Kreinmc

My buddy bought a car with a recently built 396 stroker which seemed to run great (spun second from a low rpm punch) when he first got the car, but is now running like crap. The basic setup for the car is...

396 w/forged internals
FAST w/wideband
236/242 XE
Ported Heads
11:1 compression
6 speed
no cats
bigger injectors

The car ran some very slow 1/4 times last night so we popped the hood and noticed that nearly every primary was glowing. The car will even miss if the rpms are held at 2500. We pulled all of the plugs and everyone of them was solid black! We also readjusted the rockers, but the primaries still glow and the car still misses.

Right now we think have it narrowed down to 3 things...

Opti is toast
Timing chain is off a tooth
Wideband is not correct and the car is running WAY rich

Please let me know what you think is causing the car to miss and primaries to glow.

Thank you

SS RRR

Constant miss like a dead cylinder? Does it miss more under load?
Not sure what kind of headers, but my Hooker LT's have a tendency to glow a bit around the head and is noticeable at night...

Steves396lt1

I had this happen on a Grand SPort. 2 fuel injector lugs were on the wrong injector. Real simple check, you will see if they dont look right, they will look a little stretched. Its a simple check..

med_reject

if it really ran better initially like your friend said, then its likely something that degenerated over time as opposed to a faulty install.

Glowing headers usually happens from a lean condition, but then your plugs would not be black. I had bad misfires and glowing header primaries with a toasted opti. When I took the opti out, i could hear stuff rattling in it.

If you think the car may have been running bad frmo the start, but took a while to actually notice it, then it could be any number of install problems.

Mindgame

Glowing headers are not a sign of a lean burn.... usually just the opposite. The plugs are black because the a/f is rich. That narrows it down to a rich condition.

Do you know if you have any knock retard? How much timing is being pulled? Do you have a way to scan the engine? Is it possible you could have too much preload on the lifters?

-Mindgame

Kreinmc

We are using FAST engine management with a wideband O2 so we definately have scanning capabilities. The knock sensor is not currently hooked up, so knock should is 0 and no timing is being pulled. The timing tables are very conservative though. We readjusted the rockers today and set them to 1/8 turn with comp r's. However, this did not fix the car like we had hoped. My buddy plans to replace the opti and pull the front cover to verify that everything is setup as it should be. A shop did the install, but they mostly do ls1 work and it is very possible they messed something up.

HardcoreRM125

Is it possible, that the tune is just that bad for it? If you changed the plugs, I bet it would run OK for a little while until they foul out again ... Once their fouled out, it would miss, the O2s will lean it out, and it would get hot ... I think it could just be a bad tune, too rich ...

Kreinmc

The car has a wideband o2 sensor and according to the sensor the car has never been rich enough to do what they are doing to the plugs. FAST is very easy to use, the VE table is easily adjusted using the wideband and the wideband can even make corrections to reach target A/F. Even with brand new plugs the car still missed badly and had glowing primaries. It is possible that the wideband is bad and that the tune is way rich. Most every part on this motor has less than 2k on it.

Kreinmc

One other thing that I noticed is that KPA will hit 97 at WOT, but MAP will only reach 86 at WOT. From what I understand this means that the car has way too much vacuum at wot? The car idles in the 55 KPA range with a MAP of 13.

SS RRR

Well? Is it a dead cylinder or not?

97bowtie

Mike, you are mixing that up. The Map at WOT reaches 97 KPA and the TPS is reading 86%. I believe the TPS reading being low has to do with the 58mm TB and needing to be adjusted. However, this is not related to the problem.

I'm going to replace the opti and check the timing chain. I'd also like to get the car on a dyno to verify the wideband readings.

BTW, this is the owner of the car. Thanks for the replies.

97bowtie

All 8 primaries glow...I don't think we are dealing with a dead cylinder.