I'm curious if the distrubutor being off a tooth will effect the timing reading off the crank.

This would be on a run of the mill Chevy 5.0L TBI engine.

The problem I'm having is if I set the timing according to the factory service manual, I get an idle of 1200-1300 rpm. If I set it based on idle, I get a timing result that is off(ie not CA smog complient)

Thanks in advance for any useful input,
John

the dist being off a tooth doesn't affect timing persay. It does affect the position of the dist. body at a given degree of timing, make sense? If it idles too high when timed properly, just time it properly, then reduce idle speed on the TBI to wherever you want.

Originally posted by elf_cruiser
the dist being off a tooth doesn't affect timing persay. It does affect the position of the dist. body at a given degree of timing, make sense?

So, in essence, the distributor being off a tooth will NOT effect the reading I would get using a mechanical timing light?

Originally posted by elf_cruiser
If it idles too high when timed properly, just time it properly, then reduce idle speed on the TBI to wherever you want.

There lies the problem which is why I am asking my question. There is NO way for me to reduce the idle speed at all. On my TBI, I've already backed out the idle screw as far as possible, adjusted the Throttle Position sensor to read correctly, and from my scanner, the IAC is where it is supposed to be.

I've tried 2 different TBI "carbs", 3 different ECMs, 3 new TP sensors, 3 new IACs, and it STILL will not idle below 1200-1300 rpm. I am getting NO error codes, I've watched the ECM with a scanner(error codes, sensor readings, etc) and do not see ANY sensor problems.

I've checked for vacumn leaks, replaced the EGR valve with a new one, AND taken it to a dealership at one point.

In short, the TBI system is completely fawking PISSING me off and I'm getting ready to yank the motor, set it on fire, and throw it away:mad:

Basically, I dumped more fawking money into the piece of sh1t than it is worth(ie I could have gone a bought a NEW one for all the cash I've dumped into it)

Wow, sounds like your having a rough go at it! The dist. being off a tooth won't affect the reading you get with a timing gun, but you have to rotate the dist. body further to get the same reading as if it were NOT off a tooth.

I can't help ya on the other stuff. Maybe just get the timing right, and let it idle high, then drive it around for a while. If you have changed ECU's it may need to be driven to "re-learn" the motor.

Are you running a VSS? I'm studying for a TBI swap this winter and one of the things I've read is without the VSS the engine idle can be way off....might be worth a check. IIRC, I found the info at http://www.jagsthatrun.com

Originally posted by woody
Are you running a VSS? I'm studying for a TBI swap this winter and one of the things I've read is without the VSS the engine idle can be way off....might be worth a check. IIRC, I found the info at http://www.jagsthatrun.com

Hmmm... is that something in one of their latter books? I've got two of them(EFI swapping and S10 V8 swapping) and I don't recall either mentioning VSS causing an idle problem.

OTOH, I have had the engine working properly without the VSS in the VERY distant past(98-99)

i got a timing question too...so ill throw it out. its a way newbie question...but this is my first 350!

---is it supposed to read 4 degrees (or whatever it should be)before or after the "0" mark on the timing tab wehn looking down from the front? my timing tabs are on the top of the cover so i hafta look thru the water pump cutout up top. because right now its at like 4 degrees after (or to the right of when looking from the front of the cruiser) past "0".
how or where should it be set at? thanks!

edit: its a 350 w/ a 2bbl and hei dist. thanks!

On a related note, like I said above, I did check for vacumn leaks and didn't find one:( Is it possible for the intake gasket to be causing a problem("recently" replaced)?

If you backed the idle screw all the way out (butterfly completely closed) and it still idles high.....it sounds like you have a vacuum leak. The engine is sucking air in from someplace other than the throttle body.

Lil'John, I have to agree with Flipper on this one. If you have had the intake off recently, triple check that you installed everything properly. Check the brake booster, may cause a vacuum leak also. You can just pinch the hose and see if it helps.
Keep us posted.

I have the brake port plugged(not going to use)

I have done the "hose the engine bay with carb cleaner" trick and notice no change in idle... so I agree it isn't the TBI unit and I believe it isn't the outside of the intake gasket. Is it possible for the inside gasket to pop out? :(

I don't know about pop out, but they can lose their seal.

Also metal parts can warp or crack (and leak).

you are disconnecting the ESC module from the dist when setting the timing right? Lots of stuff control the rpm. MAP, ESC, TPS, IAC, timing, and so on. Just a thought, could the coolant temp sensor be faulty. Maybe it is reporting a constant cool condition causing the ECM to stay in open loop, and kicking the idle up, thinking the motor is still cool?

Originally posted by Keith
you are disconnecting the ESC module from the dist when setting the timing right? Lots of stuff control the rpm. MAP, ESC, TPS, IAC, timing, and so on. Just a thought, could the coolant temp sensor be faulty. Maybe it is reporting a constant cool condition causing the ECM to stay in open loop, and kicking the idle up, thinking the motor is still cool?

Good point on the timing. Yes, I do disconnect the ESC module when setting the timing.

On the coolant temp, the sensor is definately working(and in the stock location). I have one of the "cheap" Xray GM readers and monitor the sensors while the engine is running. I took that reading and compared it to my temp guage(Autometer) and they are VERY close ~175-190.

Flipper, do you think it would be worth my time to take the heads and intake to a machine shop and have them checked for warping? One head may have to goto the machine shop anyways for a broken exhaust bolt:(

Before you pull the intake get a can of berrymans carb cleaner or similar product and begin searching for a vaccum leak by spraying different areas of the intake/TTB if the idle changes, you found a possible leak...

Originally posted by ItsaCJ6
Before you pull the intake get a can of berrymans carb cleaner or similar product and begin searching for a vaccum leak by spraying different areas of the intake/TTB if the idle changes, you found a possible leak...

Already did that... about 5 times now and there is nothing on the top causing a vacumn leak :(

I'm probably going to hit it one more time to see if I can find anything... but I'm not holding my breath too much(my luck has been shit lately:( )

I've got my jeep and another running the tbi's without the vss. Both idle around 650-750 when lugged for a while they both idle up around 1000-1100 that due to the vss not being used. Who's harness did you get? I'm running a painless in mine and a stripped out gm in my buddies. When I first strarted fooling with the tbi I asked all kinds of questions to friends that worked at the dealerships. How old are the tbi's your using? I was told that there are two different iac designs out there the angle on the point is different between the to, I had that problem once. Are all of your grounds hooked up to clean surface? Buddies jeep got wired at a different shop and finished due to lack of time on my part, few ground wires were moved and not hooked back up it done many different things,high idle,hard starting,coughing thru tbi.

Originally posted by odee
I've got my jeep and another running the tbi's without the vss. Both idle around 650-750 when lugged for a while they both idle up around 1000-1100 that due to the vss not being used. Who's harness did you get? I'm running a painless in mine and a stripped out gm in my buddies.

I'm on harness number three. The first was the stock harness I got with the engine(89 Camaro).... it worked fine. The second was a painless... high idle started... sold it. The third is another stock harness I pulled from an 88 Camaro... still high idle.

Originally posted by odee
When I first strarted fooling with the tbi I asked all kinds of questions to friends that worked at the dealerships. How old are the tbi's your using? I was told that there are two different iac designs out there the angle on the point is different between the to, I had that problem once.

My current TBI unit is one I got from Turbo City(ie high flow and all that crap) and is 3 years new. Before I had idle problems, I was using the stock 89 Camaro unit that was on the engine. After the high idle problem, I bought ANOTHER stock TBI unit and tried it with no luck.

Do you happen to know what the two IAC's came from? That may be my problem.

Originally posted by odee
Are all of your grounds hooked up to clean surface? Buddies jeep got wired at a different shop and finished due to lack of time on my part, few ground wires were moved and not hooked back up it done many different things,high idle,hard starting,coughing thru tbi.

I'm pretty sure my grounds are good but I will triple check. I've got the battery ground to the back of the block, the block to the frame, the frame to the body, and the body to the block. There are two ground points on the stock harness(from what I recall) that I have grounded in the stock location.

Thanks for all the good info,
John

I know this is basic so dont think I am giving you shit..


Pull the dist and set the engine to TDC again on the compression stroke and then re stab the dist..

It is possible to be off, if you were not at TDC. I always pull the plug run the piston up till its on the compression stroke and then get a flash light and look at the piston and run engine by hand until I can see that the piston is at exactly TDC.. I used to have timing problems before I started this practise...

I'm curious if the distrubutor being off a tooth will effect the timing reading off the crank

nope, be it 1 tooth or 10 it wont make a hill of beans all thats important is that the rotor is pointed on #1 wire. this is common to "make room" for things by orienting the distributor in a particular way. mine is off several teeth so that the dist. sits just the way i want it.
i dont know the whole story of the engine, but the camshaft can be degree'd too, if this was done or done wrong, that will affect the timing, if you have a badly worn chain and gears, that will also effect timing.

The problem I'm having is if I set the timing according to the factory service manual, I get an idle of 1200-1300 rpm. If I set it based on idle, I get a timing result that is off(ie not CA smog complient)

could be alot happenning here, but not knowing cal. emmision laws i'm not touching this one.

---is it supposed to read 4 degrees (or whatever it should be)before or after the "0" mark on the timing tab wehn looking down from the front

it will read before the "O" hence BTDC. if you have trouble seing the whole thing, beg borrow or steal a timing light with the little knob on the end, you can then dial 4* or whatever you want and then time the marks to "O" for your timing.

If everything else is right, timing won't really effect the idle on a tbi. They have an amazing ability to compensate for it. I could turn my distributor from about 30 btdc to 10 atdc and not make a big change in idle. You are getting air from somewhere. Either the IAC isn't closing or the intake is leaking. You should be able to close off the port on top of the throttle body that feeds the IAC to rule that out. TBI also seems to be able to compensate for the carb cleaner trick making it hard to see a difference when you're looking for a vacuum leak.

Lil John I looked and couldn't find the info on the iac. Try looking at the hole above the iac if you plug it with your finger the idle should go down if that is where it is leaking. Might also try looking at the thirdgen.org site I've found alot of info on there.