I Think I Broke My Truck..

grosss · January 21, 2008

Hey guys! Just joined the forum and was hoping you could get me off to a good start.

I've got a 93 Silverado 1500, 5.0L with 459,000kms on it... eeeverything original. Picked it up from a friend's family's business, it sat for a good few years till I took it and fixed it up to make her run again. It's been good to me until I started messing around with the ECM. I'm planning on doing an engine swap and putting in a 350 I have lying around with MUCH less mileage. Here's what happened:

I made an adapter to put in a new chip and bypass the other half of the Memcal through it so that I could still have the knock sensor/esc circuitry there, similar to the adapters sold by Moates. I'm a student and trying to spend as little money as possible, hence why I made the adapter instead of purchasing it. The chip wiring is perfect, I checked every single one before putting it in the first time, but I havent finished wiring the bypass for the ESC stuff, so that half isn't hooked up to the ECM yet.

After changing the code a bit and playing around, I noticed at low speeds every so often while trying to accelerate there was a "pop" and I'd lose power for a second... it became annoying so I put the original code back on the chip in the hopes it was a code problem. It didn't change anything, and now it's getting worse. There is popping a lot now, and the engine feels like it has no power, sometimes a double pop, and sometimes it stalls. On the highway today I almost pulled over because while accelerating it was just popping like crazy and I was losing speed. I'm afraid something's up with my head gasket or intake valve seals or something.. I changed all of the spark plug wires today, and the plugs are about 3 months old.

What I'm wondering is what exactly is the pop sound, and what's causing it? Could it be just the fact that I haven't plugged in the other half of my memcal, or is there something mechanically wrong with my engine that just happened by coincidence? I'm not planning to do the engine swap until it's warm outside again (Yay Canada!!) and I need to drive the truck all winter since my car is parked for the winter. Any help is appreciated!

Draenor · January 21, 2008

Sounds like the timing is off. With that many miles...ahem kilometers...the timing chain could be stretched. If anything, put the ECM back to its original configuration to rule it out. IMHO I wouldnt mess with the ECM, it sounds like what ever you did, started the problem.

grosss · January 21, 2008

Sounds like the timing is off. With that many miles...ahem kilometers...the timing chain could be stretched. If anything, put the ECM back to its original configuration to rule it out. IMHO I wouldnt mess with the ECM, it sounds like what ever you did, started the problem.

Is that pop a result of timing vs. physical problem with the engine? I wasn't really messing with the ECM for the sake of changing stuff or getting more power out of this engine (even though I'd like to) I'm just practising because I'm going to need to reprogram it when the 5.7L gets dropped in :-).

I'm going to try putting it back to stock tomorrow, I'd been so worried something broke I kind of forgot about the incomplete ECM adapter until tonight ;-).

grosss · January 22, 2008

Ok, so I finished my adapter yesterday and attached the other half of the memcal, and now my problem has been inverted.. sort of. She drives great at low speeds now, I've got all of my power back, EXCEPT, when I push it to WOT, sometimes it'll pop and die. Even worse, on the highway once I get above 100KPH, if I put my foot any harder on the pedal than light acceleration, it pops rapidly in succession and I can't really pass anyone. I'm now wondering if it's a fueling issue, maybe water in the tank from condensation? (Yay cold canadian winters!) I'm going to change the fuel filter and see what that does.

Any thoughts?

7egend · January 22, 2008

im no engine expert or engine change out expert. But I have had a Spark plug pop out before and it results in power loss and a pow pow pow pow noise and dies off after you let off the accelerater. Not sure if this is your problem, but just from previous popping expirence.

Good Luck with your problem.

grosss · January 22, 2008

im no engine expert or engine change out expert. But I have had a Spark plug pop out before and it results in power loss and a pow pow pow pow noise and dies off after you let off the accelerater. Not sure if this is your problem, but just from previous popping expirence.

Good Luck with your problem.

Yea I suspected spark plugs too, I had changed all the spark wires right after the problem started to see if that'd do the trick, but I haven't checked to see if any of them are loose yet.

Cadha13 · January 23, 2008

Check for misfire or backfire. It happened a lot on my Caprice and found out my timing was like a whole cylinder off and the computer adjusted the timing to make it run. It was a 305 V8 carb. with computer electronic spark timing just like the TBI models. just redid the spark wires and it worked fine.

markw8 · February 3, 2008

It sounds like the fuel mixture might be going lean and causing it to pop. Mark.

grosss · February 3, 2008

Update:

So mother nature screwed me again! Turns out it was a combination of things. First off, not having the ESC/Knock sensor circuitry in was part of the problem since it couldn't sense when there was a problem half the time, the other problem was that thanks to mother nature, we had gone from warm humid days to sub zero freezing dry days right about the same time, and my gas tank was pretty empty, so all of the moisture in the tank had condensed and my engine was trying to burn some water!

After filling up and driving for about a day the popping at high speed/high rev was gone and now she's purring like a kitten again. Now if I can just figure out why the hell it burns so much gas....