Any GM TBI experience?

[stang2be]

+1. Nearly all problems on a TBI motor come down to the ignition control module. Otherwise, you might take the fuel pressure regulator apart and check for a pinhole leak. I just had one on my lot that would fall on it's face after 3K RPM, no codes. I threw about $200 at it and nearly a week trying to fix it. Come to find out, someone had replaced the fuel injector harness and had gotten the left and right reversed.

Sounds like a good thing to check out. Thanks for the tips. Any idea if that would also cause a slow start when cold?

[SEB]

Sounds like a good thing to check out. Thanks for the tips. Any idea if that would also cause a slow start when cold?

coil

[JC316]

Oh and one more thing to check for are the engine grounds. All kinds of weird problems can show up from one being loose and they are notorious for breaking.

[shumpertdavid]

Oh and one more thing to check for are the engine grounds. All kinds of weird problems can show up from one being loose and they are notorious for breaking.

I forgot about those, the ones at the thermostat housing and the corner of the intake. Be careful around the coolant temp sensor (beside the thermostat housing), they will break off most easily.

[91cavgt]

Here's one other thing to check that is easy and free to check.

With the engine running at idle, move and jiggle the wire harness around in different spots to see if the miss comes and goes. You could have a short in a wire that has no connection until the motor rocks, thus reconnecting the wire and making the truck run good while accelerating. I've seen this on other vehicles before.

[SEB]

Any updates on this?

Hate when people don't give updates if the problem was solved.

[shumpertdavid]

He's still working on it, his Brother in law (i believe) is coming with more diagnostic tools to continue testing according to his pms

[stang2be]

He's still working on it, his Brother in law (i believe) is coming with more diagnostic tools to continue testing according to his pms

Yes my brother in law is an ex ford mechanic and has an odb scan tool on loan and a matco compression gauge and supposed to come over this weekend so we can take a look at many of the things mentioned.

I think we will start with redoing the compression test since if that is really at 50-60psi per cylinder then I probably am looking at a new longblock.

Hopefully its one of the other things mentioned here. After the compression test I'll start checking the wiring and the distributor. I'm hoping its a sensor or even the distributor as all those are much cheaper than a long block

I'll be sure and post results and findings and hopefully no more questions and just what the final resolution is

[jyro]

EGR valve

I had to change mine yesterday on a 91 5.7 van. it was running lean on the highway. the diaphram had a leak. Any leak at all and the vaccuum won't let it open correctly. Look in the hose connection on the barb on the EGR, that hole id is tiny.

BTW, this van has 270,000 miles on it, I had to chizle split both nuts off. never touched the threads.

I also changed a injector and replaced the diaphram in the throttle body fpr.

[stang2be]

Compression test update

Redid the compression test with a new gauge

After 4-5 cranks each cylinder is only building up to about 60-70psi

They will build up to 150psi after 15-20 cranks

Adding oil builds up to about 80-90psi in 4-5 cranks.

Based on that sounds like rings and/or valves?

If I'm pulling and getting into the motor I'm leaning towards just getting a new longblock to avoid having to get back into it. Was going to call Blaines and see what they have and plan on pulling/installing with help from the family mechanic.

[JC316]

Redid the compression test with a new gauge

After 4-5 cranks each cylinder is only building up to about 60-70psi

They will build up to 150psi after 15-20 cranks

Adding oil builds up to about 80-90psi in 4-5 cranks.

Based on that sounds like rings and/or valves?

If I'm pulling and getting into the motor I'm leaning towards just getting a new longblock to avoid having to get back into it. Was going to call Blaines and see what they have and plan on pulling/installing with help from the family mechanic.

Rings. If it were the valves, the pressure would never build up to 150.

[stang2be]

Rings. If it were the valves, the pressure would never build up to 150.

Guess I could just get away with a shortblock but based on pricing on blaine's site

Its 840 for a premium long block vs 565 for a short.

If I just go with a long then I should hopefully be good for a while? Or go the cheapest option and pull it and just replace the rings?

[dee]

You could do a leak down test if you really wanted to narrow the loss down.

[JC316]

Guess I could just get away with a shortblock but based on pricing on blaine's site

Its 840 for a premium long block vs 565 for a short.

If I just go with a long then I should hopefully be good for a while? Or go the cheapest option and pull it and just replace the rings?

Just get a complete junkyard engine man. These things run forever. They run about $350-$500 for a complete engine.

[stang2be]

Just get a complete junkyard engine man. These things run forever. They run about $350-$500 for a complete engine.

My worry is you spend that and could get a motor like mine that only has 113k and spend all that time pulling and not get much better off and can just spend a little more and have a new longblock with warranty