are similar. The short and long term fuel trim numbers are very similar. Hell, even the engine timing change counts are similar.
So, what gives?
You got me!
Damn ECM’s makes me insane.
tbi doesn't have monitors to have set. That is OBDII, yeah early 2000s Fords were a pita to set 7 of 9 monitors. Ford actually recalled the Econoline for reprogramming of the monitor relearn.
Just for giggles, I contacted Heath at folkenheath. I wanted to see if an aftermarket EFI system might benefit me. He recommended the Edelbrock Proflo 4. He initially suggested a lower-end EFI system but I would definitely need a new intake and distributor and the Proflo four includes them. I'm going to remove the TBI from my truck today. I'm going to inspect for any cracks in the throttle body or where the nipples are attached. I'm also going to extract the broken throttle position sensor screw.
PHOTOS OF TBI
Here is what it looks like. The MAP Sensor nipple should be 1st photo. I don't see any cracks.
Let me know if you see something
I may have missed it searching this thread, but what is the fuel pressure? That's one of the early steps in diagnosing any EFI problem. I know it's really hard to tell from a video, with a certain frame rate or whatever, but the fuel looks kind of "spurty" at some times, rather than a "misty" cone.
Is it possible the surging is all open-loop (like it's lean) and then closed loop brings AFR to something smoother?
I believe he said 12psi
In the old days, you could check it the dispersion by hooking up a timing light to the engine and flashing the fuel spray cone. It should appear a very symmetrical cone shape.
I once had a very odd running problem, surging, stalling, had me scratching my head for a day. Finally figured out that a dump bee(read:Yellowjacket) had crawled into the return line, which then was attached where it goes.
Dump bee effectively plugged the return line. Cleared the dump bee, all was copacetic.
It was causing an over-fueling problem. Which I found using the timing light method. It made the fuel cone very thick and occasionally a drizzle
I once had a very odd running problem, surging, stalling, had me scratching my head for a day. Finally figured out that a dump bee(read:Yellowjacket) had crawled into the return line, which then was attached where it goes.
Dump bee effectively plugged the return line. Cleared the dump bee, all was copacetic.
It was causing an over-fueling problem. Which I found using the timing light method. It made the fuel cone very thick and occasionally a drizzle
I have to say I don't think you will see much performance increase with a stock TBI engine. In fact, it already has TBI and it's stock, so I would recommend fixing that first. If it turns out to be too expensive for some odd reason, (or if you were changing cams or heads or something), then look at upgrading.
Also, though I do recommend a single plane intake with aftermarket TBI, you wouldn't necessarily need a new distributor, but if you do, you just spent enough for a PF4 at that point.
Make sure your 700R4 kickdown cable is not keeping the throttle just off idle. Its supposed to be very tight at WOT, but not keep it off idle. There is a procedure to adjust it, make sure you follow it.
Vacuum leaks, fuel pressure, etc. All are culprits.
Did you hook a vacuum gauge up to see what it does? I may have missed that.
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