I have a weird problem with my '95 Crown Vic. My mechanic spent two days trying to figure it out and finally he gave up and with a lot of misgivings said, "Take it to Ford". Problem is I'm afraid to go near a dealership, as I know they will probably start changing expensive parts until they hit the right one.
My engine is a SOHC 16 Valve 4.6L V8, sequential multi-port electronic fuel injection (SEFI), on board diagnosis Level II (OBDII) with Ford electronic engine control V, distributor less system (DIS) ignition system with 2 modules and 8 coil packs.
My problem started out as a starting issue. In the morning I'd hit the key and it would start then promptly stall. On a second start it started properly and ran fine. This got gradually worse as the cold weather hit. Finally last week, at -25, it would start but I had to sit in it feeding gas until the car reached about 3/4 operating temp before it would idle without stalling. Then I noticed a new problem, while driving the engine would surge. It would lose power for a few seconds and then return to normal.
So my mechanic started by replacing the IAC (idle air control). This helped the start but didn't affect the surge. He figured the surge had to be either a vacuum leak or a fuel problem. He bypassed all the accessory vacuum lines and checked everything he could think of, no leaks. He checked the fuel pressure; it was good 32 psi at start and 75 psi at max bypass. So next he swapped the MAF (mass airflow sensor) with no improvement. He now thinks it must be a problem with the ignition. The engine isnít reporting any codes, but he said this isnít surprising since I guess the early ECC-V systems first used in í95 donít report ignition codes correctly all the time. The surging is so bad now that the car is a little scary to drive. When stopped at a light with foot on the brake, the car will all of a sudden increase idle RPM and the car tries to take off. To drive it now I shift to neutral at all the lights and in stop and go traffic I have to stay about 15í back from the guy in front so that the silly car doesnít climb his back bumper.
Anyone have any ideas. Iím terrified of having to turn a dealership loose on this. I figure theyíll start by replacing the ECC and anything else that connects to it.
I took the car to a friend at a large Ford dealership and he arranged to have the car done by one of the lead tune-up guys as an after hours project. He rechecked all the things we had discussed and found that the new IAC control was fubar. He replaced the IAC again and the car still wouldn't idle. Since there is a history of IAC failures causing damage to the PCM, we decided to get a used PCM to try out. Plugged it in and the car runs perfectly!! Even better, the used PCM only was $200. :D
So there's a factiod to store in the back of your mind, if the IAC dies and your engine still runs the same after installing a new one - look real hard at the PCM. The silly thing produces no codes, it just won't control the IAC as it should.
Bill, thank you for the helpful information. I own a '96 and an '02 CV. My '96 has 122K on it now so I'm always wondering what is going to croak on it next. (Just had to replace the intake manifold a few months ago). I've recently read about some other people who have had the IAC control go bad on their Vics so I wonder how much longer MINE has to live. I have to admit my almost total ignorance with "tech" related topics. What is the PCM exactly?
Looked at the photo of your Stealth Vic, awsome looking!!
Well I'm not an expert by any means, but this go around has me starting to use the three letter codes like pro. Truth be known, I've picked up enough knowledge to be dangerous.
Powertrain Control Module (PCM)
PCM monitors engine operating conditions by inputs received from engine sensors. Control of output actuators determines fuel mixture and idle speed. The engine control system consists of the PCM, relays, modules, sensors, switches and actuators. The PCM sends out electrical reference signals to engine sensors and then analyzes the return signals. The engine sensors supply the PCM with specific information, in the form of electrical signals, to determine engine-operating conditions. In the event of a sensor or actuator failure, the PCM initiates an alternative strategy called Failure Mode Effects Management (FMEM) to allow the vehicle to remain driveability. The Malfunction Indicator Light (MIL), or Check Engine Light (CEL), will remain on whenever FMEM is in operation. FMEM substitutes a fixed sensor signal and continues to monitor the failed sensor. If signals from a faulty sensor return to within operating limits, PCM will resume using the sensorís signal.
In my case the Idle Air Control failed and at the same time the IAC circuit within the PCM failed as well. For some reason the PCM was unable to detect these failures so the PCM did not generate any codes or to switch into FMEM mode.
I posted information about the EGR filter about a month ago. This little thing can drive a mechanic nut's. And have you guy's noticed that the 4.6 engine require's plug wire's very often? I've gotten to where I change mine every year just for peace of mind
When in doubt :DON'T
Valley Station, Kentucky
Dream EXPression Racing
I had to replace my plug wires at the same time I replaced the intake manifold. Apparently the cracked intake manifold was slowly leaking radiator fluid on the wires for a while and caused some corrosion on them. My son's been using the car at college- he said, "I thought the engine wasn't running as smooth as it used to" when I told him what went wrong under the hood.
I haven't had any plug wire problems, I'm still running the same plugs and wires as the car was built with. Mind you, I only have 50K miles, but even so the car it 8 years old. I have one of those home power washers and use it once a year or so to blast all the dirt and junk off the motor. That way my wires and such are pretty clean so maybe that's why they haven't failed yet.
I have a '96 CV and have the same problems. It's like the car has a mind of his own. Sometimes it starts just fine but most at the time it won't. Just got it back from the second mechanic today, guess I'll go there tomorrow again. So far they changed sparkplug wires, cleaned the intake, checked the fuelfilter and changed 1 of the 4 sensors. The computer didn't find anything wrong either. And of course, when the mechanic started the car it run just fine. Just like when you go to the dentist, your pain is gone the second you step in to his office.
Hopefully my mechanic has some good news for me tomorrow
Bill, thank you for the information -- gave me hope again :)))
I don't quite see what your car is doing, but if it acts up in the AM and then is ok the rest of the day, it does sound like what mine did. The first indication I had that anything was wrong with my car started about a year before it got serious. When starting the car, if it had sat overnight, the first turn of the key would start the engine, but it would immediately stall. The second turn of the key would start the engine and all was correct. After about 6 months of this, the time it had to sit shrunk from 12 hours to 3 or 4 hour. Once started the car still ran perfectly. Eventually it got really bad and I got off my butt and took it to the shop. I think the problem from day one was the IAC (idle air control) and I think by letting it go as long as I did, the faulty IAC eventually cooked the PCM (power train control module). Either that or the replacement IAC which itself was faulty caused the damage to the PCM. At this point who knows!
So moral of the story, donít procrastinate when a sensor acts up, it can get expensive real quick if it turns into a witch-hunt as mine did. In the end my $150 IAC repair ended up costing me over $1,000 and it was my own stupid fault.
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