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Old 10-12-2015   #21
MunsonGTA
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GTA Year: 1987
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Re: Missfire/popping at idle gremlin

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Originally Posted by quickbird144 View Post
I did something even more fool proof. Took #1 plug out and took valve cover off. Watched the valves and as soon as intake side came up I looked in the plug hole and saw the cylinder coming up and verified it with my balancer at 0.
And the rotor button was facing #1 cylinder with the #1 wire hooked onto the terminal right where it was facing?

I wonder if one of your injectors is stuck open. Does your exhaust smell really rich?
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 10-13-2015   #22
merc3065
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Re: Missfire/popping at idle gremlin

Dribbling injectors can cause the engine to stumble a bit. Are the injectors new or used? Check their specs from the manufacturer's site, they are pretty quick to check with an ohmeter.
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Old 10-13-2015   #23
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Re: Missfire/popping at idle gremlin

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Originally Posted by rhomanski View Post
You stated you've changed the injectors a couple times. You stated you've changed the prom with a new tune. Engine timing is good. Distributor is good. All the sensors are new. What have you done to the air intake? Could you have a small leak. I guess the throttle body is clean. Could the throttle plate bushings be leaking? Is the air filter new? You said the fuel was good, if air is good, that leaves the spark and timing again. Something in the wiring harness. I've got an '88 but it uses the same computer as yours because it was built before the anti theft was ready. So I have to make sure I get an '87 computer and chip.

Try and think back, did this start when something was changed? Some sensor or something. My Dad once had a Dodge pickup with a little tick. Everything he did made it worse. He asked me to get the head redone so I pulled it. Didn't help. Turned out to be the auto parts store had V8 distributors in 6 cylinder boxes. When they checked their stock they had 15 in the wrong boxes. The rebuilder did that with the last shipment. That'll make for a bad day. After another good distributor it ran perfect. Too bad his health had deteriorated so badly he couldn't use it anymore by then.
Yeah in the course of the few years I've owned the car it has seen 2 sets of injectors aside from the multecs that were all junk when I got the car. Bosch 3's and Accel 30lb. I suspect maybe injectors but who knows at this point. I have the stock elbow from the throttle body to the MAF sensor and then some 3" piping with a K&N filter on the end for a hot air intake. The throttle body is new and so are the sensors on it. I sprayed carb cleaner around the intake and throttle body today but it made no change. I did a cylinder power balance test and with that the fluttering was still there.

Next thing I'll do is a leak down test to see if maybe a valve or something might possibly be leaking. I've thrown so many parts at it lately it's not even funny.

I also did a datalog today and noticed my O2 cross counts/sweeps are insanely slow. It might as well be not even plugged up, that's how bad it is. It's a brand new heated one since I'm running the longtubes. I definitely need to tend to that.
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Old 10-13-2015   #24
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Re: Missfire/popping at idle gremlin

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Originally Posted by MunsonGTA View Post
And the rotor button was facing #1 cylinder with the #1 wire hooked onto the terminal right where it was facing?

I wonder if one of your injectors is stuck open. Does your exhaust smell really rich?
Sure was. Got everything right where it was supposed to be. Exhaust doesn't smell rich in the sense of burning your eyes, but definitely has a smell.

Last edited by quickbird144; 10-13-2015 at 07:03 PM.
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Old 10-13-2015   #25
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Re: Missfire/popping at idle gremlin

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Originally Posted by merc3065 View Post
Dribbling injectors can cause the engine to stumble a bit. Are the injectors new or used? Check their specs from the manufacturer's site, they are pretty quick to check with an ohmeter.
The injectors are certainly in question. I checked the resistance of them when I first got the new engine together and running. They were all the same, in spec. They are fairly loud, so much that you'd think I had an exhaust leak right at the head when I popped the hood.
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Old 10-13-2015   #26
MunsonGTA
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Re: Missfire/popping at idle gremlin

Is the tune that you are running, setup for the injectors you are using?
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 10-13-2015   #27
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Re: Missfire/popping at idle gremlin

I'm running out of ideas...
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Old 10-13-2015   #28
rhomanski
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Re: Missfire/popping at idle gremlin

How did you wire up the heater for your O2 sensor? With mine I wired it to one of the air valves so when it goes open loop the valve is energized by the computer and that heats the O2. When it goes closed loop the valve relaxes and the heater goes off.
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Old 10-14-2015   #29
quickbird144
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Re: Missfire/popping at idle gremlin

The tune I'm running is setup for the injectors I'm using.

For the O2 sensor I originally piggybacked it to the 12v switched radio and then a chassis ground, now I have it piggybacked on the old fuel pump relay (I say old since I recently upgraded the wiring harness for the fuel pump when I put the Racetronix kit in, which runs straight to the alternator). I may find another source for it.

I bought a reman set of Bosch 3 24lb injectors today. Put them on but car didn't wanna start. Thinking it was the tune, I put the stock chip in, no start. Put the 30lb back in fired right up. The seller says the initial start for the injectors takes a few seconds to fire since they have oil in them. I'm gonna try again tomorrow.

I'm thinking and hoping it's just a case of iffy injectors, going back even to my old engine being they were reman Bosch 3 21lb. And I got the Accel used and apparently they are no good even new. Don't hear much good about them. Who knows, but the new injectors are pretty much a last resort for me. If this doesn't do it then I don't know what will.
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Old 10-15-2015   #30
rhomanski
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Re: Missfire/popping at idle gremlin

I tried Accel years ago on mine. I put a coil and distributor module from them in it. I had high hopes for the module since they said it was so much faster than stock. Sixty miles after installing it my engine died and I coasted to the next exit. Walked up to a Waffle House and called a tow truck. Two hours later, they came and picked it up. It's been stock ever since for me. Aftermarket is not cost effective for those sort of parts.
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Old 10-15-2015   #31
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Re: Missfire/popping at idle gremlin

I'm happy to report after getting the new injectors in and cycling the fuel pump about 5 times, it fired right up. My idle is nice and smooth and throttle response is great. I also used to have a bouncing fuel pressure needle, it's now rock steady. Also used to drop fuel pressure after car was turned off. I still have a popping from the exhaust but it has been reduced to here and there where before it was pretty often.

The longtubes I have, have always had a leak on the passenger side right where it meets the head. Plus there is a slip fit connection that I also believe leaks. I think I'm gonna throw some shortubes on soon. The longtubes are nice but nothing but headaches.

Last edited by quickbird144; 10-15-2015 at 12:41 PM.
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Old 10-15-2015   #32
MunsonGTA
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Re: Missfire/popping at idle gremlin

What fuel pressure are you running? I had a popping in my exhaust years ago. I turned my pressure down from 54 to 48 and it went away.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 10-19-2015   #33
quickbird144
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Re: Missfire/popping at idle gremlin

Spoke too soon on the new injectors. Was okay until the computer started adjusting things, plus it was on the tune for the 30lb. Cold starts were rough and idle would surge when cold. Definitely need a tune for those but my problem was still there. Oh well. Threw the 30lb back in and it's better for now.

I have 2 videos, one from 2013 and the more recent one I took of the exhaust listening for the miss. Aside from having different exhaust setups, the miss is identical between the 2. I just don't get it. Could I have 2 totally different engines that have the same mechanical problem or is it something engine control wise that's causing it. That's the big question.
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Old 10-24-2015   #34
MunsonGTA
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Re: Missfire/popping at idle gremlin

Are you using the same ecm with both motors? Same sensors?
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 10-26-2015   #35
quickbird144
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Re: Missfire/popping at idle gremlin

All sensors have been swapped out. Completely different ECM and memcal. Still does it.
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Old 10-28-2015   #36
MunsonGTA
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Re: Missfire/popping at idle gremlin

Quote:
Originally Posted by quickbird144 View Post
All sensors have been swapped out. Completely different ECM and memcal. Still does it.
All that leaves is something internal in the engine, or something wrong with the harness. Who did the tune on the car?
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 10-29-2015   #37
quickbird144
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Re: Missfire/popping at idle gremlin

I'm leaning heavily towards harness. Especially since my fans have been acting weird and another issue. Fans stopped working, replaced relays, fuse, and fusible links are good. Previous owner tied the fans together to work off the ECM trigger, been like this for years, never a problem. I have power to the relay and all but it gets lost somewhere. For now I just put a piggyback wire to send signal directly once the ECM sends command.

Also recently had a problem where my SES light would double flash every couple seconds and every time it did, the car would cut out every time it flashed. Droppped the ECM and pulled the piggyback chip and left just the stock Prom and it was good. I later put the piggyback back in and it has been fine ever since.

Scott Hanson did the tune. I have different tunes from 2 different tuners, all of them has the miss. I ran a vacuum test and it was steady for the most part, which told me it wasn't valves or anything. I filled the intake up with smoke to see if I had a leaky intake gasket maybe, no dice.

Here's the vacuum video.
https://www.youtube.com/watch?v=S11nJgQgfuM
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Old 11-20-2015   #38
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Re: Missfire/popping at idle gremlin

Just a little update. Got fans working correctly. It was a corroded fusible link next to the battery. Running cool again. I've stopped stressing over the miss for now. Car runs great otherwise.
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