84 308 qv- running too lean????

i have a euro 308 and I pulled the rear exhaust header, i found two cracked pipes just off the flange! And then I noticed the exhaust ports were all white and so wAS the exhaust header pipes inside. The white color did not wipe off. Some ferrari guy said it's running too lean. I hAVE owned the car for 10 years. It has been running great until 5 month ago. I have a slite misfire when i hold a two thousand rpm no load, and i have a jolt at 4500-5000rpm under load. Some help please!!!Bill

 

I t sounds like you had Lean missfire, I don't know what causes the crack but the white color indicates that it could be running rich. Anyway I've seen headers for sale at e-bay, you might want to check it out.

 

So u think the white is from being too rich? Some others say that it is a lean mid mid range misfire. I wonder what would cause it to lean out? Fuel head, pump,system pressure,etc. Oh I've located a couple of headers or I was giong to have them welded, and probably welded again if so be!! Thanks so much for the imput and I welcome any ideas.

 

You need an exhaust sniffer to be sure - my local mechanic 'forced' my car to run lean to pass emissions (when the cats 'fell off'). I noticed that my engine ran alittle hotter than normal. I suffered no header damage at all, probably due to the lack of exhaust gas backpressure and greater flow. Adjusting the air/fuel mixture, in conjunction with CO2 level monitoring, one can 'tinker' with this fairly easily - I think there's a special 'key' that is used on the device underneath the Air Box that pulls straight 'up'. I understand that this is a 'tuning step' in any major service? Or at least is something that is checked now and then...

 

The mixture adjustment on the k-jet only affects idle mixture. Once you get further up the rev range it has little or no effect. There is basically no adjustment on the system other than idle mixture as I understand it.

If the thing really is running lean further up the range then the KJet may need an overhaul. Best way to find out would be to stick it on a rolling road.

 

Thanks for all your info!! I'm going to check it all out. I think I need to get a hold of a fuel pressure gauge to check system pressure. Then start from there and run a sniffer up the exhaust tip,etc. fuel pressure regular......... WHO KNOWS!!! I'VE ALREADY CHANGED THE plugs, wires, caps, rotors, extentions, fuel filter. I still love my Ferrari.. Thanks again, anymore ideas are always welcome.

 

Don't forget injectors.

While on the cars w/Lambda feedback K-Jet systems the mixture adj only affects idle & the lambda feedback controls the mixture at higher flow rates. On the Euro cars w/o lambda feedback, the idle mixture setting is pretty much tracked for the entire flow range.

For a mid-range lean problem I'd start with:

1) Changeing the fuel filter, if it's partially clogged, it'll flow enough gas for idle, but not for higher demands. (oops, just saw you've already done this).

2) Run a couple of bottles of Techron concentrate in a half-tank of gas to the system to give it a good cleaning. This should take care of deposits on the K-jet's internal screen, & the injectors.

3) Check fuel pressure under load, & check fuel pump voltage to make sure neither is dropping significantly under load.

 

Let's start with the basics. Pull the plugs and see what they tell you. Especially check for differences between the plugs. Next put in a new set and go for a run. Come back and check them again. Third step is to run the car through the gears, kill the engine, coast to the side of the road, pull plugs and read them.

Or you can just put the car on a dyno and have the computer till you what's coming out of the exhaust. It's just a function of time/ money.

 

Please don't yell at me but I haven't changed the injectors (50k miles on them) The cleaner would do them good! I moved to phoenix 10 months ago and the car has bee doing some sitting because I bought a 94 348 spider. Driving both, but the 308 has seen less miles. Now that I'm selling the 348, because of garage space, I'll get to the bottom the 308 issue, I'm sure it's something easy. But, It's comforting to know that u guys are trying to help!