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Author Topic: 1989 chevy tbi troubles  (Read 6348 times)

Offline Irish_Alley

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1989 chevy tbi troubles
« on: January 15, 2019, 07:59:12 pm »
ive been talking to bd about this issue, but i think i have it kind of figured out for the most part. think i can link it to bad gas, it only had a little in it when i got it and i added about a gal. then after messing with it its seams to be running better (no stalls and no black soot) its still reading rich but then it will adjust and read lean then adjust and read rich again.

the issue that im having now is every now and then the idle will drop to 600 from 800 or so. then it will pick up a few seconds later. cant really road test the truck as its not tagged. i can run it up and down the road we live on but its only a hundred yards or so. i unplugged the egr and it does the same thing. if i press up on the diaphragm it will almost kill the engine.

from the screen shots i froze the data and took one at idle and the other around 2k. for some reason i didnt think about taking one when the idle was around 600. but ill get that when i can think of it, maybe tomorrow
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Offline VileZambonie

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Re: 1989 chevy tbi troubles
« Reply #1 on: January 16, 2019, 04:36:13 am »
What did you "mess" with? Put everything back that was messed with and disconnect the negative battery cable for 30 seconds. Get new data in open and closed loop. Swap in another MAP sensor and compare readings.
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Offline Irish_Alley

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Re: 1989 chevy tbi troubles
« Reply #2 on: January 16, 2019, 03:26:18 pm »
well i took the map sensor off my 94 and put it on this truck but that was when it might have had bad gas and it still ran like crap.

checked the fuel pressure was around 12 idle and on the gas, changed the fuel filter (still ran like crap)

swapped batteries (might have had a bad connection there) was running better but had a miss.

use carb cleaner around the base of the tbi looking for a vacuum leak with no response.

made sure the plug wires were connected good (a few were loose). started running much better put the old battery back in after a charge and it was still running ok except for the idle drop.

depressed the egr and it would almost stall, then i disconnected the plug to the egr and it would still have the random idle drop.

working on my boys pinewood derby car today so i didnt get a chance to mess with the truck.
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline ehjorten

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Re: 1989 chevy tbi troubles
« Reply #3 on: January 17, 2019, 08:49:31 am »
Quote from: Irish_Alley on January 16, 2019, 03:26:18 pm
working on my boys pinewood derby car today so i didn't get a chance to mess with the truck.

You mean you are helping your boy make his own pinewood derby car, right?!  ;)
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Offline Irish_Alley

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Re: 1989 chevy tbi troubles
« Reply #4 on: January 17, 2019, 03:45:57 pm »
yeah, i got him to design it. then i cut it all out
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Offline Irish_Alley

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Re: 1989 chevy tbi troubles
« Reply #5 on: January 17, 2019, 04:38:45 pm »
tried to get the truck act up today and it wouldnt drop below 700 or so rpms. so i decided to give it some gas, keeping my foot steady i took the rpms to a little about 3k and started to notice the O2 sensor giving some odd numbers. it still would miss and idle and pretty sure it would miss when i took the rpms up but was as noticeable
« Last Edit: January 17, 2019, 04:40:40 pm by Irish_Alley »
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

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Offline VileZambonie

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Re: 1989 chevy tbi troubles
« Reply #6 on: January 17, 2019, 04:47:08 pm »
Did you disconnect the battery yet? What's the fuel integrator and block learn now, assuming you did?
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Offline Irish_Alley

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Re: 1989 chevy tbi troubles
« Reply #7 on: January 17, 2019, 04:58:38 pm »
yes i did disconnect the battery right before i ran the rpms that high today. i didnt check the BL and fuel ingrator, what are they for?
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline VileZambonie

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Re: 1989 chevy tbi troubles
« Reply #8 on: January 17, 2019, 05:21:16 pm »
I'm going to suggest you tune it up, clear the ECM and drive it. Fuel Integrator and Block Learn are short term and long term fuel trims. The ECM is reducing fuel because it detects a rich condition.
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Offline Irish_Alley

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Re: 1989 chevy tbi troubles
« Reply #9 on: January 18, 2019, 08:11:34 pm »
i kind of feel bad, my boys car is the only one with fenders. most the cars were wedge shape but even during the practice runs his car had the best time. tomorrow we'll see what it does
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline KilgoreTrout

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Re: 1989 chevy tbi troubles
« Reply #10 on: January 19, 2019, 11:33:47 am »
Nice car. That's really cool.
I was in scouts and wanted working headlights in my car, so my dad put LEDs headlights in it and wired them to a AAA battery that was tucked in to the rear (he drilled a hole for it. He made the cabin spring loaded with contacts to run the lights. I'd slip a piece of paper between the contacts to kill the lights, then pull it out right before every run.
He's insane. But it was really fun, and I had the coolest car ever.
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Offline Irish_Alley

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Re: 1989 chevy tbi troubles
« Reply #11 on: January 19, 2019, 01:38:59 pm »
he ended up placing 1st in his den. 3.167 was his lowest time most of the other cars were 3.2??, we're going back in a couple hours to race the winners from other dens. and its up to him if he wants to go to districts, and of course he does lol.
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline Irish_Alley

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Re: 1989 chevy tbi troubles
« Reply #12 on: January 19, 2019, 05:44:40 pm »
He placed second, first place had 12 wins and he had 9. His fastest time was 3.13. I need to make it faster but I don't know what I'm doing and it was our first derby. Added more graphite before the championship races and his time did drop a  few thousands. But it might of just been how he was sitting the car on the track.

But anywho time to get back to working on trucks
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If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes

Offline KilgoreTrout

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Re: 1989 chevy tbi troubles
« Reply #13 on: January 20, 2019, 09:39:44 am »
That's awesome. I bet he was happy with those results. That's fast.
I was in a lot of derbies and had a couple top 3s in my den, but never took one.
I won a rain gutter regatta once, but that's just because I'm a blow hard.
Nice job, man.
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