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Registered User
Join Date: Jun 2019
Posts: 4
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Instant "unstable combustion"
His 911 made in 1972
The engine has been changed to a 1989 3.5L engine, before he buys The situation of trouble Idling is very stable "Strong Blipping" causes misfires I can run at slow acceleration A little more acceleration will cause a misfire. Light afterfire also occurs at the same time Ignition time at idling is around 0 degrees Fuel pressure at idling is 2.3 kgf / cm2 It rises to 2.6 kgf / cm2 when the throttle is opened Checked Change to new fuel ... No improvement Plug cleaning ... No improvement Replacement of ignition coil ... No improvement Fuel filter replacement ... No improvement MAF sensor replacement ... No improvement O2 sensor replacement ... No improvement Change to another DME unit ... No improvement Replace 2 crank sensors with new ones ... No improvement Next time I will try to replace the fuel pump Fuel pressure too low? What is wrong with the pressure regulator? ...found it now The hose to the fuel pump was connected to the return side of the fuel tank. ...    
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06-11-2019, 07:58 PM
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Mighty Meatlocker Turbo
Join Date: Apr 2016
Location: North TexASS
Posts: 18,537
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Zero degrees ignition advance at idle is not correct for any internal combustion engine that I've ever seen (would result in terrible throttle response and poor running in general). Do you know what the factory advance specs are for your ignition system?
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06-11-2019, 08:33 PM
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Registered
Join Date: May 2008
Location: Grapevine, TX
Posts: 1,106
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1989 would have been 3.2L has this engine been modified to 3.5?
Those fuel pressures appear to be correct for the 89 3.2L. Is this a new issue? Has the engine been running correctly, and now not, or is this a fresh install? |
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06-12-2019, 06:45 AM
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Registered User
Join Date: Jun 2019
Posts: 4
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I had the same idea.
However, it is also written in the manual. 
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06-12-2019, 06:52 AM
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Registered User
Join Date: Jun 2019
Posts: 4
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It was a mistake of 3.2 L engine.
He went directly to the body shop after he bought it. After the repair of the car body was completed, it was only a few moves that he drove. It was because the car inspection had not been completed. It is unknown how much the previous owner enjoyed the 911 performance. |
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06-12-2019, 07:01 AM
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Registered
Join Date: May 2008
Location: Grapevine, TX
Posts: 1,106
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Quote:
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06-12-2019, 07:33 AM
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Registered User
Join Date: Jun 2019
Posts: 4
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It was the failure of the DME unit.
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07-29-2019, 08:25 PM
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Diss Member
Join Date: Jul 2002
Location: SC - (Aiken in the 'other' SC)
Posts: 5,022
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The biggest thing I can add to the original troubleshooting:
- Don't Replace Parts. TEST! Throwing parts that are easily testable at a problem makes no sense.
__________________
- "Speed kills! How fast do you want to go?" - anon. - "If More is better then Too Much is just right!!!" - Mad Mac Durgeloh -- Wayne - 87 Carrera coupe -> The pooch. |
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07-30-2019, 01:14 AM
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Registered
Join Date: Dec 1999
Location: Novato, CA
Posts: 4,740
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It could be something as simple as a bad distributor cap. Misfire test was a good enough for me.
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07-31-2019, 05:10 PM
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