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Desperate Mom Needs Help w/ Son's '85 Regal GNX

I’m hoping someone out there can assist. My son has been a car fanatic for years and works hard to support his passion. I’m praying there’s someone out there who can figure this out because no mechanic has been able to. A while ago, he bought a 1985 Buick Regal – Engine 1987 Grand National (GNX) 60 Trim turbo. It runs meth injection and Scanmaster programming. It has a heavy duty timing chain, professionally built.

Please read everything he and the mechanics have already attempted. From the bottom of my heart, I would appreciate anyone who can help him out! He’s so frustrated at this point and is forced (gasp) to drive around in his mother’s minivan while his Buick remains in the bay.

Problem: Car wasn’t originally revving past 3000 and now it won’t even fire up.

Tried: Every fuse, clean gas & fuel filter, every wire (no breaks), checked sparks (spark all around), new coil pack, new 02 sensor, new cam sensor, new crank sensor, new computer, cleaned out map sensor. Compression Test : Has 190 lbs.

Fuel: 60 lb injectors and runs right off idle (60 lbs all the way through)
Voltage & Fuel Pump are fine.
Been timed multiple times.

Not the engine because when it was running, it ran very smooth and had no issues, but it wouldn’t run past 3000. Wasn’t the turbo because the turbo doesn’t spool up before 3500.

Engine has been rebuilt.

Emissions have been taken care of.

Can’t get a code off the computer (doesn’t have any).
Checked readings on all wires with volt meter and all is fine. Scanmaster is fine.

Pulled apart the Cam sensor and made sure it wasn’t missing any teeth.

Not the throttle position sensor because it would fire up even with a bad throttle sensor.

New plugs and wires.

Car was built by Cotton Performance.

Thank you!

Key on, fuel pressure is ok? Cranking motor, do u get plug spark?

Stoveguy, my son says "Yes on spark and yes, 60 lbs of fuel. Thank you.

Two potential problems.
As to the engine not wanting to rev above 3000 RPM that could point to an exhaust restriction; assuming the engine just bogs down with no severe coughing and sputtering. This could easily be checked with a vacuum gauge.

As to not wanting to start (and seeing as how there is spark and sufficient fuel pressure) then the possibility of the fuel injectors not pulsing should be considered.
That could be due to lack of electrical power at the injector plugs or the injector grounds are not being opened and closed. The latter is controlled by the ECM.
With the engine being cranked over, one should be able to hear the injectors click with the use of a stethoscope. A Noid light could also be used to determine if they’re pulsing or not. Hope that helps.

Simple test- remove air intake duct. While someone is cranking over the engine with the gas pedal to the floor, spray starting fluid into the intake. Does it try starting? Only sputter and back fire or nothing at all? Post back.

I’m checking with my son on both suggestions. Thank you both!

Good luck, all these good suggestions are what a mechanic should know how to do…makes me wonder about the shop it’s at…

“Checked readings on all wires with volt meter and all is fine. Scanmaster is fine.”

Try a scope. A voltmeter won’t tel you anything about the pulses.

In addition to the failure to rev being caused by an inability to breath out or an insufficient fuel supply pressure, recognize that a failure to advance the ignition timing could also limit the ability to rev. I’m wondering why you’re assuming the Scanmaster programming is operating properly. Perhaps a bit of work with an analyzer and a good diagnostician would be a wise investment. Try a speedshop that races their own vehicles. Many regular shops won’t have the experience to diagnose an engine like this.

I’, also womdering what has been done to the heads. If the engine has been converterd to methanol, has the ability to breath in & out been modified accordingly? Details if you would please. If he’s running stock heads, breathing might be the problem.

Does it have a high lift/high duration cam? Have the push rods and springs been upgraded accoringly to allow the valves to open & close properly?

You ruled out the turbo so quickly, but has anyone actually checked to make sure the turbo’s shaft isn’t frozen? If it can’t spin, it will block air from getting to the engine.

"Engine has been rebuilt.

Emissions have been taken care of.

Can’t get a code off the computer (doesn’t have any).
Checked readings on all wires with volt meter and all is fine. Scanmaster is fine.

I hate to imagine what “Emissions have been taken care of” actually means…

Sorry, but the days of being able to drive a race-car on the street are over…

Not in all states.

For the record, I’m wondering if only the short block and the fuel system were redone andthe valves are floating. Perhaps in the process of floating the valves something broke.

Thank you ALL for the input and keep 'em coming. I’m forwarding all of these to my son to review. We both really appreciate all of your expertise. I’ll post follow-up as he reviews them.

I agree with the others about using some starter fluid to see if that shows up a fuel delivery problem. Also check the CAT, it may be blocked and is causing backpressure to engine.

First I am going to suggest posting on a grand national forum. Those guys know those motors backwards and forwards. Second those cars are known for having bad ignition moduals. Its what the three ignition coils plug into. It can cause all of the issues you describe very easily.

Updates and thanks to everyone who replied: He hasn’t tried the scope yet. The ScanMaster is just a diagnostic tool to read the computer. He hasn’t tried a new chip yet. The heads have been ported and polished. He doesn’t think it’s a breathing problem because there’s no cat on it and the car started out fine but got worse. The turbo spins freely and he hasn’t had enough RPMs to build boost.

He ruled the turbo out because he hasn’t gotten enough RPMs to get into the turbo. And yes, the shaft spins freely. When they car first started getting problems, it would fire up to 3000 RPM just fine and idled as smooth as can be but after 3000, it would almost skip and not let him go above it. Now it won’t fire at all. The turbo only kicks in after 3500.

Emissions have been taken care of - Means no cat and any vacuum lines that are unnecessary have been taken off and it has been checked for leaks. Anything that would slow the car down has been taken off.

Short block and valves - He says the engine ran fine and revved right up so they don’t think anything’s wrong with the engine mechanically. Compression was fine - no noises. When it was idling and revving, it was fine up until 3000.

Hope this helps. We appreciate all of the suggestions!

More info: It has new ignition modules and coil pack. New ignition sensors, new wires and plugs. New computer.

Turbo’s have a waste gate, meaning the turbo is spinning all the time. If there is no need for boost the waste gate opens, the waste gate also deals with excessive “boost” by opening too. The waste gate uses both mechanical and computer controls depending on who made the turbo, turbo and motor design, pressure settings in the set up and programming of the turbo.

If the motor was running and then would not go above 3,000 what were the symptoms? It just stopped increasing rpm? It was breaking up and missing and backfiring when attempting to go above 3K rpm?

I think the turbo is a likely source of the problem, it might not be allowing any exhaust to pass by and creating too much back pressure to allow fresh fuel charge into the combustion chamber. I’d pull the turbo completely and see if you can get any kind of results trying to fire up the motor. Since there is no cat, and likely not much in the way of a restrictive exhaust system, the turbo could be the source of exhaust resistance and excessive back pressure.

If you haven’t tried to get the engine going by spraying some starter fluid into the intake then try that. If that doesn’t work then I can only think that the ignition or injector timing is incorrect.

It almost sounds like an exhaust restriction. That would explain the engine not revving beyond 3000 rpm. If the exhaust is then completely restricted, the car won’t start. I saw an old Columbo tv show where Lt. Columbo disabled the suspect’s car by putting a potato in the end of the exhaust pipe.

Since there is no catalytic converter involved which could rule out an exhaust restriction and the engine falls on its face at 3k RPM maybe the problem has to do with the vacuum operated waste gate on the turbocharger.

Vacuum line, or lines, incorrectly routed, problem with the waste gate solenoid, etc. Maybe the waste gate is opening at elevated RPMs or possibly remaining open the entire time.