Engine reassembly, now back fire?
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From: Lawrence, KS
Engine reassembly, now back fire? Alright, long story short, I put a cam in and didn't take the time to double check the direction of the head gasket it on the passenger side, and it blew out.
I took the whole side apart to replace it, as well as took the drivers side valve cover and coil set off to take a look at the rockers with the new springs just to see how they were doing.
Now buttoned everything back up and I have a backfire (sounds like a gunshot) coming from the drivers side (dual exhaust, dumps, bullets, non X pipe) when idling, but only has happened when the car is warming up. And it has a really really bad miss if you drive it around the block. Additionally, the 'check gauges' light flickers, almost like a short, but goes away if you rev the engine without load.
Car was running fine (despite a horrible coolant leak after the dyno session) and had no backfire prior to me disassembling the top of the engine. For what it is worth it currently has a speed density tune, effectively nullifying the MAF.
Also, no AIR, EGR, or other emissions systems.
Is there something I could have done wrong or missed to cause that to miss and backfire? Could one of the coils be bad (the coil rack was knocked over when leaning against the wall?), or one of the wires be bad?
It is not throwing any SES codes, only triggering the Check Gauges light as a flicker.
I took the whole side apart to replace it, as well as took the drivers side valve cover and coil set off to take a look at the rockers with the new springs just to see how they were doing.
Now buttoned everything back up and I have a backfire (sounds like a gunshot) coming from the drivers side (dual exhaust, dumps, bullets, non X pipe) when idling, but only has happened when the car is warming up. And it has a really really bad miss if you drive it around the block. Additionally, the 'check gauges' light flickers, almost like a short, but goes away if you rev the engine without load.
Car was running fine (despite a horrible coolant leak after the dyno session) and had no backfire prior to me disassembling the top of the engine. For what it is worth it currently has a speed density tune, effectively nullifying the MAF.
Also, no AIR, EGR, or other emissions systems.
Is there something I could have done wrong or missed to cause that to miss and backfire? Could one of the coils be bad (the coil rack was knocked over when leaning against the wall?), or one of the wires be bad?
It is not throwing any SES codes, only triggering the Check Gauges light as a flicker.
Last edited by Fosnot; Mar 25, 2012 at 12:10 PM. Reason: added info
there are many stories about poeple not pushing the plug wires all the way on. sometime they can be a pain in the a** to get them to clip on the coil or spark plug. this would cause a missfire. also where was your car leaking coolant from?
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When I first fired up my engine last year, it backfired intermittantly, and the driver's header was relatively cool, compared to the pass side header.
Someone suggested to verify that the driver's coil harness was not reversed......instead of 1, 3, 5, 7, I had it connected 7, 5, 3, 1.
The color code on a 98 (mine) may not be the same as yours, so I'm not gonna say what colors to look for.
If I read your post correctly, you said that you had removed the coil packs?
Someone suggested to verify that the driver's coil harness was not reversed......instead of 1, 3, 5, 7, I had it connected 7, 5, 3, 1.
The color code on a 98 (mine) may not be the same as yours, so I'm not gonna say what colors to look for.
If I read your post correctly, you said that you had removed the coil packs?
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From: Lawrence, KS
Backfiring thru the exhaust.
And my headers have no provisions for egr so no block off plate is needed.
How would I reverse the harness for the coils, I also have a 98.
And my headers have no provisions for egr so no block off plate is needed.
How would I reverse the harness for the coils, I also have a 98.
If you removed your coils, then you had to disconnect the coil harness.
In my case, the main connection on top of the head was plugged in, but the coil harness had been turned over.
For reference,
#1 blk--brn--ppl--pnk
#5 blk--brn--drk grn--pnk
#7 blk--brn--red--pnk
#2 blk--brn/wh--pnk--red/wh
#4 blk--brn/wh--drk grn/wh--pnk
#8 blk--brn/wh--ppl/wh--pnk
The colors can fade over time, so telling the difference between orange & red, or, ppl & red can be difficult. For this reason, I've included an extra cylinder per bank, to help differentiate.
Hope you find the trouble.
Last edited by gMAG; Mar 26, 2012 at 05:24 PM.
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The coil harness is detachable, and separate from the rest of the harness.
If you removed your coils, then you had to disconnect the coil harness.
In my case, the main connection on top of the head was plugged in, but the coil harness had been turned over.
For reference,
#1 blk--brn--ppl--pnk
#5 blk--brn--drk grn--pnk
#7 blk--brn--red--pnk
#2 blk--brn/wh--pnk--red/wh
#4 blk--brn/wh--drk grn/wh--pnk
#8 blk--brn/wh--ppl/wh--pnk
The colors can fade over time, so telling the difference between orange & red, or, ppl & red can be difficult. For this reason, I've included an extra cylinder per bank, to help differentiate.
Hope you find the trouble.
If you removed your coils, then you had to disconnect the coil harness.
In my case, the main connection on top of the head was plugged in, but the coil harness had been turned over.
For reference,
#1 blk--brn--ppl--pnk
#5 blk--brn--drk grn--pnk
#7 blk--brn--red--pnk
#2 blk--brn/wh--pnk--red/wh
#4 blk--brn/wh--drk grn/wh--pnk
#8 blk--brn/wh--ppl/wh--pnk
The colors can fade over time, so telling the difference between orange & red, or, ppl & red can be difficult. For this reason, I've included an extra cylinder per bank, to help differentiate.
Hope you find the trouble.
Alright well I'm 3 hours away from my car at college right now, but I'll check this when I get back.
Only thing I'm confused about is the harness you're talking about... how can you not connect the harness correctly? by switching sides? I took the whole bracket off... and the plug only goes in one direction right?
Any way to clarify without looking at my LS?
I went down the ole coil pack harness is backwards road. Backfired, ran rough, sounds like your issue. As to how i did it. it was just reversed. turned it around and bam it worked. First start after installiing LT"s. man was i freaked. lol
The main, large grey plug for the coil harness plugs in only one way. The main grey plug went in, but I erroneously plugged the separate, driver's coil plugs in 7/5/3/1 (by color code), instead of 1/3/5/7. All you have to do is turn the harness over. The separate coil wires are flexible enough to do this. This changed the firing order from (correct) 1-8-7-2-6-5-4-3, to (incorrect) 7-8-1-2-6-3-4-5. No doubt, there was backfire on start-up, under acceleration, along with plenty of unburned fuel!
I'm looking at both harnesses. I marked them with tape this time to help identify driver's & pass side, along with correct cylinder location.
If your harnesses are unmarked, it is quite easy to reverse driver's & pass sides (instead of just the driver's, as I did!), so that when they are reinstalled, you create a firing order of 7-2-1-8-4-3-6-5.
While this is extreme, it can happen. I'm not sure that the car would run in this condition.
A simple check of the colors, as I posted, will prove these harnesses.
To begin, the driver's side has a solid brown on each cylinder.
The pass side has a brown/white on each cylinder.
If they're off, it's a quick fix!
I'm looking at both harnesses. I marked them with tape this time to help identify driver's & pass side, along with correct cylinder location.
If your harnesses are unmarked, it is quite easy to reverse driver's & pass sides (instead of just the driver's, as I did!), so that when they are reinstalled, you create a firing order of 7-2-1-8-4-3-6-5.
While this is extreme, it can happen. I'm not sure that the car would run in this condition.
A simple check of the colors, as I posted, will prove these harnesses.
To begin, the driver's side has a solid brown on each cylinder.
The pass side has a brown/white on each cylinder.
If they're off, it's a quick fix!
i did that when i did my build, but had them both *** backwards and the car wouldnt even start and backfired while cranking it. I eventually got smart and flipped them all around. If u have it like that with one side it will start and backfire.
Make more since?
Make more since?
But still check your plugs, plug wires to make sure they are seated all the way as well.