Starting Issue

[DKneble]

I do not know anyone else with this problem and have talked with a couple of the shops in town about it whom are also shrugging their shoulder.

When the car is fully cooled (sitting overnite) the car starts immediately when I crank it over. No issues, not rough or anything, and no more then 2 rotations.

When the car is hot, as in turning it off and then going back to start it within 10 mins or so, it starts without any issues. Same as cold.

Anything in between, not so good. After letting it sit for an hour or two (or whatever) and then trying to start it it cranks for about 6-8 rotations and then backfires (badly sometimes) and then cranks a few more rotations and starts but the idle is rough (low).

Anyone have any ideas? Fuel pressure I know is good and spark is good (whether the timing is I do not know) but ground timing is at 5 degrees. Battery is in the trunk but power supply is good, doesnt sound like the starter is having any problems.

Thanks everyone, this is starting to get very frustrating.

Dave

 

[ove_98 TSI]

The coolant temp sensor that goes to the ecu can sometimes cause hard starts, rough idle, lean & rich conditions when it is going out, but it usally causes hard cold starts.. in your case im not sure if it could possibly cause a hard warm start
Has your CEL come on? if it has take it to autozone and read the code
you could try that if you want but im not sure if it will help
The sensors around 25$ i think so not to much of a loss if it doesnt work make sure you get the one for the ECU as theres another that goes to the gauge
Im sure other people will have ideas too

 

[DKneble]

Just put in brand new coolant temp sensor and sending unit a week ago so I know they are good.

 

[luv2rallye]

Sounds like your standard vapor lock: http://www.dsmtuners.com/forums/problem-diagnosis/217349-vapor-lock-hot-start.html.

If not try these: Hot Start Problem Fixes

 

[DKneble]

This is the first time I have heard about this as a possibility but it seems the most plausible. I will test it out tonight. Wish me luck.

 

[DKneble]

I tried yanking the vac line off of the FPR before starting it up (to imitate the FPS) but still no luck. Anyone else have any ideas? When she does start the idle is really low at first too...almost like there isn't enough timing.

Still puzzled.

 

[DKneble]

Sorry to bump this thread but it has been a week and unfortunately the problem is getting worse.

Same starting issue with some bad misfires sometime which are starting to sound like gun shots. In addition when she does start the idle is extremely low for the first 5-10 secs then climbs up to 2000rpm and stays there well past the time when the t-stat opens up. This only happens on the first start-up of the day...when the motor is close to fully cooled. When I start it about an hour later after it is heat soaked then the idle drops down but still fluctuates between 1000-1500rpm even though the ISC, TPS and BISS screw are setup.

Also, I replaced the ISC, TPS, MAF, O2 sensors, switching transistor, coil packs. ECU next?

 

[gofer]

your problems sound similar to the problems i was having, and it was getting really frustrated too. my car would start right up at my house, then id drive somewhere FAR FAR away and when id jump back in to get back it would run really really rough at start up and back fire...
since you verified all that stuff is you still don't mention anything about your plugs/wires (which is cheaper than anything you've replaced) i wouldn't think its that but its worth checking.
my problem wasn't any of these things that you've replaced either so i pointed at the ECU as well. i had a spare ECU lying around and plugged it up quick and the car did the same thing. found out my cam position sensor (CPS) or the camshaft position sensor (CMP) <-- thats what chiltons calls it, was acting up causing all sorts of wierd idling/spark problems. its cheaper than getting a new ECU and a local DSM'r im sure has a 4g63 lying around with one on it you can use to verify or but if its not that, id be pointing at the ECU as the culprit and hopefully a buddy has a spare one of those for you to borrow too.
good luck man.

 

[DKneble]

Well I have had the same problems with both my stock coilpacks and coil on plug setup that I have on now so I'm assuming its not them. Also, I change plugs every other month and this has been going on since before my last swap.

I thought about it being the CAS (6 bolt) but I have a blacktop which is suppose to be the best so I "assumed" it should be fine. I will try to dig up another CAS and try it out. Thanks. Otherwise the ECU is all I can figure.

Dave