KevinW Posted September 7, 2004 Report Share Posted September 7, 2004 I would have thought that the P0300 code (engine misfire detected) would have set. I think the misfire rate must exceed 2% for that code. Some scantools provide a more detailed report of cylinder misfire events. ___________________________________________________ Link to comment Share on other sites More sharing options...
KHE Posted September 7, 2004 Author Report Share Posted September 7, 2004 I am going to inspect the spark plugs this evening. The wires passed the water mist test last night. After driving it over the weekend, it acts like there's water in the fuel. I added some Iso-Heat (isoproypl alcohol water remover) to the gas tank but did not notice any improvement. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
bigfoo Posted September 7, 2004 Report Share Posted September 7, 2004 Could be a coil pack.. Best thing to do is hook up a scan tool and check the misfires. That's what I plan on doing. No codes will set unless the missfires exceed a rate at which the emission control system fails and then you will get a code...which is silly, but that's how it is. i'd want to know if it missfires more than .5% of the time just so i can get another .3 MPG Link to comment Share on other sites More sharing options...
KHE Posted September 7, 2004 Author Report Share Posted September 7, 2004 I substituted a known good coil in each of the 4 coil positions and it did not make any improvement so I think the coils are OK. I am going to pull the plugs tonight and inspect them. Since the wires passed the water mist tesat, the plugs are about the only thing left besides the ignition module. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
bigfoo Posted September 7, 2004 Report Share Posted September 7, 2004 Just because a wire passed a mist test doesn't mean it isn't bad at the ends inside the boots....what about the wires going to the ignition module? Link to comment Share on other sites More sharing options...
Phillip Posted September 7, 2004 Report Share Posted September 7, 2004 Yes, the mist test is a good test, but I wouldn't consider it fool proof. There is still a chance that they are causing the problem, especially where it is not terribly severe. Let us know about the spark plugs. Link to comment Share on other sites More sharing options...
Scotty Posted September 8, 2004 Report Share Posted September 8, 2004 The wires could also only arch on heavy acceleration when the engine hits say 3,000 rpm, when the wire is moved against metal, but at idle they are fine. bigfoo you bring up a good point I have seen lots of problems with the ends where the core is burned out, loose, or the connector doen't make good connection with the cap, coil or plug. Link to comment Share on other sites More sharing options...
KHE Posted September 8, 2004 Author Report Share Posted September 8, 2004 I removed the plugs this evening and discovered the problem. 6 of the 8 plugs were missing the platinum pad on the ground electrodes and the gap was .060-.068". The spec. is .050". The plug wire ends were fine. Since the plugs were so easy to replace, I set the gap on the worn plugs to .050" and reinstalled them. When I test drove the car, I didn't notice the miss/stumble. I am going to buy a set of AC 41-950s tomorrow but won't be able to install them until Thursday. Thanks to all for the suggestions. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Ranger Posted September 8, 2004 Report Share Posted September 8, 2004 Thanks for the update Kevin. I'll have to tuck that away in the memory bank for future reference. I though Guru said that Delco had that platinum pad problem taken care of along time ago. Link to comment Share on other sites More sharing options...
KHE Posted September 8, 2004 Author Report Share Posted September 8, 2004 I don't recall the timeframe when the weld problem on the platinum pads was corrected but mine were definitely bad. I used an air impact wrench per bbobynski's advice to break the plugs loose as I was concerned about damaging the threads in the heads. It worked great. I thought the rear bank of plugs would be difficult to access but once the plug wires were disconnected from the coil pack, there was enough clearance for the socket and extension. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Phillip Posted September 8, 2004 Report Share Posted September 8, 2004 Now you know why everyone says to check the plugs and wires first. Not only are they one of the most common problems, they are also one of the easiest to fix. Thanks for keeping us posted on your progress. Link to comment Share on other sites More sharing options...
Logan Posted September 8, 2004 Report Share Posted September 8, 2004 I think I told KHE....all along I thought it was a ignition issue.... Dead plats can do that... I think the 45-55 psi GM book is a misprint. Maybe much lower...like 40psi. Logan Diagnostic LLC www.airbagcrash.com www.logandieselusa.com www.ledfix.com www.ledfix.com/yukontaillightrepair.html www.ledfix.com/ledreplacements.html www.ledfix.com/j42385toolrental.html Link to comment Share on other sites More sharing options...
KHE Posted September 8, 2004 Author Report Share Posted September 8, 2004 I think I told KHE....all along I thought it was a ignition issue.... Dead plats can do that... I think the 45-55 psi GM book is a misprint. Maybe much lower...like 40psi. Yes - you did... I just had to check EVERYTHING out... The fuel pressure at idle is 40-42 psi and upon hard acceleration, it is 50 psi. At least I now have a benchmark for fuel pressure and I had a 4-foot hose made for my fuel pressure tester so it is actually useful. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
PAUL T Posted September 8, 2004 Report Share Posted September 8, 2004 I had the same problem with the stumbling on acceleration and just changed the plugs and wires out with OEM. The problem was cured for about a day and started back up again. I still have to get back and see if the wires are not crossed or the connections to the plugs are good. I checked all the gaps before installing the plugs and I know it would not hurt to check them again if the stumbling keeps up. One thing the new plugs and wires did cure was the hard cold starts. I was watching this post closely to see if you would come to the plugs and wires conclusion. Sometimes when trying to diagnose a complex car we overlook the obvious most common solution. Link to comment Share on other sites More sharing options...
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