Engine running really rough
Thread Starter
Instructor
Joined: Mar 2002
Posts: 236
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From: OFallon IL
Engine running really rough
Everything has been great. Engine running perfect. Then 2 days ago on my way home, cruising at 65, the Check Engine light starts flashing at me. I pulled over and the engine was running really rough, almost like it was running on 6 or 7 cylinders. I babied it home the remaining 4 miles.
Today, I searched this site. It led me to believe I have engine misfire. I checked all the spark plug wires. Each one looks perfect. They measured between 1185 and 1215 ohms. I was hoping that was the problem, but I don't think it is.
What else can I check?
Could a bad spark plug cause this?
Could it be a broken valve spring? What would that sound like?
Maybe an exhaust leak?
Could the PCM programming suddenly revert to stock?(I doubt this could happen.)
Give me something else to check.
Thanks in advance...
Today, I searched this site. It led me to believe I have engine misfire. I checked all the spark plug wires. Each one looks perfect. They measured between 1185 and 1215 ohms. I was hoping that was the problem, but I don't think it is.
What else can I check?
Could a bad spark plug cause this?
Could it be a broken valve spring? What would that sound like?
Maybe an exhaust leak?
Could the PCM programming suddenly revert to stock?(I doubt this could happen.)
Give me something else to check.
Thanks in advance...
Last edited by MQRTRS C5; May 14, 2005 at 04:26 PM.
Thread Starter
Instructor
Joined: Mar 2002
Posts: 236
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From: OFallon IL
Codes in DIC (Options + Fuel 4 times)
PCM - P0300H
BCM - 2583H
IPC - B0521H
- U1016H
Radio - U1064H
- U1016H
- U1096H
LDCM - B2282H
- B2284H
- U1064H
- U1016H
RDCM - B2283H
- B2285H
- U1064H
- U1016H
RFA - U1096H
- U1016H
PCM - P0300H
BCM - 2583H
IPC - B0521H
- U1016H
Radio - U1064H
- U1016H
- U1096H
LDCM - B2282H
- B2284H
- U1064H
- U1016H
RDCM - B2283H
- B2285H
- U1064H
- U1016H
RFA - U1096H
- U1016H
Thread Starter
Instructor
Joined: Mar 2002
Posts: 236
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From: OFallon IL
Originally Posted by JJ in FL
I would pull one plug wire off at a time, the one that results in no change is your bad plug.
A broken spring would sound bad.
A broken spring would sound bad.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
The U codes indicate that those Modules lost communications to the other modules for some reason. Most of the time you get those because of LOW voltage at the modules. Check the connection to the battery and make sure that they are clean tight and properly torqued on to the battery. it requires 11 FT/LBS tq.
Your battery may also be on its way out. How old is it?? It can start the car fine but the voltage that the battery supplies to the modules can be too low during cranking to allow them to function correctly during that period of time. That is why they are history codes. Clear them and see if they come back and when. See id they are there right after you start the car first thing in the morning when the engine is cold.
As for the sparkplug wires, are they OEM original?? If so the OEM resistance should read 250 -750 ohms. Some aftermarket wires will read that high... ie (Magnacores) Make sure that the wire jackets and boots are in good shape. Here are some examples of bad things!
I use silicone dielectric grease to seal the boots.
If the cylinder is breaking down under load, the pull off a wire method may not tell you too much.
BC
Your battery may also be on its way out. How old is it?? It can start the car fine but the voltage that the battery supplies to the modules can be too low during cranking to allow them to function correctly during that period of time. That is why they are history codes. Clear them and see if they come back and when. See id they are there right after you start the car first thing in the morning when the engine is cold.
As for the sparkplug wires, are they OEM original?? If so the OEM resistance should read 250 -750 ohms. Some aftermarket wires will read that high... ie (Magnacores) Make sure that the wire jackets and boots are in good shape. Here are some examples of bad things!
I use silicone dielectric grease to seal the boots.
If the cylinder is breaking down under load, the pull off a wire method may not tell you too much.
BC
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Originally Posted by MQRTRS C5
Codes in DIC (Options + Fuel 4 times)
PCM - P0300H Cylinder miss fire
BCM - 2583H Left Front Turn Signal MONITOR Circuit
IPC - B0521H RPM data from PCM is intermittant or inaccurate
- U1016H
Radio - U1064H
- U1016H
- U1096H
LDCM - B2282H LCDM detects voltages less than 9 VDC or greater than 16.3 VDC
- B2284H Same as above!!!!!
- U1064H
- U1016H
RDCM - B2283H
- B2285H
- U1064H
- U1016H
RFA - U1096H
- U1016H
PCM - P0300H Cylinder miss fire
BCM - 2583H Left Front Turn Signal MONITOR Circuit
IPC - B0521H RPM data from PCM is intermittant or inaccurate
- U1016H
Radio - U1064H
- U1016H
- U1096H
LDCM - B2282H LCDM detects voltages less than 9 VDC or greater than 16.3 VDC
- B2284H Same as above!!!!!
- U1064H
- U1016H
RDCM - B2283H
- B2285H
- U1064H
- U1016H
RFA - U1096H
- U1016H
I added explanitions to some of the codes above.
Dude, it looks as though that you have a battery issue. More and more of the codes are pointing to low circuit voltage. C5's will NOT run correctly on LOW VOLTAGE!!!
Before you get too wrapped up in checking and replacing things, have your battery properly tested at one of the Auto Parts stores.
Bill C
Thread Starter
Instructor
Joined: Mar 2002
Posts: 236
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From: OFallon IL
Sounds like I'll be picking up a RedTop tomorrow. The battery is getting old. The car still starts like a champ though...
Would a battery cause the engine to run rough? I thought that once the car was running, the alternator is used primarily for powering the electronics.
Would a battery cause the engine to run rough? I thought that once the car was running, the alternator is used primarily for powering the electronics.
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Le Mans Master
Joined: Jul 2002
Posts: 7,370
Likes: 8
From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
Try to find an inexpensive scanner, if you have a misfire the scanner will show which cylinder. Your P0300 code will show on the scanner as P030x and x will be which cylinder is misifring. IE if it shows P0307 then the #7 cylinder is the cause and if it says P0300 multiple and numerous cylinders then it may be a broken valve spring, if it is a valve spring it won't necessarily make any abnormal sounds while running.
The diagnostics in the C5 are great but sometimes you still need a scanner to locate the fault.
The diagnostics in the C5 are great but sometimes you still need a scanner to locate the fault.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I agree!! The acanner will show you more than the C5 ODBII diagnostics will.
The battery should not make the car run poorley unless your alternator is not operating correctly Get a voltage reading at the battery terminals with the car running with no loads and then again with lots of load. ie lights fans, defrost ect ect.. It should read 13.5 -14.7 normaly.
Batteries are funny things. They will start a C5 but still cause C5 issues. If it is at all questionable replace it!
BC
The battery should not make the car run poorley unless your alternator is not operating correctly Get a voltage reading at the battery terminals with the car running with no loads and then again with lots of load. ie lights fans, defrost ect ect.. It should read 13.5 -14.7 normaly.
Batteries are funny things. They will start a C5 but still cause C5 issues. If it is at all questionable replace it!
BC
Team Owner
Joined: Mar 2001
Posts: 25,889
Likes: 7
From: Virginia Beach
CI 3-5-6-7-8 Veteran
I just had a wierd problem with mine... it's kinda common though. Check the fuel injector wiring harness at the back side of the driver's side valve cover. Mine chafed through and was grounding out. I'd get a randoom P0200 code (fuel injector system fault) but the car would run fine and I'd just clear it. Then it fully went and the car wouldn't run right. When the wire would ground the #3 and #7 fuel injectors would fire wide open and the car would run super rich. So check that too!
Safety Car
Joined: Feb 2003
Posts: 3,865
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From: Chicago il
How about a top engine cleaner. You may have carbon deposits. I messed around with the ignition and fuel system for ever trying to find the stumble and hesitations in my car. I did a round of sea foam and it cured me. do a search there are a ton of thread on it recently
Thread Starter
Instructor
Joined: Mar 2002
Posts: 236
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From: OFallon IL
I had the car checked out today. A compression test resulted in zero compression on cylinder #5.
What should I look for when I pull the valve cover? I'm hoping its just a broken valve spring.
What should I look for when I pull the valve cover? I'm hoping its just a broken valve spring.
Thread Starter
Instructor
Joined: Mar 2002
Posts: 236
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From: OFallon IL
When I finally got it running again. It was a broken spring. The valve didn't drop, luckily, so no damage was done.
I put in some 918's with Ti Retainers. Started 'er up and its running great again.....
thanks..
I put in some 918's with Ti Retainers. Started 'er up and its running great again.....
thanks..
Le Mans Master
Joined: Jul 2002
Posts: 7,370
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From: Slave to the evil empire
Cruise-In V Veteran
St. Jude Donor '04
Originally Posted by MQRTRS C5
When I finally got it running again. It was a broken spring. The valve didn't drop, luckily, so no damage was done.
I put in some 918's with Ti Retainers. Started 'er up and its running great again.....
thanks..
I put in some 918's with Ti Retainers. Started 'er up and its running great again.....
thanks..
Thread Starter
Instructor
Joined: Mar 2002
Posts: 236
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From: OFallon IL
Originally Posted by runamuk
Thats great news, I assume you broke a stock valve spring?
