85 Turbo doesn't like to idle until it's warm. Runs OK once it is warm.

[FlyingBrickMan]

Hi all.
As title states, I recently picked up a 1985 Turbo, 80k. From what I can tell its pretty much all stock. The car will not stay running when I start it from cold. I have to keep on the throttle at around 3k until it warms up completely. It will miss and sputter at 3k on and off while waiting to warm up. Once its warm it runs OK. I verified the cold start injector is working like the Bentley says it should. I went through vacuum lines and see no obvious issues there, but I plan to go line by line and replace them all just because it will make me feel better. I have read a few threads that indicate the coolant temp sensor could be at fault, but I am not entirely sure how to check this other than ohm'ing it out (this is a real PITA given how hard it is to reach the sensor and I have not had luck getting a reliable reading). any ideas from the collective?

 

[Jamesmoore]

I’d say your pretty on track, you could make an extension harness so you can ohm out the coolant sensor from an easier postion. But I’d probably just replace it as they aren’t expensive and it’s probably original. Use only the oem quality, I believe Bosch. I’ve had issues with cheaper ones

You could be having IAC problems. Remove it give it a clean out and try again.

Try unplugging the maf see if it makes a difference also

 

[Jack]

How’s the wiring that goes through the firewall

How’s the brake check valve
When warm what rpm does it stay at

check fuel pressure

 

[Jack]

I’d say your pretty on track, you could make an extension harness so you can ohm out the coolant sensor from an easier postion. But I’d probably just replace it as they aren’t expensive and it’s probably original. Use only the oem quality, I believe Bosch. I’ve had issues with cheaper ones

You could be having IAC problems. Remove it give it a clean out and try again.

Try unplugging the maf see if it makes a difference also

There’s no MaF on the kjet cars

 

[Jamesmoore]

There’s no MaF on the kjet cars

Noted I just did a quick read whilst on the shitter at work lol

 

[bobxyz]

K-Jet uses a CPR, aka WUR, (Control Pressure Regulator / Warm Up Regulator) to adjust fuel pressure to provide extra fuel during warmup. Electronic fuel injection uses the temperature sensor to adjust warm up fuel injection.

One of the first things you should do with a poorly running K-Jet car is to check the K-Jet fuel pressures. You can make your own tester, or borrow/rent one from a k-jet expert.

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After searching all the various threads and stealing all the information I could this is the results of my efforts:



Upgraded version with hook to hang from hood. I used duct tape to hold the coat hanger hook in place until the JB Weld set...

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Thread 'Building the Best K-jet Fuel Pressure Tester: What Would You Pick?'

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I finally found the 245T that I've always been wanting. Of course, it runs like crap. I am very fond of the thrifty TBricks resourcefulness. That said, I am in this K-jet business for the long haul, so I want to be able to measure pressures very accurately. I don't want to buy a second fuel pressure tester three years from now either. Also, I am brand new to the K-jet game.

If you were building a very nice, but cost effective, fuel pressure tester, what would you buy?


I have seen these sets for sale:

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[FlyingBrickMan]

How’s the wiring that goes through the firewall

How’s the brake check valve
When warm what rpm does it stay at

check fuel pressure

Fuel pressure is ok, first thing I checked.

RPM is around 800 when warm.

I did not think to check the brake check valve...vacuum leak source I assume?

As for the wiring through the firewall... I addressed some bare wires where the insulation had broken down on the main harness, but it was an in place repair so I didn't confirm down into the sheathing if I had more issues.

 

[Jack]

The WUR has two screens that very easily get clogged, you can pick a hole in them often fixing the issues with low pressures


You checked the fuel pressures during warm up ?

 

[FlyingBrickMan]

The WUR has two screens that very easily get clogged, you can pick a hole in them often fixing the issues with low pressures


You checked the fuel pressures during warm up ?

Yes sir. I have about 20 psi and rises as it warms up

 

[dl242gt]

If the injector seals are older than three years they are due for replacement. I'd check for any soft air handling hoses, check along the seam where the intercooler grid meets the tanks. Intake manifold gasket can be split underneath where it's hard to see. The hoses for the evap canister like to split under the fender where you can't see them.