[Fwd: Re: 4kq intermittant rough/bouncing idle] 5KQ also.

[John Sherrow]

The car has 98K. I don't know if the injectors are the originals.

If it was leak down wouldn't cold start be a problem? I just started the
car after a week long trip and it fired up instantly. Idled around 1200
for 30 seconds then dropped to a solid 800 rpm.

BTW the car pulls a 2312 code sometimes. Wiring back to the ECU seems
OK. That's why I'm asking about sensor values drifting. I'll put a
resistor sub box on it next week and see if there is a change in
starting performance.

-------- Original Message --------
From: "Paul Cole" <pcole at mn.rr.com>
Subject: Re: 4kq intermittant rough/bouncing idle
To: "John Sherrow" <sherrow at westol.com>

On Sat, 21 Jun 2003 17:34:19 -0400, John Sherrow wrote:

>I have an '86 5K CSTQ with a similar problem. Cold starts fine. Hot
>starts fine. Warm starts (1-4 hours) then stalls/ rough idles. Does

John,
How many miles on the car?
I'd suspect accumulator or injector leaks as the cause here.
If it hot (immediate) starts then the sensors are working ( well good
enough).
Ditto the cold start- You can check the sensors with a DMM and check the
aux injector pretty easy.

What I think causes most heat soak start issues is that either the fuel
pressure
bleeds down ( accumulator,FPR circuit) or more likely the injectors
leak down and fill the cyl with fuel. Cars starts SUPER rich and
stalls/rough idles
until the excess fuel clears.
On an immediate hot start the intake is still hot enough and the leak
small
enough the A/F mixture is fine for starting.
A residual fuel pressure test and/or an injector leak test will show you
if this is
the trouble.

To troubleshoot CIS I'd reccomend two books- the factory Bently and
either the
Porbst book or the Watson book on CIS.
( check the archive- they are mentioned several times)

Also need a CIS pressure tester- BMP design had a really nice set for
around $65.
HTH


>anyone have data on the sensors? I couldn't find it in the archives. Do
>they drift out of spec? Mine seem to be OK around 50 ohms when hot and
>800 when cold.
>
>
>

//************************
Paul R. Cole:
'91 Quattro Coupe - Daily Driver @ 230k mi.
'84 Coupe (358k SAR)
'84 Coupe (SAR) , 85 Coupe parts car
'89 200TQ (WIP- SAR engine  & things)
'80 924Turbo ( built to Carrera GTR specs)
Bloomington,MN
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