Re. Narrowing down my start issue (84 4kq)

[Johnny B]

Spoke with the previous owner of the car this morning regarding my hunt on this starting issue. 

Apparently the fuel pressures were checked several times over, as well as each injector being tested for proper spray & pressure, all seemed fine. He noted spending over $600 over the course of the past 2 years replacing everything he can touch along the way. Fuel pump / check valve were replaced as well (so not stock units as I had previously thought). He had the DPR tested and tuned, fuel pressures checked, new fuel pump & filter put in, ECU coolant temp sensor replaced, all vac lines replaced (before I did it all over again), ISV tested and cleaned, as well as a vac leak down check on the system. Apparently all of this checked out while he was on the hunt for this problem (probably why it runs so sweet once started!). 

I am still going to swap DPR's to see what she do. I am also meeting up with a friend today to toss on the metering plate adjustment harness so I can dial it in properly apposed to playing the guessing game. The DPR installed does respond when unplugged (idle drops roughly 200rpm), plugging it back in at idle will result in an increase of idle by 200rpm. One portion of the vac system I havent checked is the charcoal canister, which will be getting a thorough once over today (though I dont believe the canister can cause this start issue). Accumulator checks out, and has no leaks. 

Correct me if Im wrong, but because this is happening at start up, and at no other time with the car, I am ruling out the ECU and sensors related to the ECU as when first starting the car reverts to the static adjustment at the fuel metering plate as to how it should run. After 5-10 seconds when warm the sensors will tell the ECU to switch over to closed loop mode, when cold it takes a bit longer as the sensors are not reading anything yet (everything is still too cold). The PO stated he has started the car with the ECU out when hunting things down on the start issue, he was surprised it fired up then quickly realized it was because the ECU controls nothing while the idle / wot switch is engaged. 

Not throwing in the towel, though it's definitely trying my patience. At least I will know everything I need to about CIS-E when this is all over! (HUGE thanks to everyone on the mailing list here!! 

Johnny



> From: cody at 5000tq.com
> Subject: Re: Re. Narrowing down my start issue (84 4kq)
> Date: Sun, 15 Aug 2010 19:52:06 -0400
> To: pre95 at live.com
> CC: benswann at verizon.net; quattro at audifans.com
> 
> Check. The. Fuel. Pressures.
> 
> -Cody (mobile)
> 
> On Aug 15, 2010, at 4:22 PM, Johnny B <pre95 at live.com> wrote:
> 
> > 
> > Well thanks for the great tip! I swapped the fuel pump relay for the fan relay from my ur-quattro and no change on start (though the fuel pump runs on a constant as you said it would, I let it run 3-4 seconds before trying to start, same symptoms. I put the fuel pump relay back in Huw!). Very frustrating to say the least... I'm, not really sure where to go from here regarding this start issue. If its not a lack of residual fuel pressure, and not a vacuum leak (just replaced all formed vacuum tubes & all cloth covered vac lines, checked the entire system over), and knowing it had this same issue prior to new injectors being installed (this problem carried over from before the engine rebuild, which included all gaskets, rings, cylinder head rebuild, and fuel injectors + seals).. where do I go from here? 
> > 
> > Starting to get discouraged... if you give it any throttle over a light touch of the gas pedal for the first minute (when cold) it bogs and wants to die. Does the same when hot but only for the first 8-10 seconds... Im thoroughly stumped. Car has great power through the RPM band, top & low end are fine, idle is always rock solid just shy of 1k, cannot source any vac leaks with the chemtool when warm or cold... not really sure what else to check. Once the start symptoms pass, the car is perfect.. it doesnt drive like it has any issues at all which just adds to my frustrations. 
> > 
> > Thanks guys, I'm not giving up hope but definitely understand why so many throw in the towel and go EFI. 
> > 
> > Johnny
> > 
> > 
> >