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93 SE 4-cyl "hot" starting issue

3K views 8 replies 3 participants last post by  CatSkinner 
#1 ·
I've been reading a lot about others with a similar issue, and several have pointed to a "near-recall" condition of the distributor wiring creating shorts when the engine is hot, but this is not 100% of my issue. Others with this issue also seem to complain about stalling while driving, but this is also NOT my issue.

Cold start in the morning fires up like she should on the first crank, but not 100% of the time... more like 95%. Hot starts (like driving to the store, and only letting the engine cool for 20 minutes) results in the issue occurring more frequently, but still only <50% of the time.

When it does occur, I can feather the gas pedal, and force the engine to continue running almost every time. But, if I pull my foot from the pedal too soon (less than a minute or two), the engine will stall. Several more attempts, and the engine will start and run like normal (without touching the gas pedal).

I have a new fuel filter and fuel pump is within spec (peak with engine off @ 37-PSI). I have also replaced the usual things (spark plugs, air filter, PCV, oil/filter change, belts and hoses as needed, new gas-cap, battery, flush/fill of coolant, new exhaust and cat, etc.), and the intake and injectors have been cleaned, but the problem still exists. It is not constant, and some days when you expect it to not start... it does... other times... you're stuck cranking for a few minutes.

When she does start, idle is perfect and steady @ 650 RPMs, and she runs like a brand-new vehicle!

It has never "failed" to start within a couple of minutes of continuous attempts, but it is becoming very frustrating because it is unpredictable... not to mention the fact that it is embarrassing when your car won't start, yet the 1970's POS (missing body panels, exhaust, and is 5 different colors) next to you cranks right up!

I get no dash lights or computer codes generated from this. Cylinder compression is also (surprisingly) within tolerance... 152/147/144/148 PSI, despite the age and 125K on the odometer. One Ford dealer and two other "trusted" mechanics have looked at it... and neither can find the cause, although they are all willing to throw parts at it... at my expense!

Could I have a sensor failing intermittently, or perhaps there is a wiring issue that is common, which I'm not aware of for this engine?
 
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#2 ·
I'm leaning towards IAC, but it's difficult to say for sure. I think heat is the clue here. When electrical connections are hot, they can build resistance which will throw off your signals. Don't know if you've ever given the throttle body a good cleaning, but I'd start there and check your terminals. While inspecting them, clean them with electronics cleaner, then coating them with dielectric grease and see if the situation improves. Makes sure you clean the MAF as well, as that may also be the culprit.
 
#3 ·
Cat, thanks for the quick reply. I had recently cleaned the MAF, Throttle body, Intake, and injectors, but had not thought of the IAC. I will check that today!
 
#6 ·
I've inspected the wiring for the IAC and MAF, and cleaned the contacts with contact-cleaner and followed-up with dielectric grease.

I only drove her once over the weekend (was too pretty out to ignore my motorcycle, lol), and had no issues starting hot or cold. But, since this problem has been intermittent, I'll have to wait and see what happens over the next week or so.

One thing I did notice when I stopped for gas on Saturday (still had half a tank)... removing the gas cap had an unusual release of vacuum pressure! I've never noticed this before... perhaps I have a bad gas-cap vent which is compounding the issue? Or does this car have a vented tank, rather than utilize a vented cap?
 
#8 ·
Okay, it has been several days now, and not one single hiccup on starting... HOT or COLD.

I think cleaning the harness contacts did the trick... most likely an intermittent issue caused by some gunk in the harnesses after 20 yrs.

If it happens again, the electrical will be the first place I check, and there is always the possibility of replacing the IAC, which seems to be the culprit.

As for venting... I believe you're right on tank vent. I've tried my old cap, and the one from my Grand Marquis... all of them have some vacuum pressure build up on the Probe's tank. Then again, even my Grand Marquis and my son's Elantra are having slight vacuum pressure build-up in the tanks, thanks to this screwy weather we've been having... When temps swing 30+ degrees in the course of a day, high humidity, rain, sun, etc... it takes a bit of time for the tanks to balance out. The only one that does not seem to be affected by the weather is my '69 F250!
 
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