: NorthStar with 366 Thousnd Miles

11-05-04, 10:46 PM
My 97 Deville has 590 thousand kilometres on it now. But I need some help finding the source of a code p0300. Background- about a month ago, it started a slight pulsation when crawling with no pressure on the gas peddle,(650rpm) it would go away above 800 rpm. No code was set at this time.
Two weeks ago, as a requirement of licence renewal, I took it in for an emission test. It was high on HC and CO. A diagnostic was recommended, I allowed them to proceed.
They recommended Sparkplugs and a catalytic converter. I thanked them for the Diagnostic; paid them for their time, told them I would change the plugs later.
A couple of days later, the engine started running really bad, thick blue smoke coming out the exhaust after coming off the hi-way. (60mile run)(My daily one-way)
Then the code set P0300, so I replaced all 8 plugs, (Delco) cleaned the throttle blade and bore with a toothbrush and carb cleaner. I can see a thick sludge deep inside the intake, looks like shoe polish. Removed the EGR and cleaned it the best I could. I don’t know if it is an aftermarket model, as I cannot see a “Pintle” or diagram on this EGR. Also, cleaned the tube and the port into the back of the throttle. Two other codes P0146 and P0147 are thrown only after a cold start. They go away after engine is up to temp.
The misfire is throughout the RPM range.
The only plug that was black-oil-fouled was plug 7, when I changed them. If it were one plug misfiring, would I get something like P0307?
I will continue to search Bbob’s posts; too bad I can only go back 500! ;-) LOL

Thanks Chris

11-05-04, 11:03 PM
The P0146 indicates lack of O2 sensor activity and the P0147 indicates a problem with the heater circuit in that O2 sensor. With the O2 sensor heating element failed the O2 has to warm up naturally from engine exhaust heat which is why the low activity code is setting when cold and why it then goes away.

The hi HC and Co indicates incomplete combustion and/or too much fuel in one or more cylinders...which correlates to the engine misfire detected code 300.... If the number 7 plug looked fouled I would HIGHLY suspect that the number 7 injector is sticking open/leaking causing the misfire, high HC and CO and causing the plug to foul....not oil. If you are feeling lucky, replace that injector. If you want to diagnose positively, swap #7 injector with #5 next door and see if the problem goes #5. You should be able to pull the plugs after one daily round trip and see some evidence. And/or, unclip the fuel rail and pull it up out of the intake so that the injector tips are visible. Turn on the key to energize the fuel pump and watch #7 to see if it drips or leaks when the rail is pressurized. That might be enough of a clue right there.

The other thing to check is the fuel pressure regulator. While idling, pull the vacuum line off the fuel pressure regulator and watch the vacuum nipple on the FPR for any sign of fuel seeping out. There should be none. This is not a postive test as sometimes the FPR can still seep when under vacuum and not when the vac is disconnected but it will usually show a bad FPR....... Since the vac signal to the FPR would feed the seeping fuel from a leaking FPR to the intake it would cause rich running, misfiring and fouled plugs and hi HC and CO. The vac feed to the FPR is near #7 I think on that engine.....

11-05-04, 11:20 PM
Thanks BBob,
Im going to check the injector and FPR right now.
Any thought on what the sludge in the intake is? I'm wondering if it could be oil vapor from the PCV condensing inside the manifold?

11-06-04, 04:25 AM
Forget about the "sludge" inside the manifold. It is a combination of soot from the EGR introduction and a tiny bit of oil mist from the PCV system and (primarily) a layer of heavy end hydrocarbons that do not evaporate or vaporize that comes from the gasoline injected into the ports over time. If you clean it out it will just come back. Ignore it. It happens to all port fuel injected engines, especially ones with highly tuned intake manifolds with lots of runner surface area and a large plenum and an airflow path that is "uphill" in places. Older intake manifolds for carburetors and TBI were always clean inside...because they had copious amounts of gasoline (good solvent) sluicing thru the manifold runners all the time the engine was running. The gasoline sluicing thru kept the manifold runners pretty clean. Port fuel injection does not have gasoline in the inlet charge that the intake runners handle so the soot and minor amounts of oil from the PCV and involitile fuel just builds up over time. Ingnore it. It is not your problem. Just make sure that the throttle body bore and back side of the throttle blade is cleaned every 50 K or so so that the throttle blade can operate smoothly and not hang or catch on deposits in the throttle body bore.

11-06-04, 02:34 PM
Thanks BBob,
I checked out the FPR, I could see no fuel leaking out, and the vacuum hose was dry. Unable to lift the fuel rail up, and fear of breaking an O-ring or worse, kept me from trying to force the bank of injectors out. I pulled plug 7 out to see how it looked, a new plug 12 days ago, it was coated, black and oily. (worse than my sons 65 Ski-Doo) I put an old clean plug in its place. I can post a photo if it helps. So I took it back to the Mechanic that did the diag two weeks ago. His tester showed that cyl#7 was misfiring about 200 times a min at idle, cyl#3 had an occasional miss. Pressure tested the fuel rail, it held steady at 60psi with the power off. He did a compression test of cyl #7, it was zero. I put my thumb over the connector coming from the plughole, nothing. So, I asked him to leave the electrical connector to the injector off, and I drove it home.
Will it hurt anything to leave the injector circuit open while continuing my daily commute of 120 miles? My wife suggested perhaps I will have a lucky 7 cylinders. :-) LOL
I’m in good spirits, as the car owes me nothing. Without knowing the cause of the zero compression, I have no idea what if any other possibilities exist to repair it? Perhaps I should start looking for a wreck for a donor engine/transmission.

11-07-04, 01:41 AM
No, there shouldn't be any problem with driving it with an injector disconnected. Amazing that it would have NO compression.... Wonder what is causing it. With that many miles on the motor it is hard to guess. I would almost have to think it is a valve not sealing but that is pretty rare even with those miles. If you connect compressed air to that plug hole you can usually hear where the compression leak is by listening at the exhaust and the intake to see if it is an intake or exhaust valve. Possibly a chunk or carbon or something is caught under a valve holding it open. The other thing to do would be to pull that side cam cover and see if the valve gear for that cylinder is operating correctly and opening the valve. Maybe it is a broken valve spring that is not holding a valve closed completely causing the compression leak.

11-07-04, 09:51 PM
I hooked up the pressure test hose to cyl 7 then started it; 30 psi is all it made.
With the ignition disconnected, I turned it over till I felt compression with my thumb over the male end of the quik-disconnect.
I blew compressed air into the cylinder; it seems to be coming out the intake.
I was unable to get a wrench on the front to turn over the engine by hand to insure I was at TDC on #7. If I take off the valve cover I should have a replacement gasket handy.
I shot some brake clean down into the cylinder, and turn it over a few times; it seemed to improve a bit. I put it all back together. Started it up, it ran clean for a few minutes, no PCM codes. 300 came back with the smoke, I see blue, my Dad sees white, we both smell oil. LOL
I need to spend more time on this, as it is getting cold and dark early now.
I need to move my snowmobiles out of the garage, so I can work on my car out of the elements. My Dad is letting me borrow his spare car.
Searched your posts regarding finding TDC, and found the word “borescope” and got thinking that I may be able to make one from a web cam and an LED.

Thanks Bbob,
I will keep you posted.

11-08-04, 02:38 AM
If you need a borescope go see your friendly neighborhood proctologist.

11-09-04, 12:29 AM
LOL, yea, jump off the table, screem, and run away with it hanging between your legs. :D free borescope :D

02-19-05, 08:09 AM
The car sat for a month while I cleaned out the garage to make room to work. The battery was dead, so I changed it for a fully charged one.

Now it will not start, it turns over fast enough.

I can hear the fuel tank pump spin up and shut off, presuming it built up pressure. Push open the Schrader valve on the fuel rail, no fuel. If I spray fuel into the intake, it will start, run out of prime and quit.

With the ignition key turned just to on, the “squares” around “PRND321” are flashing.

The SES light was “trying to come on” like a bad ground, not fully on, static’y.

Now it has quit coming on.

The codes for the PCM is “No Data” ?? not no codes, no data.

The codes for the ICM is 1552H, 2750C, and 1255C

All the problems started when I took it in for an emission test!!

I’m wondering if they fried the computer when the mechanic plugged into the data link?


02-19-05, 09:44 AM
I think you hit the nail with your bad ground comment. Maybe some critters have been nesting in there somewhere during the month of downtime?

I would inspect every exposed cable and connection you can reach. Good luck with it; I want to hear about your engine hitting 400,000 !!!

02-20-05, 06:15 PM
Found the source of the "No Data"

A corroded fuse, that supplies 10 amp to the PCM. It broke when I pulled it out.

Replaced with a new one, Started up like it was running yesterday, has not run in 3 months. Now I can get it into the garage and start working on the cause of the missfire.


02-22-05, 06:11 PM
Found the source of the "No Data"

A corroded fuse, that supplies 10 amp to the PCM. It broke when I pulled it out.

Replaced with a new one, Started up like it was running yesterday, has not run in 3 months. Now I can get it into the garage and start working on the cause of the missfire.


This may be very well the only time in recorded history a "Fuse" was the culprit of a problem! ;)

02-22-05, 11:58 PM
This may be very well the only time in recorded history a "Fuse" was the culprit of a problem! ;)

Neah! It wasn't a *BLOWN* fuse... just corroded contacts.... Doesn't count!