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Discussion Starter · #1 ·
Greetings, I am the proud owner of a 1977 Seville, 350 Rocket engine 5.7L V-8 EFI. In May of 2021 I drove the car from Tampa to Orlando Florida which is about an 1 hour and 15 mins. The car drove without any problems on the hi-way. The only minor nagging problem was if I stop some where like a store or gas station, the car will start up with no problem but as soon as I put it in drive or reverse to take off the car suddenly dies on me. I will then restart the car and after 2-3 attempts I eventually get the car back on the road and it drives very well. The car does not die or stall at traffic lights.
After driving the car in May 2021 I got lazy and busy with other things in life, I waited to October 2021 to start the Seville parked in the garage. At that point it started putt-putting and the was mucho smoke coming from the dual tailpipes. The car was rough idling and if I remove my foot from the gas pedal the car would die after about 5-7 seconds. The smoke from the tailpipe had a heavy gas smell. I discovered fuel mixed in with the engine oil.
In my attempts to repair the problem, I changed all 8 sparkplugs (did not change wires), I changed the oil and oil filter, I changed the fuel filter, I cleaned out the throttle area on the carburetor. I also disconnected all 8 fuel injectors and put a analog ohm meter on each one and the readings were the same with all 8 injectors. (that tells me that the injectors are good).
Not sure what to check next, I do not want to start throwing part$$$ at the problem, that can get expensive. I tried to upload a 23 second video but the file was too large, So I had to set up this link instead. The link is safe!

IMG_4459a.wmv

Please observe the smoke and the engine audio, this may help you guys diagnosis my problem.
Even though I checked the fuel injectors with my meter my spidey senses still tell me that the problem is the FI. I really appreciate your feedback!
 

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I would check the following first:
-Is the vacuum line going to your ECU disconnected, loose or cracked? << The MAP sensor is inside the ECU and if the vacuum supply is missing or weak the ECU thinks the car is at WOT and will try to supply fuel as such.
-Check resistance of your coolant and air temp sensors. I will post a resistance versus temp chart. You can unplug them and verify they are good. If they fail with too low resistance the ECU will richen the mixture. You are having a pretty drastic issue so I don't think it's JUST sensors but they are easy to check and it's free to check them.
-If the car idles fine unplug the vacuum from the fuel pressure regulator. See if there's any difference. If there is NO difference the fuel pressure regulator is failing to get vacuum or has failed (not really common to fail. When you unplug it make certain to plug the line which you unplugged.
-Next is more difficult but if everything else checks out you could have leaking injectors which are failing to seal when they should be closed.

If the injectors are good the MAP sensor may have gone bad. There's a member of the forum "bcroe" who is an ECU expert. He's very reasonable and he can fix most ECU issues including the MAP sensor. The service manual essentially walks you through diagnosis and if everything else checks out the assumption is the ECU. Also please see the trouble shooting trees on the Cadillacseville org site here:


You should also have the blue and white book pictured below.

Scott
 

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Discussion Starter · #4 ·
Thanks for this info. I am going to look into a possible vacum leak and the MAP sensor issue. The sound of the car makes me think it could be a cracked head! (I pray not).
 

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I was responding above based on your description which made me think it's running very rich. You mentioned gas in the oil. Normally running rich would result in black smoke. I just watched your video and it's hard to tell. The sound almost makes it seem like there's an exhaust issue. If it is running rich let's see what you find when you check the items I mentioned. The vacuum hose condition and sensors can be checked with the car off. For the sensors you just need to know the actual coolant temp. If it sits overnight that should be pretty obvious.

If the sensors check out ok I would also check the terminals of the ECU plug. Terminals can become oxidized and sometimes cleaning the terminals can solve an issue. The diagnostic chart actually says to verify electrical connections first... although they never tell you which ones to focus on.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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I was responding above based on your description which made me think it's running very rich. You mentioned gas in the oil. Normally running rich would result in black smoke. I just watched your video and it's hard to tell. The sound almost makes it seem like there's an exhaust issue. If it is running rich let's see what you find when you check the items I mentioned. The vacuum hose condition and sensors can be checked with the car off. For the sensors you just need to know the actual coolant temp. If it sits overnight that should be pretty obvious.

If the sensors check out ok I would also check the terminals of the ECU plug. Terminals can become oxidized and sometimes cleaning the terminals can solve an issue. The diagnostic chart actually says to verify electrical connections first... although they never tell you which ones to focus on.
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based on your description which made me think it's running very rich.
I agree - very - VERY - VERY rich

You mentioned gas in the oil.

Normally running rich would result in black smoke. I just watched your video and it's hard to tell.
BLACK smoke is carbon - from a rich mixture - on a completely warned up engine -

that engine is stone-cold and it's absolutely DUMPING fuel -
I bet if you held a match to that exhaust - the fumes would burst into flames!
 
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