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89 Chevy Silverado issues.

  • wacoeagle
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26 Feb 2019 19:13 #27400 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
if this is a clue or not, I dont kn ow but I looked in my brake fluid reservoir and it looked like a blob of algea growing in the bottom, I used a turkey baster to suck it out. iIm thinking maybe air is getting in there and letting algea grow?

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26 Feb 2019 19:37 #27401 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
Not really, in this case. Brake fluid is hygroscopic. It sucks up moisture,damages seals and rotts out steel brake components. Unless you’re having brake issues or funny things happening when you step on the pedal, just a coincidence. By pinching off or removing and capping the line at the throttle body you’re checking the line/hose and booster for a potential leak point. If the idle changes when you step on the brake with hose connected, there’s a problem.

Someday I'll figure this out

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26 Feb 2019 20:02 #27405 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
If you have any electronic stuff, you can pop a 200ohm resister in the tps connector harness side and that would show roughly 1.0v to the computer steady. Should confirm if tps is acting funky. Keep it more than 180 less than 220ohms. Just a thought.

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26 Feb 2019 20:48 #27407 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
Ok we moved plug connector to the o2 sensor from behind the cat to the sensor on the manifold , and started the truck. no change. I killed truck, unplugged vacuum .line from brake booster and blocked it off, no change. I unplugged IAC valve and started pinching off vacuum lines. the only thing that had a reaction was the vacuum line going from the back of the TBI to what I believe is the MAP or MAF sensor. it has a green wiring harness plug going to it. if I pinch the hose slightly, I get a high sustained idle. if I pinch it completely off, it stumbles and the motor dies. blocking off egr vacuum both before and after egr solenoid had no change nor did blocking off pcv valve. I pinched of evap purge vac line, no change.

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26 Feb 2019 20:56 #27409 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
heres just a fleeting thought, does where the IAC pintle seats to the throttle body ever wear, I know on some check valves, the ball actually spins inside, and can get out of round, so sometimes it seats, and sometimes it dont. the pintle in the Iac turns, like a worm gear, and I wonder if it can groove the sealing surface a bit and cause intermittent sealing.

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26 Feb 2019 20:58 #27410 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
tommorow I will unplug the hose from the brake booster to the TBI and recheck. when I was pulling the hose off the booster, I heard vacuum sucking, so I think its good. Im thinking if the hose or booster were leaking it would not hold vacuum very long after shut down.

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26 Feb 2019 21:37 #27413 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
Yep, holding vacuum on the booster is a good thing. You can usually get about three good pumps of the brake pedal feeling the assist of vacuum. The green connector is map it’s a speed density motor, that’s an important sensor I believe you mentioned replaced. Yes, the iac seat can wear. I don’t remember the exact procedure but there is a way to ground it out from the aldl closing the pintle all the way with key on then unplugging it,then key off, unground aldl then start back up. Definitely get the exact procedure before poking around like that though. You might find it under base idle speed or setting idle speed. I’m thinking you got it narrowed down to leaky injectors if spark timing isn’t moving around. The knock sensor shouldn’t effect idle speed and those egr’s Can be a fickle pr!?k. Even faulty new ones sticking. I have my egr unplugged right now.sticky lifters piss off my knock sensors just off idle,computer retards timing and opens egr. Runs like crap first 1/8 throttle in closed loop. Ran great cold.

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26 Feb 2019 23:16 #27416 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
have not replaced MAP sensor,. I will test it tommorow, , it looks like it tests like the tps, reference volts, signal volts and ground, with a vacuum on it.

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26 Feb 2019 23:19 - 26 Feb 2019 23:34 #27417 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
what I might try tommorow is dig out my timing light and see if the timing indicator is moving around, with the surge, this might tell me if the ecm is retarding the timing or not. if the ignition is holding fairly steady, then im thinking it should be a fuel delivery or mapping problem ?

I will check the injector spray pattern while I have the timing light out, too.
once this truck is right it should be good for a long TIME, because almost everything is getting checked , cleaned, tested or replaced.
Last edit: 26 Feb 2019 23:34 by wacoeagle.

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26 Feb 2019 23:29 - 26 Feb 2019 23:40 #27418 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
I used to cut a beer can apart and make a block off for the egr. just completely seal the hole under the egr valve. better top end and no notice in loss of gas mileage. its nothing but a power robbing component that has potential to cause ALOT of problems., as u said many are crap right out of the box. I doubt the engine reburns anything out of the exhaust gas anyway, just a prop car manufacturers used to try and appease the govt pollution committees. I took the belt off my smog pump too and put it behind the seat until inspection time, ha
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26 Feb 2019 23:50 #27419 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
another way to reset the IAC is drive the truck over 40 mph for 5 min, when I reset mine, I had the back jacked up to do the brakes, so I just put it in gear and watched the speedometer go to around 42 mph, and ran it like that for a while. Feels odd sitting in the truck watching the speedo go to 42 mph while u just sit there going nowhere ha

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27 Feb 2019 10:26 #27427 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
You’ll get it,wether or not it likes it. The ecm uses the map to control fuel and timing so a steady signal is what you want at idle. I mentioned the iac procedure because it closes the pintle and remains closed while you check and set base idle,but in this case just to narrow down what was moving around. Keep at it,I’m excited to see what you find.

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27 Feb 2019 10:46 #27428 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
ive been researching the actron 9690 scanner, being Im going to have these trucks a while, I may get one. Alot of people are seeing that these old trucks werent all that bad, and dont want to pay 60,000 for a new truck, with a 4 cylinder twin turbo engine and aluminum body. these trucks will be like the c10s, everybody is trying to own one. yes, sooner or later the root issue will reveal itself, I may have another map sensor I can try in the shed. when I get back from the doctor today, the first thing im going to do is hook the timing light up, and see if the timing is being retarded or advance while idleing.. I wouldnt thin it should be moving much or at all at idle if nothing is amiss with the ignition system? if that is the case, then the side of my brain that keeps wanting to wander over to an ignition problem, can stop haunting me. ha I will then check the MAP i have a vacuum gauge and saw a chart that shows inches of vacuum and the corresponding voltage the MAP should be sending thru the signal wire to the computer, the reference voltage is the same as the tps, 5 vdc.

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27 Feb 2019 10:52 #27429 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
Somehow I missed a couple of your messages. The way you described the surging even when cold would make that map sensor much more suspect. I think you’ll see that signal moving around. Look very closely at the vacuume line,it may be collapsing on you or some crap in it. Use vacuum rated line on it only.

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27 Feb 2019 10:55 #27430 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
you know come to think of it, when we got the engine put all back together, we didnt even realize the map sensor was missing, we knew there was a plug connector not hooked up, but we were curious to see if it would run. we started it and it Idled great. It wasnt until we went to the junkyard, figured out what was missing and eventually put the map sensor and whatever else is on that bracket on. it seems like the idling problems then started. I also didnt realize the vacuum line from the back of the TBI wasnt hooked up, it wasnt even there. yet the truck idled fine, with that vacuum leak and no MAP sensor.
Im thinking that some of the vacuum circuits in the TBI Are critical to vacuum pressure and some are not,. take the pcv valve, it sucks in an enormous amount of air. I cannot see where this would be calculated into the engine management control. it is almost an open vacuum stream. why the engine idled great with the map sensor missing and a huge vacuum leak at the back of the tbi is strange.
it also had the missing o2 sensor in the manifold at that time.
Maybe it all balanced out somehow.
"" ya know what I think we should do Norton? whats dat Ralph? i tink we should remove dat o2 sensa.."" lol

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27 Feb 2019 11:10 #27433 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
Im going to check the vacuum line, i THINK TODAY may be the day we figure it out. It would be just my luck to have gotten a MAP out of the junkyard and its bad.
would a scanner that reads OBD1 have seen this from the beginning? would it show the map voltage hopping around? or just quickly fluctuating fuel trims.?

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27 Feb 2019 12:52 #27434 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
The otc genisys shows map it’s a real important sensor in non maf motors. You need to keep that o2 sensor in the manifold. It doesn’t start working till around 600°f ,zirconia type I think. It won’t really come into play at idle,but Anywhere down stream will just give you poor performance and mpg and probably that code 43 or whatever o2 code applies. The computer will substitute the non essential inputs using a base fuel map,you still had coolant temp and tps at the time map was missing, probably sucked off idle though. I’m not intimately familiar with actron but as long as it has the 12pin gm obd1 connector it’ll tell you something. They weren’t standardized then meaning not all scan tools gave the same info. I was a little surprised how much more info I got out of the otc on my 93’ compared to a friends older little hand held. I’m guessing archeologists in a couple hundred years are gonna wonder what that little black box with rubber hose is with a 45cal hole through it.

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