[SSDanny]

Hey Forum,

So, I took my car to the track about a week ago. Car did AMAZING,
by the way. Got some decent times for just a few suspension mods and a couple bolt ons (e85 and headers)

Basically, on my last run of the day, the car was low on e85, and I didn’t have any extra fuel on me, so I pumped 91 at the tracks fuel pumps.

Car still ran good on my last run, but as soon as I came to my pit, the idle was VERY ROUGH. Then it said Cylinder 8 was misfiring. Drove the car home and drove very easy. I finally came around to trying to fix the issue, and I started with my spark plugs (havent changed them since I got the car, cars at about 35k miles). After swapping them out, the car seems to be running worse and thats when I got the P0174 code. I made sure to gap the spark plugs to .040 and used OEM AC Delco plugs. One of my plugs had significantly more fuel on it than the others (cylinder 8 that had the original misfire issue p0308. Car starts backfiring like crazy while accelerating at WOT from a low speed and high gear (25mph in 3rd or 4th gear). Really crazy backfires btw lol.

Any suggestions? I’m sure my warranty won’t cover it. I’m going to take out the injectors tomorrow and get them cleaned up. Car has been daily’d on e85 for about 3 years now. I’m also going to swap out the coilpacks just in case.

Thanks guys

[gtfoxy]

Originally Posted by SSDanny

Hey Forum,

So, I took my car to the track about a week ago. Car did AMAZING,
by the way. Got some decent times for just a few suspension mods and a couple bolt ons (e85 and headers)

Basically, on my last run of the day, the car was low on e85, and I didn’t have any extra fuel on me, so I pumped 91 at the tracks fuel pumps.

Car still ran good on my last run, but as soon as I came to my pit, the idle was VERY ROUGH. Then it said Cylinder 8 was misfiring. Drove the car home and drove very easy. I finally came around to trying to fix the issue, and I started with my spark plugs (havent changed them since I got the car, cars at about 35k miles). After swapping them out, the car seems to be running worse and thats when I got the P0174 code. I made sure to gap the spark plugs to .040 and used OEM AC Delco plugs. One of my plugs had significantly more fuel on it than the others (cylinder 8 that had the original misfire issue p0308. Car starts backfiring like crazy while accelerating at WOT from a low speed and high gear (25mph in 3rd or 4th gear). Really crazy backfires btw lol.

Any suggestions? I’m sure my warranty won’t cover it. I’m going to take out the injectors tomorrow and get them cleaned up. Car has been daily’d on e85 for about 3 years now. I’m also going to swap out the coilpacks just in case.

Thanks guys

One thing you can do is take #8 Coil & move it to a different cylinder & see if the misfire follows the coil. Same goes for a wire.

I always prefer to verify things before I spend money. I hate being wrong, but I hate it even more when it costs me money. That’s why I don’t gamble.

[SSDanny]

Originally Posted by gtfoxy

One thing you can do is take #8 Coil & move it to a different cylinder & see if the misfire follows the coil. Same goes for a wire.

I always prefer to verify things before I spend money. I hate being wrong, but I hate it even more when it costs me money. That’s why I don’t gamble.

That’s a clever idea, I’ll give it a try. Thank you.

[gtfoxy]

Originally Posted by SSDanny

That’s a clever idea, I’ll give it a try. Thank you.

Sure thing.

Just do one at a time.

A couple things are intriguing. One is you said it ran fine down the track, then misfired. That is indicative of a short pulse-width control issue. Then you said you changed to a new plug & it got worse. That would lead me to look hard at what you messed with, being the wire as the first culprit in the list of probable causes.

[SSDanny]

Originally Posted by gtfoxy

Sure thing.

Just do one at a time.

A couple things are intriguing. One is you said it ran fine down the track, then misfired. That is indicative of a short pulse-width control issue. Then you said you changed to a new plug & it got worse. That would lead me to look hard at what you messed with, being the wire as the first culprit in the list of probable causes.

You know what, I completely forgot to mention that I switched one of my spark plug wires back to an OEM one because one broke off when I pulled it off the spark plug. Could that possibly have caused the car to run even worse? Also, took the injectors out today and I’m going to get them cleaned out and see if that was an issue.

[gtfoxy]

Originally Posted by SSDanny

You know what, I completely forgot to mention that I switched one of my spark plug wires back to an OEM one because one broke off when I pulled it off the spark plug. Could that possibly have caused the car to run even worse? Also, took the injectors out today and I’m going to get them cleaned out and see if that was an issue.

Go back through that series of events to be perfectly clear.

It could be a cleaning issue, or it could be mechanical inside the injector.

If it is backfiring that is a rich condition, or simply unburnt fuel past the power stroke. So incomplete combustion caused by inappropriate flame propagation due to inadequate spark energy or just an overly rich condition, or even inadequate compression.

[Doc Oc]

Don't want to alarm you but if it were my car I'd check the compression on that cylinder.

[SSDanny]

Originally Posted by Doc Oc

Don't want to alarm you but if it were my car I'd check the compression on that cylinder.

Compression came back at 60ish psi on cylinder 8.... Oof

[Puddin]

Sounds like its time for a rebuild.

[gtfoxy]

I was pulling for you for it not to be any more than an ancillary issue.

Do you have a leak down kit? If not, do you know the ins & outs?

Might be top-end, might be rings. When I do it I remove the exhaust from the head, mechanically hold the TB open & pull the dip stick. Then pressurize the cylinder & listen for where the air leak is heard.

Step 2 is add a few oz’s of oil in the plug hole & immediately retest & note the change in leak down %. It will drop pretty quick as the oil is pushed past the rings but it will give you a quick window in how bad the ring seal is.

I’d still replace that injector or have it tested.

[s346k]

Originally Posted by SSDanny

Compression came back at 60ish psi on cylinder 8.... Oof

so.... what did it run? automagic car?

[SSDanny]

Originally Posted by gtfoxy

I was pulling for you for it not to be any more than an ancillary issue.

Do you have a leak down kit? If not, do you know the ins & outs?

Might be top-end, might be rings. When I do it I remove the exhaust from the head, mechanically hold the TB open & pull the dip stick. Then pressurize the cylinder & listen for where the air leak is heard.

Step 2 is add a few oz’s of oil in the plug hole & immediately retest & note the change in leak down %. It will drop pretty quick as the oil is pushed past the rings but it will give you a quick window in how bad the ring seal is.

I’d still replace that injector or have it tested.

Hey. So I got all 8 of my injectors cleaned with brand new seals. The injectors were pretty badly clogged. I got brand new spark plugs, and swapped over the coilpacks/plug wires from one side of the engine to the other (bank2 was reading lean conditions). Assembled the car back together and now it's stuck in limp mode with brand new codes. BY the way, a friend of mine a bit more mechanically inclined that me told me I might have done my compression test wrong, so compression hasn't been checked. Engine idles fine now, but I'm getting these new codes: P0090, P00C8, P0202, P0204, P0206, P0090, P0420, P0430, P0174, P0151..

I double checked all plugs and vacuum lines/hoses when assembling. Car just feels like it's struggling to suck in air, don't really know how to explain. Currently looking to buy a HPtuners to send all the logs to my tuner as I believe this is probably an issue out of my knowledge at this point. Any insight you can give would be immensely appreciated.

[SSDanny]

Car is now in limp mode, by the way.

[Deputy Dog]

Originally Posted by SSDanny

Car is now in limp mode, by the way.

Try clearing all your codes with a scanner. Turn car off overnight, or better yet disconnect the battery. Hook back up and retest tomorrow. See if some of the codes clear.