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89 Chevy Silverado issues.

  • wacoeagle
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28 Feb 2019 20:50 #27480 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
Why did nt it throw a code 43 ev er before I replaced the MAP sensor, maybe the ECM is trying to relearn the sensors? I will disconnect the battery for a few minutes then try again. seems like it was very sluggish running around the block, like the timing is maybe stuck in base mode and not advancing. Yet before with a bad MAP sensor, it would surge at idle but run strong thru the gears. CRAZY...

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28 Feb 2019 22:46 #27481 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
ok after replacing the MAP sensor, it starts and idles fine cold, and after it starts to warm up, it goes into a steadily declining surge. not as pronounced as before. I looked under the truck and there is a sensor in front of the starter with no wire going to it, but on the opposite side, in the block up from the oil filter there is a sensor . I dont know if the truck had 2 knock sensors, or this is a different sensor.. there is a oil pressure switch with a cone around it near the oil filter, so I dont think it is an oil pressure switch.
the truck isnt throwing the code 43 right away, as I understand it does a test on every start cycle. I erased codes, ran it for abt a minute then rechecked for codes, it was clear. then I started it again and let it run. it seems like the idle surging got progressively worse. I read that the computer will keep either retarding or advancing the timing in 1 degree increments to attempt and cause an engine knock. so im thinking this could be the issue. I can take pics of the sensors in speaking of if needed. it looks like the wire going to the sensor on the opposite side of the block, was spliced in. it is seems it was done by someone who at least knows what shrink tubing is. so folks, it seems we have another scooby do mystery to solve. as I said my oil pressure sensor is near the oil filter, not near the distributor as many seem to be. the sensor in the block had to be for something but there is no wire that goes to it, or a wire nearby that isnt plugged in,, the sensor in the opposite side of the block from the sensor in front of the starter looks a bit different., it does have a large black rubber connector plug on it,.

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28 Feb 2019 23:28 #27482 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
when we bought the truck the ignition control relay was in a bucket along with other parts. it was on the bracket, but there was no MAP sensor with it. so that is what we had plugged in when it idled good. when we went to the junkyard to find out what part the green connector plug went to , we got the whole bracket with the Ignition control relay and MAP sensor on it. it seems like that is around when it didnt want to idle right anymore. so tommorow in going to put the Ignition control relay that was on it before, along with the new MAP sensor and see what it does.
attached is the part im speaking of. possibly the circuitry in it is different, I didnt pay attention to what year truck it came off of.
I tell ya I will never by a truck again where half the engine and electronics are missing and the other half have been installed in the wrong locations.
this is getting ridiculous,, the only reason I think there would be a second knock sensor is maybe they couldnt get the original one out, and removed a block drain, installed it on the other side, and spliced an extension wire to reach. they are only supposed to be torrqued to 14 ft pounds,. shouldnt be stuck in there.
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01 Mar 2019 19:42 #27503 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
STARTING TO SEE SOME PROGRESS. ! I put the original electronic spark module back on, and didnt see any improvement. when I stepped on the throttle it missed and backfired. now before that I replace the map sensor, and the surging went away at cold start up, it went to high idle just as it should but went back to a slower surge after it came off of high idle. abt that time the mailman came with the TPS sensor, I installed it and it changed everything. truck idles good and throttle is responsive. I cant say its 100 percent fixed because every now and then I get a little slight surge. I think what is now happening is when the truck sends the signal to check for knock and pinging, it gradually retards the timing in 1 degree intervals. once the knock sensor detects a knock, the computer take it out of the check for knock mode and continues with its program. Heres what I think may be going on at this point. I had put some high octane gas in the truck last time, thinking it would help out any stale residual gas still in the tank. I think the motor is having trouble creating a knock signal with that high octane gas, as I am reading that it is harder to light it off. if it takes the computer retarding the engine several timing adjustments to get the motor to ping and knock, that would show up in the idle quality.., the reason I believe this is when it goes into this little situation, the idle quality gets progressively worse each time, like its getting farther and farther away from its correct timing. I understand that the truck checks the knock system every start up. I dont know if it repeats it if it doesnt knock when it thinks it should. so im going to put some 87 octane in it, some and see if everything gets along good. I think that when the engine checks for knock, it is so subtle when the correct octane gas is in it, you dont really notice a stumble or surge.

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02 Mar 2019 11:32 #27506 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
Hey sounds like you got her licked,in a nice kinda way. I was out fighting the snow up here in a semi a couple days,couldn’t get back to ya right away. That round barnacle on the starter side should be the knock sensor. It should have a goofy looking cap kinda connector to the center of it. The other side I gotta look up and get back to ya. That picture is the knock sensor module aka spark timing module.

Someday I'll figure this out

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02 Mar 2019 12:30 #27507 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
my book says some had 2 knock sensors, I dont know why they just had one hooked up, im going to test the one that is hooked up by banging on the block with a wrench while its idling, it should retard the timing a bit.
I cannot find any info on how the spark timing module works anywhere. Im thinking it must send the signal to the knock sensor thru the ecm. only a single wire on the knock sensor, so its output only, I think the ecm runs the program to retard the timing in one degree increments until the engine knocks, the sensor then sends a a.c voltage to the electronic spark sensor which may convert the signal to a dc voltage that lets the ecm know that the knock test either passed or failed. if passed computer goes back to its normal parameters, if failed check engine light. I have no check engine light coming on, so my sensor must be sensing a knock,, but with that 92 octane, it may be taking the timing quite a bit off the base, to make it knock, hence the little short term idle ramping episodes every now and then. . its been off all night, cold outside im going to go start it up and see what it does this morning.,

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02 Mar 2019 12:37 #27508 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
looking at the big picture this truck was quite the exception,, what are the chances of an engine having a stuck open thermostat, a bad MAP sensor, a bad TPS, THE o2 sensor in the wrong location, blown head gaskets all at the same time, but they were all problems.

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02 Mar 2019 12:47 #27509 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
Couldn’t find anything other than oil pressure and coolant temp on drivers side. When you say rubber connector, does it have three holes in it almost in a triangle shape? In a core plug hole(freeze plug)? If so it’s block heater. I’ve usually only seen them on the passengers side though, but I’m gonna put one on my drivers side as well when I change the lifters,just in case. In the negatives up here a lot.
The knock sensor gets checked at start up or near wot. The ecm wants to see 8 to 10 volts from the module all other times meaning no knock and other than the start up check,won’t use it below 900rpm. It mentions single blue wire from connector to sensor.dont run it near anything that would induce voltage, keep away from plug wires.

Someday I'll figure this out

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02 Mar 2019 12:59 #27510 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
Now you know why you got it cheap. And those parts were in the bed. No telling what there thought process was,moving things or replacing parts with a found on the floor I think it’s good part.

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02 Mar 2019 16:33 #27516 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
yes I think whoever was working on it was a drunk or meth head,, crazy things like a bolt was missing for the control arm bushing on one side, and a nut off the other side. GOOD thing Im very attentive. those bolts dont just vibrate off, someone took them off, either forgot abt them or sabotage. Its the huge bolts and nut for the camber or castor adjustment .
what happens alot around here, every joe blow and thier brother goes to these COPART auctions. if they get something good, they flip it for good money, if not so good, they try to flip it for what they paid or a smidgion more. they just want to get rid of it because they dont have the space. they always have a big story with it, like its been in storage, wife got tired of it, someone stole car and took registration sticker off and plates. yada yada. they never get the vehicle registered in thier name, its still in the title holders name. Its not an easy task getting the truth out of people anymore. the guy who sold it to me delivered it, he dropped it off and hauled azz. like he was abt to have a digestive emergency.

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02 Mar 2019 17:08 - 02 Mar 2019 17:09 #27518 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
Side note: I was looking to see if you had the same tsb’s I had on the 93’ and I didn’t find it but there was a tsb for false codes and I can’t remember the codes now,was like a 32 ad 47 or something,but anyway the fix is a new prom. The 93’ ran really rich with a slight pulse like idle, they used to have updated prom chips to fix this but I couldn’t find any. That’s how I found moates.net I was gonna run an emulator but sold the truck.

Someday I'll figure this out
Last edit: 02 Mar 2019 17:09 by Rockyroad.

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02 Mar 2019 17:11 #27520 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
the truck came from oregon before it landed in Tejas, there is a blue wire going to the sensor, , and it has the big black connector going to it, where would the switch for a block heater normally be located, or do some have a plug? like on a regular house hold item, a lamp or vacuum cleaner?

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02 Mar 2019 17:24 #27522 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
the only time my truck was running rich was when the bad t stat was in it, after that it was throwing lean, until I replaced the map and the tps. now no codes, no smoke .
Just for the Halibut, im going to order a fuel line tee and see what my pressure is running, and I may take the injectors back out and do a bench flush on them. really clean them good and see what happens. like I said sometimes it idles for several minutes, then if I rev it a bit, or drive it, it goes into like a little diagnostic slow ramping surge a few times, then levels back out and idles ok.. it seems to be either relearning something, or throwing a test out,. with everything out of whack the way it was, I think it may be trying to fine tune itself, either that or its not getting results it wants from something and its checking again.. thats what it seems like . If that little "hunting cycle "every so often would go away, it would be perfect.

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02 Mar 2019 17:32 #27523 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
I may have asked a confusing question, what im asking is if it has a block heater, will it have a 110 volt plug somewhere on the vehicle to plug into house current, or can it be heated by the vehicles 12 volt battery? there is no plug anywhere to plug it into a house extention cord

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02 Mar 2019 17:43 - 02 Mar 2019 17:44 #27526 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
The 110 cord plugs in that goofy shape connector on the block heater and you just route it out to where you can get an extension cord on it. Yeah, looks just like any 110v cord. No switch anywhere just plug it in and it’s on

Someday I'll figure this out
Last edit: 02 Mar 2019 17:44 by Rockyroad.

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02 Mar 2019 17:47 #27529 by Rockyroad
Replied by Rockyroad on topic 89 Chevy Silverado issues.
It shouldn’t be fine tuning itself,it’s not a learning type of computer. It’s definitely trying to do something based on inputs

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02 Mar 2019 18:17 - 02 Mar 2019 18:22 #27530 by wacoeagle
Replied by wacoeagle on topic 89 Chevy Silverado issues.
I just went look again, I think your right I think it is a block heater which is larger on the pass side, and a knock sensor on the driver side. the block heater looks like it had something going too it but got pulled off, there is just a prong of solder sticking out of it.
I ran the truck a while an it seems like once its warmed up good, it idles really well and steady. with the cold nature of these trucks and large radiators, It may also be switching back and forth in open loop a bit, and causing the little "episodes"< when it is warmed up good its quite steady and smooth. its like flipping a switch when it does it, then flipping it again when it comes out of it. and the engine is not in danger of stalling, it doesnt drop down that far, just enough to feel the stumble. I watch the floor shifter when its idling and it is fairly still, just a slight vibration coming thru it, and moving just a slight amount. If I had a scanner that I could see and verify this it would be cool. in hot weather I may not even see it do this. when its 105 F out it doesnt take the engine long to get to 180F. if its hopping back and forth out of closed loop, then the IAC and tps would be controlling it, and the TPS does control timing and fuel. the IAC just air. this would make more sense than the knock sensor theory.
looks like the 02 sensor comes online at around 600F. Uncle Haynes isnt too clear in the manuel on what function the 02 sensor has, though it does say it helps control fuel. Haynes makes better drawers than repair manuel s by far.!!
Last edit: 02 Mar 2019 18:22 by wacoeagle.

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