I need help again.

[Chabs]

Okay, some of you may know by now that I have a turbocharged 1984 318i, built to race in the Newfoundland Targa and boosting 12PSI. I have a huge fuel pump, Megasquirt, big injectors and coils from a Chev 350.

This is my problem now:

When I drive it, it runs relatively smoothly, but when it starts boosting a little more and the RPM's get a little higher, it jerks, big time. More than once. I just took it out and jerked about 3 times in a row, and when I ease off the gas a bit, it gets smooth. To me, this seems to be an ignition issue. The wires look pretty new, the plugs are a bit sooty but look alright and I just got a new 80amp alternator (not brand new, but tested and works well).

I don't know what else it could be, can anyone help me?

Thanks!

[xwill112x]

teh turboz iz boostinn to much

but nah really, idk what your prob is but i do see alot of boosted cars do that.

[AndrewBird]

Tuning. You need it. Stock ECU can't keep up with the boost and you are leaning out at higher RPM/boost levels.

You can't just throw a turbo on a motor and expect it to run well with non-turbo fuel maps. It doesn't work that way.

[HarryPotter]

Tuning. You need it. Stock ECU can't keep up with the boost and you are leaning out at higher RPM/boost levels.

You can't just throw a turbo on a motor and expect it to run well with non-turbo fuel maps. It doesn't work that way.

He noted that he has megasquirt.

[BenM]

Check the MAP Sensor. My dad's turbo 318is had a similar issue and it ended up being that.

[Chabs]

alright thanks guys. If its not the MAP sensor.. could it be anything else? I'll check it tomorrow.

[Mossman]

Can't you log your megasquirt to see what exactly is happening as far as the engine management is concerned when it jerks? Maybe MS's MAP signal doesn't match what your gauge is telling you, maybe....I was going to list a few things but it could be absolutely anything and you aren't giving us much to work with. Your management gives you infinitely more information than stock so start using it

[AndrewBird]

He noted that he has megasquirt.

Well shit, how the hell did I miss that?

[StereoInstaller1]

Well shit, how the hell did I miss that?

Same exzact way you missed making my chrome stickerz!

[GANSTA]

It sounds to me like a lack of fuel or fuel pressure getting to the rail. Do you have an external swirly pot and lift pump to help out the main fuel pump?

[evil_twin]

Is it a possible misfire? I believe you should run 1 step colder if this happens when you start getting on it.

[Chabs]

whoa lots of good info here. Thanks a lot everyone I'll try everything out. I haven't played around with the Megasquirt actually. From what I've heard it's quite difficult, but I will see what I can do.

[whodwho]

What are your plugs gapped to? Do you have a wideband installed to see what the AFR looks like?

[mikeedler]

my turbo M20 was doing something similar when i had it. It turned out to be the sparkplugs the first time. i changed plugs it kept doing it- then changed brand of plugs and ran great.-- the next it started doing it because the boost was too high for what the megasquirt was programmed for-- or so i guess-- cause when i then lowered the boost again it wasn't doing ot anymore.

[Chabs]

my turbo M20 was doing something similar when i had it. It turned out to be the sparkplugs the first time. i changed plugs it kept doing it- then changed brand of plugs and ran great.-- the next it started doing it because the boost was too high for what the megasquirt was programmed for-- or so i guess-- cause when i then lowered the boost again it wasn't doing ot anymore.

I ordered a manual boost controller and it should be here this week. I was planning on turning it down, it is actually so fast I'm scared what would happen to my poor M10 if I floored it. Maybe that'll fix it