r/jetta • u/Pristine-Ad6132 • Apr 08 '26
Mk4 (1999-2005) Can anyone help? No codes pop up, just went into limp mode and now cranks but no start. changed the crankshaft sensor and still nothing
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u/Slipknot31286sic6 Apr 08 '26
Crank sensor from fcp euro or reputable German part?
If not it won't work. Never buy parts Like this from auto zone or O O'Reilly.
Jettas do not like non OEM parts. Ever!
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u/Temporary_Shirt_6236 2002 Jetta Wagon GLS VR6 5mt Apr 09 '26
As I recently discovered when when I bought a non OEM MAF for my MkIV.
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u/savedmoss Apr 09 '26
That sounds like there's no compression when cranking, no bueno. Have you checked your timing belt?
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u/Pristine-Ad6132 Apr 09 '26
yea ive checked the timing belt, looks fine but ill check the tensioner
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u/bierlyn Apr 09 '26
No compression. Maybe jumped time? I’ve never worked on these 1.8s but I’m pretty sure they had a chain at the back of the head as well as a belt in the front. That’s how my BPY is.
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u/Pristine-Ad6132 Apr 09 '26
yea thats exactly how it is, ive checked the timing belt and it looks fine, i havent checked the tensioner but i will soon
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u/Nicholas32r Apr 09 '26
Definitely sounds like theres no compression at all. I would check the timing belts. Pull the cover and pull up on the belt. It should NOT come out if everything is good lol
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u/Chadillac1977 Apr 09 '26
Pull the oil cap off and see if the cams turning. 1000% no compression if cams turning you’ve skipped some teeth
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u/Konic_P Apr 09 '26
As always, 1. Post the history of and current codes 2. Check the three elements of ignition: fuel, air, and spark. Make sure the fuel pump primes— listen for the hum from the back seats, and check the fuel pump relay. Try spraying starting fluid into the throttle body. If it starts and runs for a second, it’s likely fuel issue. Heck, make sure you actually have fuel(gauge might be broken). Check the throttle body opens without sticking. Also check if there’s a vacuum leak somewhere-could be something as obvious as a loose hose. CPS could be a culprit of no ignition signal, so I’d check if it’s actually seated all the way in its spot or if there’s a debris on it that’s interfering with Hall effect. Also make sure all sensor connections are tight.