Author Topic: Amateur mechanics - Car problem (Read 9086 times)

Nick1911 · « **on:** March 08, 2012, 05:43:27 PM »

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?

Ex-MA Hole · « **Reply #1 on:** March 08, 2012, 06:46:28 PM »

Sounds like my Subie when it had bad gas....water in it, to be specific...

Frank Castle · « **Reply #2 on:** March 08, 2012, 06:49:59 PM »

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

Jim147 · « **Reply #3 on:** March 08, 2012, 07:00:17 PM »

How did the old plugs look?

Compression test time?

jim

drewtam · « **Reply #4 on:** March 08, 2012, 07:08:43 PM »

Other items to look at,
faulty idle air control circuit in the throttle body
dirty/oily MAF sensor
faulty PCV

Harold Tuttle · « **Reply #5 on:** March 08, 2012, 09:13:35 PM »

crank sensor?

never_retreat · « **Reply #6 on:** March 08, 2012, 09:15:38 PM »

Choke stuck? Cars a bit old for my experience.

Brad Johnson · « **Reply #7 on:** March 08, 2012, 11:30:46 PM »

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

Nick1911 · « **Reply #8 on:** March 09, 2012, 01:03:16 AM »

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.

Frank Castle · « **Reply #9 on:** March 09, 2012, 06:55:23 AM »

Quote

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 ?

Brad Johnson · « **Reply #10 on:** March 09, 2012, 08:23:24 AM »

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

brimic · « **Reply #11 on:** March 09, 2012, 08:32:28 AM »

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.

wmenorr67 · « **Reply #12 on:** March 09, 2012, 08:49:00 AM »

Another trick is spray water on the headers/exhaust manifold, the non-firing cylinder's spray will evaporate slower.

Nick1911 · « **Reply #13 on:** March 09, 2012, 10:29:43 AM »

Quote from: AZtoy on March 09, 2012, 06:55:23 AM

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.

Quote from: Brad Johnson on March 09, 2012, 08:23:24 AM

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.

Quote from: brimic on March 09, 2012, 08:32:28 AM

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.

White Horseradish · « **Reply #14 on:** March 09, 2012, 10:42:41 AM »

If it's temperature dependent the temp sensor could be faulty.

dogmush · « **Reply #15 on:** March 09, 2012, 10:47:13 AM »

Pull one of the new plugs and see what the build up looks like. Mismanaged fuel can also cause those symptoms.

Nick1911 · « **Reply #16 on:** March 09, 2012, 11:42:53 AM »

Quote from: dogmush on March 09, 2012, 10:47:13 AM

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.

230RN · « **Reply #17 on:** March 09, 2012, 03:52:11 PM »

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/

geronimotwo · « **Reply #18 on:** March 09, 2012, 09:00:12 PM »

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!

coppertales · « **Reply #19 on:** March 10, 2012, 11:28:05 AM »

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

Tuco · « **Reply #20 on:** March 10, 2012, 12:23:10 PM »

Quote from: AZtoy on March 09, 2012, 06:55:23 AM

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!

230RN · « **Reply #21 on:** March 10, 2012, 03:41:29 PM »

"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.

drewtam · « **Reply #22 on:** March 10, 2012, 07:05:29 PM »

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?

dogmush · « **Reply #23 on:** March 10, 2012, 07:24:45 PM »

Quote from: drewtam on March 10, 2012, 07:05:29 PM

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.

Nick1911 · « **Reply #24 on:** March 10, 2012, 10:20:30 PM »

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.

News:

Author Topic: Amateur mechanics - Car problem (Read 9086 times)