76 Riviera dies after starting

[fancy pants]

Hello all,

I have a 1976 Riviera, 2L FI which I purchased in July. Over the past month it consistantly dies after 4-5 seconds of idling. It starts up just fine - easily in fact, idles nicely for 4-5 seconds, then dies. I thought that it must be a vacuum issue, so I identified 2 bad hoses and replaced them. It ran fine for a week and then started with the same problem. If i disconnect the AFM, i can get it to start up and maintain idle. If I then let it warm up for a few minutes and reconnect the AFM, it will continue running and drive perfectly fine. At this point it will restart easily after shutting off, but the next day it will again die after 4-5 seconds. Revving the engine does not help. It looks like the AFM is clean and the needle moves upon starting, so I am guessing that is not the problem. I can identify no other bad vacuum hoses, other than those initially replaced.

One more bit of potentially relevant information (or not): I am trying to pass Oregon emissions, and thus far have failed twice. HCs are 800-900 and CO is 6%.

Thanks in adavance for your thoughts...


John Shepski, Portland
76 Riviera "Sonnenblume"
72 West "Frau Pfankuch" (for sale)
05 Golf TDI

[fancy pants]

An update...

Yesterday, upon starting the bus with the AFM detached, it would start fine and keep running after it was plugged back in. Today, no such luck.... It still starts up just fine without the AFM, but when it is plugged back in it dies immediately. I tried driving it without the AFM attached and it was difficult to keep from dying when throttle applied.

Any thoughts?

[chitwnvw]

So replacing the hoses made it run ok for a week?

[fancy pants]

yep. ran great. and yesterday it ran well after starting it without the afm attached and then pugging it back in before driving. today it will start up with afm disconnected, but it dies as soon as i plug it back in...

[bus71]

I would check temp sensor #2 located by #3 cyl. on head. Make sure it is clean and tight. Sometimes they loosen up. Good luck!

[fancy pants]

TS II is the same thing as the CHT sensor, right? Well, 2 others have told me to replace the CHT sensor, so I have ordered one from Bus Depot. After your response I checked the connection (it's the wire next to spark plug #3, right?), and it didn't seem loose at all. But, when i turned the key she started right up and ran beautifully! I think you are on to something... I'll let you all know whether I am home free, or whether this is just another false hope, but it sure looks like the right direction.

Thanks!

John

[Gypsie]

HMMMMM? Wiring integrity??? Continuity test??? Fint the connection point on the multipoint ecm module end and test continuity from one end to the other (with wire wiggling), maybe a break in the line, like a pair of cheap headphones. Might be an easy connector fix.

[vdubyah73]

Next time it does it give your double relay a couple raps with a screw driver handle. Sometimes they get sticky, the start side may work and then after it's running the run side is stuck, or you're starting on residual pressure in the lines and both sides are sticking

[fancy pants]

Thanks for all of the suggestions so far. It definitely seems to be related to the #2 temp sensor. There have been 3 instances over past 2 days where it has died immediately after starting, and jiggling the CHT sensor wire resolves it. Once it gets up to temperature, it will fire right back up and runs like a dream for the rest of the day. It died on me once while driving, but I had made the mistake of not letting it warm up fully before going. Jiggling the wire fixed it. I do have a new sensor on order, so I will let you know the results. I am also going to take Gypsie's advice and try to do some electrical detective work. It will be my first foray into electronics, so I am sure that I will need lots of help!

Looks like we are on the right track...

john