Impala ls 2000 Stalls at high speed
 

Hi, i have an Impala Ls 2000 V6 3.8 with 80k miles.

a little background first:

i bought this car used like 2 years ago, it was fine until some months ago.

i changed the upper intake manifold cause it has a coolant leak and it hydrolocked, bought one used and ordered a new one, a dorman one.

some weeks ago i was going at 75 mph at the highway and the car made a weird sound like there was something stuck, then the rpm iddle started to go down slowly until the car shutted down, i try to start it back on when it was parked it would cranck and start but dies right away, towed it to my house.

2 days later i called a tow to move it to a mechanic, to my surprise it started right away, still used the tow, the mechanic told me to change the fuel pump battery which we did, also told me that the used part "intake manifold" was leaking too so i ordered a new one, and looks like the old owner removed the thermostat "ordered one of those too".

it was all fine until i used again the highway and hitted 75 mph the car did the same sound and the rpm started to go down, but this time it started 10 mins later after putting the key in on 5 times and then starting it.

my mechanic checked the car to see if there was any error code and there wasnt, the fuel filter is new and ok too.

so i dont know what could be causing this problem?, i think that maybe the coolant is leaking again and hydrolock the car at high speed? i really dont know, im going to change the intake manifold and all that but dont know if that will solve the problem.

what can i do?

the lower intake manifold gaskets are normally also bad on 3800's. they need to be changed to the felpro aluminum framed gaskets. also dont listen to "mechanics" who tell you to shotgun parts without troubleshooting

https://www.gmforum.com/mechanical-1...ts-l36-297702/
https://www.gmforum.com/mechanical-1...2005-a-304071/

thanks man, how did you exactly did you block the plastic intake?.

so my problem of stalling at highspeed is the bad upper intake manifold?.

also will buy the feelpro.

well if you bought a used one, it is likely as bad or worse than yours for starters. your engine is getting coolant in it by the sounds of it, normally it is either the upper manifold, lower gaskets or a combination of both. and since you can get the dorman kit for the upper i listed and the felpro lower gasket set for less than a hundred bucks all together from rockauto its a good idea to do it all at once. as far as plugging the manifold you have to pull the lower and install the plugs in it.

if you got coolant in the cylinder the plugs could be fouled. i would pull them and look for whitish junk.

Ok thanks, I ordered the piece I will install it the first weeks of January.

I'm going to do it all at once better to be sure than sorry.

which piece? you check the plugs to make sure that was your issue?

The upper intake manifold that has the coolant leak, I ordered the dorman one the same you posted(I had it ordered even before this thread the leak was too obvious lot of coolant arround the piece.

I will check the plug and the lower manifold when I do the upper intake, and check the plugs an all that.

I will have to do it anyway if there's coolant in the lower intake it must be cleaned and the plugs will be probably full of coolant I hope they aren't but need to check them.

I hope that will solve the stall at more than 75mph, is that common to happen when you have a coolant leak in the manifold?

high speed dies
 

Hi, I had a similar problem with my chevy Lumina, It would die when it went into passing gear. It ended up a bad injector. once the injector was replaced, problem solved.

Sounds logic will check that too, wouldn't that appear as a check engine light or in the computer ?

bad injector is not a real common thing and on a 3800 it wouldnt die. im thinking the plugs are full of coolant which would make it easier to stall when the coolant gets into the cylinder. not many things cause a 3800 to die, crank sensor, maf, tps, and icm. icm is the most common but will normally be a start cold and die hot thing.

when you take the lower intake off you will need gaskets. and the coolant elbow will brake apart and you will need another. the aluminum ones are the better ones to get, the plastic ones will get brittle and break or at least leak

happy new year.

so i got the dorman piece, (im surprised it comes with everything). in the instructions it says the egr tube must be replace is this mandatory or if the egr tube is good can i keep it?

the new egr is a redesigned one to help keep exhaust heat away from the plastic intake, and you should use it

Ok, the piece with two egr tubes right? 3/4 and 5/8

not sure what you are asking you have to take the old ones out and put the new ones in. they are like little metal cylinders with fluted end

Ah for some reason there's a missing word in my last post, but thanks that was what I was asking.

check engine lite
 

It threw a MAF sensor code. still don't know why, the injector was the prob. but sometimes you don't know about that obd 1 system. didn't have a reader, and was counting flashes. Sounds like the other guys have you on the right track.

well i will post the results after the installation of the upper intake and gaskets.

best thing i got to test the car at highspeed (on a safe track offcourse).

so im back from vacation and i can finally work on the impala.

i drove it today some miles to test it, and it worked fine, but when i parked it started to leak a lot of coolant from the upper intake (the old one, not the new dorman) so im going to tow it to the mechanic to put the new upper intake,

after that i checked the coolant levels ,including the radiator levels, and they are ok, the car crank and run normally.

here are some pics of the impala right now (with the old upper intake and the leak) (most of the coolant evaporated).

https://www.gmforum.com/attachment.p...ine=1389804625

https://www.gmforum.com/attachment.p...ine=1389804625

https://www.gmforum.com/attachment.p...ine=1389804625

https://www.gmforum.com/attachment.p...ine=1389804625

will upload new pics during and after the work is done.

just for precaution can i move the car to the mechanic "is far from my home some miles like 10 minutes at 40 mph" or should i tow it?

With it leaking that bad, I wouldn't even idle it if its leaking coolant that bad.

ok:thumbup2

i would replace the lower manifold gaskets, they are likely as bad or worse than the upper

Ok going to check them too, I'm also going to change engine oil and clean the injectors.

I'm considering to buy a silverado ( I'm keeping this car I'm attached to it) are they good?

depends what year and what you are going to do with it. the 2001 to 06 5.3 1500's are the best to have as long as you arent hauling over 7000 lbs. they get good local economy and 20-22 all highway. you plan to daily drive it?

Well I was thinking about buying the 2014 one, I'm planning to drive it daily and make roadtrips with it, so far I have no plans to use it to haul things.

I could also get a 2013 in good condition but this time I want to buy a new car or in this case truck.

new trucks arent worth the money you lose on depreciation IMO, because the values are over inflated to begin with, then when the truck gets older and normal people buy it they are only going to give normal money. also my opinion, i dont like anything after the 07-08 redesign, tons of flaky expensive to replace stuff. the newer ones dont seem to be getting the mileage they claim either. like i said if i were to buy a newer truck i would look for a 05, 06 5.3 4wd 1500 with lower miles. because they went back to drums, they have the less expensive shocks, less of the extra crap to worry about.

Thanks bro!, i didnt knew that about the silverado, what about the tahoe is it good the 2014 model?


back to the impala

i already changed the upper intake, i still have some doubts so if you guys can help me:

i changed the part with the help of a new and good mechanic, i did notice that there was no coolant inside the engine or in the lower intakes, still changed the gasket and cleaned everything, it already had felpro gaskets "weird" and also had a new EGR tube installed.

now the upper intake did had the common failure it still looks like it could hold for some time but it also had a hole (looks like it melted or broke) that lead the air in and the coolant out, its small, but enought to make it drop lot of coolant, what could have done that? or maybe the piece had that problem (since it was used) and i didnt notice?, should i check anythinng?.

my theory was that it was bad installed,or the piece could have been damaged and it was just a matter of time for it to crack.

also the people in the mechanic cleaned the injectors and changed the air filter for free.

(going to upload some pics later, didnt had my phone or camera at the mechanic)

the new design dorman ones are thicker in those areas than the gm ones were so they dont do that. i plugged my coolant ports to keep the coolant out if it all together, its plastic, it gets brittle with age and heat cycles

as far as the tahoe or other suv, they are the same as the pickups but even more "trendy status symbols" and are thus twice the price. it sucks for people who could actually use the utility part of that name because i am not paying what they want for those either

everything works well i tested it at 46 mph and it didnt stall.

i will try to test it tomorrow in some place safe at 60 mph or more.

also i found new problems, theres a weird sound coming from the side of the accesory belt, i dont know if it could be the water pump the ac compressor (since the sound comes from that place) it sounds like when you shake a can with a bolt inside.

and it catched my attention that the lower radiator hose had a leak, i already changed it.

(im starting to hate the previous owner of this car haha well but that way i learn some of mechanic i guess).

going to upload some pics tomorrow maybe a video (so you guys can hear the sound).

relive the tension from the belt and spin the different things, and see if any feel not smooth, they should all be smooth

thanks, im going to do that : D

is this hole normal?

https://www.gmforum.com/attachment.p...ine=1390077848

is located in the back of the lower screw of the IAC valve.

Yes, its made on purpose during the mfgr process, and its designed so when the hole is tapped, the tap can go all the way through the hole.

thanks man.

im asking cause i was checking the car since it didnt pass the test i was at more than 60 mph and it died again, double checked the upper intake did everything again, no coolant no nothing, also had no leaking or anything.

so i was checking for maybe some vaccum leak, and i noticed that the IAC valve sucks air from the sides of the plug, not the conection between the body and the iac, but in the plastic, putted some carburator cleaner and it sucked it O.o, same with some water.

is that ok?, im going to check the iac (theres no check engine light on).

i heard that if i disconect the iac valve and the idle works well then the iac is bad, is that correct?.

No.

If its sucking air in where it mates to the TB, then your gasket probably gut sucked in or its not sealing well. Remove/inspect/replace.

im uploading some vids and pics.

also sometimes it take time to start "long crank" or start and dies right away, i taked the iac valve conector and it started right away "but idled to 2 x 1000 rpm"

Leave it connected, this time, crack the throttle open(I mean JUST a crack) and attempt to start. If it starts immediately, fault lies either with the IAC or its not opening all the way due to carbon buildup.

(sorry for the spanish the car is in venezuela, thats why is kinda hard to find a good GM mechanic most GM car here are those opel with new names s:)

Videos:

engine start:



and how the rpm dances alone

RPM - YouTube

also here its from where the air comes in:

https://www.gmforum.com/attachment.p...ine=1390082091

it didnt take air from the conection between the upper intake and TB but from my inexperience point of view it looks like theres an small gap between the two but again i dont know if its like that.

If the leak is right where the arrow points, then its time to replace the IAC. You'd be surprised at how much chaos a little vac leak can cause.

those iac valves are cheap i could buy one and test it.


also thanks for all the help, you are really good and helpful.

just out of curiosity why do you have a zip tie on the vacuum boot there? if it looks dry rotted or anything that will give you issues in the future as well. the fuel pressure is regulated by that and the evap purge goes into there. you will have evap code and poor running if its hard and brittle