2001 Hyundai Tiburon.. Code P1128 Please HELP !!

Question

I initially took my 2001 Hyundai Tiburon to the shop because it was misfiring and "bogging down" when trying to accelerate at higher RPM's.. this would make it jerk around and sometimes die... but would crank right back up, and run with no problems until you really "ran it" ... I changed out the spark plugs and wiring first to see if that would help, but it did not. The check engine light was on with code P0301. The repair shop installed (then removed) a new intake manifold, and ignition coil... neither helped or cleared the code... eventually they replaced the OE fuel injector, fuel filter, and put a new valve cover gasket in... the code cleared. I test drove it... was fine for approx. 40 miles then bogged down again, and check engine light comes back on... this time code P1128.. They tried a TPS, but did not help, so they removed it... Now their suggesting I replace the fuel pump, screen, etc ( which will cost me approx. $500)...... but quite honestly... I'm no expert... but the research I've done, doesn't indicate that's the problem... to me anyway... could be wrong ??.... I can hear the pump come on... the car cranks right up, and the ONLY time it has ever cut off was when it got bogged down with heavy RPM's... but even then it doesn't cut off every time... just some times...... I ran it by another shop that was kind enough to take a quick look at it, and took it for a drive.... they were very busy and didn't have time to look at it in great detail.... but the mechanic that drove it, told me it was definitively NOT the fuel pump... My car has been in and out of the shop since May 1st !!! I'm a single Mom, and lost my job several day's before taking my car in to the shop.... I can't afford to keep paying for "exploratory surgery here"....... I've already spent over $500 and it's still not fixed...... any help would be greatly appreciated !!

Answer 1

P1128 Fuel system lean Part load

Check the sparkplug condition, that will tell alot about what the engine is going through, P1128 is a condition of the engine management

 This Hyundai came in with a rough idle, PCV hoses, check out . MAF (mass airflow sensor) was brand new. it had several code one of which was a P1128 and a P0420 and P0300.

 The sparkplug was the first to be checked, it was fouled, you can tell it was getting to much fuel. This vehicle also had a complaint of intermittent stalling,

 At highway speed the engine ran good, Just the owner did not trust the vehicle due to stalling out, and when a engine stalls out no power steering , brake assist from the brake booster is no more. There no need to measure fuel pressure it runs good at highway speed.

 The problem was solved when the fuel pressure regulator vacuum hose was disconnected and sure enough fuel was entering into the intake manifold causing the engine to choke , this explained the fouled sparkplug condition, Replacing the fuel pressure regulator , change the oil ( satuated with fuel) gave the owner confident the engine will not stall out again