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Hi, Looking for some help figuring out why all of a sudden my engine does not want to keep running. Dies at idle, and surges and runs rough and jerky if I pump the gas. My manual says to test the MAP sensor with the MAP tester, but I do not have one of those. Vacuum lines all appear to be OK. I even swapped out the PCM with a spare I had and there was no change. Not sure what to try next I am not getting any error codes..
Any suggestions would be appreciated.
Does your '96 have OBD2? Is the check engine light on? Does it run better at speed or can you not get it to speed? Some cars let you run the engine with the MAF sensor unplugged which puts it in a default mode. It might not run well but it will run consistently if the MAF sensor is the only problem.
Oh, what was the last thing you worked on before this happened?
It's not OBD2, no check engine light. EEC-IV
On the road I can't get up to speed, parked I can run the engine alone at a higher speed. Got a couple of small backfires while playing with the gas pedal to keep it running. I'll need to try running with the MAF unplugged and let you know what happens.
The last thing worked on was a new transmission a year ago, along with a new fuel pump. ( After they installed the new transmission I could not accelerate, and they finally figured out it was low fuel pressure.)
You can rent for net free a fuel pressure tester at most auto supply stores if you think it might be that again. Ignition control module is another possibility if it's separate from the PCM in your year. I don't know how ignition advance works in a 5.8 but if timing is off or not advancing, you won't get power under load. Any chance you have a bad tank of gas?
I own a fuel pressure tester, I just don't know where to connect it. Has only the PCM. I tried swapping out a spare I had and it made no difference. I doubt it's the gas. I filled up a few weeks ago and it's been running fine until today when I was running errands, and when I went to start it after finishing the last stop it started doing this stuff. Although I suppose it's possible someone sneaked into my yard and put something in the tank.
UPDATE: I just discovered something in my shop manual. I made a note to myself that this van does not have an MAF sensor. This was the transition year from the EEC-IV to OBD, and the EEC-IV ignition system did not have an MAF,. only an MAP.
+1 for checking the fuel pressure and the fuel volume
When was the last time the fuel filter was replaced?
The processor needs to be inspected
They run like puke and miss like hell when the caps fail and the traces get ruined
Your problem sounds more fuel pressure related
You check the pressure of your 1996 at the test port on the rail
Right, your 1996 OBD1 truck has a MAP sensor, there's probably nothing wrong with the MAP unless you see a code for it
I think you might just need a new fuel pump, but all bets are off if the processor has issues
Thanks
One thing does concern me about the PCM. The manual says I should be getting 10.5 volts on pin 21 (White wire w/blue) from the PCM to the MAP with the ignition ON. I'm not getting anything. Continuity on that wire from the NAP to the PCM is good, although I should have tested to ground as well, but forgot.
I've got a similar problem on a 1990 Country Squire right now
One wire that needs 12v for the self test connector has 7 volts and it won't self test
I have a reman processor coming for that one, they replaced it twice so far and it still has problems
I would check all the powers and grounds that hit that processor
It needs to be 30 or higher, spec is 35-40 with the vacuum line off the regulator That is for your 1996 V8
Google it, the 6 pops, 4.9's run higher pressure at 45-60
The fuel delivery section of the PCED has that info
That's great, so it is very low. Thing is that could be caused by the regulator stuck open or the pump not receiving 12 volts. I need to check the voltage, and find a place where the return tube is rubber and pinch it off. If the pressure doesn't come up after doing that then it's the pump for sure.
There is no place where it's rubber and you can pinch off
It's hard plastic all the way and will crack if you try to pinch it off
Ford made and gave us numerous block off and adapters for our fuel injection cleaning equipment
You can find other ways to block off the return line but generally you will just test the pump itseld before the filter or regulator to test the pump
Right, check for 12 volts initial prime power to the pump, at the pump connector
Realize that juice goes through the tank selector switch to get to the pump The one on the far right is a return fuel line block off tool.
Thanks for the warning and the great idea. At this point I hope it's the pump because I paid 800 bucks to have it replaced and the warranty doesn't run out till the end of February.
That seems like a lot of work to avoid the free rental of the fuel pressure gauge from an auto parts store. Can it be the fuel pump if it's drivable yet stalls at idle? If there isn't enough fuel to idle, I don't think it'll get itself to the end of your driveway.
Have you checked voltage at the fuel pump or system voltage in general when the engine loses power?
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96 E350 5.8 Engine keeps dying.
