mrmojorisinphan

I'm not really sure what's going on with my rig right now, but My ride is just lacking the power it used to have. I've noticed that my boost gauge is showing greater boost, but producing less power with lower RPMs.... I'm not sure if it's the supercharger or the engine.

I'm also getting horrible gas mileage. like ~12MPG, (I recently put on 33"s, but it shouldnt be that bad)

I just put in Denso Iridium plugs, cleaned the MAF, & Throttle body, changed the oil, and put in a FreeFlow air filter and still no better results.

Should I check compression? Fuel Filter?

Any advise or other info is appreciated.

BTW engine has ~120K

Greg_Canada

If it's showing more boost your cats might be blown.

midiwall

Hmmm...


Yeup and Yeup.


and how much of that is SC'd?

1. What does "greater boost" mean? (gimme an example)
2. Stock pulley?
3. Any new raw fuel smell from the tailpipe?
4. Any new exhaust noises?
5. Do you run an EGT gauge? If so, does it seem to be running hotter at lower RPMs?
6. When's the last time you cleaned the injectors?
7. Are you running the original plug wires?

Wanna get scared? (I love doing this!)
https://www.yotatech.com/forums/f123/3-4-rebuild-100924/
https://www.yotatech.com/forums/f123/stuck-injector-misfire-rapid-egt-increase-92921/

mrmojorisinphan

[QUOTE=midiwall;50380839]Hmmm...


Yeup and Yeup.


and how much of that is SC'd? Not sure, I purchased the truck about 10k miles ago from someone that was no the original owner. I'd assume it was put on the truck when it was purchased in 2000. Because the truck has every option that was available for 2000.

1. What does "greater boost" mean? (gimme an example) a larger PSI reading on my boost gauge (i.e 4 PSI of boost))
   
2. Stock pulley? Yes
   
3. Any new raw fuel smell from the tailpipe? Havent noticed, I'll check later today.
   
4. Any new exhaust noises? Nope
   
5. Do you run an EGT gauge? If so, does it seem to be running hotter at lower RPMs? No, I dont run the EGT gauge
   
6. When's the last time you cleaned the injectors? They are probably stock and have not been reflowed. Maybe I should buy some new ones from gadget...
   
7. Are you running the original plug wires? The plug wires are not OEM so they have been replaced at some point in the past 120K. I did not test them at time of sparkplug replacement.

I also tried some Seafoam BTW.

I'll test the compression and the SP wires this weekend.

Thanks for your response Midiwall

midiwall

I meant more down the lines of an example like "I used to hit 4psi when I was going up this hill by my house, now I get 6psi at the same throttle position".


Umm, that's a long shot right now. There's plenty more to look at before you drop $500 on injectors.

I take it that the injectors are stock as far as you know?


Did you gap them first? What did you gap them to (0.040"?)? Did this problem coincide with you replacing the plugs?


Through a vacuum line? And did you add some to the tank as well? Now long ago was this (basically, have you run at least 1/2 can of Seafoam through the engine via the tank?)

Weasy2k

Def check the compression and change that fuel filter...if you dont know when you last changed it...then i would just go ahead and do so.

marko3xl3

I would definately perform a compression and leak down test. It is the simplest way to give you the most inside on what might be wrong with your engine. Hopefully it won't be as bad as a chipped valve or blown rings, but after extensive use with the S/C and no fuel mods, you're probably at the point when your engine is a little tired from running lean.

QSVeilside

Have non-OEM plug wires caused similar problems for folks in the past? I vaguely remember hearing about it.

midiwall

A bad set fo wires can certainly cause power issues, but that's not to say that all non-OEM wires are bad. I loved my 8mm wires. They just age, and should be replaced every couple of years.

mrmojorisinphan

I meant more down the lines of an example like "I used to hit 4psi when I was going up this hill by my house, now I get 6psi at the same throttle position".

Ahh, okay. Well, I usually never had boost above 2-3 psi going up a hill at like 65 with about 2-3K RPMS. Now going up a hill at 65,my RPMs are between 3-4K and my boost is up to like 4-6

I take it that the injectors are stock as far as you know? Yes[/


Did you gap them first? What did you gap them to (0.040"?)? Did this problem coincide with you replacing the plugs? gapped to .042 as recommended by URD. The problem occured before the replacement of the plugs.

Through a vacuum line? And did you add some to the tank as well? Now long ago was this (basically, have you run at least 1/2 can of Seafoam through the engine via the tank?)[/QUOTE] Before I replaced the plugs (about a weeks ago) I ran 1/2 bottle through PCV and 3/4 bottle in gas tank

[Could it be the ECU adjusting??? I pulled the fuse after I cleaned the MAF & TB and replaced the air filter, but not after I replaced the plugs?..

"I would definately perform a compression and leak down test".
What is a leak down test?

I think I'll swap out the fuel filter just because it's cheap and easy.

thanks guys I appreciate the comments:bigclap:

midiwall

Ummm, probably not...

Do the leak down and compression test, that'll tell us more. (and swap the fuel filter)

Leak Down:
http://www.type2.com/library/engineg/leaktst.htm

http://autos.yahoo.com/maintain/repa...ques057_1.html

mrmojorisinphan

Thanks Man. Much appreciated.

marko3xl3

The fact that you used to build 2-3psi and now build 5-6psi sounds very much like a good thing...not to day it is good in your case.

When I first installed my SC, I didn't install the one-way valve right away and I could only achieve 3 psi of boost. But, after I did put the valve in, I got 5-6 psi of 'good' boost.

Just info

marko3xl3

Any update?

mrmojorisinphan

Not yet. I havent had a chance to work on it yet.

For those who have the supercharger, do you typically have low RPMs with High boost? My RPMs are usually pretty low between 2-3K whether I'm going 25 or 65. The boost is what seems to be fluctuating all over the place from negative to +5.

I would think that if my RPMS are low I should be using less gas and should be getting better MPG.....?

midiwall

Umm... are you saying that if you're holding the throttle steady, then your boost is flailing around?

Yes, you can have high boost at low RPM - it's the boost that's making the RPM increase - but then when you get to a cruising speed and you back out of the pedal, the boost should come down. If you're seeing a _constant_ +5psi at 25mph then something's weird.

mrmojorisinphan

[QUOTE=midiwall;50387113]Umm... are you saying that if you're holding the throttle steady, then your boost is flailing around?

Yes, you can have high boost at low RPM - it's the boost that's making the RPM increase - but then when you get to a cruising speed and you back out of the pedal, the boost should come down. If you're seeing a _constant_ +5psi at 25mph then something's weird.[/QUOTE

No, if I hold the throttle steady the boost is steady. I was referring to how the supercharger acts when stepping on the pedal. For instance, I drove up to the mountain this weekend and while climbing a steep hill and demanding more power from the engine, my automatic would drop down to like 3rd, boost would go up to like 5psi, but my RPMs would not go up too much. I guess i'm just used to driving without the SC, which in this case, the car would shift to 3rd and the RPMs would jump up from like 3-4K RPMs (becasue it's doing more work). So being that the SC is doing all the work and keeping RPMs low, should'nt the engine be more fuel efficient since its not working as hard???...I think I need to read Gadgets page and learn me some more about these blowers

mt_goat

That's a common misconception. RPMs really don't have much to do with fuel economy. MPG is all about throttle position. Think of the skinny pedal as a fuel dump valve, the farther down you push it the more fuel you dump out of the tank. You can be at 2000 rpms at WOT and use a ton of fuel. You can be at 4000 rpms at half throttle and use less fuel. You can be coasting down a steep mountain pass, engine braking to the max, at 4000 rpms and not use any fuel at all.

midiwall

Ahh, okay... what you're seeing is normal. The SC is forcing more air into the engine, which allows more fuel to be burned which produces more power. Now, "power" doesn't mean RPM. Basically what you require to go up that mountain is torque at the wheels to overcome the force gravity trying to pull the truck back down the road.

In an auto, the tranny will downshift based on the load versus the power input. If there's too little power to push the load, then it will kick down a gear to get the engine to rev higher, thus producing more power (torque).

With the SC there, then you can produce more power at a lower RPM because you have more air with which to burn more fuel. So under similar load conditions {insert mountain pass here} you should see less downshifting.


Ahh, we wish! Actually, many people report that their mileage went up under normal driving conditions after adding the SC, but the reasoning behind that is you're burning fuel more efficiently to produce the same amount of power.

In the mountain pass example, you're actually burning MORE fuel at the same RPM since you're producing more power.

bamachem

you might want to check your front O2 sensor. they usually start to crap out at 120k or so and the symptoms of them going (before a CEL) is poor mileage and some sluggishness. if it's sluggish, you may be into the throttle more, meaning it's in a lower gear that it used to be, creating more engine RPM's and therefore more boost. i'm reaching on that, but it's a possibility...