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Author
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Topic: Troubleshooting a misfire on my DOHC gt
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Blind
2.3L
CAFords OG
Member # 3052
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posted
 
 
So I'm doing some checking on the 97.
vacuum is 20# at idle, drops to ~15 when revved, and then goes up to almost 25 when idling back down after the rev, settles right on 20# again.
I checked the vacuum to the EGR, it's getting a very slight constant pull, enough that I can feel but not enough to register on my gauge (at idle)
I can't really get a good seal on the egr vacuum line to my gauge, but I'm seeing about 1# when I quickly rev.
I noticed the plastic sensor immediately behind the idle control valve that has 2 vacuum ports on the bottom of it, and a breather cap on the top, has cracked where the mounting bolts are. I'm assuming this is a switch for the EGR to give it vacuum? I don't know how this switch is constructed but I can pull it off the intake, it's superglued back onto it now but if it's pulling vacuum for the EGR I doubt that will hold a seal.
At any rate, does anyone know how much vacuum the egr should pull when you blip the throttle?
I'm thinking I don't have a vacuum leak now, since it's over 20# at high idle when I start it up.
It does have an exhaust leak right now that I need to find and fix, but I'm looking for other reasons to make it part throttle stumble when cold?
I had it dyno tuned last weekend and the a/f is 12.5:1 flat across the board now, and the short term fuel trims are within 5% on both banks at all times, it picked up 20rwhp on the dyno (261rwhp on a superflow, which is ~282rwhp on a dynojet)
BUT it was misfiring on the dyno, bucking and surging part throttle, the guy tuning it thought it was a vacuum leak. Because of this he limited the total timing to 21* and said once I get the mechanical issues sorted out he'll be able to make a new tune with 27* timing and get a bunch of more power out of it...
The o2's, fuel filter, the plugs, the wires, the coil packs, the ect, the act, and the thermostat have all been replaced.
The IMRC butterfly's were deleted, if the seal between all of the ports isn't perfect (I used JB weld) would that cause my issue?
[ August 08, 2008, 08:57 PM: Message edited by: Blind ]
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89 LX Notchback ex 4cyl, 14psi
02 Harley F150, 15psi
Posts: 8521 | From: Fairfield | Registered: Jul 2003
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Blind
2.3L
CAFords OG
Member # 3052
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posted
took the intake off today, imrc's all look fine, gaskets all looked good.
only thing I noticed is one of the injectors came off the fuel rail funny, the top o-ring flew off when I pulled it, then I was cleaning it out with my compressed air gun and the filter in the top of the injector flew out, I found it and it looks fine but I'm thinking of just ordering a set of flow tested / rebuilt injectors to swap in.
I rebuilt these when I put the motor in the car (new pintle caps, new o-rings, new filters) but I just don't know what else it could possibly be at this point...
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89 LX Notchback ex 4cyl, 14psi
02 Harley F150, 15psi
Posts: 8521 | From: Fairfield | Registered: Jul 2003
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Blind
2.3L
CAFords OG
Member # 3052
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posted
figured I'd update, the problem ending up being the EGR gasket, and I swapped the "BBK catted h-pipe" for a stock 6 cat h-pipe...the BBK cat's were actually hollowed out by the p/o of the car ![[Mad]](mad.gif)
Car runs absolutely perfectly now, and passed smog with 8 hc's and 0.00% co2 ![[Big Grin]](biggrin.gif)
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89 LX Notchback ex 4cyl, 14psi
02 Harley F150, 15psi
Posts: 8521 | From: Fairfield | Registered: Jul 2003
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venommS
¯
Member # 7837
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posted
Thanks for that update Blind I'm having similar issues with my 96 cobra which I think might be the EGR so I am go to focus on that. ![[patriot]](graemlins/patriot.gif)
Posts: 104 | From: American Canyon | Registered: Aug 2007
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Blind
2.3L
CAFords OG
Member # 3052
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posted
quote:
Originally posted by venommS:
Thanks for that update Blind I'm having similar issues with my 96 cobra which I think might be the EGR so I am go to focus on that.
I changed a lot of things until finally fixing that -
plugs (autolite 764pp's and 764's, I'm running the 764pp's at .045 gap right now as recommended by my tuner)
both coil packs
plug wires
fuel filter, twice
front o2's ($$ouch)
checked/set the TPS (it was low at idle, but still didn't make much of a difference)
then of course I pulled everything on the intake apart and went over all the gaskets and put it back together with some new gaskets.
on the plus side the EGR leaking was a big exhaust leak too, so the car is quieter now, it was just so loud before I couldn't tell where the leak was coming from.
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89 LX Notchback ex 4cyl, 14psi
02 Harley F150, 15psi
Posts: 8521 | From: Fairfield | Registered: Jul 2003
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