95 4.0 EFI Eddie Bauer running rough?

[azwizard]

Hello All,
First post here and unfortunately it's for Help... I recently picked up a 95 Eddie Bauer Explorer, 4.0 EFI, Control Trac 4WD w/180K miles. Ran beautiful and Love it. About 2 1/2 weeks ago @ 184K miles it started running rough..Splutters on accelleration/shakes the whole truck. Would start great but ran like crap for the first 20 minutes or so. Tried Dry Gas and fuel injector cleaners and it seemed to clear up for a couple of tanks but then came back even worse. Now Gas mileage has deteriorated to 9 mpg and it never seems to smooth out.

First off the check engine light is not on. But I have the AutoXray multi scanner and I thought I'd check things out. This car has a OBD II connector under the drivers side dash that I used and it keeps telling me "Vehicle not responding".. Then I saw an old OBD I EEC connector under the hood by the Fuse center.

KOEO= 111 CM= 111
KOER= 111 CM= 111

This scanner can dial in and view multiple sensors I.E.. Throttle posit., O2 ect... I ran it though all the sensors in a dynamic test and viewed an appropriate response from all sensors.

Finally tonight I had my Dad help me and we braked torqued the truck in gear to 1500 rpm so that it was running really rough and I went around the engine compartment spraying a can of starting fluid at the intake and various vacuum lines. It seemed to smooth out and pick up a little when I sprayed around the snorkle. But then I ran out of starting fluid.

I didn't find anything glaring at me but then I've mostly worked on Gm cars most of my life. I have two questions?

1. Why dosen't the OBD II connector work when the old OBD I does? Why even Have the OBD II connector? I CHECKED FUSE NUMBER 5 IT'S GOOD.

2. And most important why do you think it's running rough? What other test can I do?

Any help would be much appreciated Thanks!

 

[MrShorty]

1. Why dosen't the OBD II connector work when the old OBD I does? Why even Have the OBD II connector? I CHECKED FUSE NUMBER 5 IT'S GOOD.

I don't know either. The mandated switch to OBD-2 was for the '96 model year, so they probably didn't want to design the more expensive system before they had to. Best guess is that Ford designed the dash with the '96 switch to OBD-2 in mind, so they put the connector in andyway. Seems like a waste, I know.

2. And most important why do you think it's running rough? What other test can I do?

Next thing I might do would be to put a fuel pressure gauge on it and see if fuel delivery is up to spec. (see fuel pressure mini-diary at the top of this forum).

 

[azwizard]

I have that same fuel pressure gauge.. Key on initial, fuel pressure is 38 psi. key on engine running it's 30 psi. WOT it jumps up to about 36 then settles back out at 30. In gear and moving it's still 30. Key off initial was 33 psi and after 10 minutes it was steady at 38 psi.. Not sure what spec is but my Haynes manual says 30-45 psi is addequate.

 

[MrShorty]

Fuel pressure readings look fine.

Have you checked the plugs and wires? Sometimes, the condition of the plugs can give a good indication of what's going on inside the engine.

 

[azwizard]

Pulled the wires off one by one and number 3 didn't show any change in idle, so I'm off to get a set of plugs right now.

 

[azwizard]

Put in some Motorcraft SP-486 Platinums and while I had them out I checked the Compression.... Cyl. 1 =90, 2 =94, 3 =90, 4 =90, 5 =80 and 6 =80. The cylynder I was cocerened about was #3 and it's within 10% of 1,2&4. Cylynders 5 & 6 were a little low @ 80 psi but I do have 185K miles on it.

Test drive was great with no shuddering/stumbles and the message center says the mileage is back up to 18 mpg..

Thanks for the prompts and one last question? Should I be concerened over the cyclynder 5&6 lower compression?