It's inconsistent, but some times upon startup, the RPMs jump way up to around 2000. Some times less. Some times they don't flare at all. I can find no pattern. If anything, it does this more often when the engine is warmed up than when cold. The engine starts instantly every time, hot or cold, so there is no apparent relationship to crank time.

Mine is a MAF car, running $6E (AUJM based) code, with cold start fuse pulled.

This is quite annoying, mostly because I have to wait for it to settle back down before putting it into gear. What causes this? The ECM is trying a bit too hard, here.

 

I've seen the MAF $6E code do this. I just slam em in gear. Probably not the right thing to do, but it brings the idle down.
J

 

I get this too, on my 89. I've never had the scantool around when it's happened though.

 

On my 85 trans am, the rpms would soar to 2300 rpm with a clean TB, and then very slowly come back down to idle. It was most annoying in the staging lanes, when I would have to sit there for what felt like forever for the rpms to come down.

On my 89 the rpms jump to 1500, but come right back down.

On both cars the start-up happens the same every time.

nick

 

There is a couple things that also contribute, but there is definitely a part of most ECMs'/eproms' logic and it's hardcoded. I'm still looking for the specific code in my SD 7730 and trying to understand GM's "logic" for having such a routine.

GM didn't put the "flair" there for no reason, and I am trying to understand why. Unfortunately, while I will ulitimately find it for the SD ECM, you guys are going to have to find that logic for your own ECMs.

Also, there is hardcode to limit the max RPM to 800 RPM when you put your car "in gear"...this is another "common" hardcode. I understand the reason for that one though.

 

I've been looking through the $6E code. If I ever find it I will post.
J

 

Look for max IAC park counts and max IAC counts.
Too low and the engine floods, I wouldn't make too big of change on the park count. Theres a fair amount of PID stuff for the IAC.

 

I am quite sure that I never noticed the startup rpm go higher than 1500 when I had my original chip in the car.

Originally I had a chip that said ANYJ9304 on the eprom label. I am going to compare the IAC related tables between this chip and the ARAP one when I get some spare time... Just gonna cleanup the car first, looks terrible when it's been sitting in winter storage 6 months.

Anyone know of that version for a 5.7L TPI Camaro?

Mine is a direct import from the US, so I don't think it's any chip for the european market or something like that.... (Even have a speedo thats marked in mph and km/h...).

 

WARM PARK POSIT. vs COOLANT
ARG = STEPS
STEPS Deg c COOL
LC588 FCB 125 125 -40
LC589 FCB 100 100 -16
LC58A FCB 75 75 8
LC58B FCB 50 50 32
LC58C FCB 25 25 56
LC58D FCB 10 10 80
LC58E FCB 5 5 104
LC58F FCB 5 5 128
LC590 FCB 5 5 152


Careful thou, go too low and the motor floods
The IAC prime pulse all work together to get a for sure start wothout excess cranking, and emissions. Probably a decay rate for these some where.

 

Doc has had too meny percocets and is saying tell, tell tell,

OK.

Often when working with temp sensitive stuff I just move the whole column up one grouping.
ie
there would be 4 entries of 5 and then all the others moved up one.