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Horrible Engine Bucking - 93 N* Allante


Ed Hall

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I checked the resistance on each injector and they all were around 13 ohms. I then did the injector drip test by turning on the key but did not find any dripping injectors. I then put the intake manifold cover back on and went to start the engine but it locked up. Apparently, the engine got flooded. I don't want to take the spark plugs out so I was wondering how much time it will take for the gas to evaporate.

Explain locked up, that sounds ominous

The starter turned the engine around probably 30 degrees and came to a stop. So much gas went down the intake manifold that it locked the engine up. I don't want to take the spark plugs out so I want to know how long it takes for the gas to evaporate enough that I the engine can become free. Some how when I did the injector drip test with the key on, gas filled the intake manifold rather than pressurized the injection system.

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Explain locked up, that sounds ominous

The starter turned the engine around probably 30 degrees and came to a stop. So much gas went down the intake manifold that it locked the engine up. I don't want to take the spark plugs out so I want to know how long it takes for the gas to evaporate enough that I the engine can become free. Some how when I did the injector drip test with the key on, gas filled the intake manifold rather than pressurized the injection system.

I agree with BBF.

That sounds BAD. Hydrolock is a VERY BAD THING.

I don't think you have any choice at this point but to pull the plugs.

The liquid fuel has to be got out of the cylinders.

I hope it didn't bend any connecting rods or valves, which in a Hydrolock situation is very possible.

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Pull the plugs, disable the ignition and crank it to get the excess fuel out. This sounds like a bad FPR, isnt your FPR in the intake? Where did the fuel come from?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

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If you had the fuel rail out, how did fuel get into the cylinders??? I would pull all the plugs, unplug the ignition module and crank the engine to clear the fuel from the cylinders. There has to be unmetered fuel getting into the cylinders based on the description.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Pull the plugs, disable the ignition and crank it to get the excess fuel out. This sounds like a bad FPR, isnt your FPR in the intake? Where did the fuel come from?

Yes the FPR is in the intake. I installed a new AC Delco FPR about a year ago thinking it was defective but it made absolutely no change. Perhaps I should buy some other brand of FPR. I don't know where the fuel came from. When I lifted the fuel rail, one of the joints must have let go and let gas into the intake when I turned the key on to pressurize the system.

The engine did not fire as it cranked so hopefully I'm OK. If not, this 64k mile car will probably be melted down and turned into a new Toyota.

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I think your engine is probably OK - don't write it off just yet. I wouldn't replace the FPR again - the current one is probably OK. Pull the plugs, unplug the ICM and crank it over to clear the cylinders. Then any leaks in the pipes that may have dumped gas into the intake.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Pull the plugs, disable the ignition and crank it to get the excess fuel out. This sounds like a bad FPR, isnt your FPR in the intake? Where did the fuel come from?

Yes the FPR is in the intake. I installed a new AC Delco FPR about a year ago thinking it was defective but it made absolutely no change. Perhaps I should buy some other brand of FPR. I don't know where the fuel came from. When I lifted the fuel rail, one of the joints must have let go and let gas into the intake when I turned the key on to pressurize the system.

The engine did not fire as it cranked so hopefully I'm OK. If not, this 64k mile car will probably be melted down and turned into a new Toyota.

You have to be careful with the earlier Northstars when taking the cover off. It isn't just a beaty cover as on the later vintages. That cover is a part of the intake so don't try to start when the cover is off because you'll have full throttle...and when pressurizing the fuel system NOTHING keeps it in place. Both the injectors and the fuel lines are kept in place by the cover..perhaps you encontered fuel leaking from the "main line" or around the fpr?

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Ed, have you ever cleaned the phenolic plates under the intake? They can carbon up real bad and plug the mouse holes, it can also cause a vacuum leak if the gaskets are bad or not seated properly. Your latest problem with the hesitation at light throttle and no codes reminds me of a bad coil. Mine did the hesitation thing for about 6 months. The problem was that the hesitation was not consistant therefore it did not show up on the power balance test until the coil crapped completly out. You might try switching out coils until you find the bad one. Just do NOT try to wiggle the plug wires on the coils while the engine is running. Trust me, they will light you up. :wacko: I also had problems later with a vacuum leak. Mine was between the engine and firewall on the throttle body side in the Evap lines. Follow the vacuum hose from the throttle body and you will run into them.

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Ed, have you ever cleaned the phenolic plates under the intake? They can carbon up real bad and plug the mouse holes, it can also cause a vacuum leak if the gaskets are bad or not seated properly. Your latest problem with the hesitation at light throttle and no codes reminds me of a bad coil. Mine did the hesitation thing for about 6 months. The problem was that the hesitation was not consistant therefore it did not show up on the power balance test until the coil crapped completly out. You might try switching out coils until you find the bad one. Just do NOT try to wiggle the plug wires on the coils while the engine is running. Trust me, they will light you up. :wacko: I also had problems later with a vacuum leak. Mine was between the engine and firewall on the throttle body side in the Evap lines. Follow the vacuum hose from the throttle body and you will run into them.

I cleaned the mouse holes about 2 years ago. I replaced my coils and ICM about a year ago with a used unit. I still have 3 good coils from replaced old unit that I could use. I'm going to try restarting the car again when I return home tonight.

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Update:

The engine is fine but still starts hard when warm.

I ended up pulling the plugs and let the car sit overnight to let as much gas evaporate as possible. I then put the plugs back in and started the engine. It started up but made a cloud of white smoke. The smoke smelled like raw gas. I’m thinking that the CAT got filled up with raw gas. The smoke cleared up after a few minutes and the exhaust is now clean.

I’m still thinking that I might have a leaking injector. However, I’m not sure how to test for this. I need ideas on how to test for this on a 93-94 Northstar. Unfortunately, lifting the rail and turning on the key to pressure the system just dumps raw fuel down on these earlier engines.

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I am still looking for ideas on how to easily test for a leaking injector. I tried lifting the injector rail but that dumped gas down the front drivers side cylinder. I really believe that this is my problem but I have no way to identify which injector it is.

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I'm not that familiar with the Gen 1 Northstar so bear with me. Lifting the fuel rail shouldn't cause gas to drip unless there is a leak in the rail or injectors. When you remove the top of the intake, isn't the fuel rail, 8 injectors, and the FPR visible? Can the rail be lifted along with all the injectors so that any dripping fuel doesn't run down into the lower part of the intake?

Does your car have the nylon fuel rail? Maybe it is split and leaking?

The only other method I know of is to use the Kent-Moore tool to activate an injector for a precise time (fraction of a second) and record the pressure drop for each injector. Once you find one that doesn't hold or shows more of a pressure drop than the others, you've found the leaker. But considering the price of the Kent-Moore stuff (they're not nicknamed "Spent-Moore" for nothing...).....

Maybe the bad injector is the one that poured fuel into the front drifer's side cylinder?

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I'm not that familiar with the Gen 1 Northstar so bear with me. Lifting the fuel rail shouldn't cause gas to drip unless there is a leak in the rail or injectors. When you remove the top of the intake, isn't the fuel rail, 8 injectors, and the FPR visible? Can the rail be lifted along with all the injectors so that any dripping fuel doesn't run down into the lower part of the intake?

Does your car have the nylon fuel rail? Maybe it is split and leaking?

The only other method I know of is to use the Kent-Moore tool to activate an injector for a precise time (fraction of a second) and record the pressure drop for each injector. Once you find one that doesn't hold or shows more of a pressure drop than the others, you've found the leaker. But considering the price of the Kent-Moore stuff (they're not nicknamed "Spent-Moore" for nothing...).....

Maybe the bad injector is the one that poured fuel into the front drifer's side cylinder?

Kevin,

I'm going to have look at it more closely. When I lifted the fuel rail, I had no ideas what was going on until I went back in to start the engine and it hydrolocked. I do remember finding it odd to hear the fuel pump making a higher pitch whine than I normally hear. My car has a nylon fuel rail so I'm going to check for splits and cracks.

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I agree, there is no reason that lifting the fuel rail should dump fuel. Is your fuel rail metal or does it have the plastic plumbing on it?

When you pull up your fuel rail can you see the injector tips? You should have seen the injectors leaking.

Is this engine different than the 95, I can get a FSM for a 95 from my friend and have a look

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I'm not that familiar with the Gen 1 Northstar so bear with me. Lifting the fuel rail shouldn't cause gas to drip unless there is a leak in the rail or injectors. When you remove the top of the intake, isn't the fuel rail, 8 injectors, and the FPR visible? Can the rail be lifted along with all the injectors so that any dripping fuel doesn't run down into the lower part of the intake?

Does your car have the nylon fuel rail? Maybe it is split and leaking?

The only other method I know of is to use the Kent-Moore tool to activate an injector for a precise time (fraction of a second) and record the pressure drop for each injector. Once you find one that doesn't hold or shows more of a pressure drop than the others, you've found the leaker. But considering the price of the Kent-Moore stuff (they're not nicknamed "Spent-Moore" for nothing...).....

Maybe the bad injector is the one that poured fuel into the front drifer's side cylinder?

Kevin,

I'm going to have look at it more closely. When I lifted the fuel rail, I had no ideas what was going on until I went back in to start the engine and it hydrolocked. I do remember finding it odd to hear the fuel pump making a higher pitch whine than I normally hear. My car has a nylon fuel rail so I'm going to check for splits and cracks.

I'm going to bet you will find a split in the hose or a leak in there. Since the fuel rail is under the top portion of the intake, the excess fuel is getting sucked into the mix which would affect the performance of the engine and the fuel economy.

I agree, there is no reason that lifting the fuel rail should dump fuel. Is your fuel rail metal or does it have the plastic plumbing on it?

When you pull up your fuel rail can you see the injector tips? You should have seen the injectors leaking.

Is this engine different than the 95, I can get a FSM for a 95 from my friend and have a look

Milke, the 95 engine has the plastic intake and beauty cover - completely different than the 93-94 engine.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I agree, there is no reason that lifting the fuel rail should dump fuel. Is your fuel rail metal or does it have the plastic plumbing on it?

When you pull up your fuel rail can you see the injector tips? You should have seen the injectors leaking.

Is this engine different than the 95, I can get a FSM for a 95 from my friend and have a look

My rail is plastic. I could only get the passenger side of the rail to lift up. I could see the injector tips only on the passenger side. On the drivers side, the injectors were just high enough to let me feel the tips.

Yes, this engine is different from the 95. Only 93 & 94's were the same.

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I agree, there is no reason that lifting the fuel rail should dump fuel. Is your fuel rail metal or does it have the plastic plumbing on it?

When you pull up your fuel rail can you see the injector tips? You should have seen the injectors leaking.

Is this engine different than the 95, I can get a FSM for a 95 from my friend and have a look

My rail is plastic. I could only get the passenger side of the rail to lift up. I could see the injector tips only on the passenger side. On the drivers side, the injectors were just high enough to let me feel the tips.

Yes, this engine is different from the 95. Only 93 & 94's were the same.

I actually knew that, but was just checking, I am miffed as to how you could have dumped fuel, could your FPR be dumping fuel?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I actually knew that, but was just checking, I am miffed as to how you could have dumped fuel, could your FPR be dumping fuel?

Well, I didn't look very closely at the design of this thing but maybe as I lifted one side of the rail, the connection where the other side of the rail is connected to got compromised. Isn't the rail connected to the output of the Fuel Pressure Regulator? I possibly should have lifted the FPR and the unit as a whole.

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Picture of 93 Nortstar Intake Manifold and Fuel Rail

8470H041L.gif

1. Disconnect the negative battery cable.

2. Disconnect the number 1 and 2 fuel pump relays.

3. Properly relieve the fuel system pressure.

4. Remove the intake manifold top cover assembly.

5. Disconnect the intake manifold electrical connectors.

6. Remove the fuel rail assembly with the injectors intact from the intake manifold.

7. Separate the fuel injector from the fuel rail.

NOTE: Wrap a shop cloth around the fuel lines to collect that leaks when disconnecting the fuel lines.

Remove the O-ring seals from the injectors and discard.

To install:

1. Install new injector O-rings. Lubricate lightly with engine oil.

2. Connect the injector(s) to the fuel rail assembly.

3. Carefully, install the fuel rail assembly to the intake manifold.

4. Install the intake manifold cover and tighten the bolts in proper sequence to 106 inch lbs. (12 Nm).

5. Connect the negative battery cable.

6. Start the engine and check for fuel leaks.

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Even though the manifold is a two piece design, lifting the fuel rail up should not cause fuel to flood the intake. I think you have a leaking connection under the top cover or split nylon fuel hose. Some sort of leak is allowing unmetered fuel to enter the intake/combustion chamber.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Even though the manifold is a two piece design, lifting the fuel rail up should not cause fuel to flood the intake. I think you have a leaking connection under the top cover or split nylon fuel hose. Some sort of leak is allowing unmetered fuel to enter the intake/combustion chamber.

Agree. The big difference between -93/-94 and later is that leaks around the FPR, pipes and hoses etc will be drawn into the cylinders. Any missing o-rings at the connections?

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I am still looking for ideas on how to easily test for a leaking injector. I tried lifting the injector rail but that dumped gas down the front drivers side cylinder. I really believe that this is my problem but I have no way to identify which injector it is.

As mentioned before it is easy on the later Northstars but the intake plastic cover holds the rail in place. No cover = loose rail. Try to clamp down the rail at the fuel inlet and outlet when pressurizing to avoid fuel spraying all over!

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I agree, there is no reason that lifting the fuel rail should dump fuel. Is your fuel rail metal or does it have the plastic plumbing on it?

When you pull up your fuel rail can you see the injector tips? You should have seen the injectors leaking.

Is this engine different than the 95, I can get a FSM for a 95 from my friend and have a look

There is a chance that one of the o-rings is bad/missing after R&R.

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Any progress Ed? :)

The u-joint on my 82 Suburban went out so I replaced it and decided that I had enough on car repair this week. One thing nice about the Suburban that I'm constantly reminded of when I work on it is how easy it is to work on and in addition, it gets better fuel economy than all my Cadillacs. Because of those 2 things, I refuse to let the beast go. The Allante runs the same as before (hard warm starting, rough idle when warm) so I'll continue the ongoing effort to identify the problem shortly.

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