Here is the deal. Ive been helpin a buddy of mine put an Edelbrock performer intake on his 91 RS with a 305. We have a TBI adapter plate, and are using it. Got everything hooked up and timed, fired her off, and she started right up.. But the issue is this.

The TBI is wailing like a friggin banshee. It sounds like a siren or something. High pitched, and as it idles up the sound gets more intense. however, when you give it throttle, it quiets up a second until the throttle is off and its returning to idle. We have ran into alot of problems making this swap work, but it *SHOULD* be fine right now. What could cause it to wail like this?

ANY input is GREATLY appreciated.

Thanks in advance.
-steve

 

i would guess a small vacume leak.

that is why it goes away when you give it throttle, take away vacume now sound. the leak is probably acting like a whistel, the air is getting sucked through, and making noise.

 

Dewey, what you say makes sense. I thought it was one last night, but i checked all the hoses, and everythign seemed fine. I amwondering about the trhottle body adaptor plate now myself. I wonder if its making a good seal, or if there are other holes in it that are causing the air to be sucked through where a bolt may or may not have been on right for it. I just couldnt find a place where a vacumn leak was so i was pointing blame to the throttle body itself.

Plus would a vacumn leak on the Throttle body/intake manifold cause there to be almost no vacumn pressure to operate the power breaks?

-steve

 

could effect the brakes.. esp if its as big of a leak as you say.



its not just the hoses you need to be looking at... look at where the manifold meets the heads, where the adapter goes to the manifold and between there TBI and the adapter.... all of thoes have to have a good seal.

 

a can of carb cleaner is going to be your friend here keep a fire extenguisher handy, and spray around the carb adatptor, ect, you should here the idle change if you spray it at the point of the leak.

 

Ok, that makes me worry then.

Here's why.

The car is a stock 305 (91) and teh intake is a Performer RPM. The bolts didnt match up perfectly as the angle seemed different. I wonder now if its not at all a TBI issue but an Intake manifold issue. I wonder how good of a seal it has. How can i check this?

as far as the Manifold meeting the adapter, we used a standard carb gasket on it, and then the TBI gasket on the top to the tbi. I wonder if there is a hole or something for a bolt that we missed on this adapter under the TBI, but not covered by the gasket.

sounds like i may end up taking all this back off this car again.

-steve

 

theres 2 ways.... i was going to post it but i had to do some actual work (here at work).. hehe



1st is what dewwy said.

2nd is to get some ATF and put it in a squirt bottle.. watch the exhaust when you spray it... it you spray it where it gets sucked in, it will make some nice poofs of smoke out the exhaust (it wont hurt anything though).


spray it or the carb cleaner along the head/manifold meeting aread first... once side at a time.. if thats not it, then goto the lower half of the adapter place, then the upper...

 

the ports should all match no prob.

the two center bolts changed from angled like the rest... if it is the middle of the manifold/head seal, you may have to get these lil wedge pieces that go under the bolt... they'll let you be able to tighen up the center of the manifold without probs..

im assuming you only modded the middle bolts and just used a drill to make them more oblong right? did you make sure there was no flash from the drilling on the manifold seating surface?

 

Ok, cool.. Ill try the carb cleaner around the head cause i have that readily around. Ill check all this this afternoon after 5 pm. Judging by the sounds though it sounded like it was coming from up high on the intake, not down low, but it was hard to tell cause of how Shrill the sound was.

thanks again for the info/ advice

-steve

 

just be careful with the carb cleaner.... lean away...

if you have a backfire while spraying it (it can happen) you get a nice lil fireball.

 

well that is a relief about the ports all matching.

yes, the center bolts is where we had the problem and we did drill them out to make them oblong. Yes we made sure that there was no excess flash anywhere on the manifold before we installed it.

I havent heard about the wedge pieces before though. Where would i get these things from? As it sits now, the bolts are in and torqued down to 35ftlbs on the entire manifold as best we could, but we dindt get into the two pairs of center manifold bolts as good as I'd of liked because of the angle gap of the bolt. made us nervous trying to torque them down hard. I guess I need to find these wedge pieces. where can we get them from and how much are they?

This is kind of urgent, as this is my friends only transportation and he has to go to work all week as most of us do, but at 4 am. so he doesnt/cant ask people to get up at 330 or so just to give him a ride in to work.

 

oooh.. that sounds like fun!!
I'll be careful. Im kinda partial to my eyebrows!

-steve

 

haha, this is what i am doing at work :-p

 

well yesterday we went ahead and tested the intake manifold with the carb cleaner. Intake seems totally on the heads, cant find any problmes there. Everythign seems bolted down real good, cant tell any leaks on the manifold. Im worried about screwing down the two middle bolts, where we had to modify the manifold to the full torque specs because of the angle they are at.

We've been over all of the hoses, fairly thoroughly, cant seem to find any issues there either.

Went so far as to remove the belt off the serpentine setup and start car, ruled out accessorie drives and brackets, so that stuff is good. Sound sounds like its coming from the front of the manifold area, but to be honest i cant tell. When your on the driver side, it sounds like its coming from the passenger, and when your on the passenger it sounds like its coming from the driver side.

Worried about starting car and running, as we had let it run yesterday for a while and the tailpipes started shooting out fire, about 12 inches long from each exhaust outlet. Looked under car after we shut her down, everything from the Catalytic converter back was glowing orange. Cant be good.

Im gonna take the TBI off this evening and the Throttle body adapter plate, make sure its sealed down well. May even use silicone on top of the gaskets. Then re-assemble and see if it does it again.

Vacumn hose to MAP sensor makes car idle real real high when connected to back of throttle body. When disconnected it idles relatively well, a little rough, but VERY rich.

Thinking about saying screw the TBI and get a carb, and a fuel pressure regulator. Only problem with that is thats almost 400.00 and the TBI should be working we just dont know why its not.

Help.

Any help/insight is NEEDED and greatly appreciated.

 

that tells me... shes running really rich and puddling fuel in the exhaust.. where its burning


ah ha.....

i bet its either the hose going between the TBI and MAP sensor, or the sensor itself. most likely the hose though... because if the hose sees atmospheric pressure, it assumes its at near WOT right? and that it would mean it thinks the engine needs more fuel, and its dumping fuel...


at least thats my theory from what you typed... *shrug* im assuming you capped the vac port that the MAP goes into when you did that.

btw, i may be wrong since i dont have it memorized, but doesnt the map goto the manifold and not the TBI??

 

it should be ok going to a port in the TBI, it gets vacume there.

if you aren't plugging the MAP into vacume, that could be an issue. if it runs like crap WITH it plugged in, that is another.

 

Dude,

Yea she is runnign real real rich. didnt think that the fuel would actually do that though.


The hose going from the TBI to the Map Sensor is a rigid plastic tubeing, and it seems intact without any issues. The car when it has that Sensor plugged in Idles up to upwards of 4000-5000 rpm im guessing. (tach not accurate, but its beent hat way for a LONG time before we messed with any of this.) When the Map sensor is not plugged in it idles rough, but not horrible. Runs REAL rich with this unplugged.

I am assuming that the map sensor is the correct term for what im calling this sensor. It is located on teh firewall, almost directly above the passenger side valve cover and Heater/ac box. Has a weatherpack connector hooked to it with 3 wires, Green weatherpack connector, and one rigid vacumn line.

Yes, when we unplug the vacumn hoses we alwasy cap the open ports to see what it does by doing that.

Im not sure where the Map sensor would have normally plugged up at as I dont recall. We have a buddy with a 92 rs though im gonna use as compare and double check hopefully tonight.

Dewey,

Good to know its ok to plug to TBI.

Again, Im assuming the sensor im calling the Map sensor really is the Map Sensor. See above for details as to where i describe its location.

Thanks again for all your insight and help guys. I appreciate every little bit of it.

 

other major thing that just NOW occured to me.

whats your timing set at? have you used a light on it?

 

Timing is currently set by ear. I dont think that its off much cause you bearly turn the key and the car fires over. much better than its ever fired over.

Havent put a light to it yet because of the screamin noise.. was going to final time it once we got everything together without that screaming wail.

You dont think the screaming wail has something to do with the timing do you?
-steve

 

i dont know....


i wonder if the map sensor itself is cracked and is making any noise.. *shrug*



for all we know, the noise could be the adapter plate too..


heres what we know...

extra air is getting into the engine some how.
A/F ratio is off to the rich side
Timing needs to be set



without being there, i cant think of much else to do... umm..

can you put a piece of hose to your ear and try to pinpoint this noise? we need to find where this air leak is.....

other then saying, set your timing, theres not much else to do right now then find the leak...




did you guys "mod" the TBI at all?




oooh. where did you get your adapter plate from? theres a little channel on the underside of the TBI that could be a possible big leak....

 

ok, this is starting to come together.

here is my next thought.

your throttle blades are not closing all the say. that is where the whistle and high idle are comign from.

you NEED the map sensor plugged in. the sensor you described is the map. it is really the only way for the computer to know how much fuel to use. it has to be getting accurate vacume readings.

have you checked the TPS voltage at idle with the map plugged into vacume?

 

you cant without a scan tool 91s have that newer style non adjustible TPS...

 

i've done it, my 90 has the non adjustable. you can CHECK it with a DVOM.

 

how do you attach to the pins in the connector without disconnecting the TPS?

i tried everything i could think of.. even tried shoving lil zip tie wires(sans covering) inbetween the two to get it to fit... no luck..

 

you stick them into the weather pack. i can hook it up, and snap a pic if you like

 

please do... start another thread though so we dont clutter his..