Hey all, it seems like everyone with a TBI motor is trying to fix bad idle, lack of power, and poor fuel economy, I'm no different. Common issues, but the only problem is that there is rarely ever just one magical cure-all to these issues, people think they have the answer because it worked for them, but someone else will replace that same part (say the TPS or something) on their truck and it won't make a difference. Watching posts on the internet over the last two years has taught me that as much as people like to rag on the idea of throwing parts at a car, that's really the only solution for engines like these.
My truck is a 94 with the TBI 350, rebuilt 4L60E, 4x4, extended cab, 3.73 gears and a G80 and just over 268K miles without a major rebuild, a prime candidate for the everlasting TBI issues. In the past I did plugs, wires, cap and rotor, I've replaced the fuel filter, and one of the injectors were replaced ~12 years ago. Other than that, it's all stock!
Checking the SES lights shows that I had a code for a MAP sensor and the EGR, both of which could be causing these issues. So I started there, I scraped together what leftover money I had after bills tonight and bought a new MAP and IAC (SES said an EGR, but I didn't have the money and it'll get replaced anyways.) and if replacing those two parts made a difference, it was a minimal one. Idle improved slightly, it no longer stumbles when in gear and at a stop, but it's still not as smooth as it should be. Power improved slightly as well, it lights up the rear tires at a dead stop now when the pedal meets the metal, but after takeoff and when rowing through gears, power didn't improve much. Downshifts are torquier though!
Despite my truck being an automatic, it has a tach and one thing I've noticed about the motor is that it runs out of steam at about 3800 RPM, it'll usually go to 4500 RPM before it shifts, but it just seems like the motor is spinning, but its being choked by something. I know that the exhaust and the heads are major bottlenecks on these engines, but I've driven a low mileage 95 that was equipped just like mine and it had power until about 4100 RPM, and even when it shifted at 4500 it still had more power left then mine despite them both being completely stock motors. I'm guessing my issue is more with the intake rather than the exhaust. A few thoughts I've had is that the air filter is clogged and isn't allowing the engine to breathe enough, or maybe the fuel pressure regulator isn't getting enough fuel to the engine (not sure on that one though.) Whatever it is, it's choking up the engine, and that could be the root of my problems. (lid flip just makes it louder, no power difference for me)
a bit off topic, but my 0-60 times are around the 13s range, what are everyone else's? Is 13s normal for a 200hp 4x4? I got smoked by a friends stock 99 Ram with the 5.9, 4 auto, and 4x4, and he has a 3.42ish axle ratio!
Next paycheck will most likely be vacuum lines and other rubber stuff, nothing is visibly bad, hoses still are solid, but the gasket on the stock IAC fell apart when I took it out so I know the rubber isn't in great shape. EGR will also be next since it's a known issue.
As far as other suspects go, I'd say the fuel pressure regulator and injectors, the O2 sensor, or maybe the air filter as mentioned earlier.
Anyways, anyone have any thoughts or wanna add anything to this?
