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914World.com _ 914World Garage _ Still sputter on decel

Posted by: Nemo914 Sep 24 2003, 03:19 PM

OK, I have posted before on help with a sputter (or light "backfire") on deceleration with my 1972 1.7. It happens at around 2-3k RPM and is worse when loaded on decel. Sounds like "phfft, phfft, phfft".

Most of you suspected an exhaust leak, and in agreement, I replaced the heat exchangers with SS, with new copper seals and the works. The stock muffler is also new. It all seems solid as a rock, and I don't think it could still be leaking.

In George Hussey's "tech tips" (I know, everyone's favorite dude) it says, "If your 914 "pops" or backfires when suddenly backing off the throttle, suspect..."

1. Leaking muffler or heat exchanger to head connection
2. Fuel pressure too high
3. Throttle switch bad

But, I have had it tuned by a reputable shop, fuel pressure checked, and installed a new throttle switch. Even tried different octane gas.

It is a completely stock FI 1.7. It starts, idles and runs perfectly, except for this!! It is embarassing to drive as people admire the car and then laugh as it sputters and coughs on decel

Does anyone have any other ideas?? I have driven this car since I was 16 (21 years to date) and it never did this until about a year ago. Any help would be appreciated.

Here are a few phots just because we all like pictures:

Attached image(s)

Posted by: Nemo914 Sep 24 2003, 03:20 PM

Another:

Attached image(s)

Posted by: ArtechnikA Sep 24 2003, 03:36 PM

is that the model that's supposed to have the vacuum retard in the dizzy ? if it is, you might check to see that's working - that's the engine management regime it's supposed to help...

beyond that i donno...

Posted by: robby750 Sep 24 2003, 04:04 PM

I have no idea what the problem might be, but that sure is a clean engine!

Posted by: Brad Roberts Sep 25 2003, 01:56 AM

This is the decel valve. It could possibly be bad or leaking. You can easily block it off for testing (plug the lines running to it)

Let me know what you find.

B

Posted by: Nemo914 Sep 25 2003, 05:30 PM

OK, will ops check the decel valve.

Also, can the vacuum unit on the distributer fail? If it failed, what would be the result? Can they be purchased alone or does it come with the distributer?

How about the ECU adjust. Could it be set wrong?

Thanks,

Nemo914

Posted by: fiid Sep 25 2003, 05:47 PM

Not much can be done about the ECU - it's probably not dead though if the car is running properly the rest of the time.

You can do a complete checkout of the fuel injection system by following Kjells guide to D-Jet maintainence.

http://www.914fan.net/djet.html

This will also tell you how the stuff is supposed to work, if you are interested in the theory of it.

Probably not the root cause, but checking the valve clearances is always a good idea.

Also, you might want to get an Optima Battery just so that you don't get hellhole rot ever, which is a terrible thing to happen to such a clean and fantastic looking car.

Fiid.

Posted by: Bleyseng Sep 25 2003, 06:39 PM

Hey, I was gonna suggest the Optima battery!
Check the decel valve by pluging the vacuum side hose to see if that helps.
If your ECU has the idle adjustment screw you can turn it a couple of clicks to richen the mix at idle. I suspect the problem is a vacuum leak somewhere which you should try to find. Look at those silly rubber elbows that crack and the engine vacuum hoses and connections.

Nice clean engine and bay!!!

Geoff

Posted by: Bleyseng Sep 25 2003, 06:48 PM

These crack....

Attached image(s)

Posted by: joea9146 Sep 26 2003, 11:48 AM

Have u tried to search for an exhaust leak recently.... Put the car up on Ramps...
make sure it is well secured. Start it up when it is cold get a piece of vaccum hose
about 3 feet long.... hold one end to your ear get under the
car now search all the joints and connections for an exhuast leak.

Posted by: Nemo914 Sep 26 2003, 01:46 PM

Good idea on the leak. I am pretty sure I put everything on tight, but maybe something is still leaking out at the head. Could it be warped or something? Would high temp silicone help? I only used it to seat the copper rings. I didn't use any before the heat exchangers went up in there. It sure sounds like an exhaust leak and the symptoms fit. I will keep you posted.

Thanks!

Posted by: Brad Roberts Sep 26 2003, 02:05 PM

I coat the backside of the copper gasket and I file the HE's flat and put high temp silicon on them as well.

If you have SSI's... make damn sure you bought them new.. people break the ears off and have them rewelded 99% of the tim incorrectly causing them to no seal properly to the gasket.

B

Posted by: Nemo914 Sep 27 2003, 06:53 AM

Where is the best place to get them new and how much $$$$?? If these are bad, I will be in the market for new ones.