88 5.7 low on power

[HawkDsl]

Looks like allot of veins to me, but your mileage may vary. I gave decent advice, and the ADL jumper is a good start. I bought my 89 new, and have it to this day, but what do I know. Thanks for coming in and saving the day!

 

[thered88]

I replaced the throttle body to intake gasket when I got the truck last April. as far as the fuel pressure goes, i do not remember exactly what it was but I remember that it was 1 psi over what is required. i think the main symptom that my truck has is that at below 2500 rpm it doesn’t have a lot of power but after 2500 rpm, it has a enough power to pull your head back and you can hear and feel the engine run smoother. if anyone has any suggestions on what to do I’m all ears.

 

[Schurkey]

if anyone has any suggestions on what to do I’m all ears.

I don’t have access to a scanner.

Find access to a scanner, that would be an easy way to see what's really going on.

You've already gotten the best advice. You need a scan tool. Find out what's different in the sensor or the computer output between low-rpm and above 2500 rpm.

There's dozens of possibilitites--TPS wonky, electronic spark advance screwed-up, knock-sensor crazyness, and so forth. I linked to a thread on another forum where the guy fixed his truck by disconnecting the battery, which re-set the timing advance. Have you verified that the electronic advance works properly?

 

[thered88]

Have you verified that the electronic advance works properly?

No, how would I do that?

 

[Schurkey]

Easy, not-all-inclusive test: Connect a timing light, run engine with timing connector disconnected. Base timing should be "0". Shut off engine, re-connect timing connector, disconnect battery to clear code. Reconnect battery. Start engine. Timing should be somewhere around 10--15 degrees advanced.

Time for you to download the service manual set for your vehicle from the links posted in the Sticky thread section of the Engine forum.

 

[SNCTMPL]

What elevation do you live at? If you are at a couple thousand feet or higher, I would advance your base timing a little.

 

[thered88]

ok, I have been driving my truck daily since my last post and it’s gotten worse. The thing has no power and it runs rough. It sounds like it’s missing esspecially at partial throttle. When you are at the same throttle position cruising at like 35-55 mph it shudders and sometimes cuts out for a sec. I have rechecked fuel pressure and it’s consistently at 13 psi at the throttle body. I disconnected the egr and it did nothing. Its base timing (with advance disconnected) is at exactly 0 and when advance connected and warm it idles at between 8 and 10 degrees advance. I clean connections, nothing, I tried to take 02 off, it’s stuck. I know I need a reader but I cant afford both a reader and the parts. I’ve sunk too much money in this thing and now it also has a transmission leak. I’m getting really annoyed with this thing and considering selling it unless I find what it is. So I need help.

 

[Schurkey]

Give us some data to work with. Anything else is wild guesses, and you can do that on your own.

What is the cranking compression pressures of all eight cylinders? You replaced head gaskets...did you get the lifter preload adjustment correct?

FIND a scan tool (NOT a "code reader").

List your actual location more precisely than "earth". Maybe there's someone near you that could help.

If the O2 sensor is "stuck", that's just about a guarantee that it's old and decrepit. Find the motivation to remove it in favor of a new one from a reputable brand. For the record, when I have a "stuck" O2 sensor--which is most of them--I clip the wire off, and poke a Wright deepwell impact 6-point half-inch-drive socket over the thing, and force it out with a long-handle ratchet and a cheater pipe. "O2 sensor sockets" are generally fine for installing O2 sensors, they're often weakass junk when it comes to removing them.
www.amazon.com/Wright-Tool-4928-6-Point-Impact/dp/B002VKBRCC/ref=sr_1_1?

 

[evilunclegrimace]

There are two things that will make fixing your truck alot easier. The fuel and emissions manual X-8836 and a scan tool. And Schurkey's advice.

 

[someotherguy]

There are two things that will make fixing your truck alot easier. The fuel and emissions manual X-8836 and a scan tool. And Schurkey's advice.

If you can't lay out the bucks for it (OEM manuals can be pricey unless you find a good deal on a forum or auction site) - that specific manual, and many more, are freely available right here in this thread -> https://www.gmt400.com/threads/88-98-service-manuals.43575/

Richard