Mdhwoods

So been working on the car for awhile now. Finally got her started over the weekend for the 1st time in 4 years. On cold start engine surges from approx 1200-1500 rpm. It will do this until the engine is up to temp and then drop to approx 750 and purr like a kitten. What would be the best place to start? The cold start circuit has me a bit confused. I’ve read a ton on it and have a little understanding. Hoping because it only happens on a cold start someone with much more experience can point me to the most likely culprit. Throttle does not appear to be moving during this surging. Also smells a bit rich.

Thanks in advance.

j9fd3s

iTrader: (3)

adjust the TPS first

Mdhwoods

That has crossed my mind. Would i not have warm idle issues if the tps was off? Just curious as it is solid once warm.

j9fd3s

iTrader: (3)

the cold surging is a classic symptom of the TPS being off

Mdhwoods

Fantastic. Will check that 1st.

InABox

mine did that. the muffler had big rotten holes in them and there was not the correct back pressure. New muffler fix it for me.

FC3S Timmy

iTrader: (2)

When this happened on my s4 the cause was my coolant seal going out.

Mdhwoods

Thanks for the ideas. I will know more this week. currently have the gas tank out and por-15 ing it. not for the weak of heart. Should have it back running by the end of the week. Not having coolant issues and exhaust is fine. ill look at the tps first and report back what i find.

Mdhwoods

Tps adjustment seems to have fixed the surging.

what I noticed now that when cold starting I do not get the expected 3k idle for 30 then and idle at 1500 until warmed up.

what I get is a 1500 idle at cold start that slowly ramps to about 1800 then drops to 800 once warmed as expected. No surging, idle is smooth just not the expected behavior.

I also noticed my stock temp gage reads lower then i would expect. This is after a 20 minute warm up. Going to check thermostat. This car always ran about 25%. Where is normal operation? 50%? EDIT: just read on the 88 na 1/4 on the gauge is normal operating temp. so dont think thats an issue.

j9fd3s

iTrader: (3)

normal is about 1/3 of the way up.

the lower line is 65c, and the top line is 100c, gauge is linear and they gave it a lot of room to read

Mdhwoods

Thanks, just found a thready that said about 25% is normal. Based on what you say, im at about 150f. 180 is normal. so maybe just not fully warmed up.

Mdhwoods

Thanks to all on this site that have given me guidance over the years. Was a pretty cool day with the vert . Can’t send a video but she’s running great. Still need to work on the cold
start and check some items when starting cold as it’s not working properly. But overall it ran fantastic. No hesitation, no miss. Lots of little things to work on now but happy to have it running.