Rough Idle on hot restart for a while.

[mika]

lighttech - I wonder how the tests came out with revised circuit ?

 

[lighttech]

New Circuit

Mika,

The new circuit works OK, but is not perfect. Occasionally still have slight rough idle on really really hot days. I have removed the circuit for now in another attempt to narrow down what the real problem is. A good mechanic pointed out to me that I am only masking what the real problem is.

Unfortunately since we are in Winter now, the problem does not appear often enough to do any really meaningful diagnosis. I plan on hooking up my laptop to monitor the pulse width of the injector pulse when idling normally, and when it is stumbling. (I am just going to pick one injector at random.) I need to know for sure whether the lean condition is mechanical or electronic in nature. I read on another board that this issue has shown up on other manufacture's vehicles, and it turned out that it's heat causing the fuel to vaporize in the fuel rail and/or injector itself until it cools down enough. Once started the fuel running through it cools it down. At least that's the theory.

I live in Florida, and once it warms up enough to consistently make the problem appear, I will do more tests.

Craig

 

[shadowless127]

They let you drive around Fort Lauderdale in a 20yr old car?? lol

 

[mika]

Aloha lighttech , thx for your comprehensive explanation. I have the same issue for several years with my 95 Explorer and found no solution so far. Let me know what will be your next steps.
I'm curious how to solve the problem. Greetings from Poland

 

[lighttech]

20 year old car LOL!

At least it's paid for ! LOL. Work here in South Florida is very seasonal. Usually busy in Winter for me, and dead during the Summer. So far this Winter has been the busiest I have ever been yet to date. My main scope of my business is the repair and servicing of "intelligent lighting." These are the lights that you see in nightclubs that move, change color, etc. I was thinking about trading in my Exploder/Explorer for a new/newer one, but having a car payment and the unpredictability of the Summer time business is scary.

A good paint job is a lot cheaper than car payments in the grand scheme of things.

Next week temperatures here in Florida are supposed to return to normal. I will do some more testing then. I have to make an interface box to allow my laptop to become a "data logger" to monitor the injector pulse width. Easy project.

I'll let you know what the results are.

Craig

 

[Winniethepooh]

I would consider the fuel line, after shutting down the engine heat may make the fuel in there built up bubbles.... for testing you can cool it down spraying it with break cleaner...

 

[lighttech]

Further Investigation leads me to believe fuel pump is the real issue

I have been experiencing extreme OCD over this whole issue, trying to get to the root of the problem, rather than a work-a-round. A good friend suggested that I should drive over to the local Ford dealer, park in the back, throw them my key, and then walk to the front and drive out with a new one. LOL

I have come up with the following information I'd like to share:
[I used a data logger to do this]

1. When idling normally, the injectors are getting turned on for 4ms.
2. When the problem occurs, the pulse width goes up to as high as 12ms, which makes it start to smooth out, then slowly drop back to normal 4ms pulse width.
3. As an experiment, I did a hot soak while the fuel pump relay was jumped leaving the fuel pump running for the entire hot soak period, 15 minutes. The vehicle would start up and run perfectly normal ! I repeated this many times, and always experienced the same results.

This leads me to believe the fuel pump has enough pressure (already been there and done that many many times) but perhaps not enough flow to flush the heated fuel out of the fuel rail quickly enough. I have already changed the fuel filter.

Does anyone have any other suggestions ? I really don't want to spend $300 to have the pump replaced and still see the same problem.

Thanks!
:exp:

 

[mika]

I made the exchange of the fuel pump to brand new Spectra Premium SP 6040H and nothing change.

 

[lighttech]

New Fuel Pump

Thanks Mika for your reply. Considering the expense, and your experience, I am not going to change the fuel pump. I do know for a fact that it is a fuel related issue of some sort, as my last test proved. Perhaps the injectors are getting too hot, and they get stuck ?

Can you possibly run the same test that I did with mine:

1. Jump out fuel pump relay with a wire connecting the forward connection in the relay socket to the rear connection of the socket. This should immediately turn on the fuel pump.

2. Start engine, drive around with A/C on, get it nice and hot.

3. Turn off engine and wait the 15 minutes or so (hot soak). Fuel pump will continue to run with engine off.

4. Start engine and note whether or not the problem is still there.

5. Repeat this several times to confirm the result.

6. Be sure to remove jumper and put back in fuel pump relay.

Thanks in advance !
Craig

 

[mika]

Craig
Just discovered leaking at upper intake manifold / EGR Tube.
Exhaust Air Supply Gasket (O-Ring) / (Felpro - EGR Valve Gasket Part # 72266)
http://www.google.de/imgres?imgurl=http%3A%2F%2Fwww.explorerforum.com%2Fforums%2Fattachment.php%253Fattachmentid%253D79942%2526d%253D1409700261&imgrefurl=http%3A%2F%2Fwww.explorerforum.com%2Fforums%2Fshowthread.php%3Ft%3D413879&h=476&w=590&tbnid=7JHDQPNWDcPQRM%3A&zoom=1&docid=P69BJ7RT3VMWiM&ei=VpP-VILjEYT5yQOKtoA4&tbm=isch&iact=rc&uact=3&dur=271&page=1&start=0&ndsp=53&ved=0CCEQrQMwAA
This means that I have to replace them in the first place before I can manage a test
Part already been ordered in the US and I'm waiting for delivery ;-))