Stumbling Idle

[Wolfie_85]

It starts just fine. Once it starts to come down to regular idle, it either almost dies, then bounces back, or on occasion stalls. No CEL. New MAF. Running regular 87 octane with no ethanol.

Vacuum lines are ok, that was my first suspect. Plugs and wires are 3 months old and gapped at .54. I do have an intermittent pinging issue I am tracking down as well, though not sure if that has anything to do with this, short of a fuel delivery issue.

If you keep your foot on the gas for a few seconds after starting, all is well.

 

[acschilling]

TPS and IAC valve might be worth checking out. They could be on their way out.

 

[acschilling]

How many miles? Just curious

 

[2stroke]

Rough idle and pinging tells me EGR problem. Since it seems to have a bouncing idle, I would have to say DPFE.

 

[Wolfie_85]

I just learned why it never shows a CEL. The CEL doesn't work. Sooo....going to replace that bulb. And she just hit 170,000 miles.

 

[acschilling]

I'm at 178k. I don't have EGR so have never dealt in it. what does it do exactly? turbo?

 

[2stroke]

It recirculates exhaust back into the engine. 91-93 don't have it. You can also check codes by putting either a light bulb or a DMM (volt meter) in where you jump the wires. You coun't their flashes instead of the CEL.

 

[Wolfie_85]

Noted! But, I still feel a CEL would be helpful. Lets me know when something is amiss after I get this little hiccup worked out.

 

[xplorernewb]

had this problem when the fuel pressure regulator went out on my 93. changed that and rail gaskets and it went away

 

[Wolfie_85]

CEL light fixed! Pulled a 341 (octane shortening bar pulled out) and 558 code. So, EGR regulator wins! Thanks, guys! It may also explain my lovely pinging issue.

 

[2stroke]

I'm just curious, how did you fix the CEL? I somehow broke mine the last time I had my dash out. Maybe I just bumped it enough to ruin the bulb?

 

[Wolfie_85]

I pulled the cluster to discover that the bulb had come loose. I fixed that and all was well.

 

[FR-425]

It's a good thing to fix at least hear in AZ or CA because it won't pass emissions without a working CEL.

 

[FR-425]

It's worth it to go to a dealer for these bulbs, even though they are a standard bulb.

There are "high vibration" application specific bulbs that will last 20 years.

Or the cheap'os you can get a the AP store.

Direct from the bulb manufacture is another option for "specialty" bulbs.

Nothing worse than having to replace idiot lights every 6 months to save $2.00 on a bulb.

I "talked" Ford into selling me a bag of 20 for $30 Normally $80 or $6.50 each.

The counter guy at the Ford dealership will squint at you when you ask for just one of these!

You can see the difference with the naked eye. The internals, glass and element are for more heavy duty than your run-o-da-mill bulb. And the contacts were "tinned" not just lead dipped.

 

[FR-425]

On the stumbling idle issue

Can be as simple as the temp sensor for the PCM.

Usually the first symptom is a rough idle after restart when the engine is up to operating temp. (starts as if cold...too rich) (thinks the engine is cold all the time)

But they can fail such that the mixture goes lean too early and causes a stall. (thinks the engine is hot all the time)

The resistance of the sensor varies through the temp range, so I can't tell you what it should read at say 80* but you can visit your AP store and take your multi-meter with you to get a base line.

Then you would need to test yours at the same ambient temp to compare. Me I just replaced the stink'n thing, cured a number of performance issues, including the poor gas mileage.

I think I will replace this particular sensor annually when I do the cooling system flush.

 

[Wolfie_85]

I bought a temp sensor and planned on replacing it anyway. But the code it's throwing is a 558 (egr solenoid, DPFE..). This means a new solenoid (or vacuum regulator, depending on who you ask). It's cheaper than the DPFE to start with, and my mantra is anything I replace right now won't hurt, given its age. Advance Auto has a great rewards program.

 

[Wolfie_85]

Ok, I've ruled out the solenoid, still getting a 558 code with a new one. I had them order a new DPFE and might return the solenoid if it isn't needed. If there is anything I might be missing here, please fill me in! You guys have more experience than I do with the gremlins in these things. I still haven't even had it for a year. I do thank you guys, though. If it wasn't for this forum filled with tips and tricks, I'd be far poorer!

 

[FR-425]

Never heard of the solenoid go'n just the DPFE.

Just replaced mine twice this week. They gave me one that was bad out of the box.

I got 8 months out of the last one, but here in Phoenix we switch to "summer blend" gas at this time of year. It kills the DPFE every time.

As soon as I get e85 ethanol the engine starts producing water like mad. (it's the condensation that kills them)

Buy the lifetime warranty and always carry two.

Each time mine is about to fail I start to get an intermittent CEL, comes on for about 30 seconds and goes out after about another 30 seconds, I know I have 2 days at this point before steady CEL and 332, 335, 336 and/or 558.

DPFE every time.

There is a mod to replace it with a late model OBDII DPFE which ford uses to this day on their vehicles.

The newer ones have a different plug. You can get the late model DPFE and the pigtail and cut off the old pigtail.

There is a thread on here with handy dandy pictures but I haven't found it.

YET

I'm definitely going to do this mod, just being lazy and carrying a spare.

Once it fails completely my engine will start knocking real bad at half throttle. Wouldn't want to get caught without a spare out on the highway in tim-buck-2

In a pinch you can just take it off shake the water out of it and let dry for a few minutes. It will last at few more days. Keep your foot out of the throttle though. knocky knocky = butsed piston

 

[FR-425]

On the DPFE sensors the engine size doesn't matter, V8, V6 whatever.

The reference voltage and the output is the same as the older ones.

The design of the internals was changed to fix this issues.

You will still get failures, but years apart instead of months apart.

This is because they also changed the position of the sample tubes from the exhaust to further reduce condensation from getting into the sensor in the first place. As well as better drainage in the tubes, and the sensor itself.

 

[FR-425]

The part number for the old DPFE is EGR 151

The new one is EGR153 IIRC or maybe that's the solenoid?

Correction it's EGR155 for the late model DPFE. Ask the parts guy for the pigtail.