idle question

jjboncik1 · 06-12-2002, 02:26 PM

If my car is at idle, and i give it a shot of gas, on the way down my rpm's drop below idle and the car seems to almost stall but never does. After a second or two of hesitation it jumps back to normal. Anybody have any info?

Kenne944 · 06-12-2002, 02:37 PM

Mine did the same thing could never figure it out. I just install a jacob's ignition system and the problem went away.

Kenne944
86 944na

jjboncik1 · 06-12-2002, 02:40 PM

I'm planning on installing one of those soon so maybe that will do the trick. oh yeah, forgot...... 86 na 944

kreamedkorn4 · 06-12-2002, 04:33 PM

sounds like injectors could be shot, had the same problem on my 88 jaguar. Cleaned out the injectors and that was it, it fired right up and was runnin strong.

Lawrence Coppari · 06-13-2002, 03:07 AM

Kenne944

Which Jacobs do you have? I had no luck with the one I bought.

Carroll Laird · 06-13-2002, 07:27 AM

The problem is different depending on the model year. -85 cars don't have an idle stabilizer valve and so the computer tries to keep the rpm at about 900 by varying the ignition timing but it can only do this within limits. The basic idle airflow must be adjusted according to a procedure so that the timing can control the rpm easily. If it is set too low then the rpm will fall too low during engine deceleration until the timing can bring it back up. To make maters worse the fuel is turned off during engine deceleration and is restarted just before the engine slows to idle speed. I don't remember the #s but this turnon speed is lower for US spec cars than for Europe so we see the problem more often. Some folks make chips that cure the problem by turning on the fuel at a little higher speed if the problem can't be fixed by proper idle settings.

Cars from 85.5+ mostly (all?) have idle stabilizer valves to control idle speed. If the basic idle airflow (airflow with the stabilizer valve fully closed) is set too low then the valve takes a moment to bring the idle speed back up to normal. Again a procedure is followed to correctly set this (not very hard to do). The valve sometimes gets dirty or damaged and sticks or becomes slow and must be cleaned or replaced.

Sorry, kinda long but it can be a complicated problem but there are definate fixes.

jjboncik1 · 06-13-2002, 07:34 AM

Thanks for the input Carroll, i'll look into it

Kenne944 · 06-13-2002, 07:48 AM

I have the mileage master with the ultra coil. Its a few years older that i just reinstalled. If you need part numbers let me know i have all the info it.

Kenne944
944 na

Lawrence Coppari · 06-13-2002, 08:14 AM

I'm glad yours works. Last year I bought the one that had a cpu about 8 inches long, 4 inches wide, and two inches tall that wired directly to battery and existing coil leads. Kit also came with a large coil and wires. Can't recall the model number. It worked for about 5 minutes. I immediately noticed the engine idled more smoothly and seemed to have more uumph. Then it began missing above 2K. I ended up putting the old system back in use and returned the whole thing to Jacobs. I installed it twice just to make sure there were no bad connections. It seemed like the rev limiter got screwed up because the trouble always began at 2K and would not let engine speed more than that.

todwic · todwic's Garage

the problem is addressed here:DME

jjboncik1 · 06-14-2002, 07:02 AM

Yesterday i tried the "shudder" solution and didnt care for it too much. It did turn the gas back on almost right away, but it takes too long for the rpm's to go down and the "shudder" is still there when it returns to idle. gonna try plugs and new ignition soon