Daniel6718

got another car 96 fleetwood with lt1, all stock surges at idle...

no misses...on my scanner everyything seems to work great o2 are active and fast, tps map maf all is good..the iac is causing the surging going from 45-125 it starts this after 180 degrees...it stays around 190

i also noticed on my scanner the rpm jump before the car revs...the scanner will quickly say 1800-2500 then the car revs?

causes?

Injuneer

Could be a problem with the optical cam position sensor in the Optispark distributor. Sounds like an erratic signal.

96capricemgr

The IAC symptom is going to be it reacting to something. Be that an erratic opti signal causing it to try to stabilize a an actually stable idle or just trying to stabilize the rpms from the surging.

Guest47904

I wouldn't believe it if it's the same scanner you mentioned in this thread.

https://www.camaroz28.com/forums/sho...d.php?t=737497

2 vehicles with faulty opti feedback signals and we know the scanner didn't pick up the first one.

Daniel6718

thanks...check it the same as the other car the square 5v signal cranking the car by hand?



thats true same scanner...its a matco 09 model...
whats a normal map readin? about 9?

this car has 2 dtc...one if for the mil light circuit the other is for p0029...which i cant find



and just so you guys know how i get these cars...im semi well known in my area for lt1 cars and a lot of ghetto people race their caddys/caprices ect. Most of them try to fix their cars first them bring them to me when 5 other mechanics and themselves cant figure it out. I see some of the weirdest lt1 **** ever. Ive had a impala ss's on 26's in my shop that got a stock rebuild and with random missfire and one back fuel trims were +125%, only to track down the car had a cc305 cam which i couldent hear in the exhaust with stock exhaust, stock valvesprings and tune.

Guest47904

You would expect a signal that appears to come and go to be a bad connection rather than a component problem.

Don't know if the wiring is the same for B and F bodies. The fact that you indicate the car is 96 (usually OBDII) but it has OBDI trouble codes tells me something is fishy. Procede at your own caution.

F body wiring to the opti is Pink/black is reference.
Red is 12 volts.
Purple/white is Hi res and
red/black is low res. This holds for 94 thru 97 F bodies.
You won't see a square wave unless it is running and you look at it with a scope. You could use a Snap on Vantage.

I like folks to use a DVM and rotate it by hand, not the key, so they can see the transition of the signal from 0 to 5V and back again. Be sure to use the reference and not frame ground.

However if you did not have a low or hi res signal. You would expect to have either a 16 or a 36 code. A 36 does nothing. A 16 shuts off the fuel system. Another indication of lose of the low res signal. We also know that if the low res signal is lost, you will have no trigger to the ICM. Makes sense but you can't find mention of it in the shop manual.



According to the manual, it should be over 4 V when idling and 1 volt or less when disconnected.

The 29 is for the air pump. More than likely the relay is disconnected or the fuse is bad/gone. Not a great concern as nothing will happen as the result of it. But what's the other code? You need to prove that "matco" something or other works. You didn't prove that from the last thread.

One more thing. Why don't you have a shop manual if you have a shop?

Injuneer

A MAP reading of 9" - 10"Hg at idle would be normal. But some scanners read MAP in kiloPascals, and 9kPA at idle would be setting a code. Like anything, an incomplete description is useless.

If I understand this correctly, you have a shop where you repair these car.... so you come here to find out what is wrong with them, and charge people to repair their cars???? Please clarify.

Daniel6718

thanks it was a typo the car is actually a 95, and what kind of shop manual? normally we dont have stuff this difficult normally you get codes or parts fail...not parts that work and read fine but cause problems...my brothers ASE and between the 2 of us never really have problems...but the last 2 cars have been a lil difficult...but i like to diagnose a car and know what the problem is rather then throw parts at it like most mechanics do

i gotya...and if you want to put it like that correct. just looking for some lt1 help from people that might know more or have seen more then i have, i dont get on here all the time posting looking for help, i actually havent made any until this last week and been open a year

Injuneer

If that's the case, I think it would be a bit more ethical to state that when you post a question. I've seen people come here before, and start the post with "I'm working on a customer's car and need some help.........". And I haven't hesitated to help them. But, from a purely personal point of view (not as a Moderator), I don't like the way you handled it.

Daniel6718

Ok well i apolagise to you and anyone else about that. This is not my car it is a customers car! Thanks for the advise, i never knew about the square signal to check the opti before these past 2 thread and i think will greatly help in the future. Does that test it 100% as if it has that signal its always good?
(no diagram in front of me but other then if it needs the oblivous referance/ground/power)

Guest47904

Don't brag. It usually ends up biting you in the A$$.

A shop manual is available for every vehicle made. Knowing where to get it is the trick. If you have a shop, you should have a Mitchell system AT LEAST. If you estimate a job, you should already know this. Without having done a job, you must refer to "estimators" so you can accurately quote a repair job. Once you had the estimator, you would have been aware of the shop manuals. Mitchell is available entirely on CD.

Start here: http://www.mitchell1.com/AutomotiveR...tions/home.asp

You also referred to codes and sensors previously. Let me give you a little friendly advice. Don't ever replace a sensor without at least checking for the presence of voltage and ground. Depending on the sensor of course. If you merely get the code and replace a sensor based on the code, you will get burned eventually. And that only makes anyone as good as a counter person at AZ.

A couple of last notes. If you need electrical info for F bodies at least. Shoe has several pages including the opti wiring you would have found useful.
opti wiring
and others
http://shbox.com/1/schematics_wiring.html

If you already don't know, become familiar with Donk, Box and bubble. From the sounds of where you are located, you should already know these terms.
For those who don't see here:
LMAO
I do not like "wagon wheels".

We can and will help you with any problem. Just don't ignore our answers like many others have done. It seems that many folks have an idea in their head and only look to us to "qualify" their idea. If we suggest something other than they had in mind, they usually just ignore our suggestions.

We're here to help.

Daniel6718

gotya...ive got alldatapro online...it gives me hour quotes and wiring ect...i always check a sensor for its referance/battery/ground before replacing...

i have half of shoebox's site printed out and kept at the shop for all the lt1 stuff i do. i apprietiate it guys

and finally im familiar with donks...i hate them, but the best part is those guys have money, and always pay, cash.



lastly seems like between the 2 of you yall dont have anything for me to check...speedy seems to say id have a code if i had opti problems, injuneer says it might be erratic?

the other code i believe was 0011 mil circuit

Daniel6718

with a regualr DMM by hand it goes from 4.9 volts to .00x dc...seems normal...i dont have a scanner to show me a graph of what the dignal does

Daniel6718

well i let it sit and idle a while this morning and got some codes...im afraid are intermittent and the reason the mil light doesnt work
11
22
29
33
34
48


checked fuel pressure its stabile at 36 at idle(little low?) and right before it revs is starts to go on the fritz from 33-39 with the vac line off its 45 solid...did a volume test and its fine

had some spare time and parts and swapped the maf/tps/iac,cleaned its passage/map/icm
problems still there...

lt fuel trims are 125

im going to pull all the plugs and wires and ohm them in a minute when it cools...idles smoothe for the most part

i also unhooked the aftermarket stereo(fuse) and voltage stays above 13 at idle

topped off the tranny fluid and oil

blew compressed air into the opti to cool it see if that helped

blocked off brake booster vac hose, evap, and pcv valve

Guest47904

The TPS and MAP use the same PCM reference voltage. The IAC is obviously the result of one of the sensor problems. Check the gray wire on both for 5 volts.Then check for voltage at the 29th pin of the black PCM connector.