Loss in power

I have noticed recently that my 97 is loosing throttle response and power. It just doesn't have the get up and go it used too. It has 125k on it and is a 5.0L 305. What usually causes this. Also, what grade of fuel is best for this engine for optimal performance?

Have you changed the fuel filter lately? What about running a fuel system cleaner through to clean your injectors? How many miles since you changed your spark plugs? Incorrect timing will also cause a loss of power.

Three words: MAJOR TUNE UP!

1. Before starting anything, get a manual for your truck. I own a Chilton and a Haynes manual. This is until I can afford a factory one from Helm Publications. Anything I say in here will sound like Greek unless you have something to reference it to. I don't know how much you know about your vehicle, so if I am to be of any help to you, we both have to be on the same page. Please get a service manual before working on your vehicle!
2. Check for what I would call obvious: vaccumn leaks from plastic lines, rubber fittings, and anything else questionable including possibly your vaccum brake booster. Check for broken, frayed, loose, crushed, and burnt wires AND hoses. Make sure that your battery connections are tight and free of ANY and I do mean ANY CORROSION you can find on the terminals. GM positive terminal side posts are notorious for corrosion especially our GM truck double stacked positive terminals. Don't ever buy an ACDelco battery! It's the only thing from ACDelco I refuse to buy, because of substandard construction. Get a MAXX battery from Wal-Mart. They have unbeatable warranties and prices. Not to mention, Wal-Marts batteries are the same thing you buy from any parts store, just with a different sticker. They're also made my Johnson Controls.
3.Once cleaned, make sure that your charging system is healthy, any parts store(or Wal-Mart Tire Lube Express) can check your battery and alternator for proper output of Amps and Volts. If your not getting the appropriate amount of voltage to your vehicles computer, it can't do it's job correctly! Your truck probably has either a 100 or 105 amp alternator. At about 2000 Engine RPM your Voltage output should be around 14.2volts with no accessories on. Your current draw should be around 30 Amps or so. Last obvious thing is FUSES. Check FUSES: the ones underneath your hood by your brake resivior and the ones on the inside of the driver's side dash, exposed when you open the door.




As long as you haven't thrown parts at it already,and the truck has not been modified, here is what I suggest: The distributor cap(about $25) and rotor($12) are two items that need to be checked initially. There seems to be a common occurance with these items not giving any sign of failure, they just burn up the electrodes inside over time, giving you a loss of power and acceleration. Be sure to go with a quality replacement part such as ACDelco. It's hard to go wrong with ACDelco parts; however, sometimes there are cheaper equivalents. I actually use the Borg Warner replacement from Oreilly Auto Parts. Be careful when you remove the two Torx screws securing the distributor cap, they have blue Loctite applied from the factory and the plastic areas they screw into often crack. Bottom line: remove them slowly and be gentle! You don't want to have to replace the plastic distributor b/c of this!(And it is a form of plastic, believe me!) Second, your plugs are platinum ACDelco and as long as they are still at the proper gap (your white emissions sticker under your hood will tell you what is correct/ .045 or .060in),and there is no erosion of electrodes when you pull them out, I would save yourself the money of buying new ones. Again, stick with quality, don't get champion or autolite just to save a few dollars, get ACDelco($4 each plug for platinum) or NGK Original Equipment(OE) replacements. I've even heard a few people suggest Denso, but I haven't tried those yet. I wouldn't suggest Bosch Platinum either, my experience is that they run too hot and end up causing weird running problems. As long as your wires are orginal, it's kind of a toss up wether or not you want to replace them. I would wait to replace them last. If you have a problem with a cylinder not firing or missing, I would replace the wires.

Here's a trick: take some water and fill up a spray bottle, something that gives a mist of water. At night, start your truck and warm up. Spray a lot water above the wires and wait to see if you can see a lightning show! Be careful that you leave enough room between the water mist and you. About 12 inches should be enough. There is enough energy to jump from the droplets of water and ground THROUGH YOU!! Gives you quite a shock(pun intended). Won't kill you, but definitely gives you a surprise. If you see electrical arcing going on between the wires themselves and/or any metal close enough to the wires, the insulation of the wires had deteriorated enough to warrant replacement of them. Sometimes you make even hear the arcing of electricity but not see it, this may cause the truck to idle really funny. This is also a sign of needing new wires.

Besides your cap, rotor, wires, and plugs, I would just go ahead and pay $8 for a new fuel filter(I use Purolator, ACDelco, or Wix). It's not that hard to change, it's underneath the driver side, inside of the fram rail. If I remember correctly, all you need is 16mm thru 20mm wrenches. The fuel filter should be changed out every 30,000 miles anyway. Replace your PCV valve ($2) on your passenger valve cover. And please make sure you are using quality oil and filter. I use Mobil oil and ACDelco oil filters exclusively on my truck.

I should tell you that I use Mobil 1 synthetic (5w-30) with 155,000 on my 96 Z71 4x4 and get around 24miles/gal on the hwy about 14 city. Your results may differ alot depending on how you take care of your truck and how you drive.

I should make one mention that I don't believe your fuel pump is the culprit. If the truck runs, it's most likely not the pump; however, fuel pumps can go bad gradually. If your curious, you may be able to rent or borrow a fuel pressure tester. You can buy one for about $40 too. Check the pressure AFTER you replace the fuel filter at the little valve that looks like a tire stem on the drivers side fuel rail, near the back of engine, on top. It should have a little black cap covering it up. Connect up a pressure tester and turn the key on but don't start it. The pressure should come up to around 55-60 psi and stay there. If the reading drops down quickly, you probably have a bad pump or a fuel injector (Heaven forbid that, those are expensive to fix). If not, start up the truck and make sure that it stays at around 50-60 psi.

Here are some other things I would check or change at 125,000mi: Your pre-catalytic O2 sensorS (there's 2 of them at about $50 ea). All 4 of your O2 sensors are supposed to have a service life of 100,000 miles. Sometimes they go longer or shorter than that. I have found that the Pre-Cat sensors take more of a beating, they are closer to the hotter exhaust. Your Service Engine Soon (SES) Light may illuminate because of these. Your transmission fluid and filter is probably in need of service also. It should be changed out every 30,000 miles for long tranny life.

As for PuffNStuff's comment about fuel system cleaner I would wait until you change the fuel filter first. I like SeaFoam, that stuff performs miricles for me. And as for the timing, as long as you haven't turned the distributor, you shouldn't need to have it timed. Which by the way actually has to be fine tuned by using a Tech 2 scanner or equivalent(aka the DEALER). And as for your timing chain, you shouldn't need one of those either for at a least another 50,000 miles. Check your air cleaner also, if you haven't already. If you've installed a K+N air filter element, make sure you haven't saturated the filter in K+N oil, too much oil on the filter will cause droplets to get onto the Mass Air Flow(MAF) sensor elements and cause engine running problems. If your unsure go get a OE paper filter, MAF's are expensive parts.

And for your own good, if you still have the orange Death Cool in your cooling system, have that crap flushed professionally, and refill with good ol' green antifreeze. You'll be glad you did, because your radiator won't have this brown crap forming inside clogging up the works. The same is to be said for your heater core. Your overflow bottle may be turning brown already and your radiator cap may be crusty with orange crap. GM technitians all know about this issue, but the customer suffers. 150,000 mile Dex-Cool is BS, get rid of it before it really hits you in the wallet! You may have noticed on the passenger side of the engine that a hose running from the firewall to a metal fitting on top of the engine near the front is leaking at the fitting. If it hasn't yet it will sometime. This is caused by the Death Cool. The fitting(or nipple) can be replaced, but I would not attempt to do it yourself, unless you've ever done one before, they break off easily and then you have to remove the entire intake manifold and drill out the threads. It sucks if you break one off. I can explain a better way if you want me to, but it's pretty in-depth with procedure. In short you should end up replacing that nipple with a nipple used on GM cars, DO NOT GET DO NOT GET THE GM TRUCK REPLACEMENT! IT IS CHEAP POT-METAL. You have to get this nipple from the dealer. I haven't found a parts store that carries this yet, nor will the parts store have any clue what to look under to find it. The nipple used on the GM CARS is actually steel and there for 100x less likely to break off in the future. The nipple ends up corroding from the inside-out and makes it weaker. If you have any questions regarding this nipple, ask a GM dealer technitian if possible, but sometimes the dealer parts guys know about this if your lucky. I have the GM part number back home but I won't be home for another month. Sorry. But if anyone wants it. I can get it later.

You asked about the fuel you should use: your truck is designed to run on 87 octane. Higher octane fuels may have cleaning additives in them but they are really more for cars with higher compression engines and therefore higher compression temperatures. In short, higher octane just means that it has a higher resistance to pre-ignition by temperature. Don't be fooled by high octane, unless your owners manual says to use it or you've got a super charger, turbo charger or any other wild modification that was not put on from the factory, use 87 octane from a well known brand gas station. Buy from one that sells a lot of gas, this way you know that the gas is fresh and that way you don't end up getting crap from old, unserviced underground storage tanks.

Two last items, check with the dealer and ask to see if there are any programming updates available for your truck. There were a few for my 96 Z71. I know that most service writers will try and get you to have everything done there. Do not let this happen to you. There should be no charge for looking up your VIN in the massive GM vehicle service database and seeing if your vehicle has PROGRAMMING UPDATES available.

I've given my VIN to the dealer and they have printed me out a report of all my Regular Production Options (RPO codes that are printed in your glove box) and there meanings. This also came with a report of where my truck was first bought, what warranty work was performed, where it was performed and if there were any outstanding SAFETY RECALLS. Just ask the service writer to do this, preferably one that has the time to do so. I usually have better luck with women service writers, they actually don't treat you like a walking dollar sign. I had a windshield wiper circuit board recall on mine that could have cost me a lot but it was fixed for free in 15 minutes. I keep all these papers for my records.

Sometimes updates solve problems that can not be solved by any other means. You should get multiple quotes from multiple dealers including some independent shops that have access to the GM Techline Information System (T.I.S). But the dealers should be your first stop. This is because they have genuine software, written by genuine GM electronic engineers and is the most current information available for your truck. Also know that reprogramming takes less than 20 minutes. Here's how its done:

The technitian hooks up a GM Tech 2 OBDII scanner($3000) to your Assembly Line Data Link(ALDL) black connector underneath your steering column, communicates with the vehicles Powertrain Control Module(PCM), and reads the version numbers that are currently loaded(2 minutes). Then the technitian disconnects from the ALDL and takes a copy of that info, along with the VIN(stored on the TECH2 Scanner), and hooks up to a dealer computer that is connected to T.I.S(2 min). He searches for updates and may or may not ask you about any drivability issues you may have. This is so he can load the proper updates into your vehicles PCM. He then down loads the updates into the Scanner(5-7min). He hooks the Tech 2 back into the ALDL and proceeds to re-program your PCM(5-7min). This process is not that complicated but the dealer knows that they can make a killing off of it. Caveat Emptor! (Buyer Beware!) The technitian is really your friend, you are his bread and butter, it's the service writers that are vultures. They are the one's that get most of the money you pay for labor. The technitians get screwed most of the time. Ask to talk with a tech, if you can find one that is not pressed for time at that exact moment and get some recommendations. Most dealer techs want you as a customer, but you wouldn't believe the BS they put up with on a daily basis.

If you need to have your vehicle scanned just to check why your SES is on, take it to Autozone and sometimes Advance and ask to have your codes read for free(most do). I have yet to have an Oreilly's or NAPA do ANYTHING for free. The codes that they give you will be very generic. Just write them down and then check on the internet for their meaning. Some codes will not be able to read by Autozone because they are specific to GM vehicles only. Remember, Autozone's scanner can be used for any OBDII compliant vehicle. All they use is a Actron Scanner they take of their own shelf. Sometimes you get a good parts person, sometimes you get an idiot. Depends on the area. They really do this so you will end up buying parts to fix your SES light from coming on. The parts you buy may or may not be the cause of the code being set. This is where having an excellent parts pro you trust really pays off.

If you want to have your codes erased, say if you replaced whatever part they told you was wrong, and now you want your SES light reset, they can erase the codes stored in the Vehicle PCM. Sometimes they won't erase codes though. I've been told by some stores that they will not read or erase codes from vehicles because the local shops that charge way to much for just a code reading, are angry that places like AutoZone are doing it for free. I've worked both sides of that fine line, and I can say that if a shop wants my money(which they will never get) they have to earn my trust first with numerous recomendations.

Other than what I have explained, and I know that I covered a lot, all the items I mentioned that you should check or change can be done by anyone that is willing to get just a little dirty. They only tool that is special is the Torx bit(or star bit, whatever you call it), you may need pick up one. You just need a size 10T, 15T, or 20T , I don't remember exactly. You can also get fancy with that fuel pressure tester. I don't know your ability level, but basic hand tools are all you need, just remember that 98 percent of your truck's fasteners are metric.

You may wonder why I just spend all this time writing way too much down. I love my toys that are back home. I am currently on Temporary Duty for your USAF in Guam, in the Marianas islands of the Pacific and I can't wait to get back to home to my home station in Louisiana. It's 0400 Thursday morning(Guam time) as I write this. I can't wait to get back to going out exploring and meeting new people in my truck. So if this has helped anyone reading this, I'm glad. Just writing this large chunk of info has helped me to take my mind off where I am. I'm doing what I like to do in my spare time, help my friends with their vehicles by educating them. I just want as many people to know that your military is out there doing what we do best, defending our freedom to have big trucks, big back yards, and big dreams. - Chris

Holy Long Post Batman!! :eek7:

WOAH... thats alot of reading..or cut/pasting!! lol

No, there is no cut and pasting to this. Every thing that spoke about above is all personal experiences. And all of it comes right out of my head. I've read so many posts now and they all seem like shots in the dark. What's wrong with actually going into some depth and really giving someone some information that could really help a person in need of some answers? Has anyone learned anything from my reply that has helped them in any way? I'm sure more than one person will say yes.
-Chris :feedback:

oh i wasnt dissing your reply dude..just picking at you b/c it was long..i've made long ones before too...no harm meant :sorry:

I do have one last thing to add, however, to my first reply. Because of Death Cool, the intake manifold gaskets are prone to leaking, causing a loss of power.

Thankx, for the reply. I wasn't sure if I made some people mad by actually responding to a question. :dunno:

Chris - Thanks for the info. If you have a second, check out my post in this thread. Curious what you might think.

http://www.automotiveforums.com/vbulletin/showthread.php?t=288737

TIM

Chris,
I'm a new guy to the forum, trying to soak up the experiences of those who've "already been through it," and the seasoned mechanics here. I do the same thing on the Harley Davidson forums over on Delphi. (there's nothing to match this forum over there!)
Read every word of your post and thank you for it.
Presently have the intake manifold gasket leak - just replaced the thermostat housing, and plan on having the orange stuff flushed out soon/replaced with green.
(96 Tahoe with 134000 miles, trying to get it back into like-new condition - just bought it a couple of weeks ago).
Oh, and it's no small "by the way;" THANK YOU for your military service - was in Guam in the early '70s, tied up along side a tender - submarines. . .

Wanted to ask this: My '82 GMC pickup would lose power cause of the spark knock sensor erroneously telling the ECM (?) that knock was happening. I simply disconnected the connector and isolated the cable by hanging it in the oil dipstick - restored the power. (I only ran high test in it so didn't worry about pre-ignition too much) Could this relate to the original power loss question?

'Nuff for now - best to you.
Don

Yo
You are using my ideas and will cost you lots of money lol

Here's a trick: take some water and fill up a spray bottle, something that gives a mist of water. At night, start your truck and warm up. Spray a lot water above the wires and wait to see if you can see a lightning show! Be careful that you leave enough room between the water mist and you. About 12 inches should be enough. There is enough energy to jump from the droplets of water and ground THROUGH YOU!! Gives you quite a shock(pun intended). Won't kill you, but definitely gives you a surprise. If you see electrical arcing going on between the wires themselves and/or any metal close enough to the wires, the insulation of the wires had deteriorated enough to warrant replacement of them. Sometimes you make even hear the arcing of electricity but not see it, this may cause the truck to idle really funny. This is also a sign of needing new wires
MY lawyer will be in contact with you!!
lol
The biggest GM loss of power is the fuel filter. Gms are very unhappy to fuel pressure drops.

Hey SpitDirt I hav a suggestion for you. If you are going to invest in a real service manual, don't get the helm. Get the OEM 4 volume set published by North American Operations -General Motors.

I have a question for Rainbird, You say u had a 1982 GMC truck with a ECM? I thought there was no such thing as a 82 truck with computer controls. I know it was first year for Generation 1 for midsize cars.

I have a question for Rainbird, You say u had a 1982 GMC truck with a ECM? I thought there was no such thing as a 82 truck with computer controls. I know it was first year for Generation 1 for midsize cars.

I figured I'd probably screw that up - couldn't remember the proper acronym. It was "Electronic Spark Control," I think - ESC??

Maybe the only thing electronic about it was retarding the ignition when the knock sensor told it to?

(Just ordered the Helm manuals a couple of days ago - hope they're good enough - at almost $150 I sure hope so.)

RainRider

Hey you got that right!! The techs really do get screwed over. Thats why I got out

If anyone was wondering you can now check your GM vehicle for computer updates by visiting this Official GM site. It will only have the most current information about your vehicles software load by the last time it was checked at a dealer. So if your car hasnt seen a dealer since before it's warrenty period expired, the information will only be that current. http://calid.gm.com This is the site that you can use to check to see if you have any outstanding computer updates that may cure previously "unsolvable" drivability problems. Merry Christmas and a Happy New Year to everyone. -Chris