756puller Posted November 26, 2022 Share Posted November 26, 2022 Got a 99 Mercury cougar I've been fighting for a while. When it's probably below 35 degrees it won't idle. I have to keep it wound up to keep it running. It's throwing codes for bank one and two are lean. I've checked fuel pump pressure and it's right at 30 psi at an idle. I'm at a loss of what to think next, I'm leaning towards oxygen sensor but I'm not 100 percent sure. Can a fuel pump throw fits when it gets Cold out? Quote Link to comment Share on other sites More sharing options...
New Englander Posted November 26, 2022 Share Posted November 26, 2022 What does your scan tool show as coolant temperature? If the ECM thinks it's warm then it won't enrich the mixture properly. 1 Quote Link to comment Share on other sites More sharing options...
756puller Posted November 26, 2022 Author Share Posted November 26, 2022 I've just got a basic code reader that can read and erase codes. Quote Link to comment Share on other sites More sharing options...
nomorejohndeere Posted November 26, 2022 Share Posted November 26, 2022 trade some parts around and see if the codes follow where you go with them.... Quote Link to comment Share on other sites More sharing options...
756puller Posted November 26, 2022 Author Share Posted November 26, 2022 Already did a new EGR valve and new ignition coil. Started it up today when it was maybe 45 degrees out and it ran perfectly. Quote Link to comment Share on other sites More sharing options...
TRAVELETTE Posted November 26, 2022 Share Posted November 26, 2022 Major vacuum leak? Quote Link to comment Share on other sites More sharing options...
756puller Posted November 27, 2022 Author Share Posted November 27, 2022 How would you check for a vacuum leak? Quote Link to comment Share on other sites More sharing options...
nomorejohndeere Posted November 27, 2022 Share Posted November 27, 2022 spray either or some such around fittings and flanges and see if the engine vrooms ......... Quote Link to comment Share on other sites More sharing options...
Gearclash Posted November 27, 2022 Share Posted November 27, 2022 If the fuel pressure is at spec it ain’t the pump. I had a fuel pump take a dump, it would act up more when hot, would idle just fine, part throttle was fine, ask for full power and the pressure would drop off, engine would cut out like the ignition was getting switched on/off. It was a Nissan 5.6, and those infinitely wise nitwits don’t put a pressure test port on the fuel rail. Idiots. Quote Link to comment Share on other sites More sharing options...
New Englander Posted November 27, 2022 Share Posted November 27, 2022 23 years old hoses may be getting crunchy. As NomoreJD says, you can spray brake cleaner or ether, careful with ether, on suspect areas including the intake manifold. It's tough to do much troubleshooting with only a code reader as it tends to load the parts cannon to blast at it. I've got an inexpensive Autel that's been good enough for my kid's BMWs but they've been reliable cars so far. For GM I have a Tech2, which is bi-directional and pretty descent but obsolete after '13 so when we replace the current vehicles I'll need something newer/better. There may be a forum out there for your vehicle/engine that may help. Quote Link to comment Share on other sites More sharing options...
vtfireman85 Posted November 27, 2022 Share Posted November 27, 2022 14 hours ago, 756puller said: Already did a new EGR valve and new ignition coil. Started it up today when it was maybe 45 degrees out and it ran perfectly. When it is cold out does it smooth out once the car warms up? I had an intake hose not in place underneath where I couldn’t see it, fortunately it caused running issues before I dusted anything, but symptoms were similar, it was causing MAF sensor to get all out of whack and lean things out. Quote Link to comment Share on other sites More sharing options...
756puller Posted November 27, 2022 Author Share Posted November 27, 2022 It does not smooth out when the car gets warmed up, seems like below 30 degrees I have to keep my foot on it so it will run, it wouldn't idle by itself. Quote Link to comment Share on other sites More sharing options...
vtfireman85 Posted November 27, 2022 Share Posted November 27, 2022 39 minutes ago, 756puller said: It does not smooth out when the car gets warmed up, seems like below 30 degrees I have to keep my foot on it so it will run, it wouldn't idle by itself. 39 minutes ago, 756puller said: It does not smooth out when the car gets warmed up, seems like below 30 degrees I have to keep my foot on it so it will run, it wouldn't idle by itself. Starting fluid or carb cleaner sprayed around will help you find your issue i bet Quote Link to comment Share on other sites More sharing options...
Dirt_Floor_Poor Posted November 27, 2022 Share Posted November 27, 2022 Does it have an “idle air control valve”? Quote Link to comment Share on other sites More sharing options...
gearheadmb Posted November 27, 2022 Share Posted November 27, 2022 On fords of that era the first step when you have a drivability problem is to clean element in the mass air flow sensor. They are very sensitive to any type of contamination and will cause all sorts of running issues. It's not a guaranteed fix but it's a very common fix, and its free. 1 Quote Link to comment Share on other sites More sharing options...
td9inidaho Posted November 27, 2022 Share Posted November 27, 2022 33 minutes ago, gearheadmb said: On fords of that era the first step when you have a drivability problem is to clean element in the mass air flow sensor. They are very sensitive to any type of contamination and will cause all sorts of running issues. It's not a guaranteed fix but it's a very common fix, and its free. And on some of them, you can lightly tap the mass air flow sensor and if going bad, engine will stumble, those early computers are in open loop mode when you first start the car, so they are really only looking at crank position sensor for timing and temp sensor for enrichment. Vacuum for fuel pressure regulating, a cracked intake hose, or other lines be my first check. Good luck Mark Quote Link to comment Share on other sites More sharing options...
Cattech Posted November 27, 2022 Share Posted November 27, 2022 First step in diagnosis is getting something to see what sensors are reading what values. Without that info, you're just doing a driveby shooting. An adapter like above that works with whatever phone, tablet, laptop you have via Bluetooth, and a free app/program will get you said info. Quote Link to comment Share on other sites More sharing options...
Owen Aaland Posted November 28, 2022 Share Posted November 28, 2022 It is pretty hard to find a vacuum leak by listening for a change in engine sound when spraying ether or carb cleaner. The computer will compensate for the added fuel entering from the leak and cut back on the injector pulse width. If you have a scan tool to monitor the injectors you will be able to see when you find the leak. 1 Quote Link to comment Share on other sites More sharing options...
TRAVELETTE Posted November 29, 2022 Share Posted November 29, 2022 I have used water in a spray / squirt bottle when hunting for vacuum leaks. listen for a stumble, and or, steam out the tailpipe. Just did this on a 2008 Silverado with a 5.3. found a bad intake gasket. Quote Link to comment Share on other sites More sharing options...
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