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Troubleshooting Poor Cold Start on a 3.2
This issue has been driving me a bit crazy and has me running in circles. Rather than continue to throw $100 at it each time I blindly replace a part I wanted to get a few other opinions before my next step.
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... and thats where I'm at today. I have a friend who is going to let me plug in my DME into their working car to rule that out, but I'm not sure where to look next. I read through a bunch of threads on the various subjects. Based on those I am looking into a few other items, but I'm not convinced they are the issue. DME Relay - I get power to the fuel pump. My understanding is it wouldn't even start if this was the issue, but I may be wrong. Crank Position Sensors - They are gapped correctly. I do have an over the transmission oil line from ER that runs near them, not sure if that could cause problems. My understanding with these is also that the car wouldnt start at all if they had failed. Throttle Position Sensor - This would explain the hesitation under power, but I dont believe it would impact the cold start and idle. Anyhow, I think thats everything I've done to this point. I'd love to hear your thoughts or just some words of encouragement so I don't give up. :) |
There are a lot of threads on 3.2 starting and idle issues, so please continue to search and read through those to gain as much info as you can.
my initial thoughts: If it were mine, Id start by smoke testing the intake system to make sure there are no additional vacuum leaks. There are a lot of opportunities for leaks on these engines including the multi layer stack of intake manifold gaskets. smoke testers do a fantastic job, so I would not skip this in an effort to improve your chances of finding any leaks. Poll and inspect the connection of the vacuum lines at the fuel pressure and damper locations. if you have any wetness or smell of fuel at these vacuum connections it is a sign of diaphragm failure of the damper or regulator. replace as necessary. replace fuel filter make certain that connector for CTH is secure at left manifold. verify condition of all fuses, clean and replace as necessary |
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I forgot, but the fuel filter was also replaced, I added it to the list. I inspected the fuses and everything was good. |
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How old's your fuel? White smoke can indicate water in your fuel, and modern petrol can be hydroscopic.
What colour are your plugs? That might shed some light on the mixture. Does the idle change in response to removing the oil cap? It will do if you have good vacuum. Check the resistance of your sensors at the ecu if you can, as it confirms continuity of the wire all the way back. Sent from my SM-G988B using Tapatalk |
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There are new plugs in, I’ll have to pop one off and take a look. When I pop the oil cap nothing happens. I figured the same as you, vacuum leak. But when I was reading threads on here it suggested the DME would just compensate for that and nothing would happen. Is that not true? I’ll have to check resistance at the ECU to confirm sensors are functional and there isn’t a separate wiring issue. Thanks for the ideas! |
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My previous post (4) indicated that your temp sensor is bad. Replace that! Don't become overloaded. |
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If there's not a noticeable change, at least momentarily, when you remove the oil cap then you probably have a vacuum leak.
This probably won't be your whole problem because it usually just causes a rough idle rather than anything worse. Unless you have a lot of unmetered air going in, which could cause a significant lean running problem. Check the easy to access spots first. If you bend the hoses around the oil cap, there's sometimes hidden cracks at the elbows. Check all hoses are connected. The hoses to the two fuel pressure controllers at the backs of the fuel rails, and a key spot is the three on the back of the throttle body. If something comes off back there it often goes unnoticed. You'll need a mirror or reacharound and take a photo with your phone. Sent from my SM-G988B using Tapatalk |
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I will go through and double check the other lines. http://forums.pelicanparts.com/uploa...1711087795.jpg |
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Before wasting more time and money, the OP needs to follow what he mentioned in post #1 now; Quote:
Please, no more guessing. |
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If there's not a noticeable change, at least momentarily, when you remove the oil cap then you probably have a vacuum leak. And that's a 100% scientifically verifiable true statement. The PROBABLY I put there accounts for rare exceptions such as e.g. if the whole vacuum system is blocked off. Quote:
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This probably won't be your whole problem because it usually just causes a rough idle rather than anything worse. Quote:
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If not, sadly, this complicates the situation quite considerably. The way the Bosch DME system works, is the vacuum hoses connected to the fuel pressure regulator and stabiliser, maintain the fuel at a constant pressure RELATIVE TO MANIFOLD PRESSURE. Without those connected, your fuel delivery will go leaner at open throttle and richer at closed throttle, and the effect will be more pronounced at higher revs. Left alone, this will mean you're rich at idle, you're still rich at half throttle, but not so much, and when you open to full throttle, the mixture will correct itself. But with the rich idle, there could be unburnt fuel hanging around or sooted up plugs, messing up performance with the engine at other states. Additionally, it's likely somebody could adjust the mixture to compensate at idle, resulting in a lean running situation at open throttle. My recommendation would be to connect the vacuum system back up and go from there. It looks complicated and daunting, but it's not too bad if you have another car to copy. Many local owners would be willing to accommodate that, I'm sure. If the hoses are missing and you don't want to go to a new system such as ITB's or carbs, then my recommendation would be to find a shop which backdates Carrera's or adds ITB's, and they will have a load of Carrera manifold systems going spare. I know Rennsport in the UK have six or seven listed on eBay, but I assume you need one in the USA. If you wish to verify the vacuum system functioning then fit a fuel pressure meter to the port at the front left fuel rail. Fuel pressure should drop with manifold vacuum. If that's not happening then this is one of your problems. Finally, a common failure on these at this age is the diaphragm of one of the fuel pressure regulator/stabilisers starts to leak fuel. After running the engine for a while, pop the vacuum hose off each regulator and check for traces of fuel in it. If the regulator is leaking fuel in the pipe, the regulator needs replacing. Good luck! |
P.S. Just going on instinct, my view is this:
Your fuel pressure regulators don't have vacuum because removal of those pipes has opened something to the air. Consequently you are rich at idle Given the removed hoses, most likely this is the oil tank. Solution: seal any openings in the oil tank / seal open hoses coming from it. Second likelihood is vacuum failure in the hoses leading to the fuel regulators. Verify this by checking the regulation of fuel pressure relative to manifold pressure. Third likelihood is fuel leaking into the vacuum lines from the diaphragms of the regulators. (Easily checked) Finally, once all these are ruled out, you may still have other disregulation. Those pipes were probably removed because there was another problem pre-existing. And other maladjustments may have been made to compensate. |
@mysocal911 @RobFrost
I appreciate both of your insights, all the feedback is helpful. It is entirely possible this could be more than one problem. The motor did sit in storage for a year and a half before going into the car. Even though the motor was refreshed many of the parts could have become stuck or brittle from the lack of use. |
I had this problem once. The thing that saved me was Air Fuel Ratio meter. That told me the engine was running rich and the computer was trying to compensate but unable to.
The solution for me was to open up the Air Flow Meter, and found that the previous builder has changed the factory setting to compensate for a different injectors / computer. He then removed said modification to sell the car and never reversed the AFM changes. Put back the factory setting, and the car ran solid after that. That maybe a problem for you, but you need to NOT guess and just get the Air Fuel Ratio meter. |
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Sent from my SM-G988B using Tapatalk |
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