What the hell did my truck just do?

[RecklessWOT]

So my 87 Burb still needs an engine so I don't care how well it runs at the moment, but it needs to at least run in general so I can move it around the driveway and not have it be in the way all the time.

I replaced the battery and started it for the first time in months. Had it idling for a a good 5-10 minutes while I went to go grab my 2500 and a chain so I could drag the other car out of the way that is blocking the burb (both vehicles are parked in the way of snow plow, we're actually supposed to be getting some snow tomorrow night into tuesday for only like the 2nd time this entire winter, I wanted to move them so I can hook the plow up to my other truck). It was running as it usually does, a little rough but good enough to sit there and hum along no problem.

All of a sudden the idle shot up to about 3k so I ran over and shut it off real quick. Now I can't get it to fire at all. It turns over fine (a little fast if anything so I probably lost more compression running it while it's so cold), but it won't so much as sputter. I'd figure a fuel or spark issue if it just up and died, but the fact that it revved way up is what's got me scratching my head. It obviously still had fuel, spark, and compression to be able to rev so high and the only reason it shut off was because I turned the key. But now it refuses to start, I'm confused. Any ideas what the hell just happened?

 

[HotRodPC]

Did it get hot? I assumed it's obviously a TBI with an ECM since the idle went way up on it's own. A sensor detected something it didn't like and raised the idle is my guess. Whatever that sensor did, it raised the idle and told something to do something else. So whatever the something else is, is likely why it won't start now. Can you try to unhook the battery, let everything to do with the ECM clear itself and try to start it again. Worth a shot. I seen an older Grand Am have this problem before. It did restart but the idle did stay high. I was then told it had a blown head gasket that it was a common problem on those cars. I thought, how the hell does a blown head gasket make the idle go way up? But I didn't argue, it wasn't my project to work and the guy working on it was more knowldegable than me with this 89ish Grand Am engines.

 

[RecklessWOT]

Yes it's an '87 with TBI. It didn't have a chance to get hot, thermostat hadn't even opened yet, the needle was just starting to move. The truck does have a had head gasket at the very least (I actually suspect something is cracked). I had planned on replacing the engine this spring/summer anyhow, I just want to be able to move it around the driveway. I have the battery unhooked now, I suppose I can try again in a little while. You're right it probably is electronic

 

[Vbb199]

Sounds like a defunct CTS

 

[shiftpro]

Does the first gen FI have the spider under (inside) the intake like the Vortec V8s have? If they spring a leak and start to flood the intake yes the rpm will go off. I know from experience they can leak intermittently causing a high idle that comes and goes. But to shoot up to 3000 I'm thinking a line split or major seal fail.

 

[Ricko1966]

Does the first gen FI have the spider under (inside) the intake like the Vortec V8s have? If they spring a leak and start to flood the intake yes the rpm will go off. I know from experience they can leak intermittently causing a high idle that comes and goes. But to shoot up to 3000 I'm thinking a line split or major seal fail.

No TBI does not have the central injector.

 

[RecklessWOT]

Does the first gen FI have the spider under (inside) the intake like the Vortec V8s have? If they spring a leak and start to flood the intake yes the rpm will go off. I know from experience they can leak intermittently causing a high idle that comes and goes. But to shoot up to 3000 I'm thinking a line split or major seal fail.

I have friends that have had that issue with the MPFI, but no the TBI just has two injectors that fire straight down the throat like a 2 barrel carb.

 

[RecklessWOT]

Sounds like a defunct CTS

or it may just be getting confused by the exhaust in the coolant? Is there a way to trick it to think everything's fine? I don't suppose unplugging it would work in the short term? Once again I'm not trying to fix anything the whole engine is getting tossed in the spring, I just want it to run good enough to move it around the yard without dying completely.

After resetting the ECU I cranked it for a couple seconds and it kind of sputters and tries to start now, which is better than what it was doing earlier, but I had other stuff goin on so I didn't have time to play with it, just wanted to see if anything changed. So I bet I could get it started, but once it is running I don't want that to happen again

 

[bucket]

An injector could have failed and started dumping fuel down its gullet. And now it's too much fuel for it to fire up on a restart.

If you have no helpers around, try mashing the throttle to the floor while you crank it over. Doing that will shut off the injectors and clear it out if it's flooded.

 

[Itali83]

Could be a vacuum leak. That’ll raise rpms. If it’s big enough, that’s why it won’t restart. Check all vacuum hoses and connections.

ben

 

[Ricko1966]

Pull the fuel pump relay hold it floored and crank it.post back

 

[shiftpro]

I have friends that have had that issue with the MPFI, but no the TBI just has two injectors that fire straight down the throat like a 2 barrel carb.

Oh ok thanks you're right. I gapped on the TBI.

 

[Camar068]

An injector could have failed and started dumping fuel down its gullet. And now it's too much fuel for it to fire up on a restart.

If you have no helpers around, try mashing the throttle to the floor while you crank it over. Doing that will shut off the injectors and clear it out if it's flooded.

Good to know, didn't know that.

 

[RecklessWOT]

An injector could have failed and started dumping fuel down its gullet. And now it's too much fuel for it to fire up on a restart.

If you have no helpers around, try mashing the throttle to the floor while you crank it over. Doing that will shut off the injectors and clear it out if it's flooded.

So yeah you may be onto something. I was able to get it to start with my foot to the floor. It ran like complete **** and any time I tried to move the truck it would backfire out the intake and stall. Finally I got it running good enough to drive it around the driveway long enough for what I needed to do, but man it's running eye wateringly rich. And blowing straight up black smoke out the tailpipe like a friggin diesel. Sounds like it has a gnarly cam too lol.

I'll check out the injectors/ spray pattern when it's not so ridiculously cold and snowing. Obviously the truck has other issues so it's not top priority right now, but it will need to be addressed sooner or later anyhow

 

[Ricko1966]

The reason I said pull the relay and floor it and crank was with no pump it should crank, start clear up for Just a second, then lean out and die. That tells me it's flooded.Then first thing I usually check is its as @Vbb199 the cts, and it's usually the cts