Armed Polite Society
Main Forums => The Roundtable => Topic started by: Nick1911 on March 08, 2012, 05:43:27 PM
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Car is a 1989 Crown Vic. 5.0L, 302 windsor V8. EFI, Ford TFI ignition.
Won't idle cold without throttle. Revs up, then slows until it dies, or nearly dies. It will cycle like this until it's warm. Persistant misfire across entire power band. Warm idle doens't lope, but still has a bad misfire.
The loping idle is very similar to what a vacuum leak does. I haven't found a vac leak though. This is a fairly sudden problem; it did not develop slowly.
I've replaced plugs, wires, cap, rotor, and the coil.
Thoughts?
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Sounds like my Subie when it had bad gas....water in it, to be specific...
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You need a paperclip and pen and paper=D All 5.0 are the same this should help.
http://dfwmustangs.net/forums/showthread.php?t=7908 (http://dfwmustangs.net/forums/showthread.php?t=7908)
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How did the old plugs look?
Compression test time?
jim
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Other items to look at,
faulty idle air control circuit in the throttle body
dirty/oily MAF sensor
faulty PCV
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crank sensor?
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Choke stuck? Cars a bit old for my experience.
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Throttle position sensor would cause idle problems but not a miss. EGR might cause something like this, but it would be a progressive thing. Sounds a lot like you have a vacuum leak.
Brad
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Thanks for the replies.
I'm thinking it's a vacuum leak still. Wish I could find it.
No choke on this car - it's EFI.
Also no crank position sensor. About the only sensor for engine rotation this thing has is the one in the distributor to fire the coil.
I've cleaned and tested the IAC valve.
Replaced the PCV valve
Has new TPS sensor.
Tested the EGR.
Tested the MAP sensor.
Jim, I hope you're not right. Not wanting to deal with an internal engine mechanical problem right now. =|
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I'm thinking it's a vacuum leak still. Wish I could find it.
Get a can of starting fluid . Slowly spray the engine a listen for RPM change. You also have hose going to the brakes power booster make sure you check that one too.
Did you check for codes ?
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First you need to identify which cylinder isn't firing properly. The old "pull each plug wire in succession without getting zapped out of your shoes" process may be painful, but it works and it's free.
Brad
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I'd check plugs and wires first.
If you park it in a garage and start it up, or start it up at night, you can often times see arcing if the plug wires are bad.
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Another trick is spray water on the headers/exhaust manifold, the non-firing cylinder's spray will evaporate slower.
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Get a can of starting fluid . Slowly spray the engine a listen for RPM change. You also have hose going to the brakes power booster make sure you check that one too.
Did you check for codes ?
I tried that with a can of carb cleaner. Didn't have any luck.
It's pre-OBDII There were no codes I could find stored in the proprietary ECU memory.
First you need to identify which cylinder isn't firing properly. The old "pull each plug wire in succession without getting zapped out of your shoes" process may be painful, but it works and it's free.
Brad
I tried this too. And got shocked, of course. I found no appreciable difference in how it ran when any particular plug wire was pulled. Stupid v8 and all it's redundant cylinders. I'm not convinced that any particular cylinder isn't firing. Which again leads me to either a vacuum leak, or an ignition system problem.
I'd check plugs and wires first.
If you park it in a garage and start it up, or start it up at night, you can often times see arcing if the plug wires are bad.
Plugs and wires are brand new.
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If it's temperature dependent the temp sensor could be faulty.
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Pull one of the new plugs and see what the build up looks like. Mismanaged fuel can also cause those symptoms.
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Pull one of the new plugs and see what the build up looks like. Mismanaged fuel can also cause those symptoms.
Will do. I'll post pics of the plugs tomorrow.
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Check tech/service bulletins. I had a Crown Vic of about that vintage which would crap out at the most inopportune times, like making a left turn while the light was green... uh-oh!
Or when I was showing a horsey property out in rural areas... damned embarrassing.
Finally diagnosed it to a faulty Electronic Control Module (ECM, on-board computer, whatever) which cost umpteenmany bucks according to the dealer. Called around the junk parts places, finally hit one where the guy didn't have one, but said there was a tech bulletin on it and the dealer should replace it for free.
So I axed how come the dealer didn't tell me that.
He said the dealers would often replace tech bulletin things, charge you, and then charge the factory for the repair under the tech bulletin.
Double-dipping is the polite phrase for it.
Might not be a freebie for a car that old, but at least you might find there is one, and what to do about it on your own.
I also found one for hard power steering in cold weather on one vehicle I had which was out-of date, but at least I knew how to correct it. New rack 'n pinion, but I let it go and developed massive triceps muscles every winter. I had arms that looked like frog's legs.
Terry, 230RN
REF (Sample):
http://www.cleverdude.com/content/find-technical-service-bulletins-tsbs-for-your-car-online/
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my first thought was vacuum leak. not likely that you will get the same result with carb cleaner as starting fluid. clue for you, if you pull the spark plug wire at the distributor you will not get a shock (unless you are touching the coil wire!). check for play in the distributer shaft? check the vacuum and centrifical advance mechanisms. check flow, psi, and quality of fuel. good luck!
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I had a 96 F150 with that engine that did the same thing, but only when it was rainy/foggy out. When the weather was dry, everything was ok. After a bit of warmup, the engine would start working normally. I sold the truck on a dry day to a dip sh*t relative.....chris3
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Get a can of starting fluid . Slowly spray the engine a listen for RPM change. You also have hose going to the brakes power booster make sure you check that one too.
Unlit propane torch is cheaper and gives less of a hangover.
Mind the fan and belts!
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"Unlit propane torch is cheaper and gives less of a hangover."
Huh! Good idea! Sounds less dangerous than spraying starting fluid ether all over a hot engine, too.
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Nick, you mentioned before it doesn't have a crank pos sensor; check for a cam pos sensor. If it is fuel injected, it must have a position sensor.
Whats the condition of the fuel pump?
(You can check the quality of idle AFR by carefully spraying fuel into the intake to see if it helps idle. Use a spray bottle set "mist" for best results, make sure it is clean.)
Don't these engines have hydraulic lifters?
Are you getting any valve train noise while cold?
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Nick, you mentioned before it doesn't have a crank pos sensor; check for a cam pos sensor. If it is fuel injected, it must have a position sensor.
On the TFI system the crank position is supplied to the ECA by the PIP sensor in the distributor. That 5.0 should fire the injectors in two banks of 4, once each per rev. That said if the sensor in the distributor is failing and giving bad info, it would lead to both faulty injector firing and bad ignition timing. You could through a timing light on it and see if at least the number 1 hole was firing at the appropriate time.
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Replaced TFI-IV ignition module
Replaced PIP hall-effect sensor in distributor.
Pumped smoke into intake manifold under slight pressure - no leaks evident.
No change to engine running conditions.
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I'm thinking it's a vacuum leak still. Wish I could find it.
I wouldn't give up chasing a vacuum leak yet. I've used WD-40 to find a few sucking engine wounds.
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The TFI isnormally a good or bad thing. The hall effects seem to have hot problems when they act up.
I have a low mile '91 460 EFI down here if you want to try to shoehorn it in. >:D
I have the in-laws coming down to take us to lunch for Sherri's birthday tomorrow but I should be able to get free in the later afternoon. I have fuel PSI tester, compression tester, ect. I can bring up.
Does that motor use the plastic intake spacers between the heads and the intake? They can burn through and cause an internal vacuum leak.
For chasing vacuum leaks, I have used water several times. It's not as quick to show as starting fluid but you always have some around.
jim
Also, just found the last piece of the governor that went flying when the cam broke. [ar15]
Maybe I shouldn't help with your car. =|
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That 460 should fit into that Crown Vic just nicely. If not I have a 93 F-150 that it would fit in. >:D
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I had a problem very similar to this with a 1992 Caddy Brougham.
Turned out to be a gummed up Idle Air Bypass in the TBI.
Sorry if that's already been tried, I mostly skimmed the thread. ;)
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dropped exhaust system - no change
replaced fuel filter - no change
Neighbor Tom (who use to build 302 and 351's for racing) got it to run by spraying wd40 into the intake. He assures me it's a fuel problem.
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This weekend - pulling injectors, ecu and MAP sensor from the junkyard. I'm at a loss at this point for what else to do.
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Nuke it from orbit.
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Nuke it from orbit.
Aww, but I like this car!
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This weekend - pulling injectors, ecu and MAP sensor from the junkyard. I'm at a loss at this point for what else to do.
Have you tested the temp sensor? And if you have, are you sure it was the one for the ECU and not one for the dash?
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I would tend to suspect a fuel pump before the injectors.
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I would tend to suspect a fuel pump before the injectors.
could be a little of both, weak pump with dirty injectors
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could be a little of both, weak pump with dirty injectors
Yeah, good point. Especially if the injectors are spraying the walls too much or dribbling out now and not getting good atomisation while cold. When the engine is hot, it may cause the wet port walls to evaporate and make the problem go away.
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[quotecould be a little of both, weak pump with dirty injectors][/quote]
My TB gets an engine misfire/injector code once or twice a year, clearing the code with the OBD scanner only means the code pops up again the next day. Neighbor, who is a mechanic advised me to buy a quart of GM Top Engine Cleaner (~35) and dump it into the gas tank. Code usually goes away 1/2 tank of gas later and comes back on 6-8 months later.
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This weekend is pretty free for me. If you need something just ask. I think I owe you one or more.
jim
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Got it!
Mass Air Pressure sensor. (Note: not MAF sensor)
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Got it!
Mass Air Pressure sensor. (Note: not MAF sensor)
Huh. Thanks for posting the answer/resolution. One more thing from which to learn.
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Got it!
Mass Air Pressure sensor. (Note: not MAF sensor)
Awesome!
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The replacement of a 50 dollar part is brought to you today by 700 dollars of diagnosis.
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Glad you got it taken care of.
Since you don't need it, I wounder if I can shove that 460 in the tractor.
jim
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Glad you got it taken care of.
Since you don't need it, I wounder if I can shove that 460 in the tractor.
jim
Stock?
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Got it!
Mass Air Pressure sensor. (Note: not MAF sensor)
Cool, glad you got it. So it was a fuel problem.
For future reference, The MAP sensor on early FI systems is a Manifold Absolute Pressure sensor. It was replaced by a MAF, or Mass Air Flow sensor. MAP's are used in conjunction with an Inlet Air Temperature sensor and engine speed information to find the mass air flow rate by speed-density calculations. Ford switched to a MAF in the early 90's (depending on year).
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IIRC the 460s stayed with speed density injection til they were replaced by the 6.8L V10 in the late 90's. Only the CA models got mass air.
Brad