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Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713238 August 19th 2016 9:11 pm
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You need to have the base timing set correctly, If you cant set it then have a professional do it, its that critical. If your setting the timing by ear you could be 15 degrees off the mark or more and not even know it. We used to bump it by 2 degrees if a customer asked us and they were using good fuel, but it still requires you are able to see the marks. That probably explains the knocking you had.

I agree, fix the safety issues before driving the van to a mechanic to set the base timing correctly. While there he can use a scan tool to look at items like the ECT and TPS to make sure its reading correctly. They both have a huge affect if they are not working correctly.

Early TBIs were really sensitive to faulty o2 sensors too. You tap in to the sensor and purposely make a lean and rich condition. A worn sensor will be really lazy or not hit the voltage limits.



Last edited by Don_F; August 19th 2016 9:20 pm.
Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713322 August 22nd 2016 7:54 pm
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Ive gone through most of the things, bout pulling my hair out from all this BS, replaced the fuel pump today, the old one worked just fine apparently so I guess I have a spare now.

I'm at the ICM now. Didn't even bother looking under the distributor cap til now. I was mistaken, distributor is the original one, PO replaced cap and rotor only. ignition module was covered in a lot of nastiness, lines to the pick up coil covered in green corrosion. removed the ICM, under it was all like oily nasty, no thermal paste or nothing. I'm not gonna hastily say that this could have been the problem all along but damnit.

I don't feel like I have the patience required here. If I replace this ICM and she still runs like crap, I might just set her on fire, sit in a lawn chair with a cold beer and watch it burn to the ground..

Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713324 August 22nd 2016 8:47 pm
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Just put in for a new ICM. Only 8 bucks, not delco but there's a ton of them floating around and people say they work so for diagnostic purposes I'm game and if it lasts longer than that cool.

I'd really like to get rid of all this electronic distributor nonsense, get a vacuum advanced HEI unit. What would be the correct one for my vehicle, and would not having all these formerly used wires plugged in somewhere cause an issue?

Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713334 August 22nd 2016 10:07 pm
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Went down to autozone and had my old ICM tested. Apparently it's in perfect working order, according to their testing machine. He told me to check my IAC valve. Could very well be I guess, it does seem to always be sucking a unfluctuatingly massive amount of air. Just sucks that I can't perform a relearn on it until I have tires. man, this van is gonna suck me dry.

Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713579 August 29th 2016 6:28 pm
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I tend to get frustrated when I work on things and nothing seems to help. But I have a list of things I've done to this van now, so maybe that'll help eliminate possibilities and get down to the problem. Unfortunately, It seems like I've done some parts chucking and likely wasted a good bit of money, but considering this at least now I have a good factory spare part for just about everything. Never hurts to have spare parts.

Anyways, the list:

Spark plugs and wires
Idle Air Control valve
Ignition Control Module
Positive Crankcase Ventilation valve
Vacuum lines here, there and everywhere
Cleaned all vacuum orifaces in throttle body
Cleaned entire fuel meter assembly
Blasted down the injectors with carb cleaner
(Used a 9v battery to open the injectors while blasting)
New gaskets for throttle body
New O-Rings for Injectors
Coolant Temperature Sender in side of Block
Coolant Temperature Sensor on top of intake
Fuel pump and filter, all in-tank rubber lines
Cleaned positive terminals and grounds

Now, after cleaning out the injectors, it seems that one squirts super phenomenal perfect nice cone spray, whereas the other one has kind of a turdy slop cone spray. They both do squirt fuel but the one with the bad pattern is the one I can unplug the injector and have the engine stay running. Could this injector be on its way out, be squirting less fuel and causing a lean state the computer tries to compensate for?

Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713581 August 29th 2016 6:42 pm
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my 305 ran like that because the cam lobes were worn down, then it skipped a tooth or two on the timing chain then went BOOM lol


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Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713582 August 29th 2016 8:37 pm
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There is a lot is "could" be, but clearly your over your head diagnostic wise. Unless you want to slowly replace one part after another, I would suggest finding a good diagnostic mechanic with GM TBI experience and pay for an hour of their time. Its not that expensive compared to buying a part at a time at the auto parts store and hoping that this is finally the one that fixes it. I would see this time and time again where people would come in to the dealership with all new parts and the problem would be something else and then after fixing the problem I had to go back and fix all the other stuff they messed up doing repairs themselves. Sometimes the bill would be many times more than if they just left it alone until they got a proper diagnostic done. I'm not saying it would be the same with your work, but clearly you need to take a different path. The professional will be able to scan the ecm and set the base timing correctly, they can also look at the injectors and do a fuel pressure test. Once all that is done you can rule out a lot of parts store trips very quickly.

Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713615 August 30th 2016 5:21 pm
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Yeah, you're right. It doesn't take a monkey to swap parts, but it takes someone who knows what they're doing/looking at to diagnose a problem. Unfortunately, to take it to a shop isn't an option as she doesn't roll at the moment.. bad tires. So, I'm landlocked in that regard, stuck doin it myself with no scan tool, just the old fashioned process of elimination. I might go see if the parts house will accept a crisp benny and my laptop as collateral to borrow theirs for a few hours. Right now though, I'm gonna head over to pick n pull and see about grabbing up a mess of injectors, a throttle position sensor and a map sensor. At least they're cheap there and i can pick up a few, better chances of getting good parts.
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[censored] YEAHHHH I forgot to send this last one earlier but SHE RUNS LIKE A CHAMP!!!!!! That damned driver side fuel injector, I had a feeling it was the culprit and now its confirmed!! So smooth startup no more hunting, just nice clean idle laugh laugh laugh laugh so freakin happy I almost started crying lol happy dance. And she got a nice bit of freshening to boot with all those changed parts, and I have plenty of spares should any future problems arise :P WOOHOO!

Re: 87 G20 with a 305 Engine that runs like crap
BungoBass #713616 August 30th 2016 6:06 pm
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Just wanted to thank yall for all your assistance, it greatly aided me in my learning process of all the different components of the engine, knowing what I'm looking at and how to troubleshoot symptoms. From where she started to now, I feel like I have a good working knowledge, and am no longer afraid to tackle them problems laugh

See yall on the road ^^

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