Coolant Sensor Related? Starting Issue

**MidwestA4** · 07-05-2008 04:18 PM

EDIT: Good link to Service Bulletin and Part Numbers for updated 30V 2.8L Engines
www.rebuiltautoengines.com/audi-articles.html

Ok:

Car: 1998.5 A4 Quattro 2.8L V6 30Valve (115k)

Having an issue with start up when the car sits for any time under an hour.

Car had an issue with starting before (2 months ago) which resulted in me replacing the following: Coilpack, Plugs, Wires, Cleaned the MAF, Fuel Filter, Related Fuses, Cleaned the throttle body, checked air filter, ran seafoam and later ran an injector cleaner.

After that episode (It started right up after the pack was replaced) the car has been running "good" ever since. Sometimes the car doesn't want to start without a little pedal tap when it's been sitting for under an hour.

Today the car drove fine to the bank (5 miles) but after it sat for a few hours in the driveway it wouldn't start. I pulled the fuel pump fuse and tried again.. nothing.

- It's getting A LOT of fuel... I know flooding can happen when trying to start a car that's not firing but WOW.. it was flooded within 3 trys.
- It finally cranked over BUT... i had to have it sit at about 3k rpm for a few minutes for it to not want to die..
- Once it would hold idle it would rise to about 900-1000k then drop back down to 700-800 then rise again and..etc...
- It's now holding an idle now that the car is warm but I've yet to drive it in fear of getting stuck.

**my temp gauge works flawlessly**

Other items replaced:
100k = timing belt
100k = tensioner
Oil changes every 3000-3500k miles

I've done a little research on the coolant temp. sensor and I'm wondering if this could be the issue? I've ordered the replacement from ECS and am awaiting delivery. Just wondering anyone elses opinion on the matter? I read a lot of threads with similar problems BUT.. no one is ever smart enough to post their fix. I WILL!!

**Affinitive** · 07-05-2008 08:01 PM

There is a TSB for AHA engines needing updated thermostats (hotter T-Stat), updated fuel injectors and a new temp sensor. If you have the old purple injectors, then nix them for the new red ones. The have a different spray pattern.

Basicly the issue was for "Hot Soak" stating issue like you mentioned when they build up even just thge slightlest carbon build up. The thermostat needed to be hotter to help keep the spark plugs from getting fuel fouled and minimise carbon build up. The injector would also help with the carbon. The temp sensor needed to be replaced, well,... because all Audi's and VW's have issues with temp sensors when they reach a certain age. the TSB refers to a certain date stamp on the sensor, just disregard it and relpace it regardless. No disrespect to the folks at ECS, but temp sensors are Genuine OE only type of deal or "BEHR" (which is the OE manufacturer) when dealing with an old style sensor like this. If the folks at ECS are selling you Genuine OE or BEHR, then great, if not, then don't waist your money.

Just because the temp gauge has never acted up doesn't mean the sensor is OK. See faults all the time for sensors only in the ECM but not the cluster.

Back to the brand name. Same goes for T-Stats as well. BEHR and WAHLER are the ONLY aftermarket brand names acceptable if Genuine OE is not available. Audi's and VW's have enough issue with temp sensors and T-Stats that you should really use only OE. The reason BEHR and WAHLER are ok is because they are the OE manufacturers for AUDI/VW.

Long story short, the new updated injectors, T-Stat and Temp sensor should do the trick. I know it sounds a little strange but trust me.
BTW - At 100K, a new fuel filter wouldn't hurt either.

C

**MidwestA4** · 07-06-2008 07:03 AM

Wow, thanks for the heads up and details! I've tried to find the part numbers for what you're talking about and have come up short.. Do you by chance have them for the t-stat and injectors? I'm not quite sure what you mean by "reds". I've read the service bulletin for upgrading the spark plugs in the 30V engines (if there's a starting issue) and plan on buying those today as well just to see..

The fuel filter (and surrounding rubber/plastic fuel lines were all replaced recently.. and there's no doubt it's getting fuel.

Thanks again!

**MidwestA4** · 07-06-2008 07:23 AM

updated the main post with a link to all part numbers for the updated spark plugs, t-stat, and fuel injectors.

**MidwestA4** · 07-10-2008 08:14 AM

Seems that replacing the Coolant Temp. sensor solved all of my starting/jumpy idle whoas..

**Nebone** · 07-10-2008 12:47 PM

One time a local dude asked me for help on his 2.8. Car ran rich, lean, idled bad, had maf problems with a bunch of CELs. I narrowed it down and replaced only the coolant temp sensor and everything became marvelous.