88-93 chevy truck owners


dr_of_lovephd
01-20-2005, 05:34 PM
Greeting everyone,

I wanted to let everyone know about a problem I found with my 89 pickup that was robbing me of a lot of horsepower. This is for people running the stock air intake assembly.

On the stock air intake there is a valve that controls whether the air comes from the outside or from that little pipe that runs down to the exhaust manifold. The valve is to give the engine some warm air for cold starting. When it gets hot it should open. Well, mine got to where it never opened. My motor was getting all of its air from that little 2 inch pipe. I perminatly opened it with some screws and it probably gave me 25+ extra horses. I think they changed the intake style in 94.

Later, my uncle asked me to check his 93 chevy truck because it was not running well, and it had the same problem.

I don't know if anyone else has noticed this problem, but if your truck seems to have lost some power, it is worth the time to check it out.

TaNK_Em
01-20-2005, 06:31 PM
I have a 93 i will have to look into it.

- Kevin

broughy84
01-20-2005, 07:49 PM
Yep...already tore that little puppy outta there and plugged that hole!

chevytrucks92
01-20-2005, 08:08 PM
I got an AIRAID intake on my truck now, but never really noticed any loss in power with the factory set up.

Now this new AIRAID intake makes the truck like night and day power wise.

tirefryer93
01-21-2005, 07:27 PM
Flip the stock lid upside down.

LT1 Kayker
01-23-2005, 12:58 AM
I used an acetylene torch and cut the whole thing out a few months ago and welded a plate on the bottom where the valve was. It doesn't seem to do much different than before though.

rjrhoades
01-23-2005, 01:29 AM
The pupose of the door is to help the engine run better while warming up (and help on emissions). A better solution would be to fix the problem, probably pretty inexpensively.

Your rememdy can cause drivability problems when cold, unless you always let it warm up for 15 minutes before driving.

tirefryer93
01-23-2005, 03:37 AM
I guess I wouldn't worry about cold starts, because engines are much happier with cold air anyway. If you are in search for power, it is worth a few minutes of warm up time.

roadrunner_70
01-26-2005, 07:43 PM
I've just bought a '93 cheyenne and it came with no hose for that valve. I also don't think the valve works, but given that the prevailing temperature here is below zero celsius(-20), I installed a new stovepipe. When it's this cold you want all the warm air into the intake that you can get. I also installed a winter cover for the front to lessen the effects of windchill. I drive about 15 miles to work so it doesn't really get a chance to warm up fully. This can mean alot when it comes to preventing fuel saturation in your oil. It actually might burn off some of those contaminants. The replacement valve has to be screwed in, whereas the original is rivetted, which you must drill out. It's a good investment to maintain it.

J-Ri
01-26-2005, 09:34 PM
It's definately better to keep the valve working. Mine doesn't work. Even after the engine is up to temp, a big gulp of cold air will make the engine stumble a bit. Also, it takes at least 5 minutes of revving to get it to accelerate quick enough to get on the highway without getting hit. If you live in the south, it may be worth removing it... but if it gets cold where you are, it's probably best to leave it on there.

J-Ri
01-26-2005, 09:41 PM
Oh, and I forgot... the trucks that have the heat riser go back well before 88, I know 86's have it, and I think it goes back to the earliest models.

v10_viper
01-27-2005, 12:06 AM
Yeah that damn thing got stuck shut on me one time for awhile and i couldn't figure out what the fuck it was until i took the hose off because i thought something was clogging it and it was that. It actually took some force to loosen it so i dont' know what happened but I just left it, it opens now so that's good enough for me. I really dont think that valve or w/e needs to be there because with the warm air coming from that hose it should take it in, open or closed.

big_blue_chevy2006
01-27-2005, 09:13 PM
i dont have a stock air intake nemore but i did notice that i have a k&n air intake assembly. well about that adding 25 horses i REALLY HIGHLY doubt that, my k&n air intake dont even add that, when air intakes say they add up to 15 horses or so that normally means with very big mods otherwise it might add like 3 or 4 horses.

Xrrider280
02-14-2005, 11:54 PM
how does the motor know when to change that little valve anyway, there are no wires or anything just that tube going to the heat sheild.

rjrhoades
02-15-2005, 12:22 AM
how does the motor know when to change that little valve anyway, there are no wires or anything just that tube going to the heat sheild.

That tube is a vacuum tube. The "motor" is powered by vacuum (instead of electric) produced by the motor. In the older vehicles, the vacuum was controlled by a mechanical thermal switch (sort of like a temperature sensor) mounted in the engine block. I haven't followed the evolution, but the switch could now be an electrical vacuum switch controlled by the vehicle computer. If an aftermarket air cleaner is used, the whole assembly was probably thrown away.....

rjrhoades
02-15-2005, 12:29 AM
Oh, and I forgot... the trucks that have the heat riser go back well before 88, I know 86's have it, and I think it goes back to the earliest models.

Yes, it goes back into the 70's (god, am I that old?) at least. These also complement the work of the heat riser valve in the exhaust manifold (I think that is what it is called) that helps to divert warm exhaust air through passages in the block to aid in a quicker warm-up. The heat riser valves are spring loaded. The springs operate with exhaust tube temperature and open as the exhaust pipe warms. As the metal ages, they can "stick" with age and the bolts that hold the manifold to the exhaust tend to loosen, especially on replacement exhaust systems. I always had to periodically retighten these bolts when I started hearing an exhaust leak (which can sound like its coming from the exhaust header at the block).

roadrunner_70
02-15-2005, 07:00 PM
The ones used back in the late 80's and early 90's, and possibly even now are a "wax pellet" type. No vacuum hoses like the older versions of the eighties. As the wax in the small cylinder heats up, it expands, and moves the lever forward, closing off the heated air from the stovepipe, and allowing the cooler air from the fenderwell. I checked mine out the other day and found that it worked fine, except the valve had jammed so it was stuck on hot air intake. Most of the time, it's the sensor that karks it, and won't move no matter what the temperature.

Xrrider280
02-15-2005, 10:42 PM
what would happen if I were to take this stovepipe off? would it hurt my engine or just take longer to warm up?

rjrhoades
02-15-2005, 11:13 PM
what would happen if I were to take this stovepipe off? would it hurt my engine or just take longer to warm up?
When it is not functioning (whether from mechanical malfunction or removal) it can be difficult to keep the motor running at a cold start before warming up (pumping the accelerator syndrom). So while it probably won't directly cause mechanical destruction, it can cause mental destruction and early engine wear from unburned fuel/possible engine backfire from misfiring.

roadrunner_70
02-16-2005, 10:20 AM
Remember the old days? You used to have to wait five minutes or more for your truck to warm up? It would run rough if you attempted to just start it up and drive away. The technology then didn't allow for immediate driveability. Sure, they had stovepipes since the sixties, and heat riser valves, but carburetors used anything from manual chokes to crude bimetal springs that slowly moved them off. Modern fuel injection systems are much better at metering fuel, especially when coupled with sensors that give feedback. Defeat any one of those and the others suffer. Think about it, if you take away the warm air during warm up, the fuel takes longer to vaporize, therefore you'll need more fuel to reach the right ratio. This richer mixture may not completely burn, and passes those HC down the line to your oxygen sensor, and your catalytic convertor. Neither one of them are receptive to excess amounts of anything. Since your oxygen sensor doesn't even come into play until around 600 degrees, when it starts to register Oxygen in the exhaust, doesn't it make sense to make the conditions as close to ideal as possible until the system goes into closed loop?

rjrhoades
02-16-2005, 10:45 AM
Well Said!!!

TOMMCCONATHY
02-16-2005, 11:00 AM
The Guys In The Cold Climates Are Right. It Is Best To Fix The Valve Rathar Than To Block It Open. You Might Not Care About The High Emmisions During Warm-up, But On The Other Hand, It Came From The Factory Running Good With That Valve Working. As Vehicles Get Older We Kind Of Expect Them To Not Work As Well As They Did. Keeping All Of The Mechanical Parts Functional Will Help Your Vehicle Running The Best Possible. Sure Advances Have Been Made, After Market Parts Are Available, So Take Advantage Of Any New Info You Can. Just Make Sure If You Up-grade A System, That All Of The Original Functions Are Present In The Upgrade [unless The Original Functions Have Been Prooved To Be Wrong].

tacoma200
02-16-2005, 02:56 PM
i dont have a stock air intake nemore but i did notice that i have a k&n air intake assembly. well about that adding 25 horses i REALLY HIGHLY doubt that, my k&n air intake dont even add that, when air intakes say they add up to 15 horses or so that normally means with very big mods otherwise it might add like 3 or 4 horses.

Just wondering about the sound of the K&N or Airaid intakes. I have heard that it adds a great sound to the motor. Is it kind of like the sound of the old 4 barrels when they kicked in? Any input welcome.

Xrrider280
02-16-2005, 11:26 PM
Do most aftermarket air systems have a valve for the stovepipe. I was thinking about getting a cold air intake for the summer and was wondering if it would be best to switch back to stock for the winter. I live in the Upper Penninsula of Michigan where it is pretty cold in the winter

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