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Fuel Cut


Killtodie
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I had a thread going on this a bit ago, I was able to troubleshoot some things.

 

Main problem: When I give the car full gas, it will fuel cut.

 

I have done the following since:

-Checked for boost leaks

-Installed T-Clamps on all hard piping.

-Put more washers in the BOV

-Replaced spark plugs

-Swapped out MAS (tried 2 different 1Gs)

-Checked for leaky injectors

-Checked compression

-Filled up 30/70 mix of e85, did not fuel cut but had issues running on stock injectors

-Installed a boost control valve, tried turning it up and down

 

I have a narrowband gauge waiting to be installed, I need to get around to that. I know its not the best thing but I got it for free.

I have a fuel pressure gauge, it reads 36psi at idle. I cant see what it is when I drive cause its on my TB. I can try and jimmy rig a camera to it and make a recording.

 

High pressure fuel filter was replaced by me when I first got the car, pickup screen was replaced, tank had no sludge in it, pump was replaced by the previous owner.

 

What other troubleshooting can I do?

 

 

Update

 

So I replaced the damaged ignition cable and the miss fireing seemed to stopped but now there is what sounds like raspberries around 4.2k rpm.

 

 

Update v.2

 

My car does not missfire at stock boost anymore, it does start to missfire around 18lb. Currently at 15 or so. I gaped my plugs down to .030, this made a negligible improvement.

Edited by Killtodie
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You using a non OEM regulator? Why are you playing around mixing in that alcohol? First of all I want to make this CRYSTAL CLEAR there is NO FUEL CUT on any 87+ ECU. You have ignition MISFIRE. What have you done now? You using some gimic spark plugs?
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I was in the middle of starting a rebuilt on it and had the cap off, but then I found out that the one I was using had been rebuild already. The springs in it looked fine and it had fresh grease. Vac advance on it is also new.

 

I checked my timing 3 times since, 10 degrees BTDC

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When you replaced the spark plugs - what was the plug gap? If you installed 'em straight out of the box - ya might try taking the gap down to 0.036" and see if you still have plug miss fire. If not, then gradually increase plug gap 'til ya get miss fire and then drop back to the gap were there was none.

 

How old are the spark plug cables, what brand and type are you using, and are any of them touching each other or the engine's metal anywhere? Check the spark plug cables for resistence IAW FSM 8-150.

 

How old is the distributor cap; is there any evidence of tracking between the poles inside if it; and do the poles show any evidence of being burnt. What does the rotor look like - is the contact tip burnt? What brand cap and rotor are you using?

 

How clean are your coil's male and female electrical terminals?

 

How old and what brand and model is the ignition coil?

 

For What It's Worth.

 

KEN

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Ignition Coil is MSD Blaster II, the stock coil I used before also had the same problem

 

Plug gap was .43 or .44, I checked them all before installing.

 

Ignition cables are NGK, #3 has cracked plastic layering due to turbo heat, its been wrapped in electrical and turbo now has a blanket. They are still insulated.

 

Dont know about rotor cap or brand but they appeared to be new, saw no scarring. I will double check on them.

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Ignition Coil is MSD Blaster II, the stock coil I used before also had the same problem

 

Plug gap was .43 or .44, I checked them all before installing.

 

Ignition cables are NGK, #3 has cracked plastic layering due to turbo heat, its been wrapped in electrical and turbo now has a blanket. They are still insulated.

 

Dont know about rotor cap or brand but they appeared to be new, saw no scarring. I will double check on them.

 

Toadie,

 

Are you going to try reducing the plug gap and gradually increase it like I suggested in my reply above?

 

If #3 plug cable insulation is cracked due to turbo heat that could very well be your problem. That cable is fried!!

 

Are you going to take a set of spark plug cable resistance (ohm) readings like I suggested?

 

The dizzy cap will not show evidence of "scarring." You are looking for evidence of carbon tracking between the cap's internal poles. Are you absolutely sure that ALL of the spark plug cables are bottomed out seated in their female holes on the dizzy & coil and bottomed out on the spark plug male ends?

 

High RPM/engine load misfire correction is basic stuff. I gave a BASIC list of things to check first in my post above. If you accomplish/check those and you still have the miss fire - at least we know that the basic ignition system/circuit appears to be in good shape - then we'll move onto something else. Don't blow any of the list off or you will be chasing your tail 'til hell freezes over. ;)

 

If the points on the check list all check out within spec and you still have miss fire at a plug gap of 0.036" then it's time to check out the secondary injector AGAIN. Remove the OVCP. Swap the primary injector clip onto the secondary injector. Remove the coil wire at the coil. Shine a flash light into the TB throat and have someone turn the ingnition switch to run to energize the fuel pump - see any dribbling/weepage out of the injector nozzle? If you don't see any, turn the ignition switch off and then stuff a rag into the TB throat tightly against the secondary injector nozzel and wait 5 minutes. Pull the rag out and see if the are any wet gas spots. If so the injector needs to be cleaned or is shot. If not then have the the other person crank the engine over and you verify that the injector spray is conical in shape. If it isn't then send the injector out to be tested and cleaned. Oh, and check the ohm reading of the secondary injector - it should be less than 3 ohms. If it's more than 3 then the injector is shot. Ya might want to do the same thing with the primary injector too.

 

AFTER you have done all of the above THEN tell us what you found covering EACH point specifically. You have a game plan - USE IT. ;)

 

For What It's Worth.

 

KEN

 

Edit - Check that your injector clips are seating tightly on the injectors and clean. Check the injector's male terminals for corrosion.

Edited by Starfighterpilot
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I will look into that list Ken.

 

As far as the wire.

http://www.pertronix.com/prod/ig/flame/wires/img/wire_diagram.png

 

The outer jacket is what's cracked exposing the fiberglass braiding below. The main insulator still remains. The cable should not loose any functionally with just a cracked outer jacket. I do have some spares and will try them out first, since that's the easiest thing to do.

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Look under there in the dark and rev it up or if you think its not jumping over to the head instead, :) grab it. Cracked wires are no good. Tiny holes can burn through insulation and you just see a little black spot.
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Look under there in the dark and rev it up or if you think its not jumping over to the head instead, :) grab it. Cracked wires are no good. Tiny holes can burn through insulation and you just see a little black spot.

+1

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I looked for sparks before, didn't see any. I can check again.

 

 

K, its 5 am, I replaced that one bad ignition cable, had a few spare NGKs, replaced additional vacuum lines with my silicon GP and washer sprays.

 

I forgot to look at the cap, but w/e. Car is very loud so I will wait till noon to drive it and see if that fixed it.

Edited by Killtodie
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huh, okay. doing something weird now.

 

 

So I replaced that bad ignition cable and also replaced my exhaust gasket from the turbo housing

 

Anyway, when I floor it this time, it does not seem to cut fuel or missfire but makes something that sounds like raspberries. around 5k rpm eh?

Edited by Killtodie
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Raspberries? :unsure:

 

Does the sound sound like a shrieking noise? If so, you have a loose exhaust manifold fastener(s), loose fasteners at the turbo to exh manifold or the fasteners holding the down pipe to the waste gate casting are loose. It could also be the exhaust housing volute/waste gate to the turbo cartridge attachment clamp's nut is loose.

 

For What It's Worth.

 

KEN

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So I replaced that bad ignition cable and

 

Anyway, when I floor it this time, it does not seem to misfire but makes something that sounds like raspberries. around 5k rpm eh?

So it was the ignition wire after all? :lol: Now did you ever replace that sized spark plug that was in there for ages?

 

What the hell do raspberries sound like?

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So it was the ignition wire after all? :lol: Now did you ever replace that sized spark plug that was in there for ages?

 

What the hell do raspberries sound like?

 

 

Yes and

 

http://www.youtube.com/watch?v=R3oQFa-SqfM

 

The only thing I did to the exhaust was replace that gasket out turbo housing, the 3 studs are good 'n tight, just checked and I went over most of the manifold bolts and they were all tight.

 

i'll try to make a video of this.

 

 

 

here is my video

http://www.youtube.com/watch?v=-pGyXLrpL5I

Edited by Killtodie
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Well sounds like rod knock. We had a DSM here with a bad exhaust leak, clogged CAT and he had just had an oil change and they put in 5w because that's what his EVO used. We pulled the Inner flex joint material out that clogged the CAT entry, replaced the leaky manifold gasket then drove it after it would finally rev up, lol then it was knocking so bad we barely made it back home. Hope you don't have a similar story to tell.
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Rod knock, I hope not. I dont hear any other noises. And this only started happening after I changed that plug. I'm pretty sure its the ignition system. The missfires got better after I changed the plugs about a month ago.

 

And dont scare me like, I dont like hearing that crap right now.

Edited by Killtodie
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I have a fuel pressure gauge, it reads 36psi at idle. I cant see what it is when I drive cause its on my TB. I can try and jimmy rig a camera to it and make a recording.

 

 

 

Instead of hooking up a camera, why don't you just run a hose off the FPR to the Fuel Pressure Gauge and tape it to the windshield for testing purposes? That is how I test my FP on boost ;)

 

Bill

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The outer jacket is what's cracked exposing the fiberglass braiding below. The main insulator still remains. The cable should not loose any functionally with just a cracked outer jacket.

 

Your not paying attention Toadie ;) I had a problem once with what I thought was a lack of fuel at higher RPMS. It turned out to be one bad Spark Plug Wire.And they all looked fine ;)

 

Bill

Edited by Caliber308
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