Warm start issue

I have a problem I have battled for years now I drive my truck only every week or two but when you start it up it just barely chugs and will only stay running if you are giving it throttle but it has no power and runs like crap for approximately two minutes from the time you started then it clears up all of a sudden like the flip of a switch and it only does this on warm starts never on cold start but not always on warm start it's random what do you think about that. I tend to think it's a fuel injector because I actually was able to pop the hood fast enough to see it one time and one of the injectors was doing some funky spray and the other nothing but when it's running poorly it seems like it's getting too much fuel, not lacking fuel. It is a 88' with the 454 engine. It tends to do with the most after you have driven it to operating temperature then you shut it off and started back up a half hour or more later. Other than this temporary issue on warm start up the engine always runs perfect

Almost sounds like a vapor lock scenario. If one injector is spraying and the other isn't sounds like heat soak we used to get on old carbuerated engines.. bad injectors maybe? Maybe vapor lock in the injector pods? I pulled the injector pod apart on my tbi and the orings and small filters were shot. Could be dripping down when the engine is hot (expansion of the pod and less sealing of the o rings) and having to clear the vapor out of the pod when you start... just an idea

Something like that sounds like it makes sense. It only tends to do it after you have been driving and you stop and let it sit for 20 minutes or so but not if you just shut it off then started right back up.

Grab the ac delco tbi rebuild kit from amazon. Cost me 12$ three beers, a gallon carburetor cleaner can, and a little cussing getting the injectors to reseat (lube the o-rings with a small amount of atf....) but was well worth it

I like the sounds of that it's right in my price range! thanks

Another thing that may be worth looking at is the engine coolant temperature sensor. A faulty one can cause hot start issues, calling for the computer to dump too much fuel and requiring you to floor it to get it to turn over. Doing so makes the computer shut off or reduce fuel to clear a flooded condition.

Not sure where it is on an 88 454, but on the 350 vortecs it's by the thermostat housing on the intake manifold.


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I can tell you exactly what is wrong with it. It has a weak fuel pump that is not able to build enough pressure to open the pressure regulator. It takes a minute or two to pump out all the vapors through the injectors, then you're good to go.

When your truck hot soaks, vapor builds up in the supply line. Normally, once the pump comes on it builds pressure in the system, the regulator opens, and any vapors are on their way back to the tank.

Here's a simple test. Unscrew the return line at the TBI unit and unseat it slightly. Have an assistant turn the key to on. I'll bet no fuel comes out. You can probably start it and no fuel will come out. The pump is supplying enough fuel to run and drive the vehicle, but does not open the regulator. It is a very rare scenario to get a weak pump that won't open the regulator, but supply enough fuel to operate the engine normally with none of the usual fuel starvation problems that you usually get with a weak pump.

If you check fuel pressure, it might make 13 or close to it, but it isn't making enough to open the regulator, and you are essentially experiencing "vapor lock".



Tom

I had a development late last night I had my wife start it while I had my head under the hood and it actually did it while I was looking at it! I noticed the injector on the left side was not spraying anything and it was running like crap and as soon as I wiggled the plug-in on top of the injector it cleared up and ran perfect and started spraying so I'm wondering do I just need to replace that plug in or was that just a coincidence? but that seems way too simple.

could be a good posibility. The plug wires over time get solidified from heat and fuel vapors/oil/gunk and can cause issues. Also- the rubber grommet can degrade, and the air filter assembly if not seated correctly can cause a short on those four wires.

these tbi,s are a pain..305-350-454-v-8 turn the key on.check the spray.the fuel just runs back.to the tank.via return line.both injectors should be.spraying the same.when running.some times the wire plugs on the injectors want be.locked on one lose engine can jump around.run bad..next.if the TBI has never been off.the base gasket is most likely bad.and sucking air.mnd was.you can not tell.by looking pull it off.do the rebuild kit.bought mind.ebay..read the directions.do it right.but do not over clean the parts.specially where the fuel runs down in to the engine.it has to be smoothe.each engine uses it,s own injectors.cant swap them-like 305 in to the 454..these engines were famous for the base gaskets going bad.and the regulator in the TBI unit.it all comes in the kit..