94 2.3l rough idle when warm, worse after new radiator. Possibly mass air flow sensor?


STPL

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Quick update: I tested the vacuum on the line from the old EGR solenoid to the EGR valve and the vacuum pull wasn't very consistent when I blipped the throttle. I replaced the EGR solenoid and unfortunately it didn't change anything. I'm still thinking its somehow related to the vacuum system, but I'm all out of ideas. I can spend money and throw parts at it all day, but I want to diagnose the problem the correct way. I'm going to throw in the towel and drop it off at a reputable shop tomorrow and see what they say. They should be able to give me a diagnosis and advice on how to fix it myself.
 


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STPL

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Update: I dropped it off at a local shop to see what they think, and they weren't very helpful. I think the guy took one look at my truck and didn't want to touch my it because an amateur, myself, has been working on it for the past two years. He noticed that the battery terminal ground clamp was a little worn and loose and recommended replacing that. He also said my battery was at 500/850 CCAs and was in need of replacing. He suggested I start with the battery ground to make sure the basics are in place and go from there. I was hoping for a more definite diagnosis at this shop, but I think they just pointed out the first thing wrong and took my 100$. I hope they're right! I don't know if i need a new battery, but I do have a 3 year warranty at advance auto so maybe i will try swapping it out. I will definitely replace the terminal clamp.

Now heres my question. The engine idles a little rough, rough enough to shake the exhaust pipes and cause some noise. But if you grab the throttle and crack it just a little it smooths right out. If my ground is bad, is it possible that all of the sensors aren't getting the correct voltage, thus sending the computer the wrong information and the computer is incorrectly compensating for a condition that doesn't exist? When i apply a little bit of throttle the electrical system is now being provided more voltage and the sensors are giving the correct reading so now the idle smooths out? That's my hypothesis if this ground clamp is really causing a problem.

I'm going to start throwing parts at it every now and then and see if I can track this issue down. I would rather be spending 30-50$ a week on parts than 100$ on a shop to guess on whats wrong. Im going to start with the ground clamp, 02 sensor, fuel filter, fuel pump then move onto the TPS, DPFE, MAF and other electronic parts. The only code thats stored is a 172 Bank 1 Lean code so im going to track down fuel and sensor problems first.
 

STPL

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Quick Update: replaced both battery terminal clamps and cleaned the ground to frame connection. Its possible the truck starts a little better now, but the isdle and loss of power problem still persists. I bought an 02 sensor and I'm going to throw that on this weekend and see if that makes a difference. I'm noticing my fuel pump is whining pretty loud, I can hear it outside the truck when the truck is running. If this 02 sensor doesnt solve the problem im going to tackle the fuel pump next.
 

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What does the inside carburetor or throttle body look on the inside. Particularly where the idle air controller and butterfly valve are? If they are pretty filthy, that might be something to look at cleaning.
 

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What does the inside carburetor or throttle body look on the inside. Particularly where the idle air controller and butterfly valve are? If they are pretty filthy, that might be something to look at cleaning.
The throttle body is clean, I recently took apart and cleaned the whole intake side and changed the pcv valve. So I'm ruling that out for now.
 

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Update: I changed out the 02, heater core and ECT (engine coolant temp) sensor. Since this problem oddly started after I cleaned out my radiator I thought I would go ahead and replace some inexpensive parts on the cooling system. The heater core was original to the truck and full of black sediment so that needed to be replaced anyways.

I did notice a new condition driving home at night the other day. I normally don't drive after dark, but sitting in the driveway I noticed that the dash gauge lights slightly flicker when the truck is idling poorly. When i give it a but of throttle, the engine smooths out and the lights get a touch brighter and stay solid. Also, when the truck is not moving and I turn the wheel and engage the powersteering, the battery gauge dips from about 3/4 down to 1/4 and the lights on the dash dim. When i press the gas and turn the wheel I dont get this problem. I do notice that a lot of times when I start the truck up the battery gauge is at about 1/4 and idling poorly, but if I tap the gas the engine smooths out and the battery gauge jumps back up to its normal 3/4 position. Could this probably be an alternator or battery issue? What would cause the battery gauge to drop when the power steering is engaged?
 

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The alternator requires speed to generate properly... when the engine is running rough and about to stall... it's not spinning things fast enough to keep up with the electrical load. Lights dim... voltmeter falls... seems normal for whats happening to me.
 


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