Rough idle and stall when starting - sometimes.

[Raschied]

Hi everyone. I just joined the rank of Explorer owners this week. I picked up a 94 XLT, great condition, 109,000 miles, every switch works, body in great shape, runs solid, EXCEPT...

Every once in a while, after starting, it idles very rough, like a cylinder or 2 aren't firing. If I pull it out of Park and take off like this, it'll stall in 20-30 seconds, and won't start up for 4-5 minutes. If I give it some gas in Park, usually it starts idling fine. If I turn it off, then back on, the problem has always gone away.

I've been trying to isolate the conditions that put it into this bad state, but so far it's been very random. 2nd stop after freeway trip, 3rd stop from house, car sits for 20 minutes, car sits for 2 hours, etc.

It has NEVER dropped into this rough idle state after startup. It only happens right after I turn the key, and then it's about 1 in 7 starts.

I got a great price on the car overall, and would rather troubleshoot this out than try and yell at the previous owner about it. Any ideas? Thanks!!!

BTW - great board! I can't wait to hit the Sierras and give this thing a workout!

 

[Raschied]

bump

bump

 

[Alec]

It's probably that you need to give the fuel pump a little more time to pressurize the system.

Try this: Everytime you go to start the truck, turn the key to "on" and wait about 3 seconds, then start it. If it's what I think it is, this should fix your problem. Please try this and tell us if the problem goes away or not.

 

[transmissionguy]

i have a 94xlt and i have the exact same problem ! I will try your suggestion and see if it helps

 

[Raschied]

Heh

On my way around town, I was thinking the EXACT same thing, especially after hearing about the fuel pump in the gas tank. So far, it's worked like a charm!

Thank kew!

 

[Majisto]

Clean the Idle Air Control valve. It's a small silver cylinder by your throttle body. Spray some O2 safe Carb Cleaner in it. Should fix your idling problems.

 

[Rhett]

I was thinking fuel pump relay possibly...

If it ever dies while you're driving it's probably an O2.

 

[Raschied]

Okay, the problem came back with a vengeance. It seems to be related to length of time between stops. If the X is cold, like in the morning, it'll start fine. If I let it sit for less than 10 minutes, it's fine. The "problem window" seems to be 15-35 minutes. After 35 minutes, it'll usually start and run fine. But during that 15-35 minute window, like running into the grocery store to stock up, it'll get cranky.

I can immediately tell how it'll act when I crank it up. If the RPM jumps up to 1000, then backs down slowly over 10-15 seconds to about 600-750, then I'm golden, and it'll run fine untill I shut it off again.

If I'm gonna have problems, the RPM starts at 750, and runs really rough, eventually (if I let it) dropping as low as 250 before stalling out.

I am concerned because the length of "bad time" has gotten longer since I've had it. I had 1 spell where it wouldn't start for almost 20 minutes, but then started up fine like nothing ever happened.

Fuel system is definitely suspect at this point, since it feels like the engine isn't getting fuel to all injectors, and then finally starving out. I'm thinking of changing the fuel pump relay first, and going from there. (Thanks, Rhett, for the suggestion.)

 

[Raschied]

bleagh.

It also seems to be more prone to doing it on very hot days. We've already had one 100+ spell here in the Sacramento valley, and it was the worst then...

 

[Alec]

Have you changed your IAC?

 

[Raschied]

Crossing fingers

Okay, I pulled the fuel pump relay, examined it, and shook it a bit before reinstalling it.

When I started up, it did something it hasn't done before - it started in the 'bad state,' but then within 3 seconds the engine revved to about 1200 RPM, and then evened out.

I went up to NAPA auto parts, got a new relay (5 bucks!) and installed it right there in the parking lot. All conditions were right for the problem to show itself, yet it started like a charm.

Only time will tell if that fixed it, but again a hearty thanks to this board for the suggestion! If it still acts up, I will try the IAC next.

 

[dogfriend]

I think that your IAC is sticking - I had the same symptoms you are describing - I live in Sac Area - the problem started when the weather warmed up --

Check these threads:

Dead Link Removed

Dead Link Removed

 

[JayTye4k]

What is this relay that you speak of?

 

[spinfisher]

senator ford........???????

Took my exploder in to have a some noises checked out and they said the "bipass valve" was creating some noises along with some others I knew about, They replaced the "bipass valve"(IAC). and since then I've had the same problem your descibing. I'll try the delayed start and let you know what happens! Spin

 

[Rhett]

What is this relay that you speak of?

Its the fuel pump relay. It's located under the hood in the relay center with all the other electrical relays. On a 1st gen it's on the drivers side near the batt.

It is identical to the ABS relay (and some others, possibly), I believe, so the two can be interchanged if you're ever trying to diagnose a problem.

It's a lot cheaper to replace a relay first then to go buy a new IAC.