Looking for help with mystery diagnosis... October 18, 2012, 01:17:38 PM Hey guys, I'm new to this forum and posting for the first time. My journey has led me here where I'm hoping somebody can shed some light on a nagging engine problem I have had with my 84 Cougar 3.8 V6 for quite some time, even after countless shop visits and repairs.After trying to find the best way to explain everything that has happened that led up to this point, I couldn't figure out a way to do it that didn't turn into a novel, so I will merely list the symptoms the car currently has and the repairs that have been made in attempt to fully remedy the problem.SYMPTOMSThe car is running very rich, with a very pungent exhaust odor when it's started up, idling and while driving. My MPG is very poor and the car stumbles and dies while coming to stops after you drive it for a few minutes and the engine gets warm. Basically, this car ran well as a daily driver until it stalled one day on the highway and wouldn't restart, which led to the first repair in this scenario; replacement of the timing gear set and chain.REPAIRSHere I will just list everything that has been replaced on the car since it died and wouldn't restart, starting with the timing work. It should help rule out a lot of potential causes.Timing chain and gear setFuel FilterSpark plugs and wiresDistributor cap and rotorIgnition ModuleThrottle Position SensorEngine Control ModuleEGR Control SolenoidEGR ValveBoth O2 SensorsCatalytic ConverterThermostatIdle Speed Control MotorIt's been through several shops, and at this point nobody seems to be able to identify what's causing the remaining problems. It's been cleared for codes and at the last repair shop passed a self test.Any ideas? Quote Selected
Looking for help with mystery diagnosis... Reply #1 – October 18, 2012, 04:21:49 PM EGR valve. You're probably stuck open, which is dumping unmanaged egr into the engine. This is a problem, because EGR is inert, the PCM dumps as much fuel in as it can to try to even out the mixture, it can't because EGR is inert and not even useful as an oxidizer. End result:bad idle, poor fuel economy, delayed power on WOT and extremely rich exhaust. Ask me how I know. Quote Selected
Looking for help with mystery diagnosis... Reply #2 – October 18, 2012, 05:36:47 PM That sounds pretty spot on, but the EGR valve has been replaced per my request. I was told the old one was not stuck open. Maybe a bad part? Quote Selected
Looking for help with mystery diagnosis... Reply #3 – October 18, 2012, 06:26:34 PM You want to make sure the spacer gasket under the throttling isn't leaking her into the intake. Quote Selected
Looking for help with mystery diagnosis... Reply #4 – October 18, 2012, 06:41:33 PM Pardon my ignorance, but is that a gasket at the bottom of the throttle body? Quote Selected
Looking for help with mystery diagnosis... Reply #5 – October 18, 2012, 07:24:08 PM Sorry, I was using my phone and auto correct is stupid. Under the throttle body. Its a spacer with gasket bonded on to each side. This is another place to look for EGR bypassing the valve. Quote Selected
Looking for help with mystery diagnosis... Reply #6 – October 18, 2012, 07:47:48 PM OK, I will definitely check that out. Thanks for the info! Quote Selected
Looking for help with mystery diagnosis... Reply #7 – October 18, 2012, 10:07:18 PM Fuel pressure regulator?Also, what's the condition of the vacuum line to the EGR? Quote Selected
Looking for help with mystery diagnosis... Reply #8 – October 18, 2012, 10:35:29 PM Is there vacuum at the EGR port? If you were to apply vacuum to the EGR manually, what happens? Did you get the old EGR valve returned to you? If you spray carb/throttle body cleaner on the gasket seams, does the motor idle change? Does she smoke? If so, what color is it? You stated that she stumbles and dies after a few minutes, but din't indicate whether she runs alright before she gets warm. Quote Selected
Looking for help with mystery diagnosis... Reply #9 – October 18, 2012, 10:36:31 PM Did you get any codes from the computer? Quote Selected
Looking for help with mystery diagnosis... Reply #10 – October 18, 2012, 11:41:07 PM A closed her won't cause his problems, so you can rule out any control side problems. The only other thing I can think of would be some sort of fuel leak into the engine. I can't imagine the odds of that are very good. It's been a good long time since I've messed with a 3.8 cfi but I'd still pop the throttle body and see what the egr chamber looks like. Quote Selected
Looking for help with mystery diagnosis... Reply #11 – October 18, 2012, 11:42:31 PM I will have to check that out, but in general from the top the vacuum lines seem to be in good shape. IDK if it included the line to the EGR but the vacuum lines were checked and a few replaced after my vent controls stopped working. The car does not smoke, and starts right back up if/when it dies. It's been sitting a few months as I had other transportation recently but today I took it for a drive. It still had rich exhaust especially at start up and idle, but it ran OK and didn't die on a short trip. The idle seems a bit unsteady to me personally, always has been I think, and it does seem to lack power a bit. The last codes scanned were for a TPS and EGR control solenoid to which both were replaced. Quote Selected
Looking for help with mystery diagnosis... Reply #12 – October 18, 2012, 11:54:40 PM What am I looking for in the EGR chamber? Quote Selected
Looking for help with mystery diagnosis... Reply #13 – October 19, 2012, 06:50:12 AM First, damage to the gasket, second, you want to check for carbon build-up. I thought a bit deeper about it, and it might be smart to first check that the vac line that opens the valve isn't for some reason pulling the valve open when it shouldn't be, so pull the line off and plug it then go for a drive. Quote Selected
Looking for help with mystery diagnosis... Reply #14 – October 19, 2012, 10:50:13 PM First off click on my DIY link and scroll through all the things CFI related there. Please excuse any spelling errors I'm trying to learn Siri on the iPhone and trying to not misspell any words. To give you a hint, the CFI has a gasket kit and if there is a huge amount of carbon buildup you will be the only one that'll care enough to really check and find that out.– What is the fuel pressure right now on the engine while it's running and under a load such that you have the transmission and drive while the fuel pressure tester is hooked upb– Do you have bluish white spark on a spark plug, just pick any spark plug and test for blue white spar anything other than bluelight is telling us that is Stader assembly down the distributor is possibly going bad– For the symptoms you're calling out as the car runs today it's almost impossible to not have codes like you've indicated. I would think that a shock should be a little pull the codes as easily as shown in my DIY link as well as many others who can share with you how to pull codes– Did the shop perform a compression test on all six cylinders and come up with a percentage delta of less then 10 pounds per cylinder approximately, that's just a common value that would be nominal for the 38 L engine– Can you unhook the exhaust where it first enters the coupling up to the catalytic converter? If so you'll be running straight exhaust out to the world but it would give you the opportunity to run the engine with the exhaust open eliminating the clogged up catalytic converter if that were the fault – Let's do a quick test, let's start up the engine and let it run and Park, and then shut off the engine. Next let's go to the Schrader valve on the right-hand side of the CFI and push that little pin in does fuel pressure spray all over the place? If so then the likelihood of low fuel pressure is probably not the CaseThese are just a few ideas to get you started but believe me the 3.8 L engine is not that complicated, it's just a fuel injected motor and your fuel injectors need to be spraying and even fan of fuel over top of the butterflies, if you can't see that too well with the engine running shoot your timing like down inside one of the barrels and you'll be able to see the hole and see the fan stream of fuel.Give me a call if you have to have this is like an emergency 304-772-3411 and welcome to the board Quote Selected
Topic: Looking for help with mystery diagnosis... (Read 3770 times)
previous topic - next topic
