Lacking power, 87 Sierra 5.7l TBI

[Pmcb]

I will look into the knock sensor, maybe i can change that first while trying to get O2 sensor off .

 

[squaredeal91]

Sorry for not clarifying, it seems to have less power than it did just two weeks ago. I notice it going up hills the most.

Yes if going up hills. Ping alert. Knock sensor possible

 

[Redfish]

I will look into the knock sensor, maybe i can change that first while trying to get O2 sensor off .

Knock Sensor.

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[Pmcb]

The lack of power problem solved. As I was looking for vacuumed leaks and wires crossed, I discovered that the U shaped brackets that holds down the distributor had slipped and the distributor moved. I reset the timing let the ECP reset and the power is back, I did replace the O2 sensor. the one in there was stripped so I had to clean up threads. I have not replaced the knock sensor yet. At my age there is a limit as to how many times i can crawl under a vehicle.
Thank you all for the support, I am enjoying working on my cars again.

 

[squaredeal91]

Awesome! I love the simple ones

 

[89GMCJimmy]

I need some help, let me give you background:


I have a 1987 GMC Sierra v1500, 5.7l TBI. 51,000 original miles. No rust, had accident when new, some signs of it underneath. Only one fuel tank working. It was in a barn for 10 years, someone started getting it running, change hoses, tires, belts, dash…. In the process they cracked intake manifold (over tighten cold temp. Tried to fix with stop leak. When i purchased starting was difficult, but ran good warm, missing some.

Things done: New manifold, replaced CTS, TPS, EGR, Plugs, Wires, Rotor and Cap. Fuel filter, Added TBI spacer, new accelerator cable, Oil, filter…

Each of those fixes were a story in themselves. Had it die a couple times on the road, changed Ignition module seemed good, but then would not start, (engine would start with a little gas) spark good. Bypassed relay, pump working. Noid light, no power to injectors. Replaced fuse, but only one injector working. Replaced injector all good again (i assume injector went bad blew fuse) Driving a few days later and water pump goes, but at same time while driving home slowly and not overheating it died twice. New water pump, but died out again, Changed out new ignition module and it worked fine (note to self, no cheap parts).

Now she runs smooth, water stays inside engine where it belongs, but it doesn’t seem to have power, running smooth, no misses, but just lacking power, noticeably.

My thoughts: Fuel pump weak? Coil?
Has good compression.

I had same issue 89' TBI I was lacking power and overlooked my timing. The smog test guy had set my timing to 0* to pass. I reset it to 8*BTC made a noticeable difference!

 

[chairmnofthboard]

I had low power on my 87 tbi. Everything I did helped it regain it's lost power. It wasn't one thing, it was multiple things stacking up.

The two/three things I can think of that made the biggest difference in power were the ICM and intake gasket/throttle body rebuild. The ICM would only run right when the timing was advanced to about 12 degrees. It would have no power and the "vtec would kick in yo" if I set the timing to zero. I replaced it with a ACdelco D1943A ICM and the power was back.

 

[JT58]

Mine had no power for a long time- I thought it was just attributable to a low HP 350. Brought it to a couple of shops, no one seemed to know. Check the basics- like the fuel lines. While replacing the valve cover gaskets I discovered the main fuel line- the 3/8 one on the LH side to the TBI was badly crimped near the connector- almost completely crimped. I don't know how the engine even ran but it did. It was quite a job replacing it- I had to get a straight connector from Rock Auto, cut and bend and flare the ends and put in a small section of fuel injection hose with fuel injection clamps. Night and day difference now in how it runs now.