new-to-me mint '93 limited stalls when cold

[yglide123]

Hi All,

A few months back I purchased a really nice '93 Limited that had been sitting in a garage with minimal use for the last 10 years or so. Exterior and interior are in great shape for the age, ~135,000 miles on the clock. Had to replace tires and do some suspension work to replace rotted bushings, but she's up to speed now.... except suddenly she is dying on me and the problem seems to be getting worse.

On cold start the engine revs to 2,000 RPM or so for about 15 seconds, then drops super low (500rpm or so) and dies unless I tap the gas at which point it revs back up for another 15 seconds. When warm, the RPM seems to stabilize around 1,000 RPM. No check engine light is on. Engine doesn't feel like it is missing, shaking, or otherwise until the RPM drops too low. When put in gear it used to stay at appropriate RPMS, although recently it has started dying in gear as well. It does appear to be losing coolant slowly too. No evidence of it in the oil.

So far I've tried changing air filter, cleaning MAF, changing the IAC valve and PCV as some other threads suggested but with no change on behavior. I'm wondering about an intake manifold leak (might explain coolant loss?) - but didn't get any surging of the engine when spraying brake cleaner near the intake gaskets.

It's my extra car - so not in a rush, but would love suggestions on how to troubleshoot this further before I rip the intake apart as a blind guess. Thanks in advance!

 

[MrQ]

Nice Limited!

A bad lower intake leak could cause this, but you would also see some oil consumption as well. You probably have a vacuum issue. Check all you vac lines for cracks. Places the vac lines go off the tree:

• Fuel Pressure Regulator (Passenger side fuel rail, bad regulator can cause fuel to be sucked into the intake)
• Transmission vacuum modulator (runs behind the upper intake down toward the passenger side of the transmission, bad modulator will cause transmission fluid to be sucked into the intake)
• Cruise control servo (driver's side fender)
• Vacuum reservoir (long thin canister on top of the evaporator core box, passenger side firewall)
• Vac line from the reservoir to the recirculate door actuator (behind glovebox)
• The brake booster
• The vac line to the PCV valve
• Line to the heater control valve (passenger side firewall in front of the heater core)

There is also a vac line coming off the bottom of the throttle body that goes to the evap system charcoal canister (driver's side fender, big box with two caps on it) through a purge valve located under the intake manifold.

Also meet my 93 white Limited, Stripe

 

[Roadrunner777]

I have had this with a bad MAF. I see you have cleaned it, but you might look on-line for ways to test it, such as this webpage:

Part 1 -How to Test the Ford Mass Air Flow (MAF) Sensor

This is the engine struggling to get to the right fuel/air mixture. So, any unaccounted for air in the intake system after the MAF will do this. Vacuum leaks will do this, as you obviously know. A bad MAF will do it, as I said.

You know what else is really common in this generation of explorer? Holes/leaks in the plastic tube between the MAF and the throttle. I'd pull that off, it's easy to do, and inspect the underside carefully.

 

[yglide123]

I’m glad to see I’m not the only one who loves these old Limiteds!!

thanks for the advice. I checked the lines today and didn’t see anything concerning. The engine bay is super clean and all the hoses look new despite being 26 years old. Is there any way to check the lines besides visual inspection and feeling for cracks/tears?

Also, I tested the MAF as per your suggestion, everything seems to check out ok according to my multimeter.

Any other suggestions before I just start tearing the intake apart? Definitely loses coolant, doesn’t seem to have any oil consumption. Oil looks clean.

 

[Roadrunner777]

If you checked the plastic tube between the MAF and throttle, and that was ok, along with what you have said... no, I don't have any experience to offer.

 

[MrQ]

Before you pull the lower intake, you might try and spray brake fluid around the vac line areas as well. Those hard lines are know to get brittle and crack over time. Definitely check you fuel pressure regulator (pull the vac line off and see if there is fuel coming out of it). Also change your fuel filter. Last but not least, disconnect the negative battery terminal for ten minutes. Sometimes when you replace parts it helps to reset the computer so it can relearn.

 

[mgmgmg]

Question I have is you have no cel? Turn key to on postion and see if it lights up? I had same issue was EGR Valve, solenoid. What I did was unplug the vacuum line behind it and see if it doesn't stall...

 

[Centaurious]

If the truck has cruise control pinch off the vacuum line and see if it changes.

 

[smegun]

after experimenting with MAF from aerostar and such it would run but stall on idle my cross reference was bad the girl at the salvage yard says 94 is specific to one year only but the astro van and ranger I pulled the last two out the astro van was brighter all around but would stall the ranger didn't do anything right

 

[yglide123]

Thanks for more ideas everyone.... I checked fuel pressure regulator valve and no fuel in it. Turns out I don't have an EGR valve, so can't be that. I tried pinching several vacuum lines but no change in behavior.

The Check Engine light did come on briefly the other day when it was very cold and it was running poorly, but went off again.

I broke down and got a scanner for it.

KOEO gives me codes of 172 and 176 (both banks lean?)
KOER gives me a cylinder 6 code of 136 and a 538 code (not up to temp?)

I haven't changed the fuel filter (as they are a pain in the butt) - but do we think that would make a difference at this point?

 

[massacre]

Def change the fuel filter. They seem to lead to problems if you don’t stay on them

 

[MrQ]

Thanks for more ideas everyone.... I checked fuel pressure regulator valve and no fuel in it. Turns out I don't have an EGR valve, so can't be that. I tried pinching several vacuum lines but no change in behavior.

The Check Engine light did come on briefly the other day when it was very cold and it was running poorly, but went off again.

I broke down and got a scanner for it.

KOEO gives me codes of 172 and 176 (both banks lean?)
KOER gives me a cylinder 6 code of 136 and a 538 code (not up to temp?)

I haven't changed the fuel filter (as they are a pain in the butt) - but do we think that would make a difference at this point?

Fortunately the system kicked out codes. And you are definitely having a fuel or vac issue.

The OBD1 system, at least for me, is notoriously stubborn about spitting out codes. (I know I had a misfire, check engine light even flashed at me a few times. Pulled the codes, nada. Very annoying. Turned out to be spark plug fouling on cylinders 1 and 3)

Have you checked the fuel pressure? Needs to be over 30 psi at idle and 40 at WOT. That will tell you if its a fuel issue. Also if the system bleeds down fast (within five minutes) you may have a bad fuel pump even if the pressure is good.

Fuel filter isn't too bad. You will need to unbolt the cage and remove some retaining clips for the brake and fuel lines. Also make sure that you get the "Blue" Ford ford fuel disconnect. I have had good experience with these:

Lisle Angled Disconnect Tool Set-LIS39400 - The Home Depot

 

[yglide123]

So I finally figured out the issue! Apparently a previous owner had mickey moused a plug for one of the vacuum ports out of non-automotive hose that had pretty much disintegrated and was just barely dangling off the port. It was hidden in the back so I hadn't seen it before. Plugging the port properly totally fixed the problem and she's running great. I still need to dive into the coolant loss issue, but at least the engine isn't dying all the time now.

Thanks all for the suggestions and help figuring this out!

 

[MrQ]

Looks about right. Anything breaks coming off that vac tree leads to a hell of a lot of problems