Ozz1967

iTrader: (4)

Hey guys,

What sensor is in the pictures below? I remember seeing this before because I took it off when I did the motor swap. There has always been a power connector hooked to it however there was no vacuum line hooked to it until it came back from the shop after the dyno tune. When I had the 305 in it, the vacuum line wasn't hooked up and eveything seemed to run fine. Now it has a vacuum line that is attached to a port on the carb and I don't know why or what it's supposed to do.

InfernalVortex

iTrader: (4)

I think that's the MAP sensor. It looks a little different from mine, but that's the same place mine was. It measures vacuum in the manifold so the computer knows how much load is on the motor. For my TBI car the line ran to the back of the throttle body.

F-Body Demon

iTrader: (1)

MAP Sensor. Its supposed to help adjust the tuning (im not sure if its fuel, spark or both) when you takeoff. It lets the engine know how much air its getting. If your not running a computer in your car I would be willing to say you shouldnt need it. Did you ditch the CC Q-Jet and the old CC Distributor?

naf

iTrader: (7)

No MAP sensor on the carbed cars. That is your Baro sensor and should NOT have a vacuum line connected to it. There should be an identical sensor on the driver's side firewall that is the Vacuum sensor. The Vac sensor should be connected to the rear vacuum port on the carb by a small, hard plastic vacuum line that runs through the engine harness.

The Baro sensor provides an atmospheric reading for reference against the Vac sensor to adjust for altitude, etc. If it's connected, your car will run like crap.

You're still running the ccc-qjet system? Using EGR?

Ozz1967

iTrader: (4)

yes, i am still running the ccc qjet due to emissions reasons. i will disconnect the ''barow'' sensor and see how that affects things. My vacuum sensor is hooked to a vacuum line off the back of the intake manifold. i see the vacuum hardline, but i will have to retrace it to see if i can see what it goes to.

Ozz1967

iTrader: (4)

ok, pulled the line from it, capped the port on the carb and it didnt affect my idle problem. fired it up, ran as long as I held my foot on the gas. soon as i took my foot off it died.

transam85dudeman

do you got vacuum advance? hopefully TPIS.com responds.(off subject) one time going up the mountains the car stalled in the middle of the road. of coarse highway patrol shows up-only dude i seen in an hour- shows up in three mins, writes me ticket for no chains on tires.. haa damn Baro sensor. i acted like the car was driving, while in neutral with engine off. until i got a few thousand feet where the oxygen baro sensor pickupd again. followd me the whole way, (didnt want another ticket for inoperatable engine. damn old BMWs. since then ive pickupd a new one, but that was an experience.. no snow day that day ;(

Ozz1967

iTrader: (4)

The advance on my car is electronic.

naf

iTrader: (7)

The vac sensor should be connected to the rear port on the carb.

Have you verified timing, TPS voltage and dwell?

Ozz1967

iTrader: (4)

The vac sensor is connected to the rear port on the carb. I have another someting that is connected to a vacuum port off the rear of the manifold, I will get a picture of it later today.

I'm having a hard time even keeping it running, but I will see if I can check it tonight. How do I check the TPS voltage and dwell?

naf

iTrader: (7)

You've swapped motors and probably only need to adjust the Idle Air Bleed for proper dwell. It should, however, be able to idle without too much trouble. Give us a little more info. You say it just came back from a dyno tune? Did it, at one time, run fine with this motor? EVERYTHING from the LG4 hooked back up to this new motor?

Ozz1967

iTrader: (4)

Ok...from the top...

The car is a 1984 Pontiac Trans am. The engine was an L69 that was leaking nearly 2 quarts every 2500 miles or so. Sure it had 120000 miles on it but it ran good other than leaking. Wife said "Fix it!!" So I set about fixing it. (she hates leaky cars lol)

Before I decided on the motor, I purchased a CCQjet from Jet Performance Products to replace my original CCqjet. I also put emissions legal headers on it at this time. Then I decided instead of going with a simple rebuild, I wanted to put a new motor in and was talked into going with a 350 over a roller-block 305. For two years while waiting to put the motor in, I never had a problem with the carb or headers. The car ran great on the old 305.

The motor I put in it is a 350, 4 bolt main bored .040 out of a 98 silverado. I went with World Sportsman II heads, an Edelbrock performer intake, my Jet Products CCqjet, Lunati Voodoo Cam (Lun60121 at summit), comp cams pro magnum roller rockers, Scat rotating assembly and SRP pistons.

When I put the motor in the car, I installed a few new items. A new radiator, Jet Fan switch, Serpentine Belt set up (with accessories) to replace my V-belt set up, holly red electric fuel pump, Mallory fuel pressure regulator, a 3" catback, and then some other stuff like rear-end, sub frame connectors etc.

The biggest "change", was on the emissions stuff. I got an emissions set up from an 88 Firebird which came with my serpentine set up. The set up for an 84 has vacuum lines running to the diverter valves, the 88 does not. That's about the only difference I can verifiably say happened.

The things I didn't change: Transmission, Torque converter, EGR, multiple sensors (the ones on the water neck or original, the one on driver side head is original), throttle cables.

I got the car back from the shop in late October last year (I did 90% but setting the initial timing was beyond me)...and it drove pretty good for 400 miles...then I broke a valve spring. Then another, then another. I went through 6, each about 400 miles apart. got fed up with the lunati springs, bought a complete comp spring set and haven't broken one since.

The car ran..."OK", but never idled well unless I had the idle set high, close to 1200, then I wouldn't have any problems with it. ALso, it constantly fell on it's face at 3500 RPM.

My car club here in Utah pointed me to a dyno shop that I took my car to back in May to try and solve the aforementioned issues. They changed the secondaries, adjusted my fuel pressure to 6.5lb, set up my timing to 36* total advanced, set the idle to 900rpm, and ran the snot out of it for six pulls. Attached is the result from the best Dyno Run. they also apparently hooked up my barometer sensor to a vacuum port...which you told me about yesterday (thank you very much--I really do appreciate that!). they said that the "falling on it's face issue) was due to lack of fuel pressure. They also had a bugger of a time getting the idle to work below 1000rpm, something I found only worked once the car was warmed up. Also, ever since installing the motor, it didn't like cold weather and would constantly stall out until it warmed up unless I "helped it" with the pedal. The high idle from the choke never seemed to work right once the new motor was installed.

Following the dyno tune, the car ran really, really well. I drove the car just about every day after that for 3 weeks, when I lost the wiring to the starter...pain in my backside. Long story short, someone put 14 gauge wire where 10 gauge should have been. Fried the whole harness back to where the 14 was spliced to the 10. Once those wires were fixed, it ran good again.

Three weeks after that, I was pulling off the freeway on my way to work when, as I slowed to a stop at a stop light, the car started running rough...like really choppy idle. Upon acceleration, it had no power, barely accelerated and wouldn't idle. At freeway speeds (took long time to get there), it would sort of smooth out but intown I had to feather the gas just to keep it running.

From that I discovered 4 cracked boots on my spark plug wires, three on the passneger side and one on the drivers side that were grounding out to my headers. Since my wife just had a baby, I had to save up to replace the plug wires and spark plugs. I finally got them and installed them last weekend. So after sitting for just about 2 months, I tried to start the car and nothing happened, it would crank but it wouldn't fire. Poured some gas down the carb and poof, it cranked up.

Now it starts, sounds good when I rev it, but won't idle. I can even drive it, however as soon as I take my foot off of the gas or slow to the point where my foot is essentially "off" the gas, it dies. I do see the tack level off at 1400rpm, like a hiccup, but then it dies. It only does this hiccup if I rev it really high (over 4000rpm). Most times I fire it up, it reves to 2000 becuase I'm pumping the gas, then just crashes to 0.

Anyway, i hope this is the info you were looking for.

five7kid

iTrader: (14)

Wonder how they determined 36 degrees total timing.

Sure sounds like something went bad, rather than something not set or hooked up correctly. Could be some crude in the idle circuits, or a valve problem. You might want to hook up a vacuum gauge and see if the needle bounces all over at idle and then smooths out (indicative of a valve not closing at low engine speeds), and/or do a compression check.

You haven't mentioned an SES light. Is it coming on? Does the light work?

JTNKTZ

iTrader: (10)

Alright you are getting the wrong info. That sensor IS the MAP sensor. I will bet my life on it unless they put the same exact looking sensor in the same exact spot with the same exact mounting brackets.

I have 3 camaros and each and everyone one of them is a MAP sensor. These are on a TBI car though. I am not exactly sure what it does but when it is unplugged it barely runs right and can and will shut off at random times.

On all my camaros it plugs into a port in the middle rear of the TBI carb.

naf

iTrader: (7)

Wish you had bet something I could collect on.

The Vac sensor and Baro sensor are the exact same part. One reads the vac at the carb, the other reads the atmospheric pressure (hence the name baro"meter" sensor. The ECM reads them differently. Uses the baro sensor as a kind of baseline from which to adjust the vac sensor readings.

I've played around with several, built a few and currently own three carb'd thirdgens. I try to only post from experience and when my suppositions are empirical, I try to note it. Only played around with a handful of TBIs-so you won't see me posting much on that forum.

JTNKTZ

iTrader: (10)

So what you are saying is a map sensor can be a barometer as well?

I looked in both my Chilton and Haynes and they both say that it is a MAP sensor.

Ozz1967

iTrader: (4)

Ok, I hooked a vacuum gauge up to two points. First, a port on the carburetor...this one started at 0 vacuum when I started the car and eventually creeped up to 8hg...buyt the gauge was rock steady, never wobbled or deflected.

I then took it off of a hose coming out of the intake and it started at 10, then when I revved the motor it went up to around 15-16. It was never "rock steady" but it wasn't going nuts like it did when I broke my valve spring (wildly waving back and forth). Maybe deflecting 1hg.

Strange thing happend though, when I was revving the motor to 2500 to get a steady reading, I felt something of a hiccup, the engine jumped rpms, then settled back to 2500 where I was holding it for the vacuum reading. I let my foot off the gas and it held idle...for about 4 minutes, then it slowly, slowly dropped idle until it died.

At idle, it's reading 9-10hg on the meter.

Ozz1967

iTrader: (4)

I took pictures of the two hoses and vacuum sensors on the drivers side firewall.

The first, comes from a sourse on the intake itself. The second, is the line that comes from the back of the carb. YOu can see that it goes down onto an item on the firewall that I can't see clearly. IN the background of this picture, you can see the item from the first picture.

Shinobi'sZ

I agree with you. I have the MAP sensor on the passenger side of the TPI on my 91 Firebird. All of the maps look really similiar...in fact I am using an 89 GM Buick 3 Bar Map on my 01 TT Z06 (maybe it was a TA but 1989), and there is a MAP sensor on the back of the LSx intake (I just unplugged it on mine) that looks almost the same (check my sig and look on top of my fuel rail and you will see it)...but that looks like every GM MAP that I have seen..the 1bar, 2bar, 3bar...all look the same except they are scaled differently (1-5vdc).

naf

iTrader: (7)

The item in your first pic should be a check valve for the vacuum operated accessories. Should go from there through the reservoir under the charcoal canister. Behind there should be your Vac sensor, connected to a hard plastic line that runs through the loom that passes behind the dist then up behind the carb.

Sounds like your issues are intermittent? May be electrical. You can take your coil and control module to AZ, or one of the others, to get them checked. Re-check all your plug wires. Ignition issues, in my experience, tend to act out when hot. I'd be curious what your timing is doing. Don't throw parts at it yet, though.

Check your trouble codes. There's a tech article here if you haven't done it before.

Attached is a controls location diagram for the LG4/L69 that should put this MAP/VAC/BARO sensor issue to rest. Amazingly enough it came from an on-line Chilton reference. In the diagram it refers to the VAC Sensor as a "Pressure Differential Sensor".

Ozz1967

iTrader: (4)

I will try and check my timing this afternoon, too tired right now to check it, and besides, I don't want to wake up the baby lol. The coil, cap and rotor are only a year old, replaced those when I dropped the motor in. Plug and plug wires are new last weekend.

It's not throwing any check engine light except sometimes for the exhaust when I was coming down an off-ramp from the freeway.

Ever since the dyno shop mentioned that the distributor might have bad bushings, I've been contemplating getting a new or refurbished one from Classic Industries. I can get an identical one for $100 or so which I might do. Only thng I'm really scared of doing is trying to set the timing myself. That's one of the main reasons I had the shop finish the install once I got the motor in.

Shinobi'sZ

Nice engine diagram...interesting that it looks just like a MAP sensor.

naf

iTrader: (7)

It should look exactly like a MAP sensor. It performs the same function, in that it sends a voltage signal to the ECM that varies with air pressure, albeit atmospheric pressure for the BARO vs. manifold absolute pressure for the MAP.

In that the shop pointed out that your dist may be bad, I'd lean that way. I was hesitant earlier to suggest the dist, cause I don't like throwing parts at a problem. The dist on yours is, however, 20+ years old and failure could cause erratic spark AND be intermittent.

A reman one at one of the chains can be had for usually a hair under $100 and should come with a new module (save your old one though you can likely turn in the core without it). With care a new one can be installed correctly clocked to preserve your current timing setting. We can walk you through it.

I still don't want to recommend a new distributor and leave you still with the same issues but $100 poorer. If you were close I'd pull the dist out of mine and try it.

Ozz1967

iTrader: (4)

I think I mentioned this earlier but can't find it in my posts. The car isn't throwing any SES lights. Only one I was getting was occasionally when decelerating from the interstate on an off-ramp, the check engine light would come on.

Ozz1967

iTrader: (4)

I do appreciate the offer!

In the dyno pictures I posted early, you can see how the power curve isn't smooth, it's all wavy...the shop said that's most likely due to timing issues where the bushings in the distributor are worn out and causing it to fluctuate because it can't hold the gear perfect etc... they never mentioned I'd have this type of issue though.

Another thing I recall the car doing, is occasionally, after coming to a stop light, or after stopping to show my ID to get back on the base, I'll push the gas and the car will sort of flat line, be suck at like, 600rpm and not accellerate, no power, just....barely anything. I'll let off the gas, pump it a few times, sometimes it'll sort of stutter then take off like normal with no problems. Other times it'll stay dead for a time longer than a few moments before kicking over and going. It's just wierd. This car...is wierd.

Anyway, I'm going to attempt to check timing this afternoon and take the module over to AZ to have them check it. Sadly they aren't able to check my coil though I do still have my old coil I could swap in as well as my old carb to try. I will also check on a distributor while there just to see. Only thing I'd have to swap over is the melonized gear I installed to account for the roller cam if I got a new one.

naf

iTrader: (7)

You should still check to see what codes are stored there. Even if it isn't lit it will store the codes in memory (until it's disconnected from power).

Could possibly be fuel delivery issues...maybe try the old carb before going further?

Ozz1967

iTrader: (4)

Sorry for the delay, wife in hospital, we're having a baby tonight! lol

Pulled the carb, went to install the old carb and found 2 of the vacuum tubes pulled out and missing...no way to hook up the vacuum lines or seal those holes properly at the moment. Put the "new" carb back on, tightened and torqued, hooked all back up, same problems. I really don't believe it's the carb but...?

naf

iTrader: (7)

Congrats. You'll have your hands full for a while now.

Which two vacuum lines? Did you plug them up when you installed the other carb?

Ozz1967

iTrader: (4)

Thanks! 7lb 4oz baby girl!

The one missing off the older carb is...right under the three pin connector on the front of the carb and goes to a divertervalve which splits off to the PCV, the large vacuum line which returns to the front of the carb, and to a sensor on the intake up near the thermostat housing (but not on the housing) and no, I didn't plug it...don't even know what to use to plug it...since this is just a test I suppose I could use RTV but that would make that spot unusable completely...still, for a test to see if my new carb is bad, might be an option.

Ozz1967

iTrader: (4)

Could this whole issue because by a vacuum leak? If so, I know all the vacuum lines are good as they are new...where else could I look?

naf

iTrader: (7)

Use a short piece of vacuum line, about an inch long, and place a screw or small bolt in the end of it to make a temporary plug. Vacuum leaks could cause idle problems but the dyno shop should have noted any obvious sources of leaks.

Ozz1967

iTrader: (4)

The actual tube coming out of the carb is what's missing, there is no place to stick a vacuum line on it. I'll have to actually fill the hole on the carb to plug where it went.

naf

iTrader: (7)

Are you certain there's an opening in the carb for it? Some models had an extra vacuum port. If you need the fitting for the carb and can't swap it over from your other carb let me know which it is and I may have one I can send.

Ozz1967

iTrader: (4)

I'm certain. I could use a longer piece of hose and go to the unused port on the top rear of the carb for the test but I would still need to seal the hole to prevent an obvious vacuum leak on the carb. I'll grab a few pictures when I get a chance to show you which one it is.

transam85dudeman

did you change the knock sensor, 305/350 different sensors. dont recommend teflon tape

Ozz1967

iTrader: (4)

Yes I put a 350 knock sensor in and used teflon tape on the threads.

transam85dudeman

did you get a reply from tpis.com., congrat on the bouncing baby

Ozz1967

iTrader: (4)

no reply yet and thanks.

Ozz1967

iTrader: (4)

Ok, here are the pictures of the old carb. They are a little blurry, for that I appologize.

The vacuum tube that popped out fo the carb is under the three pin connector on the right side of the pictures. It's the "hole" in the second picture that's relatively clearly visible immediately below the three pronged connector. The larger spot on the bottom is the fuel/air adjustment.

I am going to clean that and attempt to tape it off. Car will run fine with that line disconnected for this test. I'm also going to try and get the timing to see what that's doing. kind of hard though since the care doesn't like to idle on it's own. maybe my wife can feather the throttle for me while I check it.

ljnowell

Seeing 0 and going up sounds like you were hooked to ported vacuum(above the throttle blades).

IMO seeing 10 and then a max of 15 seems a little too low. How wild of a cam are you running. Low steady vacuum can be indicitave of a vacuum leak.

Ozz1967

iTrader: (4)

The spot I used was high on the rear of the carb. So should I have used a spot lower on the carb?

This is the cam I used...

Lunati Voodoo Cam 60121

Ozz1967

iTrader: (4)

Ok, got the other carb hooked up and on. blocked off the hole in the front of it where the tub went, fired it over and damn, it's holding idle.. 1500 and steady.

Going to let it run for a few to warm up and drop to low idle and see what happens. It'll be really mad if my new carb is what's been causing all these problems.

Ozz1967

iTrader: (4)

Ok, timing, at idle, with the distributor hooked up, is about 15*? I can't tell exactly, it's higher than the 12* on the timing marker. Baby just woke up so I"ll have to wait a few before I can check it without the distributor hooked up.

naf

iTrader: (7)

The missing tube for that port should just be pressed in. Can you swap it over from your old carb or do you need me to check for one in my parts bin?

Ozz1967

iTrader: (4)

Well, I will hate trying to pull the tube out of my new carb to make the old one work but since it appears that my new carb is at least mostly responsible for my issues, I need the old one to drive the car. LOL

Ozz1967

iTrader: (4)

i swapped the piece over but it doesnt feel like its in very well. i dont know what kind of seal it will make

Ozz1967

iTrader: (4)

timing with ecm disconnected is 6* advanced at idle and holds steady.

Camaros_Rule

Ozz, That looks like the map sensor it reads manifold ambient pressure that vacuum line should hook to the emissions thermal switch on intake

naf

iTrader: (7)

When I've swapped them around and they were loose I placed a little loc-tite on them. How's it doing?

Ozz1967

iTrader: (4)

Sorry for the delay...

For this fix, it's doing good, little bit of copper RTV works wonders for sealing stuff up. Had to make sure I didn't over-do it though, didn't want any of that stuff getting into the carb. Idles like a champ though now it bogs really bad when I give it gas from an idle ot the point if I"m not careful, it'll just flat out die. On the vacuum gague, you can see it bottom out the vacuum. At speed, say I rev it slowly to 3000 and punch it, it works fine, no hesitation, no vacuum loss. Any thoughts on that?

Found an oil leak, torn valve cover gasket on passenger side, making a disconnect in the wiring harness so I can get to it. Man you'd think they would give you more room to work with than 1" in that harness. Ugh...once the disconnect is in and I have all the wires marked properly, there are 4 black ones in the harness, talk about crappy, I'm going to fix the valve cover gasket and get back to working on why the vacuum drops out when I punch it from idle.