kokamo

Ok, as some of you have seen in some of my posts that I am in the process of a TPI swap into my 73' nova. I just got it running and have an idle and start problem with no codes.

To first tell you what I have.
The TPI came off of an 86' T/A with a 305. So, it is a MAF system with 19# injectors are on the engine.....(it's a 10.5 to 1 compression 283)....all of the emmisions gone, including the egr valve. It has a pretty decent cam that has a lopey idle to it. I got a custom made chip from ls racing chips to accomodate this setup. I want it to idle at around about 950 RMP's and that is what is programmed onto the chip too.

It will not start without me giving a little throttle and when it does start, the idle will occilate up and down and finnally die. Otherwize, it runs REAL good under normal highway speeds and under full throttle. but it just dosen't want to idle correctly.

The startup and idle problem consists when it is cold or hot.

I know, I know...I need to put a scanner on it and read BLM's and such but at the moment i can't get my hands on one.

The things I have done is set the timing at about 7-8* and tried to set minimum idle (kinda hard tho) and set the TPS to 0.540 volts. I also have checked the fuel pressure and it is about 45 when engine off and about 50 when idleing.
It is coming out of open loop cause the engine light flashes pretty slow when it is all warmed up.
I'm kinda thinking it might be a IAC motor. Some of the local mechanics tell me that a bad IAC motor will not set a code sometimes. Dunno bout that. I don't really know how to test it out of the car to see if it really works.

PLEASE GIVE ALL YOUR SUGGESTIONS!!!

THANKS!

Joe

P.S. I havent bought new sensors other than a MAF, knock sensor and an oxygen sensor (delco p/n afs-74). I am kinda on a budget at the moment and really don't want to throw parts at it.

Vader

It's never a good idea to just throw parts at a problem until you get lucky 9or not). Even if you're made of money, it's just not good, sound diagnostic procedure.

If you suspect the IAc may be contributing to the problem, remove, clean, lightly lubricate, and reinstall the IAC. It only take s avery little dirt or varnish to completely "kill" an IAC so that it is non-functional.

Search the archives for "IAC cleaning". You should find several good threads.

92blue

iTrader: (1)

Your car might be easier to get running smoother at idle (not to leave it like that indefinitely, but to work on until you get the problem straight) if you disconnect the iac connector all together. I had some problems getting my car to run on a stock memcal after my TPI swap so I can set timing and start tuning. I have a decent cam as well. I disconnected the iac connector, and although it didn't make it run well per say, it helped keep the car running until I finished setting timing.

If I were you, I would turn it on, let it run roughly for a bit, and shut it off. Pull a plug. I suspect its going to look like your running rich. If so, drop your fuel pressure down some. Why do you have it so high?

Guest

What sorta cam is in this thing? 950RPM seems like a high idle speed to me, thats why I'm asking. Does it actually attempt to idle there? Whats the vacuum reading at idle? If you have a big cam in there and low vacuum, thats what you are fighting with. The chip needs to be right, or it wont idle very well.

Try throwing the minimum idle guideline out the window, and open up the throttle plates about 2-3 turns from where you have it (or where it seems happier) and reset your TPS on the low side like .35V and see how it runs then.

You are setting the timing with the ecm's timing control out of the picture right?

kokamo

MADMAX....Yes I am disconnecting the timing connector up on the firewall to set timing. The cam I have in here is an 1107 summit race cam. I had my chip programmer build my chip to that cam. At this point, I don't know what the vacummew is. As far as the fast idle goes, it really liked the idle to be around 900 to 950 RPM's when it had the carburetor on it. Thats just where the motor likes to idle I guess. Anyways, it has a 3000 converter so it does pretty well in gear.

92 BLUE... The FPR is the stock one on it. Never touched it. I dont know why it is so high.

VADER....The IAC housting was taken apart and thuroly cleaned in a vat. There is nothing inside there as far as varnish there isn't any at all. I have not oiled the IAC at all. I suspect a bad IAC because I hear no clicking or nothing.

Well last night I took the IAC motor off (before I even touched the ignition key, so the motor is still cold) I took the IAC motor out and places it on the top of the motor. I had my girlfreind cycle the switch for me to on....then off after about ten seconds, and it did absolutly nothing at all. No clicking no nothing. Soooo, I crossed pins "A" &"B" and all it did was vibrate a little.....I mean very little. I figured it might need to be grounded to the chassis so I did so and still nothing.

I figure that when the motor is cold, the ECM sees this and adjust the IAC motor to open up the "controlled vacumme leak" So the motor will run a little faster until it warms up. When I did this it did NOTHING at all so....I guess I'm going to the parts store today and getting one.
By the way, my dad owns an auto parts store and I can get parts at cost so that's not a bad deal I guess. He told me he could get me a new IAC motor for about 29 bucks. Not bad but I still hate to throw patrts at it.

Does anyone know how to test an IAC motor out of the vehicle???

P.S. sorry for the long post.

THANKS FOR THE HELP!!!

Joe

Guest

Yikes! That cam in a 283? Thats why it dont run. Try doing what I said first, but something tells me that chip probably isnt exactly right either.

kokamo

OKAY!!!! I FIXED IT!!! It was the IAC motor. I replaced it and it went to running like it was supposed too. Now the idle is fairly stable but is WAAAAAAY to high. Now all I gotta do is reset the minimum air and reset the TPS. THANKS FOR ALL YOUR HELP GUYS!!!!

Joe

kokamo

Oh MADMAX... The cam in there works pretty good for the compression it has. It has the ole "Power Pack" heads on it which have the small valves. This cam gives it a much higher lift and therefore it makes really good power in the 3k to 5500 range. When I had the carb on it, I had it wrapped up to around 6500 and it was still pulling real hard. I had to shift cause I didn't want it to come apart. I am used to the good ole 350's that redline in the 5500 range. This will be my first 283 motor. It has a really short stroke and real low gears (4:56) and a 26" tall tire, so it gets up and goes pretty fast.

Now that I have the TPI on it, it seems to run MUUUCCCCHHHH better! I like the fact that I don't have to pump the gas about umpteen million times for it to start. I like that quality in a classic car.

Thanks again!

Joe

P.S. here's a pic of my setup

Vader

RED FLAG!

Looks good, but since you're using a MAF TPI system, you need to get rid of that breather type oil filler cap. ALL PCV air needs to come from the hose fitting on the throttle body, and the rocker covers need to be sealed.

kokamo

VADER... so I need to take the breather and put it on the other side of the motor and use the one on the throttle body. Ok, got that, now, I need to plug the other side of the valve cover? At the moment it dosen't have a "plug", it has a breatheable cap on it.

It does still have a little of a idle problem but it's not real bad. I'd still like to have it fixed. Vader....I will do what you say and see what happens. I'll keep ya posted.

P.S. since the IAC motor change, I no longer have a start problem.

THANKS!!

Joe

Vader

Don't disassemble anything just yet. Installing the oil filler breather cap in a different location is not the solution. You need to eliminate the breather cap entirely, and install a filler cap that is sealed. It doesn't matter which side of the engine it is located.

A breather type oil filler cap will allow PCV air to enter the engine through the cap. This is extra air that is not metered by the MAF sensor, and the ECM will therefore not consider this air when calculating the correct injector pulses to maintain correct mixture. The tendency will be for the mixture to always be lean, and your pistons and valves aren't going to like that.

The correct installation is to supply the PCV air via the ½" hose connection on the right side of the throttle body. The PCV valve is typically located on the opposite side of the engine to insure good vapor scavenging from the crankcase. In any case, the PCV air is metered by the MAF with that type system.

And while we're on the topic, make sure you have a PCV valve that is calibrated for your engine. Yes, the pintle, housing, and both springs are actually calibrated. A PCV sized for a larger engine (like a 350) will allow more air to flow than it should at high vacuum. Thsi alone could be part or all of your idle problems. The extra air is like opening the throttle plates too far at minimum air position. At the least, get a PCV for a later model EFI engine, like a SBC L99/265CID from a '90-ish full sized car, or one designed for a later CPFI 262 V-6. Those will be calibrated closer to the needs of your 283 than something for a 305, especially since your valve timing is perhaps a bit longer duration than a stock camshaft.

I had a reall SOB of a time trying to get a 262 V-6 to idle at the correct RPM, and got EGR and MAP errors constantly. I checked all the usual suspects, from EGR to vacuum leaks to MAP sensor to gaskets. I finally replaced the cheapo Fram PCV valve that I had recently installed with the correct AC/Delco unit, and the problems immediately disappeared. It seems that some of the aftermarketers aren't as rigid about quality standards.

JERRYWHO

Max

What will setting the TPS to .35V do for the idle.

Jerry

rgarcia63

Good Job!

FYI
I also think it's a bit high for 19# injectors, but that may be what the motor wants, but the Fuel Pressure should be 50psi @ engine off and then drop to 45 @ idle because of vacuum, sounds like vacuum source is higher than it should be at idle, and increasing instead of decreasing which sounds like a ported vacuum source instead of manifold vacuum.

With the IAC out of the body the pintle will flyout when power is applied, point it into a container to keep from losing parts if you're going to test it that way.