Many B21fts are pretty tired. They've been hacked, neglected and misunderstood by most/all for about 10+ years without a dime put into even determining exactly and repeatably what the car needs, what was overlooked in the past/damaged and what it will need I the future before parts cannons are fired and getting distracted with what it doesn't need happens. Before the last 10 years even, few mechs spend the time and few owners had the money to repair them in logical, large, preventative chunks like many required to wind up with a good solid all around far at age 30 (hard enough to do as is). Tough motor but time takes its toll, sitting or running (usually running fairly badly). Many 240t there isn't much left and it's a huge time and money sink at best.
I saw a mech actually trying to "tune up" a motor that made a little odd noise and idled smoothly. He spent 2-4 hours trying and sruggling to "dial it in". At that point, i gently suggested a basic compression and leakdown test and it was found to have 90-100psi. A phone call was made to the fairly clueless kid who fairly recently bought this heap someone gleefully (whoever sold it was probably laughing themselves silly that someone came and got the roach heap) offed on him actually confessed that previously he brought it somewhere else and it started with 80-90 psi on all holes and compression "improved" to 90-100 after surfacing and pressure testing the head, grinding the valves and replacing the head gasket.
And this is a fairly typical cycle Internet or not. In denial about what owning a 30 year old car that's a little bit of a rare one is going to possibly really need at the best of times, trying to be cheap, take a couple places and get a jumble of opinions, get distracted and buy some wheels and swag or god knows what, do things 2-3 times over, avoid getting at the root causes and making a set in stone plan.
It's pretty pointless to speculate. Compression, lean down, pressure test. Determine lambda function, fuel tank condition and pump function, vac leaks/hoses, catylst stuffed up? And so on.
Correct size tires, tire pressures, wheel bearings good, belly pan intact, alignment, dragging brakes (30 year old octopus and all that crap? And 6 rubber hoses with 10 pistons?).
At sea level timing set decently right (12-14), in good tune a stick shift turbo isn't going to be a hyper miler driven normally all stock in good repair all around. 15-25 more or less depending would be expected. 20-30 not so much. 10-15 not so much either.
Many people get caught up naming their thread "kjet 240t problems" or "kjet problems." Really it's more like "30 year old roach coach odd model 240t neglected, beat down with hack work and no pressure gauge or basic sniff out of the basic condition of the car or engine"
