Intermittent Starting and Power Loss 93 Cabriolet - Volkswagen Forum - VW Forums for Volkwagen enthusiasts


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Old 07-25-2017, 09:39 AM
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Default Intermittent Starting and Power Loss 93 Cabriolet

Over the last few weeks I've been having an intermittent starting problem. The car will crank and crank but not start. Sometimes it will start after cranking a long time or after multiple attempts.

Problems and Symptoms:
-Intermittent starting problems
-Sudden loss of power while driving (engine drops down to idle and won't rev up. Has trouble running at all)
-Doesn't seem to be affected by humidity
-Can go hours or a week between problems. Runs great 95% of the time

What I've done within the last year:
- replaced both fuel pumps and fuel filter
-replaced spark plug wires and checked spark plugs
- cleaned electrical connections on ignition coil

Testing I've done while having problems (using my VW service manual as a testing reference):
-Tested for fuel pressure. Pressure was good so not a fuel problem
- Checked for spark before plugs. Not getting consistent spark. Sends one or two sparks then nothing
- Checked for primary power to ignition coil (negative to ground). Ignition coil was not getting power.
- Checked resistance across the ignition coil. Fell within the specified range.

Based on my service manual I suspect it's either a bad ignition switch or wiring harness. I'm also wondering if it could be a bad computer. Any suggestions on further testing or what the problem might be would be awesome! Thanks!
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Old 07-26-2017, 07:02 AM
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First post normally go in introduction!!!

Its hard to diagnose problems on the web.

A 93 model you can't use VAG-COM\VCDS without you use the 2x2 adaptor.

The other thing is if it has a 109 relay which do go faulty you can crank it all day and it will never start. Its the main power relay for the ecu. You should keep a spare relay in the car just in case.


Please tell us your car spec in your signature
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Old 04-09-2018, 05:40 PM
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Did you ever find a cause or solution to this problem? My 92 cabby just started exhibiting the same "sudden loss of power" issue. Road grade doesn't seem to matter, though originally I thought issue manifested only when going uphill.

The car starts solid, and runs fast & fine when driving; but there's a periodic, yet regular, loss of engine power for an interval of 30-40s, after which the engine/power suddenly kicks back in and car again drives fine?!

When in neutral and with foot on pedal, the engine will initially hit a RPM, then fall back down to idle; then ~20-50s later jump back up to the original RPM ... with no change in pedal input.



Quote:
Originally Posted by Pepe24 View Post
Over the last few weeks I've been having an intermittent starting problem. The car will crank and crank but not start. Sometimes it will start after cranking a long time or after multiple attempts.

Problems and Symptoms:
-Intermittent starting problems
-Sudden loss of power while driving (engine drops down to idle and won't rev up. Has trouble running at all)
-Doesn't seem to be affected by humidity
-Can go hours or a week between problems. Runs great 95% of the time

What I've done within the last year:
- replaced both fuel pumps and fuel filter
-replaced spark plug wires and checked spark plugs
- cleaned electrical connections on ignition coil

Testing I've done while having problems (using my VW service manual as a testing reference):
-Tested for fuel pressure. Pressure was good so not a fuel problem
- Checked for spark before plugs. Not getting consistent spark. Sends one or two sparks then nothing
- Checked for primary power to ignition coil (negative to ground). Ignition coil was not getting power.
- Checked resistance across the ignition coil. Fell within the specified range.

Based on my service manual I suspect it's either a bad ignition switch or wiring harness. I'm also wondering if it could be a bad computer. Any suggestions on further testing or what the problem might be would be awesome! Thanks!
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Old 04-15-2018, 11:39 PM
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Yes I did! My symptoms were actually a combination of two problems. The intermittent power loss you are describing sounds exactly the same as the as the symptoms I was experiencing, and they were so intermittent that the problem was almost impossible to diagnose. The intermittent power loss issue turned out to be a bad relay switch for the digifant control unit. I put a link to the relay diagram below. The digifant control relay is in position 1, and has the number 53 on it. Autozone had it for under $10.

Relay diagram: http://www.cabby-info.com/images/Ele...3FusePanel.png

The hard starting problem turned out to be a failing ignition switch.

Hope that helps and good luck!
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Old 04-16-2018, 03:03 PM
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Thanks for this info; in my case it turned out to be the AFM (air fuel meter); new one cleared up the issue. But I'll keep your info in mind in case needed in future; in particular, might be a good idea to buy a spare digifant control relay; I searched autozone for "digifant control relay" but got no hits, do you happen to have a link or part #? The part "141951253b" from cabbyinfo didn't return any hits, either.

Quote:
Originally Posted by Pepe24 View Post
Yes I did! My symptoms were actually a combination of two problems. The intermittent power loss you are describing sounds exactly the same as the as the symptoms I was experiencing, and they were so intermittent that the problem was almost impossible to diagnose. The intermittent power loss issue turned out to be a bad relay switch for the digifant control unit. I put a link to the relay diagram below. The digifant control relay is in position 1, and has the number 53 on it. Autozone had it for under $10.

Relay diagram: http://www.cabby-info.com/images/Ele...3FusePanel.png

The hard starting problem turned out to be a failing ignition switch.

Hope that helps and good luck!
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  #6  
Old 04-16-2018, 10:27 PM
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Location: Wisconsin
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Glad you got the issue fixed! I couldn't find it Autozone's website either but they found a cross-referenced part for me when I went to the store in person. The relay was made by BWD, part number R3024.

I also found one (several people are selling them) on ebay using the part number 141951253B from cabbyinfo, linked here: https://www.ebay.com/itm/281665868895.
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  #7  
Old 05-01-2018, 02:42 PM
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Default 1992 Cabriolet regularly loses engine power

Rats ... the problem has returned - here's the story to date, appreciate any advise or leads on this.

The car starts solid, and had been running fast & fine when driving. Starting a few weeks ago, though, there has been a periodic, yet regular, loss of engine power for an interval of 30-60s, after which the engine/power suddenly kicks back in and car again drives fine.

When in neutral and with foot on pedal, the engine will initially hit a RPM, then fall back down to idle; then ~30-60s later jump back up to the original RPM ... with no change in pedal input.

When driving around town - again, car drives fine for a space, until it loses practically all power and is inching along at <10mph; after a minute or so, suddenly power is restored and car runs like a champ for a minute or two, until the problem recurs.

My mechanic - after checking voltage throughout engine components - narrowed the issue to the air mass sensor - I believe he said it was outputting voltage that wasn't in spec. Sure enough, after installing a rebuilt AFM unit, the car again ran solid and without issues.

Until late last week ... after having driving perhaps 200 miles w/the rebuilt AFM, the problem started up again. So either the AFM was a red herring, or there is some other root cause that's at play, possibly causing the AFM to go bad.

Background info...
Car had an ABA engine swap performed in 2004; since then, <5k miles has been put on car.
  • ABA 2.0 Shortblock (from 1999 [email protected] miles), bored to 2.1
  • Digifant 1 (CA version) fuel injection system / ECU
  • GTI "big valve Digifant hydro" 1.8 head, ported & polished
  • 83.5mm piston kit (from A3 2.0 8v)
  • OEM HD valve springs from Audi turbo
  • BRT custom-grind 266 camshaft (from Bugformance)
  • ABA Distributor
  • stock ABA crank (magged/polished)
  • 10.3 compression
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