Random missfire with Intake swap

**beach cruiser** · 01-17-2010, 06:40 AM

Intake/header swap, now a randon missfire. Here's the deal, 2000 WS6. I swapped the intake for a LS6 intake and installed headers. Now I have a problem I can't track down. car has not been tuned yet. From off idle there seems to be a little stumble, then it clears up and the car is strong. On the top end, there seems to be some random misfiring and the car doesn't seem to have the power it should. At idle, this is also random "pops" you can hear coming out of the exhaust. Kinda seems to me like it's running rich at Idle and lean at RPM, but It's not setting any codes. I put the stock injectors back in, should I have upted the ante for some LS6 or Z06 injectors? None of these issues were there until I did the swap. Also note that the TB is from the LS6 and it's ported. MAF is stock. (and clean). Plugs and wires are all new

Any help would be appreciated

**Hi-Po** · 01-17-2010, 07:26 PM

Originally Posted by beach cruiser

Intake/header swap, now a randon missfire. Here's the deal, 2000 WS6. I swapped the intake for a LS6 intake and installed headers. Now I have a problem I can't track down. car has not been tuned yet. From off idle there seems to be a little stumble, then it clears up and the car is strong. On the top end, there seems to be some random misfiring and the car doesn't seem to have the power it should. At idle, this is also random "pops" you can hear coming out of the exhaust. Kinda seems to me like it's running rich at Idle and lean at RPM, but It's not setting any codes. I put the stock injectors back in, should I have upted the ante for some LS6 or Z06 injectors? None of these issues were there until I did the swap. Also note that the TB is from the LS6 and it's ported. MAF is stock. (and clean). Plugs and wires are all new

Any help would be appreciated

You can not swap injectors with out a tune, unless maybe they are the exact same injectors. If you upgrade, it needs a tune.

You installed headers. Are you absolutely sure you got all the plug wires snapped back on the plugs? It can be difficult, but make sure you hear/feel both audible 'clicks'. Are you sure none of the spark plug wires are not touching a header? When you installed the intake, where all the intake gaskets good? No cuts etc? Did you properly torque the intake down and to the correct TQ spec?

**0rion** · 01-17-2010, 09:16 PM

did you take the plugs out when you put the headers in? I've seen people crack the ceramic on the plugs when doing a header swap if the plugs are left in. Like Hi-Po said....check and make sure you got all the wires seated down on the plugs and coils and maybe check those plugs and make sure none are cracked.

**Too Fast** · 01-18-2010, 02:19 AM

Yup! Many people here have descibed the same thing you are talking about after a header install, go back over your plug/wire connection carefully. It's easy to have one or two not quite snapped on. Should be what it is, 'specially since it had no problem!

**beach cruiser** · 01-18-2010, 04:03 PM

Ok guys, I feel like a dumb a$$ now. I went over all the coil pack connections and plug wires. Guess what, it was the front plug on the drivers side that had a loose boot! That's what I get for having someone help me and tell me, "yeah, they're all snapped in" LOL! Anyway, seems better now, I'll know for sure when I drive to work tomorrow. On the 30th , she's going on the dyno, so I'll have some numbers for you on the Ebay headers.

**joedude02** · 01-18-2010, 04:17 PM

subscribed....I've been waiting 3 months or better to find out the dyno results of these headers.

**Too Fast** · 01-19-2010, 03:49 AM

Originally Posted by beach cruiser

Ok guys, I feel like a dumb a$$ now. I went over all the coil pack connections and plug wires. Guess what, it was the front plug on the drivers side that had a loose boot! That's what I get for having someone help me and tell me, "yeah, they're all snapped in" LOL! Anyway, seems better now, I'll know for sure when I drive to work tomorrow. On the 30th , she's going on the dyno, so I'll have some numbers for you on the Ebay headers.

No need to feel like a dumbass, dumbass, glad to hear it was a simple fix!

**jb3golf** · 01-21-2010, 09:07 PM

Originally Posted by joedude02

subscribed....I've been waiting 3 months or better to find out the dyno results of these headers.

Uh.....Yeah!!!!! Didn't WE pose this question in that header thread!!! Let's get some dyno numbers!!! I thought they'd be in by now......

**jb3golf** · 01-21-2010, 09:08 PM

Originally Posted by beach cruiser

Intake/header swap, now a randon missfire. Here's the deal, 2000 WS6. I swapped the intake for a LS6 intake and installed headers. Now I have a problem I can't track down. car has not been tuned yet. From off idle there seems to be a little stumble, then it clears up and the car is strong. On the top end, there seems to be some random misfiring and the car doesn't seem to have the power it should. At idle, this is also random "pops" you can hear coming out of the exhaust. Kinda seems to me like it's running rich at Idle and lean at RPM, but It's not setting any codes. I put the stock injectors back in, should I have upted the ante for some LS6 or Z06 injectors? None of these issues were there until I did the swap. Also note that the TB is from the LS6 and it's ported. MAF is stock. (and clean). Plugs and wires are all new

Any help would be appreciated

Hey did you throw any DTC's??? Maybe P0300?? Just wondering.....

**beach cruiser** · 01-22-2010, 03:43 AM

It never threw any codes on the ecu. But when I had a snapon scanner on it, it showed that it had some missfires on cylinder #1, that was the loose plug wire.

**jb3golf** · 01-22-2010, 08:18 AM

Originally Posted by beach cruiser

It never threw any codes on the ecu. But when I had a snapon scanner on it, it showed that it had some missfires on cylinder #1, that was the loose plug wire.

Oh.......ok. I'm having a similar issue right know except I have P0134......Hopefully it's nothing major....glad it all worked out for you!

**beach cruiser** · 01-22-2010, 09:03 AM

This is what I got off the web for that code:

The powertrain control module (PCM) provides a baseline voltage of about 450 mV on the oxygen sensor signal circuit. When cold, the PCM detects the the internal resistance of the sensor is high. As the sensor warms up the resistance is lowered and it starts producing voltage based on the oxygen content in the exhaust. When the PCM determines that the time it took for the sensor to warm up is greater than one minute or that the voltage is inactive (not reading outside 391-491 mV it views the sensor as inactive or open and sets the P0134 code.

**jb3golf** · 01-22-2010, 09:31 AM

Originally Posted by beach cruiser

This is what I got off the web for that code:

The powertrain control module (PCM) provides a baseline voltage of about 450 mV on the oxygen sensor signal circuit. When cold, the PCM detects the the internal resistance of the sensor is high. As the sensor warms up the resistance is lowered and it starts producing voltage based on the oxygen content in the exhaust. When the PCM determines that the time it took for the sensor to warm up is greater than one minute or that the voltage is inactive (not reading outside 391-491 mV it views the sensor as inactive or open and sets the P0134 code.

Great explanation! Thanks!! Like I told Hi-Po, I better inspect my O2 sensor and make sure it was hooked up right......appreciate the info.....

**jb3golf** · 01-22-2010, 01:07 PM

Originally Posted by beach cruiser

This is what I got off the web for that code:

The powertrain control module (PCM) provides a baseline voltage of about 450 mV on the oxygen sensor signal circuit. When cold, the PCM detects the the internal resistance of the sensor is high. As the sensor warms up the resistance is lowered and it starts producing voltage based on the oxygen content in the exhaust. When the PCM determines that the time it took for the sensor to warm up is greater than one minute or that the voltage is inactive (not reading outside 391-491 mV it views the sensor as inactive or open and sets the P0134 code.

Thanks again......BTW....I finished installing the same headers you have, so I look forward to the dyno numbers......what did you have on the car before these? Stock manifolds? Another header?

**beach cruiser** · 01-22-2010, 02:33 PM

Stock Manifolds and stock y pipe. I also swapped out the Intake for a LS6. I can feel a big difference in the car now that the miss is sorted out.

**jb3golf** · 01-22-2010, 04:30 PM

Originally Posted by beach cruiser

Stock Manifolds and stock y pipe. I also swapped out the Intake for a LS6. I can feel a big difference in the car now that the miss is sorted out.

Nice......I haven't swapped my LS1 intake out yet but I'm sure that really woke the engine up. Just wait until it's tuned!!

**Too Fast** · 01-22-2010, 05:25 PM

^^^I agree. One of my resolutions is to get the car tuned by spring, and maybe by fall to get the LS6 intake installed. Headers/ORY really woke up Too Fast!

**jb3golf** · 01-22-2010, 05:50 PM

Originally Posted by Too Fast

^^^I agree. One of my resolutions is to get the car tuned by spring, and maybe by fall to get the LS6 intake installed. Headers/ORY really woke up Too Fast!

Yep!! +1 on that...I NEED the LS6 intake!!!! Do you have a cam in that beast or is it stock???

**Too Fast** · 01-23-2010, 02:13 AM

Originally Posted by jb3golf

Yep!! +1 on that...I NEED the LS6 intake!!!! Do you have a cam in that beast or is it stock???

Stock. However, with the LTs and ORY, that got Too Fast its' first 12s at the track. 1 year after the header install I was running 109+ MPH for 7 runs at the drag strip, with a best that night of 12.89 @ 109.85. Damn near 110 MPH in the1/4, I think is fast as hell for a car with street tires. And, it still gets 25-28 MPG highway! A tune, and LS6 intake, won't take anything from the gas MPG and will only improve the track times. That's my goal for the car, 12s @ over 110 always, with great MPG. If I have to put 4.10s in, I will, I've read a lot of people here who've done that and they say highway MPG suffers maybe by 1, since we have such a tall OD.

**beach cruiser** · 01-23-2010, 06:48 AM

FWIW, I'd get the LS6 Intake first, and port the Tb before I had it tuned. I'm going on the Dyno next sat with the stock tune, then this summer if I can find enough money, I'll have it Dyno Tuned. The 98-00 cars have the bigger cam and the LS6 Intake really wakes them up. I can be cruising at 65mph in 5th and the car will still put you back in the seat!