unfixable 84 silverado?

oldchevyfan · April 22, 2005

I need help. I purchaced an 84 chevrolet with a 305 engine from an 82 year old man the bought it new and was driving it daily until i purchaced it.

I can get in it after it sat for a hour or so and it runs perfect for about 10 minutes or so then it just loses power. you cant give it gas, it will not take it, if you let off of the gas it will hit a (sweet spot) and start to pick up speed again but only in that spot in the throttle, if you try to give gas it slows down again.

condition of truck is near perfect well taken care of.

most all the vaccum hoses were dry rotted but were replaced one at a time by me.

what ive done: full tune - plugs wires cap rotor air fuel pvc

carb replaced the carb with correct reman qjet. thought it was bad got another same thing. none of the tune has even helped in the least. exhaust heat riser is working.

can my problem be electrical? fuel? plugged converter?

this is a very nice truck and i would like to keep it all stock including emmissions

if any one has any ideas please let me know

feel free to E-mail me ([email protected])

saturday im taking to an exhaust shop to chech back pressure.

forgot to mention that sometimes it has an exhaust backfire on de-celeration.

and after you drive for a few minutes in the (sweet spot) it will take off like a bat out of hell for a few more miles then the same thing

Wingnut · April 22, 2005

That sounds a lot like a fuel problem.

Is is really sucking gas?

snoman · April 22, 2005

I disagree with the plugged filter. The fact the it running well the first 10 mins when engine is cold and fuel flow is the highest tend to confirm the filter is not plugged. My guess would be the you possibly have eithe a bad engine temp sensor that is sending wrong temp info to ECU or possibly a bad O2 sensor or the ECM itself is bad. The fact that is does run well for a while tends to suggest that the MAP sensor and TP sensor is okay. Could also remotely be a bad fuel pump the weakens as it warms up but no too likely.

Wingnut · April 22, 2005

Who said plugged filter?

snoman · April 22, 2005

Who said plugged filter?

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A typo, I meant fuel problem in the sense that there is a filter, injector of pump problem. If it was fuel problem it would likely never run correct for the start unless he was dealing with water in tank that gets stiring up and injested in pump after it runs for a bit. My feeling is that it is starting rich (as normal) and never leans out/adjusts properly as the engine warms up annd cause problems because of possible sensor problems.

tmf6902 · April 22, 2005

I have a 86 Blazer with the infamous 305. What you are experiencing is called a TPS, a Temporary Power Loss. It's a feature of these wonderful engines. Sorry, but it's a fact of life.

snoman · April 22, 2005

I have a 86 Blazer with the infamous 305. What you are experiencing is called a TPS, a Temporary Power Loss. It's a feature of these wonderful engines. Sorry, but it's a fact of life.

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You mean TPL?

tmf6902 · April 22, 2005

I have a 86 Blazer with the infamous 305. What you are experiencing is called a TPS, a Temporary Power Loss. It's a feature of these wonderful engines. Sorry, but it's a fact of life.

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You mean TPL?

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LMAO yeah been watching to much office space I guess.

Frank S · April 22, 2005

If you have an intermittent cut out along with the loss of power, pull the distributor module and have it tested at a parts store.

A lot of times that's exactly how they act when they go out, by allowing the vehicle to reach operating temperature and then malfunctioning. Definitely sounds ignition related to me though.

oldchevyfan · April 22, 2005

That sounds a lot like a fuel problem.

Is is really sucking gas?

Thanks alot guys for your replys, this will give me somewhere to go from here

I will replace the fuel pump (because they are inexpensive)if it fixes or not.

i was thinking because of the backfirethrough exhaust on decelleration that happened that it may be with the spark or ignition problem not firing the fuel and loading the cyls with fuel and igniting later.

snoman · April 22, 2005

If you have an intermittent cut out along with the loss of power, pull the distributor module and have it tested at a parts store.

A lot of times that's exactly how they act when they go out, by allowing the vehicle to reach operating temperature and then malfunctioning. Definitely sounds ignition related to me though.

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My nickle is it on being a fuel related problem with falty sensors or ECM.

oldchevyfan · April 22, 2005

That sounds a lot like a fuel problem.

Is is really sucking gas?

Thanks alot guys for your replys, this will give me somewhere to go from here

I will replace the fuel pump (because they are inexpensive)if it fixes or not.

i was thinking because of the backfirethrough exhaust on decelleration that happened that it may be with the spark or ignition problem not firing the fuel and loading the cyls with fuel and igniting later.

And yes its really really hard on gas right now. when it runs correct its twice as good

oldchevyfan · April 22, 2005

That sounds a lot like a fuel problem.

Is is really sucking gas?

very badly!! get about 5-6 miles to a gallon when running crappy.

snoman · April 22, 2005

That sounds a lot like a fuel problem.

Is is really sucking gas?

very badly!! get about 5-6 miles to a gallon when running crappy.

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I still say the engine is stuck in rich cold start mode due to bad temp sensor or ECM. It could have a bad O2 sensor too as they all can cause engine to go over rich when warm, run bad, drink a lot of gas and backfire from excessive unburned fuel getting into hot exhaust manifold. This is not a distributor problem as the symptoms do not add up for that.

oldchevyfan · April 23, 2005

That sounds a lot like a fuel problem.

Is is really sucking gas?

very badly!! get about 5-6 miles to a gallon when running crappy.

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I still say the engine is stuck in rich cold start mode due to bad temp sensor or ECM. It could have a bad O2 sensor too as they all can cause engine to go over rich when warm, run bad, drink a lot of gas and backfire from excessive unburned fuel getting into hot exhaust manifold. This is not a distributor problem as the symptoms do not add up for that.

That makes perfect sense and sounds very logical. I have access to an OTC neymisis scanner and was looking for the test port for the ecm??? would try reading the values of all sensors and switches to check for operation but i cant find the plug. Im more used to the later model dianostics obd 2 etc. havent had an 84 that even had all the emissions on it much less computer still intact. Ive had a boat load of Monte SS (have one for sale) and the ecm is in the RH kick panel but the test port is in the standard location on the LH side below the column.