With the load of the defrost on, why does my computer "hunt" so much, I went out this morning, started the car and set the defrost on high, went back in the house. From inside the house, I can here the computer hunting constantly, revving the motor up and down constantly. My iac is probably all over the place right?

I have a scan tool, should I scan it when it does this again? what would I be looking for?

 

Probably the AC cycling off and on.

 

5.7 is probably correct. In most ECMs the stock programming will add extra rpm when the A/C is on. To the computer, the Defroster IS the same as the A/C. So. as it cycles, the ECM keeps adding (and removing) the extra RPM added by the ECM

 

Not to mention the A/C clutch is engaging and disengaging in about 10 second intervals. The compressor does put a load on the engine and it takes the ECM a perceptable amount of time to compensate for the extra drag.

 

Thanks everyone for your replies here. I am still looking to tame the cycling down though....I think the rpm swing is too much. maybe it cycles between 200 rpm?

didn't do it like this stock. only after zz4 and afterparts/chip.

 

I suspect the chip. Contact the person that wrote it and ask them to fix it.

 

On the $8D I think it's an IAC adder for A/C. I think it's 5 steps, whatever that corresponds to in RPM, I don't know. I haven't looked at that in ages.

You "could" be running on the lean side too, it seems that when the computer has to add fuel at idle, the engine gets grumpy. At least on mine it does. When the ECU takes away fuel, it seems to like that better.

Watch the BLMs and your IAC counts first. If the IAC counts correspond to the A/C cycling, there's not a whole lot to be done with it. The RPMs go up to counter the extra drag from the A/C.

 

91Z28, I don't think this guy has clue what you said (though much of what you said is true).

 

Alright Glen-
In this case you are wrong, I do understand what 91z28 is saying here...I have a scanner and understand 91z28's explanation of my blm's and iac counts.......

thanks for giving me credit for reading other posts without inquiring jeeez.


And yes, car is running lean. per scanner.

I have visited the prom board and have been studying to do my own chip.

 

I'm sorry. I didn't mean or intend it as an insult. I meant the answer 91Z28 gave was a "techie" answer using "eprom buzz-words" which generally means nothing to the general public and is often a complaint. That is why I try to explain things in "ordinary everyday English" (except on the DIY Prom Board. Normally, only those actively involved in eprom burning understand eprom jargon). BTW, your car doesn't use the $8D SD calibration but the $6E MAF calibration.

 

One other thing may be at play too. The AC may be low on R12 and right on the verge of shutting down/starting up when the pressure is low. It has a pressure switch to shut it's self down if the pressure is low so it doesn't damage it's self.

 

I am also sorry for taking offense quickly, I thought about that very situation being maybe not everyone gets the techi type answers.

another side note....
halfinch may be on to something here...I have no more r-12 in the AC syst. it blows hot at the moment.


I think I may have to live with this until I burn a different chip.

I will check the block learns against the iac counts, but won't be able to do anything about that w/o chip work.


Also, at idle I have around a 200 rpm idle swing normally, not enough to set codes, but when rpm dips to say 650-700, motor acts like someone cut out needed air or fuel. still running maf.

 

No problema IDaddy. That is the problem when you "type" versus speaking "face to face". You don't get the benefit of the facial expressions.

Lack of R12 will definitely cause a problem...more with the pump though. I had that occur on another car I owned and it seized the pump.

But, as a tuner, a hunting/searching idle is also indicative of a tuning problem with the eprom. Do you have your original? If so, put that in to confirm whether or not it is an eprom/tuning issue.

MAF is EXTREMELY forgiving with idle. I was having an "startup" issue with my buddy's solid roller setup (248/258 @ .050). Even though the injectors were wrong in the eprom; I wanted to eliminate check if the "startup" problem would occur with the another eprom. The only eprom we had was his original memcal and we didn't have an eraser handy.

So, we installed the original eprom (not expecting the car to run...but it would resolve whether it could start the car without hitting the gas pedal). To our surprise, the original memcal with the original tuning actually started and ran the car reasonably well (until the car warmed up and the idle speed was too low for the cam).

So whip out your original memcal and try it out to see if the problem persists.

 

Will do Glenn-



Once again; can't stress enough how so many of you are correct on the boards about burning your own chip.