Weak acceleration puzzle.

Splashin · #1 (**permalink**) 07-05-2012, 07:41 PM

I have been lurking for the last month or so trying to solve the puzzle that is my new (to me) truck. I just got a 97 PSD crew cab, automatic with 4.10 gears and it is a serious dog; I mean scared to pull out on highway with out a mile of open road dog. I have cleaned the EBPV tube, the FPR screen, changed the oil, and fuel filter. I have unhooked and rehooked the MAP sensor and EBPV solenoid. The truck starts great and sounds silk smooth at idle. But lacks any take off power and seems to drag through the RPM range until it hits ~2200 RPM where it seems to blaze all the way to 3k. If you stop on a hill and take off it slowly climbs the hill until the higher RPMs where it starts to move and then up shifts and I'm back at little to no acceleration. Other than exhaust and a new RIffRaff intake the truck is stock with 212xxx. Now today I after I got home and turned the key off I heard a whooshing coming from the exhaust for a couple of seconds that reminds me of what the stuck EBPV sounds like, but it does not sound like that when the truck is running. The only smoke the truck puts out is some black smoke when you swat the throttle in Park. The truck has not put out any computer codes either.

I also have a 96 PSD with an open K&N filter, exhaust, and 3.55 gears. It is just a long bed single cab to compare to the crew cab and it runs circles around my "new" one and it has 267xxx on it.

Thanks for any more insight as I am at a loss at what to look at next. Unfortunately, I do not have any gauges to check fuel pressure or boost, so my next move is to take it to the dealership to have them hook it up and see what they find.

85_305 · #2 (**permalink**) 07-05-2012, 07:45 PM

You say the truck is slow until 2200rpms... Welcome to owning a v-series diesel. They lack a bit in off-the-line torque, but really scream in high rpms. A chip and 1.0 exhaust housing will bring torque down closer to 1500rpms and offset the lower initial torque. Your truck sound like a normal OBS stroke though. They are slow stock.

madpogue · #3 (**permalink**) 07-05-2012, 08:20 PM

It's more than that ^^^^ if it feels that different from your regular cab truck. What exhaust mod(s)? Just the downpipe, or did you remove the kitty cat? Does it sound different from your other truck, exhaust-wise?

With a 6637 and a downpipe, you should really be able to hear the turbo whine, even with moderate acceleration. Are you hearing it? Maybe you need to hook up a real-time data reader and see what it's doing out on the road; check MAP (to determine boost), exhaust back pressure, injection pressure, etc.

Dumb question, maybe, but did you change the oil when you bought the truck?

Splashin · #4 (**permalink**) 07-05-2012, 08:39 PM

The regular cab has a short exhaust that comes out at the cab. The crew cab comes all the way behind the rear wheel. So, I assume the exhaust will always have a different sound since it has a longer travel. There are no cats on either truck. And yes changed the oil. I can hear some turbo whine with a little acceleration. Are the real time readers able to check everything (boost, fuel pressure, exhaust pressure, ect.)?

85_305 · #5 (**permalink**) 07-06-2012, 04:06 AM

w/ my 5" exhaust you can REALLY hear the turbo just putting around town... is that the case for you?

madpogue · #6 (**permalink**) 07-06-2012, 04:23 AM

Nothing (besides an in-line mechanical gauge sender) will read fuel pressure, since it's mechanical. Boost is basically MAP minus BARO (absolute pressure in the manifold minus ambient barometric pressure). Exhaust back pressure is a PCM input, so yes, it's available. Oil temp is also; coolant temp is not (not a PCM input).