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AlfromNH
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Joined: August 04, 2024
Posts: 241
Location: NH
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 Posted: Mon Aug 18, 2025 2:18 pm Post subject: Another “runs lousy when cold” thread |
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My ‘88 Westy auto with stock 2.1wbx runs great except when first started from cold.
It will start right up and settle into a high-ish idle of ~1100 rpm. After 10-15 seconds, or if I step on the gas, the idle will drop to ~800 then keep dropping, often stalling. If I keep the rpm’s up or get it in gear and drive off it will be fine after a minute or so.
I had a spare temp 2 sensor that I installed and that helped a little.
I have the Digifant manual and can do all the troubleshooting steps, but any suggestions on where to start?
Thanks
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‘88 2wd Auto Westy project |
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jlrftype7
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Joined: July 24, 2018
Posts: 4792
Location: Chicago
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| Posted: Mon Aug 18, 2025 2:36 pm Post subject: Re: Another “runs lousy when cold” thread |
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With a Cold engine just started, even at higher ambient temp like most of us still are enjoying, you need an enriched mixture for a bit. Won't be as long of a cycle like in Winter with much colder temps, but is still needed.
So, Vacuum leak testing via Smoke testing if you haven't already done it, and pulling the Injectors out to see the Spray Pattern as well.
Condition of Tune Up parts as always.
Last one is valve deposits on the backside of your Intake Valves. They'll soak up excess fuel like a Charcoal Briquet, throwing off the enriched fuel mixture of a cold started engine until it warms up a bit.
_________________
'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto |
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Mateo83
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Joined: September 14, 2021
Posts: 647
Location: Lodi, CA
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| Posted: Mon Aug 18, 2025 2:53 pm Post subject: Re: Another “runs lousy when cold” thread |
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| jlrftype7 wrote: |
With a Cold engine just started, even at higher ambient temp like most of us still are enjoying, you need an enriched mixture for a bit. Won't be as long of a cycle like in Winter with much colder temps, but is still needed.
So, Vacuum leak testing via Smoke testing if you haven't already done it, and pulling the Injectors out to see the Spray Pattern as well.
Condition of Tune Up parts as always.
Last one is valve deposits on the backside of your Intake Valves. They'll soak up excess fuel like a Charcoal Briquet, throwing off the enriched fuel mixture of a cold started engine until it warms up a bit. |
What's the solution for the last one?
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83 Air-cooled 2.0 Tin Top |
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DanHoug
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Joined: December 05, 2016
Posts: 5948
Location: Bemidji, MN
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| Posted: Mon Aug 18, 2025 4:01 pm Post subject: Re: Another “runs lousy when cold” thread |
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intake valve deposits can be chemically removed, well LESSENED, with a mix of attacks... Techron in the fuel tank, sucking GM/Delco Top Engine Cleaner in thru the vacuum lines, and physical removal with walnut shell media after removing the intake manifolds. the latter makes a bang up mess and is not that practical for this, but it works with the head and engine intact.
funnily, i stumbled upon an intake valve varnish remover by experimentation. varnish is a different beast that you might be facing, a glue that can hold the valve open until the engine heats up then it releases its schmoo-ey grip on the valve stem. come to think of it, this MAY be your problem. anyway, i had a Briggs twin cylinder engine with a nasty sticking intake valve when cold from fuel deposits. tried every solvent i had in my cupboard and the thing that released the varnish was pouring brake fluid down the carb while it was running. made HUGE Armageddon-like clouds of white smoke but the frickin' valve stayed free. it's not a polite solution in a neighborhood.
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-dan
60% of what you find on the internet is wrong, including this post.
'87 Westy & '89 Westy both 2.1 4spd
Past projects can be found at--
www.thefixitworkshop.com |
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jlrftype7
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Joined: July 24, 2018
Posts: 4792
Location: Chicago
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| Posted: Tue Aug 19, 2025 10:41 am Post subject: Re: Another “runs lousy when cold” thread |
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| Mateo83 wrote: |
| jlrftype7 wrote: |
With a Cold engine just started, even at higher ambient temp like most of us still are enjoying, you need an enriched mixture for a bit. Won't be as long of a cycle like in Winter with much colder temps, but is still needed.
So, Vacuum leak testing via Smoke testing if you haven't already done it, and pulling the Injectors out to see the Spray Pattern as well.
Condition of Tune Up parts as always.
Last one is valve deposits on the backside of your Intake Valves. They'll soak up excess fuel like a Charcoal Briquet, throwing off the enriched fuel mixture of a cold started engine until it warms up a bit. |
What's the solution for the last one? |
What Dan posted. Media Blasting Valves on Direct Injection Engines has become a norm since running any type of cleaner is not going to get you a spray at the valve like with the older Port Injection that we have on our VWs.
Also, Modern engines having oil consumption issues on top of valve deposits often have major build up , with pictures from shops and owners posting how amazed the engine is running as well as it is with all that crud inside.
Techron was once the Gold Standard for cleaning, then I believe the Formula had to be tweaked to keep the EPA happy with the VOCs.
Back in the 80s and 90s, you'd add a bottle or two, of Techron to a gas tank, go drive the vehicle ,and it wasn't uncommon for the car to blast stuff out of the tail pipe at higher speeds once the deposits were being worked loose.
It helped that valve stems and valves in general were still pretty normal in size compared to todays tiny stems and smaller multi-valve engines.
If you were going to cough crud out of the engine, the bigger and thicker valves were up to the task.
I did Walnut Blasting at my time with BMW, they'd bought a whole kit for a huge Service Campaign to address hesitation and poor Cold Engine Running from valve deposit build -up. It was a bit before my time with BMW, but at one time dealers were popping intake manifolds off and blasting the valves as a regular event while BMW was footing the bill to keep Customer's happy.
Eventually Gas Companies worked with the Car Manufs to help get the right package of detergents in Gas formulas at your Pump, which really lessened the need for all the drastic cleaning that had cropped up.
Now it's a "Thing' again , but for a change in engine fuel systems, not actually gas itself. The Direct Injectors don't spray the back of an Intake Valve, but are SO much smaller in their ports compared to Pintle injectors, that even chemicals have a hard time keeping the 'atomized' spray of Direct Injectors going deposit free over the life of an engine.
_________________
'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto |
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