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Discussion Starter #1
1990 v8 5.0L starts up fine, but once i put it into gear (drive, or reverse) and give it some gas it hesitates before moving, or sometimes even dies.

The other day I went to the gas station and it made it there fine, but when I tried to start it after about 30$ worth, it wouldn't start. It turned over, but wouldn't fire up. If I gave it a little gas it would almost start. After like 10 minutes it finally started up.

I got home, put it in reverse, and gave it just a bit of gas and it died. Had to try starting it for another few minutes before it actually did start. and i parked it for a couple of days.

After it sat for like 2 days, i just started it right now. It started up fine, idles smooth, but as soon as i put it into drive and ease on the gas it hesitates and the RPMs drop and it almost died.

After a little bit of driving, when the engine temp comes up, it runs perfectly and never hesitates.

Not sure what it is, so any advice would be appreciated.
 

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Chemfrk had this same problem up in big bear. Look for, I think it's called an air temperature sensor, or an air density sensor, on the right side (looking at the engine) of the lower intake manifold.
 

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I've had similar syptoms caused by IAC valve (Idle air contol).
 

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Discussion Starter #4
by the way, I think i have a vacuum leak because if i try to put the heat or a/c on air only blows out the top vents like it's on defrost.

the book i have says it might be:

1) Vacuum Motor Inoperative
2) Air cleaner duct and valve door not operating properly
3) CWM inoperative (cold weather modulator)
4) Bimetal sensor inoperative
 

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i just went threw the same thing. did u adjust your timing recently?? either way check your timing and make sure you remove the SPOUT connector
 

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by the way, I think i have a vacuum leak because if i try to put the heat or a/c on air only blows out the top vents like it's on defrost.

the book i have says it might be:

1) Vacuum Motor Inoperative
2) Air cleaner duct and valve door not operating properly
3) CWM inoperative (cold weather modulator)
4) Bimetal sensor inoperative
check the vacuum hose coming off of the little metal diaphram (?) actuator on the heater box.
pop the hood and it's visible on the heater box on the pass side.
There should be a plastic vacuum hose hooked to it and they get brittle due to the heat and age.
This can cause a tiny vacuum leak and may be the problem with your defrost staying on.
 

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Discussion Starter #7
moonraker, i dont have to take the dash apart to get to the heater? how about the heater core. I think my grandpa put in some stuff to block up some leaks, but i think it ended up just clogging everything up.

The engine temp gets warmer lately and the heater doesnt blow as warm.
i dont know if thats just because it's only coming out of the defrost vents or if its because of the heater core being clogged up with some stop leak stuff.
 

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Discussion Starter #8
i just went threw the same thing. did u adjust your timing recently?? either way check your timing and make sure you remove the SPOUT connector
Haven't touched the timing. BUT, some shop just changed the harmonic balancer if that might have done it. Other than that, it hasnt been touched. But it starts and idles just fine, and once it warms up it runs smooth even while accelerating.
But when it's cold it hesitates on acceleration before moving, but warms up and runs fine. If it runs fine after warming up, would that be timing?
 

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Runs fine after warm up? most likely IAC, idle air controller, it keeps the idle "steady" Probably needs a cleaning.
 

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moonraker, i dont have to take the dash apart to get to the heater? how about the heater core. I think my grandpa put in some stuff to block up some leaks, but i think it ended up just clogging everything up.

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I doubt if this will fix your dying engine but may help w/ the defrost only situation. As I mentioned before, I had a similar problem with dying caused by the IAC.

Look for the little valve I mentioned.
It's on the heater box/AC box or whatever you want to call it (or at least it is on '87 thru '91's). I can't recall for sure on 80 to 86 or '92 up but probably there too.

It has a plastic vacuum line on it and if you trace it down into the wire loom you may find that it has gotten brittle and cracked or deteriorated.

My F250 was constantly blowing air in the floor vent and this was the culprit.

However, there might be another valve under the dash that controls the defrost/floor vents, etc.
 

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Discussion Starter #11
Runs fine after warm up? most likely IAC, idle air controller, it keeps the idle "steady" Probably needs a cleaning.
yeah, it runs perfect after it warms up.

i have an engine/emissions-diagnosis shop manual and cant find anything about a "IAC". Im going to keep looking, but any idea what else it might be called?
 

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Discussion Starter #12
alright moonraker, Im gonna check out some under the hood vacuum lines first. Then get into the dash if i need to.
 

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1990 v8 5.0L starts up fine, but once i put it into gear (drive, or reverse) and give it some gas it hesitates before moving, or sometimes even dies.

The other day I went to the gas station and it made it there fine, but when I tried to start it after about 30$ worth, it wouldn't start. It turned over, but wouldn't fire up. If I gave it a little gas it would almost start. After like 10 minutes it finally started up.

I got home, put it in reverse, and gave it just a bit of gas and it died. Had to try starting it for another few minutes before it actually did start. and i parked it for a couple of days.

After it sat for like 2 days, i just started it right now. It started up fine, idles smooth, but as soon as i put it into drive and ease on the gas it hesitates and the RPMs drop and it almost died.

After a little bit of driving, when the engine temp comes up, it runs perfectly and never hesitates.

Not sure what it is, so any advice would be appreciated.
Is it cold where you iz Blockhead ?

If it gets warm and cold and cold and warm on you, when you have less than a full tank, water forms inside you tank due to condensation.

Sounds like you're passing water

Sixlitre
 
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