probinson

I just finished TB/WP and cam gear replacement on my 85 32 valve. The car had been in storage for 15 years before I did the work. Prior to the work I was able to start the car and it idled just fine. I never took it above an idle due to the age of the TB.
After the work the car seems to start for 1-2 seconds, backfires through the intakes and quits. I have checked the spark plug wiring, it is correct. The EZK and LH were both checked and are OK. I have replaced the relays for EZK and LH, . I did notice the connector on the TPS was broken. I have temporarily taped the wires. Fuel pump, spark plugs are new. Any suggestions?

Rob Edwards

I don't know S3's well at all, but there are several threads in the archives about these LH2.2 cars backfiring, and blowing the intakes off and denting the hood. So (of course) proceed with caution before trying to start again.

Are you 100% sure the timing is spot on? (Got Ken's 32V'r?) From the threads linked below it sounds like A) never touch the gas pedal when starting, to avoid advancing the timing. If you're off a tooth in the right direction, you might be significantly advanced.



Some links to threads:

https://rennlist.com/forums/928-foru...n-my-hood.html

https://rennlist.com/forums/928-foru...-backfire.html

https://rennlist.com/forums/928-foru...xplosions.html

probinson

Thanks Rob,
Timing using Ken's tool was dead on (-/+) 1/2 degree. Set 1-4 @ -2 and 5-8 @ 0. The engine starts momentarily then runs very rough before backfire and stalling. Read a post that a bad battery can cause this by not having enough voltage to signal the ecu to fire the injectors after cold start. I did notice the throttle position indicator wiring harness connector was toast. I taped the wires until a new harness arrives but I don't think that would cause a no-run condition.

John Speake

A very weak mixture could cause the backfire and cutout. ..... check temp 2 sensor... on top of the water bridge, usually has a blue 2 pin Bosch connector.

Measure each pin in turn to the engine block. At 20degC each pin should measure 3,000 ohms. At normal engine temp of 80degC about 270 ohms.

probinson

Thanks for the info, checked at 75F 600 on one terminal and 0 on the other.

probinson

Oops, checked the temp sensor.. I am getting 2312 and 2295 at 75F

dr bob

Throttle switch needs to see that the throttle is closed to enable the idle stabilizer. Possible the backfire is due to engine stalling/starving, rather than the other way around?

probinson

Good point, the engine is certainly starving. Runs smooth for a few seconds on cold start then backfires and dies.

James Bailey

it would be good to KNOW that the fuel pump is running more than just while you are cranking on the starter motor...... consider jumpering the fuel pump relay as a test..

davek9

Also recheck you're spark plug wires for a miss wire and or short as in bad wire
Do one at a time, trace them to the plugs.
Edit: also make sure the distributor cap(s) not cracked.

probinson

Great points. I have jumpered the fuel pump, same results. Double checked timing and spark plug wiring hook up…all good. I will check the wires for shorts, distributors look good, no cracks or burn marks.

dr bob

Check fuel pressure. Cuts out about 30% of the guessing if you know it's OK.