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1999 Tahoe Stalling Issue

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  • 1999 Tahoe Stalling Issue

    Hello. I have an automotive shop in Florida. My customer brought in a 1999 Tahoe with a blown engine, and long story short we went ahead and dropped in a big block 454 out of a 1998 Fleetwood motorhome. Everything went well, it was running great for awhile. Has some transmission shifting issues but may be another issue. The problem we are having now is that it wants to stall in gear. It will start and idle just fine, revv the crap out of it and everything. Put it in gear and it will move no problem until the second you take your foot off the throttle then it dies as if the ignition was cut off. Flat dead, no sputtering or anything. It does have a 0411 PCM swap in it, we werent able to do a crank relearn because the transmission range switch has a code that wont go away, but its been running fine for a few months before this current problem came about. Any ideas on what it could be? The customer was able to get it to drive mostly fine when he reconnected a ground wire but its still stalling when you give it a load and let off the gas

  • #2

    Re: 1999 Tahoe Stalling Issue

    clearly has transmission issues so thought would be a torque converter lockup solenoid. had a 4l80e that had strainers in the valve body packed with aluminum duist and shavings that did not allow fluid to go where it was needed. I am pretty sure the converter locking up in any gear other than fourth will just kill the motor. Mainly sounds like gremlins that make you change everything.

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    • #3

      Re: 1999 Tahoe Stalling Issue

      clearly has transmission issues so thought would be a torque converter lockup solenoid. had a 4l80e that had strainers in the valve body packed with aluminum duist and shavings that did not allow fluid to go where it was needed. I am pretty sure the converter locking up in any gear other than fourth will just kill the motor. Mainly sounds like gremlins that make you change everything.
      It doesn't seem like its doing that, I imagine it would be more of a sputter kind of stall. Plus, when its in drive or reverse, it moves just fine until you let off the gas and then it cuts off like someone turned the key. He was having trouble with the TC not engaging overdrive, which sounds like the exact opposite of what you described. Yeah, gremlins makes more sense at this point after all the work thats gone into it lol.

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      • #4

        Re: 1999 Tahoe Stalling Issue

        Still looking for ideas. I have never had this happen before, any help is appreciated.

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        • #5

          Re: 1999 Tahoe Stalling Issue

          I just have a 99 Jimmy. wont hold in 4wd high, if I leave the car off for 3 days it does not start.If its in 4wd low, it stays there it revs up to about 5 miles per hour and slams into second. It slams into second if I take it on the expressway and we go from wide open traffic to bumper to bumper back in chicago.
          They seem to have an ignition issue to me, like there is enough battery to engage and have the starter rotate, no problem with the fuel pump side since the non start ends up with a flooding issue, but does not have enough for ignition to light the mixture.
          So when you say trans issues, I see electrical, dying for no reason, voltage drop that kills ignition. So it adds up to me that something is drawing power on the trans that is taking away the necessary voltage to keep the car running. Its like overall voltage drops below 11.5 the ignition just fails miserably. Add a computer into it and hence the gremlins.
          So I get its a Tahoe and all, different motor, but the mindset of 1999 seems like the ignition is not on the proper level of importance.
          You go 1996-1998, the best alternator trouble light is the ABS light.
          Last edited by anotheridiot; January 15th, 2020, 07:44 AM.

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          • #6

            Re: 1999 Tahoe Stalling Issue

            I just have a 99 Jimmy. wont hold in 4wd high, if I leave the car off for 3 days it does not start.If its in 4wd low, it stays there it revs up to about 5 miles per hour and slams into second. It slams into second if I take it on the expressway and we go from wide open traffic to bumper to bumper back in chicago.
            They seem to have an ignition issue to me, like there is enough battery to engage and have the starter rotate, no problem with the fuel pump side since the non start ends up with a flooding issue, but does not have enough for ignition to light the mixture.
            So when you say trans issues, I see electrical, dying for no reason, voltage drop that kills ignition. So it adds up to me that something is drawing power on the trans that is taking away the necessary voltage to keep the car running. Its like overall voltage drops below 11.5 the ignition just fails miserably. Add a computer into it and hence the gremlins.
            So I get its a Tahoe and all, different motor, but the mindset of 1999 seems like the ignition is not on the proper level of importance.
            You go 1996-1998, the best alternator trouble light is the ABS light.
            Voltage drop is not the issue, its getting 14.2v even when its in gear and under load. Going to run through grounds again, it seemed to happen less or almost not at all after the customer reattached a ground behind the head.

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            • #7

              Re: 1999 Tahoe Stalling Issue

              90 suburban. In gear at long lights, dies. Other than that.. Fine. Changed lots stuff. Said to be torque converter...

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              • #8

                Re: 1999 Tahoe Stalling Issue

                90 suburban. In gear at long lights, dies. Other than that.. Fine. Changed lots stuff. Said to be torque converter...
                That was why I was thinking solenoid, especially when he said there was trouble engaging overdrive. If it does not engage when its supposed to, it could be trying when its not supposed to. Letting off the gas is that little lull you get when you are in overdrive and it makes it feel like you let up the gas, have that little lag when you go to accelerate again.

                The only thing that made my 98 Malibu just die for no apparent reason was tied to the pass key system. Sometimes it would not start, no crank, nothing but security lite on, wait 5 minutes, it would start. If you drove for more than 20 minutes, you could be driving and it would just die for no apparent reason, if you were driving, bump it to neutral, turn key to start again and just keep driving. Troublesome spot was if you were in a turn and lost power steering at that time because it died. If you eliminated everything else, I guess I would go there..

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                • #9

                  Re: 1999 Tahoe Stalling Issue

                  what's the fuel pressure? a failing pump on that spider-efi could cause that.
                  outside of that, have you checked all the connections and grounds? if it ran fine before (how long? miles?)
                  what is the starting procedure now? do you have to hold the throttle down to start?
                  Doing it all wrong since 1966

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                  • #10

                    Re: 1999 Tahoe Stalling Issue

                    what's the fuel pressure? a failing pump on that spider-efi could cause that.
                    outside of that, have you checked all the connections and grounds? if it ran fine before (how long? miles?)
                    what is the starting procedure now? do you have to hold the throttle down to start?
                    Fuel pressure is fine, and I can rev it all day long. Its when I have it in gear with the brake on I can torque it up to about 2k RPM, it holds no problem, but the second I let off the gas it kills the ignition flat dead. Its not the 5.7 with the spider, we put in a big block 454/4L80 combo out of a motor home, all the connectors were the same and it was a relatively easy swap. Was running great for a while but then he started having some strange transmission issues that we couldnt figure out but it kept going. He got in one day and it wouldnt stay running, found a ground wire and it would run but then it started this current issue. Im open to the idea of maybe theres a safety feature where it kills the ignition when it tries engaging OD in 1st gear, but I need proof lol

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                    • #11

                      Re: 1999 Tahoe Stalling Issue


                      Fuel pressure is fine, and I can rev it all day long. Its when I have it in gear with the brake on I can torque it up to about 2k RPM, it holds no problem, but the second I let off the gas it kills the ignition flat dead. Its not the 5.7 with the spider, we put in a big block 454/4L80 combo out of a motor home, all the connectors were the same and it was a relatively easy swap. Was running great for a while but then he started having some strange transmission issues that we couldnt figure out but it kept going. He got in one day and it wouldnt stay running, found a ground wire and it would run but then it started this current issue. Im open to the idea of maybe theres a safety feature where it kills the ignition when it tries engaging OD in 1st gear, but I need proof lol
                      The truck stock, controlled the ign through the ecu.
                      You don't say if this 454 is a tbi and computer controlled distributor ign , or a csrb and mechanical timing with vac advanced can distributor.
                      THe 350 ecu is not going to fuel and ing advanced maps correctly for a tbi 454.
                      and the 350's fuel system, the fuel pump is to high of pressure if it is using a carb.
                      Those trucks go into a limp home mode also. if (iirc) the pink wire going into the transmission looses power from the ign switch.

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                      • #12

                        Re: 1999 Tahoe Stalling Issue

                        He's running it off off 0411 computer which I think goes to a 5.3 LS motor with a automatic. That's about all I'm good for . Well other than say run it off a aftermarket engine management system .
                        Previously HoosierL98GTA

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                        • #13

                          Re: 1999 Tahoe Stalling Issue

                          If the vehicle has transmission codes and you want to fix it 'properly' then you need to find out what the codes are before you go any further. The ECM talks to the trans, and if they're not having a good conversation you're going to have issues..

                          Another thing to consider,.. motorhomes spend a lot of time idling and pulling around a lot of weight.
                          Parts tend to wear out faster if the motorhome is actually driven, especially in warm states where they're driven year round.
                          Maintenance wise you have to treat a motorhome like a medium duty truck because that's what it essentially is.

                          You can check for easy stuff now sans retrieving the trans code. From the symptoms you've described I'd check the following items..

                          Try this first.. IAC solenoid. Pull the IAC and check for a carboned port/pintle, and clean everything thoroughly with carb cleaner.
                          A carboned up IAC and IAC port will cause the issues you're describing.

                          Vacuum lines. They're always overlooked, check ALL of them.

                          MAP sensor. Make sure it's working, and not broken, cracked, and make sure the vacuum line going to it is good.
                          A faulty MAP sensor can and will stall an engine.


                          Check the timing and check the timing chain for slop.
                          Hook up a timing light and do an initial reading in park at idle.
                          Then have someone put the vehicle in gear, and see where the timing marks end up.
                          Pull the distributor cap and turn the crank pulley back & forth to check for excessive play, lag in the distributor Vs the amount the crank is being turned.
                          A sloppy chain will throw the timing off enough to stall an engine in gear.

                          Torque converter, lock up solenoid. It's been said here already because it can and will cause the issues you've described. Pull the pan and check for debris.



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                          • #14

                            Re: 1999 Tahoe Stalling Issue

                            He's running it off off 0411 computer which I think goes to a 5.3 LS motor with a automatic. That's about all I'm good for . Well other than say run it off a aftermarket engine management system .
                            The auto detect on my scanner pulls it up as a 1999 Tahoe 5.7, I think its an LS1 map, maybe. Not sure how they do it.

                            Comment


                            • #15

                              Re: 1999 Tahoe Stalling Issue

                              If the vehicle has transmission codes and you want to fix it 'properly' then you need to find out what the codes are before you go any further. The ECM talks to the trans, and if they're not having a good conversation you're going to have issues..

                              Another thing to consider,.. motorhomes spend a lot of time idling and pulling around a lot of weight.
                              Parts tend to wear out faster if the motorhome is actually driven, especially in warm states where they're driven year round.
                              Maintenance wise you have to treat a motorhome like a medium duty truck because that's what it essentially is.

                              You can check for easy stuff now sans retrieving the trans code. From the symptoms you've described I'd check the following items..

                              Try this first.. IAC solenoid. Pull the IAC and check for a carboned port/pintle, and clean everything thoroughly with carb cleaner.
                              A carboned up IAC and IAC port will cause the issues you're describing.

                              Vacuum lines. They're always overlooked, check ALL of them.

                              MAP sensor. Make sure it's working, and not broken, cracked, and make sure the vacuum line going to it is good.
                              A faulty MAP sensor can and will stall an engine.


                              Check the timing and check the timing chain for slop.
                              Hook up a timing light and do an initial reading in park at idle.
                              Then have someone put the vehicle in gear, and see where the timing marks end up.
                              Pull the distributor cap and turn the crank pulley back & forth to check for excessive play, lag in the distributor Vs the amount the crank is being turned.
                              A sloppy chain will throw the timing off enough to stall an engine in gear.

                              Torque converter, lock up solenoid. It's been said here already because it can and will cause the issues you've described. Pull the pan and check for debris.


                              The codes, as stated, are for the "trans range switch" and the crank relearn. The trans switch wont go away for some reason to be able to do the crank relearn but it ran for a while no problem until recently. All the things you suggest seem like something that will sputter and stall gradually, what Im experiencing is the ignition completely cutting off like a light switch the instant you let off the gas over like 1500RPM. Engine is very strong and has a lot of newer parts in it that got swapped over when we put the engine in it. Fortunately almost all the 350 parts like ICM, coil, distributor, etc fit no problem. Transmission may be where we are heading but I'm not sure if its going to be internal mechanical or electronic. The guy that tuned it says he can take out the range switch so we can do the crank relearn but Im not entirely convinced thats the issue yet, just a secondary problem. The odd thing is that I can put it in gear and hold it under a load as long as I want and it will sit there and take it no problem. Let off the gas, engine cuts straight to zero and dies. Darndest thing I ever did see.

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