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my catera 98 model is misfiring my codes are po302,po304,po306,po443,po505,po300 i have replaced my wires,plugs,coil pac,manifold gaskets, plenum seals and im still having the same codes pop up the car runs very rough idles about 300 checked my convertors they are okay someone help please may not have any hair left by the time this is over:bigroll:


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99 Catera. Same problem, missing at 2, 4, and 6. I noticed my MAF sensor reads 0.00g/s all the time... hoping once i get to replacing that it might take care of it. If not I hear a bad cam sensor will break up bank 2. I have also replaced coils, plugs, and plenum gaskets. The injections has been cleaned as well. I havnt trying the IAC tho. I clean that up and get back to ya's
 

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I'm really curious to see how this turns out for us all! There seems to be a lot of misfire problems on the forum as of late (me included) could we list all the known problems and side effects of known sensors that could effect the spark?

Crank Position sensor:

Cam position sensor:

What else and what would a bad sensor cause the car to do from your past experiance if your car has had a similar issue?

Please someone help us figure this basket case out! low spark or misfire on #1 cylinder for me coil and plug swap complete, no change.
 

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Got this diag chart off mitchell.. maybe it'll help some one??


DTC P0300: ENGINE MISFIRE DETECTED (3.0L "V" BODY)
NOTE: For circuit reference, see appropriate wiring diagram in WIRING DIAGRAMS article.


Circuit Description
Crankshaft Position (CKP) sensor sends pulses to ECM as reluctor wheel teeth rotate past sensor. Besides using these pulses to synchronize ignition and fuel injector operation, ECM also times interval between each pulse and compares each new time interval with previous one to determine when an excessive change in crankshaft speed has occurred.

A misfire causes an unexpected change in crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if crankshaft speed changes more than expected amount, ECM will interpret this as a misfire. ECM continuously calculates crankshaft position from CKP sensor signals.

This information is used to determine which cylinder is misfiring so ECM can increment appropriate misfire counter and set appropriate DTC, if necessary. If ECM is able to determine a specific cylinder is misfiring, DTC for that cylinder will set. If misfire is random and on multiple cylinders, DTC P0300 will set. Conditions for setting DTC:

Misfire greater than legislated limit (amount of misfire ranging from 1.0-12.5 percent).
Condition must be met for at least 5 camshaft revolutions.

Diagnostic Procedures
Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.

If DTCs P0201-P0206 are also set, go to applicable DTC. If DTCs P0201-P0206 are not present, go to next step.

If DTC P1460 is set, go to step 5 . If DTC P1460 is not set, go to next step.

If DTCs P0301-P0306 are also set, go to applicable DTC. If DTCs P0301-P0306 are not present, go to step 8 .

Using scan tool, monitor fuel level voltage. If scan tool reading is greater than 6.8 volts, go to next step. If scan tool reading is not greater than 6.8 volts, go to step 8 .

Add 5 gallons of fuel to fuel tank. If fuel level voltage is less than 6.8 volts, go to step 13 . If fuel level voltage is not less than 6.8 volts, go to next step.

Repair fuel sending unit or circuit problem. After repairs, go to next step.

Start and idle engine. Using scan tool, monitor all misfire current counters (6 counters, one per cylinder). If any misfire current counters increase, go to next step. If any misfire current counters do not increase, go to step 10 .

Inspect vacuum hoses for splits, kinks and proper connections. Check throttle body and intake manifold for vacuum leaks. Check PCV valve operation and system for vacuum leaks. Ensure ECM grounds are clean and secure. Ensure all injector harness connectors and spark plug wires are installed at correct locations and secure. Repair as necessary. After repairs, go to step 13 . If all components and systems are okay, go to next step.

Turn ignition on, with engine off. Review FREEZE FRAME data for this DTC and note parameters. Clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0300 is set, go to next step. If DTC P0300 is not set, see DIAGNOSTIC AIDS .

Remove spark plug(s) as necessary and inspect for signs of oil or coolant fouling. Replace spark plug(s) or repair engine as necessary. If spark plugs are okay, go to next step.

Check spark plugs for cracks or damage, excessive wear or improper gap. Check for carbon tracking on insulator. Replace components as necessary. After repairs, go to next step. If components are okay, see DIAGNOSTIC AIDS .

Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0300 is set, go to step 2 . If DTC P0300 is not set, go to next step.

If other DTCs were present during OBD system check and has not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.
 

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Gunther, 505 is the idle air contriol valve and the 443 is the evap purge valve, that said I would make real sure that there are no vacum leaks, especially on the vac lines running to the purge valve which I believe is up near the front left of the engine.??.I doubt both valves are bad, probebly neither one of them.? a vac leak will cause a misfire. Trace the vac lines. I had a similar problem but the cause was a leaking inj. but that was very obvious due to the fuel smell etc. Are the plugs good? not fuel fouled, they may look good to the eye but if once fuel fouled they can be hard to clean up by driving alone.
Next, (unfortunatley I no longer have my manuals) you may want to check the wires that go to the coil, the primary ones, and see if they are specific to the 246 side of the engine, you will need the book for this. I bring this up because it appears specific to the one side of the engine and if memeory serves me this may be a batch fire spark system..?? some thing to consider.
 

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Thanks for your help Frank!

I should give you the full story on this problem, as I am getting very lost here.
First it started on a trip to MI from TN, I was in an ice storm and it was raining, the car started to miss just like it still does but once I stopped where I could check it out at the gas station I heard a knock. It sounded from inside the car like maybe a really strong spark plug wire arc maybe so I figured that the moisture caused a short but this was not the case once I opened the hood. It was a metalic loud knock directly proportionate to rpm.

Coming from the top valve region of what sounded like the drivers side of the motor. like a piston hitting a valve or somehow a bad lifter. The car made it up and nearly home to tn with the same noise ever present. On the return trip I added some lucas oil treatment to see if it would quiet the noise and about 400 miles into the trip the noise was gone but the same miss and loss of power was still the same.

After removing all the plugs and checking the spark all were fine except the #1 cylinder. It was wet with fuel and had no spark. Now the TC light was on as well as the Service enging light the whole trip. Now however the TC light is back to operating like normal with the SE light still on. I bought a scanner which only showed a randome 300 code as well as #1 4, 5 misfire codes. So I got a replace ment coil and replaced it. Same codes and same no spark on #1.

Checked commpression on #1 last night and it is at 80psi! The next cylinder back on the passenger side has 150 psi.

I did get a small amount of spark out of the wire using a screw driver to short it on a bold but not enough to make the plug fire im sure.

I havn't had the time to check all the cylinders yet but plan to do so.

There is not much oil in my plug holes. Little to none that I can see.

Odd thing is, I swapped two cylinders at the coil by mistake once and it ran really rough while I started it but didn't trip any codes for those cylinders...

I do not think ther is a vacume leak and I have checked everything vacume wise.

Any more ideas?

Thanks
 

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I think a misfire will cause the knocking your talking about if there are a few cylinders missing at once. The ecm tries to advance the timing to correct its self causing the valve to come in contact with the pistons. Which would also explain your compression loss at cylinder 1. Probably a bent valve. Lets hope not... Driving with that noise might have been a mistake. Not that ya had a choice, it seems. A faulty ckp sensor can cause a multiple misfire code. I think you should start testing things like the ckp sensor and the cam sensor if ya havnt found the source with in the basics. Good luck!
 

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Gunther, you may gave found your problem, the cyl in question at 80lbs is extremly low and clearly has a mechanical problem. Get ready for some heavy work and vehicle down time. Before you go any furthur on the misfire you need to find and correct the problem for the low compression, you most likely have a valve not seating, it's more then likely an exhust valve, if your very lucky you may have a damaged lifter. Regardless you will have to lift the cams and go through the timing belt repalcement process.
Go back to the tail pipe and listen for a miss noise in the exhust, if it were an intake you would have really noticed by now.
 

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Very noticable thud in the exhaust tone. A bassy dead sound. I noticed it right away. I do think there is a valve issue but why in the hell would it not spark? If it is pulling spark then why the weak spark from a screw driver test?
Also nothing mentioned in the codes? My goal was to get that cylinder firing to see if the knock came back but its not possible.

Do you think this car can sense it and has cut spark only and not fuel? Wouldnt that just destroy the converted also? Not a good plan if so.

still lost...

Brent
 

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in your earlier post you said you were getting some spark, the screw driver method is not always the best method. If you are getting some spark your OK, the fuel fouled plug will be very hard to fire. You need to get the low cylinder situation corrected first, right now your rearranging the deck chairs on the Titanic:), the o2 sensor on the problem bank is probably calling for full lean, this also will contribute to a misfire situation.
Hate to tell ya, but the cylinder problem needs to be your first concern.
 

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I hear ya, and I knew that it wouldn't be a nice process to begin with but in trying to pinpoint just what is wrong with it I was getting stuck at the non spark issue. So what would be my next plan of attack? Get a reman. Head and have it waiting along with all gaskets to replace it and then set out taking that head off to replace it and hope for the best upon completion?

Other than that or maybe finding a mini camera to probe into the cylinder I don't know what else to do to figure out why it is low on compression on that cylinder. I think there would be a long list of other repairs to do at the same time like the valve cover gaskets and oil cooler and well the timing belt also.

If after all that the damm #1 cylinder didn't fire I think I would go insane.

What would you do from here if you were me?

Thanks:thepan:
 

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I hear ya, and I knew that it wouldn't be a nice process to begin with but in trying to pinpoint just what is wrong with it I was getting stuck at the non spark issue. So what would be my next plan of attack? Get a reman. Head and have it waiting along with all gaskets to replace it and then set out taking that head off to replace it and hope for the best upon completion?

Other than that or maybe finding a mini camera to probe into the cylinder I don't know what else to do to figure out why it is low on compression on that cylinder. I think there would be a long list of other repairs to do at the same time like the valve cover gaskets and oil cooler and well the timing belt also.

If after all that the damm #1 cylinder didn't fire I think I would go insane.

What would you do from here if you were me?

.

Thanks:thepan:
First, is the car your DD and is it worth fixing?? how many miles on it? that you will have to determine. First step, I would lift the valve cover on the problem head, you may be lucky and have a lifter problem, but there can be other problems associated with that failure??. there is also a possibility you may have a broken valve spring, none of this is good news, get the cover off and see what that looks like first. Pulling the head is a significant job. On this engine you have to go through the entire timing belt replacement process, this step also applies to a lifter replacement.
At this time I would not invest in a head, should you have a valve problem any decent machine shop can handle it. This is one of those jobs that you really dont know what your facing until you see it all apart with the head off.
Keep us posted.
 

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It is my daily driver and only car. It has 75,000 miles on it and is in great shape other than this only issue. It has been a great car for the year I have owned it minus some small front end parts and a battery cable problem. At this point a head is still cheaper than a new car and I can do the work myself (although I am not looking forward to it). I have a junk yard with a head for $150. SO I think having that on hand and going at this might be the best way to get to the bottom of it. I would still have to remove the cams to get anywhere near the valve's so once im that deep into it I should just replace the head. Now if I do all of this and it still wont fire I may go insane.

Thanks for the help Frank, I will update this once I get it solved.

:hmm:
 
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