pulsing while cold in gear driving

[Black_Noise]

I have mentioned this before and it was discussed briely, but im still looking for answers/ideas.

Off a cold start waiting less than 1 minute before putting car in gear and starting to drive around, there is a pulsing while on the gas.

It has been discussed that is it not very noticable with the stock tune, and gets more noticable on a 91 tune, and 93 tune.

lets get back on talking about this.

[Local Boy]

It's normal, Brutha...

Your EEC is in warm-up mode, for the first few minutes of operation...

That's it...That's why the first discussions were short...LOL

Now, if you were looking for a more technical answer:

When you start your car, the (IAB) intake air by-pass opens 100%...

Now, the colder the ambient temp. is, the more fuel will be dumped into the engine, and the more timing added...

The EEC does all this in an effort to get the motor and converter up to running temp. as fast as possible...

Conversly, as she warms up, fuel and timing are pulled...

The EEC looks for 185* temp. to then go into "Warm Idle Mode"...

So, the surging or pulsing, you feel is the EEC cycling the injectors, timing, + the converter stalling...

When you drive away, in this mode, you add the MAF into the equation...and it comes together in the car surging, at low speed, for the first few minutes of operation...

ALOHA

[Stranger in the Black Sedan]

There is a weird resonance around 850-900 rpms on my car, and I have talked to others who found the same thing. If I bump my idle w/ the tuner up above 800 rpms, I get a droning through the front of the car. When the car is cold and coming off its cold high idle, I have about 30 seconds of the droning in the 900 rpm range. Just the way it's made. I am tuned but run the stock ~575 rpm idle speed.

[Vortech347]

Mine does it all the time, even warmed up. It started when I took the factory airbox off.

I'm selling it with the stock airbox.

[Black_Noise]

i never noticed it when i put the JLT on... only after I had the programmer for about a month did i notice it. (not a daily driver)

[dpotter]

Glad this was brought back up as I have wondered why my MM had this brief surging at start-up.

Thanks guys.