# Engine won't run with temp sensor plugged in



## warmerwagen (Aug 10, 2003)

Well, here we go again. I posted this question last year after i got the KE-Jetronic 87 Jetta running . But it was only running after I unplugged the coolant temp sensor to the computer.
The answers given were all the same, check for vacuum leaks, tune up.
There are no vacuum leaks. How do you do a tune up if it still runs like crap because you can't plug in the temp 2 sensor?
Tune -up is not the issue. 
This is what happens:
Hard starting. You must unplug the temp sensor or it will start and stall. 
Unplugged, it's slow to warm up, and you have no power. You can't do any fast accelleration.
I'm aware that this is due to the sen







sor being unplugged. 
So the question boys and girls is :
Who knows why the engine won't run with the coolant tem sensor plugged in? 
The sensor is NEW. I have 2 other good used ones I tried also.
I don't need a tunes up or to look for vauccum leaks anymore. 
I need to hear from someone who knows what this prioblem is before i just take it to the VW shop and pay 80.00 to 500.00 to have the tech there figure it out. I don't have the money, UI need this car because my Vanagon engine went out. 
I don't know much about the CIS-E system . This car ran good for 8 years until 2004.
It's taken my 5 years to get it running to this point. 
Only experienced tech answers please.
Thanks
Robert


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## BSD (Jul 8, 2008)

I would respond, but I am not an experienced tech.








Steve-


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## ShaggysGTI (May 15, 2009)

Trace the wiring, make sure it is not faulty. After the vehicle is warmed up, can you plug the temp sensor in?


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## warmerwagen (Aug 10, 2003)

*Re: (ShaggysGTI)*

No, cold or warm, pluging the sensor in causes the rpm to drop, the engine stutters and stops.


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## ziddey (Apr 16, 2006)

*Re: Engine won't run with temp sensor plugged in (warmerwagen)*

You definitely need a tunes up and to look for vacuum leaks more.
Here's the deal:
With the CTS unplugged, when you run the car, there's over 150mA current going through the DPR. That's A LOT of fuel.
Normal running is a centering around 10mA, with oscillations of just 1mA really in either direction.
So you see, you being able to run at 150mA without needing to constantly manipulate the throttle to prevent stalling means that your mixture is way off. Why did it get way off? Bad tune? Vacuum leaks?
If you've been driving it like that for a while, your catalytic converter is probably melted through and through. Hope you don't have to deal with smog.

So, what do you do? Build a DPR test harness to track DPR current. Check your o2 sensor functionality with a voltmeter.
Check your grounds.
Ignition components. Vacuum lines, airboots.
Clean the airplate, throttle body, etc
fuel filter
etc etc etc


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## warmerwagen (Aug 10, 2003)

*Re: Engine won't run with temp sensor plugged in (ziddey)*

I got this car running in April for the first time since it quit in Aug. 2004., by unplugging the CTS. 
Only drove it a few short test trips. Does better at freeway than in town. 
So you are saying that this is what happens when there is a vauum leak, or the car is out of tune.
The tune up items are new plugs, wires, cap and rotor, fuel is fresh( gas consumption is high, tailpipe black. 
Checked throttle plate position. tried swapping out fuel distributor, computers.removed and carefully inspected intake boots, intake tube. 
Battery is new, charging system OK. 
Checked all vacuum lines. 
Swapped DPR, swapped FPR.
I have'nt looked at the 02-so l measure the voltage on that, also the test the DPR,


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## ShaggysGTI (May 15, 2009)

Speaking of which, how is the cat?


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## ziddey (Apr 16, 2006)

*Re: Engine won't run with temp sensor plugged in (warmerwagen)*

In my experience, with the CTS unplugged, it'll just get stuck in open loop, pushing around 158mA through the DPR.
So if you can imagine a "normal" car having a DPR current centering around 10mA, with 1mA fluctuations in either direction being enough to throw the mix into the rich/lean oscillation of closed loop, just imagine 158mA fulltime.
For sure your tailpipe is black and your fuel tank is emptying.
Look up how to set the mixture. Chances are, you may have to dial it clockwise many many turns to begin with, since with the CTS plugged in, DPR current will TANK.
You may also back out the idle screw temporarily if it'd make working on the car easier. Be careful of that o-ring though. Real old, tends to leak and not keep the screw in place (causing it to back out all the way or tighten all the way)
Adjust the mixture so that you have a proper centering, so that when the car is cold, and o2 isn't active, the car will be driveable.


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## warmerwagen (Aug 10, 2003)

*Re: (ShaggysGTI)*

I just looked st it when I replaced the trans shift cable, it was intact. I haven't looked at it since I drove it about 100 miles ( not all the miles at once). I have to remove the pipe from the cat back to get a ppor weld fixed-I'll look at it again.


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## warmerwagen (Aug 10, 2003)

*Re: Engine won't run with temp sensor plugged in (ziddey)*

This I will do these adjustments before driving again. I don't want to wreck the CAT.
I'm going to have to get this corrected before going to emissions testing .


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## warmerwagen (Aug 10, 2003)

I'll study the adjustment procedures in the Bosch Fuel Injection & Engine Management book.


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## warmerwagen (Aug 10, 2003)

*Re: (warmerwagen)*

It runs now with the CTS plugged in!!! 
I started it up and got my ear down near the FD where I heard air sucking. 
Pulled the FD off and the o ring was broken in half with one half down in the air metering box.
I put another O-ring , started the engine, plugged the CTS back in, it started to stall then corrected itself and revved up high, slowly bringing back to a correct idel. 
I took it around the block- the power is back!!!!!!
Thank you guys so much- I must have pinched the O-ring 2 years ago when I was trying to figure it out in the dead of winter. 
It's not idling smooth- I'm going to get some gas and take it on the highway to see how it does.


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## warmerwagen (Aug 10, 2003)

*Re: (warmerwagen)*

Now there has been a trade -off of symptoms. Runs much better now driving but is hard to start when warm. Also pops and bangs on decelleration and idles rough.
So I pulled the FD up and pushed the plunger in a few tims, gas came out of the control plunger .
I don't think this is normal- this gas present at decelleration is probably what the popping and banging is about- fuel leaking . 
So, gas coming out the bottom of the plunger is bad , no?
All the popping and roughness is also more pronounced since I put a Borla exhaust system in.


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## warmerwagen (Aug 10, 2003)

*Re: (warmerwagen)*

I just found that I had the wrong fuel pressure regulator installed.
2 years ago out in the snow and I swapped out for a nicer looking FPR. But, the numbers are not original on this replacement. 
I did some research and my findings show the correct FP for a 87 Jetta GL is a Bosch 0 438 161 010. The one I swapped into it 2 years ago is a 002. 
The number ending in 002 is for the 86 Jetta, etc.


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## warmerwagen (Aug 10, 2003)

*Re: (warmerwagen)*

SIlent bunch, aren't you? 
Well, changing to the correct FPR did the trick. At least I hope. Yesterday it was hard starting when warm. it now starts first rev.
Also, much more power, the exhaust smells normal, and the idle is at about 900 RPM. I changed the thottle position sensor to one that had a higher reading in OHMs at full open than the original. That's is, 5065 Ohm, the roiginal 5016 Ohm. 
During alll of this I discovered that one of the screws that holds the FD down, the screw fathers from the throttle plate, was longer. It was preventing the throttle plate from rising fully. is this normal?
One thing I remember is this car never was really fast on hard accelleration. 
But now it is.


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## warmerwagen (Aug 10, 2003)

*Re: (warmerwagen)*

Let me make a little noise here!








I got it to run perfect! As i was digging into this, I rmembered that i had changed the FPR. I checked and it was he worng part number. I swapped that at also trying to get it to run. 
Well, putting Bosch 0 438 161 010 in did the trick. 
The engine cold starts and warm starts instantly, runs smoothlty, and has more power than it ever had. 
So , I drove up to the license agancy yesterday to transfer the title . Guess what?
The title I have is no good. The seller gave me a bill of sale, and the title she was supposed ot surrender to the DMV, she sent to me instead, and then got another title, and has had this title over 3 1/2 years.
I'm mailing a DMV form to the seller tomorrow. They have to notarize them and mail back with the title. 
If I don't hear from them in 30 days, I'll have to sue in small claims.
So, now I don't have a car to drive after all this, which now has me turning my attention to the 84 Westfalia, which I'm reconditioning for resale-looks like i have to finish tthe dash wiring and take it up for registration.
Thanks for your help- I might not have found the problems without you.


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## chois (May 12, 2000)

Glad you are progressing with your saga.
Did I read correctly that you swapped an FPR for an 86 CIS-E car for one for an 87 CIS-E car? They should provide the same pressure. Maybe one was faulty.


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## NA 8v for life (Apr 11, 2007)

*Re: Engine won't run with temp sensor plugged in (warmerwagen)*


_Quote, originally posted by *warmerwagen* »_
Only experienced tech answers please.


wow... if you want that go to a legitimate mechanics website and pay the money for their advice, Beggars cannot be choosers IMO. I just stopped reading when I got to that point, no sense attempting to help someone with that attitude.


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## ziddey (Apr 16, 2006)

*Re: Engine won't run with temp sensor plugged in (NA 8v for life)*

you bumped an old thread to say that? sheesh


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