Idle adjustment screw

[turbojimmy]

Originally posted by darkred87T
Very frustrating, there must be an obvious problem we are overlooking.

It's learned its way around the new settings and is idling crappy again. Wheeeee!

Jim

 

[Rickracer]

Anyone remember this?

using the screw to set IAC counts might possibly cause overlooking another problem. There is more than one way to skin a cat, some more efficient than others, some more thorough than others.

There are a variety of things that could cause a rough idle or miss, starting with a shorting plug or wire, to an intermittent injector or driver, bad ECM ground, all the way to possibly AC voltage leaking from the alternator. Usually when these problems start to surface, the ECM/PCM will attempt to compensate, which will tend to mask some problems, unless you know what to look for. If driveability diagnostics was so easy, everybody'd be doing it.

 

[turbojimmy]

Re: Anyone remember this?

Originally posted by Rickracer
There are a variety of things that could cause a rough idle or miss, starting with a shorting plug or wire, to an intermittent injector or driver, bad ECM ground, all the way to possibly AC voltage leaking from the alternator. Usually when these problems start to surface, the ECM/PCM will attempt to compensate, which will tend to mask some problems, unless you know what to look for. If driveability diagnostics was so easy, everybody'd be doing it.

Plugs are new, wires are new, injectors are new, ECM has been swapped out twice. Could be an ECM ground. We'll have to look at them. BLMs are way low, too.

It's kind of stupid but I have no idea what chip is in it. I *think* it's a stock emissions chip, but my memory is fuzzy. We've swapped in other stock chips, though, and they didn't make a difference. I'm reasonable sure it's something electronic rather than a physical thing like a vacuum leak.

We'll get it figured out, it just takes a while (and $$) to narrow down the possibilities.

Thanks for the replies.

Jim

 

[nero]

I thought the TPS only needed to reach 3.75 at WOT. Power Enrichment mode is engaged at 75% which is 3.75V...anything higher is useless...or achieves the same goal!! Don't knwo if I articulated it right, read up!

www.vortexbuicks-etc.com

 

[darkred87T]

Every time I give it gas and let off, the RPM drops to the point where it almost stalls and then picks back up. When it does stall, it's always after I just let off the gas. And it always smells rich.

 

[gofstbuick]

What size injectors? If you're using a stock chip, I hope there are stock injectors (or no more than 33 lbs) in this motor. IAC counts of 10-20 should be after the engine warms up and is in closed loop. You may need to set TPS during the IAC adjustment, because the TPS may interfere with the adjustment. What are you maf readings at idle? Since it appears you're changing chips during this process, you'll need to disconnect the ECM connector for 10 seconds and reconnect it, then fire the engine up and allow the ECM to relearn. Then you can mess with the IAC, TPS and look at the MAF readings at idle. I'm at work from 7:15-4:15PDT, if you want, email me and I'll send you a phone number and we can attempt to work this out over the phone or through email.

 

[turbojimmy]

Thanks for the offer. If we can't figure it out I may take you up on it. Before we bug you tho, I want to try a few more things.

We've had the same chip in it through all of this. It just occurred to me last night that I'm not 100% sure of it's origin. It runs similarly with all chips in it. The car is a recovered salvage car and was bone stock except for a Hypertech chip. The guy was a packrat and had every receipt for everything done to the car since 1987 stuffed into the glovebox. We weren't surprised, therefore, to find the Hypertech box in the trunk. Assuming the chip in the box was the stock chip we popped it in. It ran like crap so I blew the dust off of one I had laying around. I'm pretty sure it's an emissions chip that Testa burned for me many moons ago. But I digress......

The car has "new" (low-mileage used) stock injectors and an adjustable FPR (new new) that we put on it. Part of the problem is that most the "new" parts we're swapping in are out of a box of stuff I had laying around. I'm pretty sure it's all good but who knows.

We changed the IAC motor first. Then the MAF. My old MAF caused the SES light to come on so we took it back out. O2 sensor is new. Coil pack and module are off of my GN so I know it's okay. I haven't looked at the plugs in a while - maybe it's time to see if they're fouled. It's running super rich.

When I adjusted the IAC counts the TPS got out of whack so I adjusted that back to a decent number (.46). Over a couple of days, however, the IAC counts are 0.

MAF is 6 GPS at idle if memory serves. I'll look at it again on the way to work. I have some Directscan recordings of idle and cruise. Just have to find the time to throw them on the server.

Thanks again - keep the suggestions coming!

Jim

 

[85TurboTtype]

IAC readings

Hey TurboDave, When you say between 10-30 on the readout and you say it depends on how radically modified the car is.... Would you say that it would be closer to 10 for cars that are not so modified and closer to 30 for cars that are? Also, does it matter if the car is warmed up or not? Should that make a difference if the car is warmed up or not? Please take a quick look at my signature and make an educated guess on what my IAC readout should be..... Thank you... Also the TPS should be between .40-.46 or so with that setting.?? Correct?

Thanks,

Matt

P.S.- Didnt mean to thread steal here, but I figured it was appropriate for that question to be asked here as I have the same exact problem.....

 

[TurboDave]

Re: IAC readings

Originally posted by 85TurboTtype
Hey TurboDave, When you say between 10-30 on the readout and you say it depends on how radically modified the car is.... Would you say that it would be closer to 10 for cars that are not so modified and closer to 30 for cars that are? Also, does it matter if the car is warmed up or not? Should that make a difference if the car is warmed up or not? Please take a quick look at my signature and make an educated guess on what my IAC readout should be..... Thank you... Also the TPS should be between .40-.46 or so with that setting.?? Correct?

Thanks,

Matt

P.S.- Didnt mean to thread steal here, but I figured it was appropriate for that question to be asked here as I have the same exact problem.....

Yes, car should definately be warmed up, idling in park/neutral. Yes, it makes a difference, since IAC is what controls idle rpm, the idle rpm is going to be higher the colder the engine which equates to higher IAC numbers obviously. The 10-30 number is not a hard fast rule, but is pretty close for most cars.
BTW, that's for stock or mildly modifieds
For some reason, more heavilly modified cars (bigger cams, etc.) generally like lower numbers, some even work best at 0. Go figure.
TPS is always best when set anywhere from .38-.44
.46 is a little too close to the .46 maximum that trips out of idle.

All above (except TPS) are generalizations. Every car will like something a little different, but most (not all) like the 10-30 numbers. I've seen very few that like anything higher than 50 (starts loosing control), and most don't like 0 (again, no idle rpm control).


Your car is a lot like mine, which I consider very light modifications. But mine likes very low numbers (2-15). FWIW, they very seldom settle in on exactly the same numbers all the time. One traffic light you might see 10, the next one you might see 4, and so on.

Lot's of things can try and influence your car's idle rpm. The computer is always trying to maintain almost exactly what's in the idle table (for given conditons).

 

[85TurboTtype]

Question?

Say that I had my car runnig and not set properly... shoulc I reset my comp so that everying else matches up with the proper settings? I heard that the BLM settings will set themselves in your comp unless you unhook the battery? Thanks again!

 

[gofstbuick]

Disconnecting the ecm brings all settings back to base. It will not affect TPS or IAC settings. It will affect block learn and integrator. It will force the ecm to re-learn fuel and timing strategies. If you have issues with vacuum leaks or excessively rich mixture, and they are not corrected, the ecm will eventually return to it's prior settings (before the ecm wire was disconnected).

 

[turbojimmy]

Re: Re: IAC readings

Originally posted by TurboDave
.46 is a little too close to the .46 maximum that trips out of idle.

I thought .50 was the threshold to kick it out of idle?

In any event, at .46 I can't get 4.5 at the top end anyway so I'll need to mess around with it.

The car started running really crappy over the weekend and we narrowed it down to the #3 injector not firing. We changed the injector. No dice. Wiring checked out okay so we swapped ECMs. It's back to normal now, but still not running 100% (misses at idle when cold).

Funny thing is I popped the "bad" ECM into my GN and it's fine. So I guess we may have a wiring problem at the ECM.

Jim

 

[gofstbuick]

You may end up needing a digital storage oscilloscope or graphing multimeter to look at the injector patterns. If you have access to one, it may help you pinpoint a problem. If not, don't go searching to buy one as this tool usually cost between 1100-3000 dollars. If you can get you hands on one to borrow, I can describe time and voltage settings for you the look at the injector patterns

 

[Big rich]

Does anyone know how to use red devil river ALDL CABLE