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1987 tsi runs fine till operating temp then misses and want to die in boost?


questtuner82
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So after two years of my 87 tsi sitting in storage and some work being done through the 2 years I finally had to put it on the road as my daily driver. Now it's having issues and I have no clue what it is. Any help? It runs great and boosts great the first 20 minutes of driving it from cold start but as soon as it reaches full operating temp it starts to miss and wants to die out in boost and gets worse the longer u drive it. Seems like it's losing fuel pressure or fuel pulse kinda like a fuel cut or something. It's mostly all stock just a Walbro pump and manual boost control and hard pipes any help would be great. Has a new tune up plugs wires cap rotor and a accel coil what is going on??????
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Have you gone and downloaded the service manuals yet? If not you can grab a pdf version at www.starquestgarage.com. As far as your issues go I'm sure some members more knowledgable than I will chime in. Maybe test your cts and see if its within spec and correctly installed?

 

Allen

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Not to sound like a dummy but what is a cts? Coolant temp sensor right? Also that could be an issue bc the fans don't kick on I had to wire them to a toggle. Also the p/o did an egr delete and did the vac line delete. There's like only 3 or 4 vac lines now
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It sounds like the previous owner did some poor maintainance / repairs. I would really suggest you go download the service manuals and then go over the engine wiring and vacuum system. It sounds like you have some things connected incorrectly.

 

Also yes CTS = coolant temp sensor. That sensor is important and greatly effects how well it runs.

If your fans are not turning on it has nothing to do with the CTS, those are instead controlled by the thermo switches that are threaded into the radiator.

 

Allen

Edited by speedyquest
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I'm being told that as soon as the ecu goes into closed loop that's where the issue is and maybe look for boost leaks but I've already checked boost leaks and none are there. Only thing I can think of is fuel pump heats up and looses pressure or injectors heat up and don't spray but they were recently sonic cleaned and flowed
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How exactly did you check for boost leaks? Did you pressurize the whole intake system? And unless your fuel filters are clogged or the wiring for your pump has issues your pump would not heat up let alone enough to cause it to stop functioning correctly. As far as the injectors heating up that is definitely not an issue.

 

I think that the car goes into a "limp" mode when it does not detect the presence of the CTS sensor. That may very well be your issue among other things.

Edited by speedyquest
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Yes I checked for boost leaks thru the inter cooler piping the inter cooler to the throttle body. My buddy made a tool to use to pressurize the system with 25 psi of compressed air. I have no leaks at all. Also in some chevy vehicles with a external fuel pump they had issues where u test fuel pressure at start up and it's in spec but as u leave it run the fuel pressure would drop. This was happening with my cousins bonneville and we never could figure it out till chevy dealer told us to test fuel pressure while the car has been running for at least 20 mins and sure enough about 25 minutes later the fuel pressure dropped from 35 to 15. As it ran it got worse till the car would stall at 5 psi fuel pressure. Not saying this is happening with mine but till I get fuel gauge to test won't know. I'm thinking it's the coolant sensor putting the car in limp mode as about 20-25 minutes sounds right in spec with the car going into closed loop
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  • 3 weeks later...
Mine did the same thing.. I know this post is about 20 days old but my CTS wiggled around in circles inside the sensor when i touched it the inside has came loose and now it wont ground itself out and it goes into closed loop and will not boost after she is full temp. put a new sensor on and boom it runs like a champion again. To bad I was trying to sell the car and this happend on a test drive the guy looked at me like I was a crook, it wouldnt boost and I told him it ran great lol... Its as if the car knows I was trying to sell it.. it doesnt wanna go out of my garage lol
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it sat for 2 yrs?did it run fine before it sat in storage?there's part of the problem.my guess.sensors don't,shouldn't go bad just sitting,maybe its possible but I don't believe it,my guess would be a bad injector.clogged by crap from it sitting with gas in it.in them...had that prob with mine after my injection mixer stuff lived in a sealed box inside for a few yrs,runs fine warming up since ecu richens.once warmed up and back to normal flow isnt enough fuel....secondary prob same condition,if wasn't from the gas in the injectors could been fro fuel in line or tank or filter even.thats my guess based on my own experience and headaches,check all the other stuff as mention if ya want but id look to injectors first.
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Does the sensors prong spin when you try to move it if so its not getting a groung and not sending a singal to the ECU. I wouldnt think it would be something as simple as a CTS but I would try anyway..ps when you go to take it out and the prong spins odds are the sensor will break in half in your water neck housing {happend to me} you have to take the water neck off and back it out with a needle nose plyers it sucked really bad and took around 40 mins...why do these hold so much antifreeze geez
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It's most likely your fuel pumps having a hard time sending fuel because of a filter is semi clogged or something.

After a while the pump will over heat and not pump fuel as good. The wiring that powers the pump is quite small so they can over heat with a aftermarket pump that's working hard . Just a thought because of my experiences over the years.

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I have another topic on here about fuel regulator questions. If u read that topic ul see that the car has new cts new regulator new fuel pump with the relay/rewire ul see it also has fresh sonic cleaned and flow tested injectors and new fuel filter. Has new remanned turbo application dizzy. Also a remanned mass air flow sensor. I've changed the knock box and eci in the car with ones that came out of a good running 87 tsi. As of right now the car seems to be running ok but it does have a bad o2 sensor. The eci is pulling a tps and o2 code but the tps was tested and passed sweep test good. Did a tps isc reset and the tps code came right back as soon as I fired it and revved it a couple times
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There's like 5 screens and filters starting at the in tank sock. If it's collapsing from tarnish ect it's gonna run really weird.
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Also the car has a new tank new in tank filter new pickup tube and no prefilter before the fuel pump other than the one intank the only filter in the car is the one under hood. Also all fuel lines are new with stainless braided fuel lines from fuel pump to filter and to the mixer from filter. Return line is the same also. I'm now getting just the o2 and tps codes from the computer. The tps passed ohm sweep test great and the car idles at .5volt but at full throttle I go to 7.1 volts not the 5volt that is what the car should have
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  • 4 weeks later...
FIXED!!!!!! After driving myself and some ppl nuts with this car I started doing a lot of digging and a lot of off the side of the road testing when the car starts it's issue. After all kinds of tests I found out that my new "junk" accel coil was the culprit. This oil filled canister was split at the weld and leaking it's oil coolant out causing the coil to overheat and short out. Installed a new coil and it runs like a new car! But now I decided to hotrod the car for a bit and something is locked up in the drivetrain. The tranny is done for as the case is cracked and it's jammed in third but seems like the rearend is locked up also. The rearend was rebuilt 2 years ago with a 4.22 gear swap and literally has 275miles on it now. I think it grenaded itself never any issues or noises but a little clunk when shifting gears never thought it was an issue but now I do. Posted a new topic. Anyone know what it may be?
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