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Old 06-02-2005, 06:51 PM   #1
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Default Misfire plus more **UPDATE**

I think the title really doesn't give the extent of the wonderful problems I am having.

Here are my issues:

- Misfire under load
- Won't idle, not for anything
- Revving the engine just results in a stall, or if light throttle, barely any engine speed increase, just misfires and more misfires.

Here is what happened. Fired the car up initially [after the top end rebuild], car ran excellent. Sounded great, engine seemed to be in perfect order [ask jrs3800.. he'* the only member who heard it]. Next day I go to start the car, runs, but has a decent misfire. The engine still ran good, idled fine, everything, but as soon as you gave the engine throttle; misfire. Day after that, I pull the intake due to an oil leak. Put it back on, start the car up, misfire is gone for the first minute of the engine running. But returns after that. Switch the Delco Ignition, same results. Change plugs + plug wires [Belden 8mm and TR55s] same results. Bolt up the MAF Sensor Body, EGR Valve, and other misc little ****. Same results.

This is where things get a little weird. When I pulled the intake, I also retorqued my rocker bolts with a fucked up torque wrench. My guess, is that I torqued it wrong. But the other weird thing, is I didn't torque them when I initially fired the engine.. just put them on 'good enough.' I also never put thread lock on when I initially put the rockers on. But why would the engine not show signs of a misfire that day, but show them the next? I can definitely tell you running a car with just headers makes the whole engine shake like hell.. I mean like a TON of shaking.. so it is a very viable option that the bolts became loose [although they seemed fine].

I keep thinking this is an electronic issue, but it just doesn't add up. No codes, nothing. AFR trick leads to nothing but constant flashes [5-7x /sec, but it'* consistent, never faster never slower]. Nothing in the ECU would make it fire like this.. unless the ECU is fucked. The only thing I have not tried, is cutting the wire which gives 5v to the ICM to tell it to back down, and let the ECU take over the timing. With the ICM controlling timing, I would only get 10* advanced, and of course it would throw a code, and I believe the ECU will never go into closed loop.. but I could be wrong about that.

I only have $65 for any sort of tools or whatnot. So whatever you guys suggest, suggest the cheap stuff first . I want to pick up a torque wrench at Sears, and use that to double check all my torques, because I really think the one I had from autozone was fucked to the max right when I got it.

What are your opinions? I'm stumped on this one. Situations such as these, are where experience pays off, and I am sure it shows I have none.


-justin
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Old 06-02-2005, 07:41 PM   #2
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Check your voltage and wiring going to the ICM?
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Old 06-02-2005, 09:06 PM   #3
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Start with your basics first-always remember the KISS rule
Go back & re-check all your connections & wires.
Triple check your plug wire routing since youve been in there.
TPS voltage correct? MAF working right (tap tap)? IAC working right? Checked fuel pressure yet?
Also check your oil & antifreeze to be sure theyre not getting mixed anywhere. I think you did a great job so far so this is doubtful, but worth looking at.

I'm gonna say your rocker nuts are fine. Most factory rocker arm nuts are staked (they will look as if someone hit them across the top with a bladed chisle). This is so the nut will dig into the stud & stay there, eliminating the need for Loctite. Thats also why they wont just "spin" on like a normal nut would on a bolt. Stock ones will usually be good for a few removal/installations before they are trash, so you should be good. (This is a pedestal style valvetrain right? There is no lash adjustment, just torque down the rocker nuts & its done?)
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Old 06-02-2005, 10:23 PM   #4
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No worries about wiring, trust me, its good. And the misfire is only under load. If I just have light throttle, the car is fine. Or when it did idle, it was fine also.

Can't get the car to idle, and my mom is too retarded to start the car [takes some pumping.. i'd say it'* about five times harder than cold starting a carb]. So I can't test the MAF Sensor, but the car doesn't change anything with or without it. EGR Valve too. TPS I have not checked.. but it'* on my list. I have not checked the Fuel pressure, however I do not think there is anything wrong with it, since it worked fine that Monday.

Yes, the rockers are a pedestal-based setup. Torque 'em down, and you are done. And yes they can just spin out. The bolts can't come out of the pedestal, but the pedestal can come out of the rocker body.. if it gets that loose. I have loctite on them now.. but I have a feeling I should go and do the tightening I did previously and see if that helps.

No coolant/water/anything in the cooling system as of yet. Can't really test for leaks when you can't keep the damn car running. I have yet to have the car running more than 2 minutes at a time, so it'* not that bad. It does get a little warm.. but it has yet to burn me.

lakeville: Why do you suggest testing the voltage to the ICM? And would you care to share how to do that? I'm guessing I can just turn the ignition on, and use a DVM on one of the terminals [I can find which terminal it is, I should test].


-justin
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Old 06-03-2005, 01:16 AM   #5
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Quote:
Originally Posted by opensourceguy
lakeville: Why do you suggest testing the voltage to the ICM? And would you care to share how to do that? I'm guessing I can just turn the ignition on, and use a DVM on one of the terminals [I can find which terminal it is, I should test].


-justin
I don't know which terminal to check, or what the values should be off the top of my head though. Also even though your wires are new....I would still check the resistance on them to be sure that they're good. I've had wires bad out of the box before.
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Old 06-03-2005, 01:23 AM   #6
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fuel problem perhaps?
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Old 06-03-2005, 10:47 AM   #7
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Default misfire

I'm going to say fuel problem or mechanical.
If you want to start with the cheap solutions try isopropal gas dryer in tank along with mystery oil. Rislone in the crankcase. You could have an intermitten valve sticking open until it wears in. Did you do head work? Compression check?
All low cost suggestions.....
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Old 06-03-2005, 03:52 PM   #8
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Tons of head work. Everything was cleaned and lubricated, valvetrain wise. Replaced the Valve Stem Seals, too.

I'm not sure why a fuel problem would cause a misfire?

The weather is acceptable tonight, so I will go back and do what I did initially to torque down the rockers. I know why the engine doesn't want to rev, it'* because it is super rich. I forgot to mention I fouled my new plugs. So that does kinda constitute a fuel problem, but it certainly isn't a lack of it.

I'm also going to go out and triple check all connections and whatnot when I delve under the valve covers.


-justin
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Old 06-03-2005, 10:53 PM   #9
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I would definitely check the fuel pressure although fouling the plugs could be caused by multiple attempts to start the engine. I don't remember if you did the extensive mods to the deck height or had the heads shaved extensively, but do you know how much preload you have on the lifters? They could bleed down so it starts okay, but hangs one or more valves open when they pump up a bit? Running way rich could be caused by many things, a bad MAF sensor, very high fuel pressure (maybe), a vacuum leak, bad plugs, wires or swapped spark plug wires, maybe an injector stuck open (usually only one cylinder affected), possibly a bad temp. sensor (reads cold with engine warm), even a bad ECM. If it won't idle, the IAC could be stuck closed too, although pressure on the throttle would bypass that.
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Old 06-04-2005, 12:02 AM   #10
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Aye.. vacuum leak you say? I don't have any vacuum components connected. The vacuum distribution block isn't even on the intake. It'* just a big empty hole. Could that be it, maybe? My biggest worry is a bad ECU. That seems to be what everything is pointing to.. but idk?

You might be right about the lifters bleeding down and whatnot.. because that seems to make the most sense. The car initially starts good, but then after it runs for a minute, it will stall then never want to start back up. It'll fire and sounds like ti wants to, but it just won't.

I just purchased a Craftsman Torque Wrench [a cheapie.. but it'* a whole lot better than the Autozone loaner I had]. I took a nap instead of working on my car today, so I will get right on it tomorrow. Torque 'em down to specs, and go from there.

Hopefully you are right about the lifter bleed-down.. that'* gotta be it .


-justin
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