Stuck in DQ drive thru

Well, I was an hour ago, managed to get home. Idle started to drop, had to hold the throttle down slightly to keep it running but then it sounded like it had dropped a few cylinders and eventually shut off. Restarted several times but once again shut off. CEL was on briefly. Managed to get it home, had to clean dirt out of the EEC-IV connector but couldnt find my reader or voltmeter to pull KOEO or KOER codes.

Truck has had a history of brief moments of shaky idle, loss of power under load while on the trails. Drove it 50 miles to work and back today with no issues till I decided I wanted an Oreo blizzard.

Only thing I did find was a cracked vac cap on the vac tree. But I don't see that being the entire problem.

Any ideas on where to start? 93 4.0 non-egr Automagic.

Maybe the coil pack? Had similar issues a while back and that turned out to be the problem. Good luck with it!

I've been thinking coil pack for a while now. Going to pull the plugs after work tomorrow and see how they look. I think I have a spare coil pack somewhere in the garage.

thanks for the reply

pulled the plugs, didnt look the best for only being in there <10K miles, 3 of them smelled like fuel so i went ahead and put a brand new coil and new plugs on the truck thinking i had weak spark but it was idling bad as soon as i started it up.

hit the throttle a few quick times and i started smelling something from the exhaust, not sulfur, not coolant, smelled like stale gas and noticed water spitting out of the tail pipe. 20 miles before the whole dairy queen incident I had put $20 in gas in the truck when I left work. shut it off, started it back up a few mins later and let it idle for 20 mins and it idled fine. started it back up today and the idle is rough again. hmm. picked up some dry gas for it, going to try and putting some gas in from the station I use regularly and see what happens. Something tells me its not going to fix anything as I have said the idle has stumbled intermittently for some time now. any ideas on what to look for?

If you really think it may be bad gas, and it was me doing it I would get all that gas out of there. as much as you can, into a 5 gallon gas can. You "could" pull the fuel filter line off, and run it into a gas can, then run a jumper from the battery to the fuel pump socket in the fuel pump relay circuit and let the fuel pump drain the tank for you.

Then get some gas from a different station, see what happens?

Yeah I thought about that as I was laying in bed awake in the middle of the night. sad huh? lol going to try a throw a new fuel filter on there too. couldn't hurt..

borrowed a fuel pressure tester from a tech at work, with truck idling I have 65 psi, yes.. 65. normal range is 35-40 ive been seeing. so i checked the vac line for fuel, dry, pulled the tester off bc it started to leak.

went back out later and started the truck, pulled the vac line off the FPR, nothing changed.

so a list of symptons and tests ive done:
loss of power
rough idle
vehicle shut off
plugs blackened, smell like fuel
vac leaks checked and fixed
no fuel in vac line to fpr
65 psi fuel pressure at idle
removed vac line to fpr, idle did not change
checked maf, iac, tb
new coil and plugs

should i look into unbolting the cat from the y pipe?

The fuel pressure is way too high. You should have seen a change with vacuum disconnected also. Do you feel vacuum on the FPR hose when the engine is running?

Turdle said:

The fuel pressure is way too high. You should have seen a change with vacuum disconnected also. Do you feel vacuum on the FPR hose when the engine is running?

Click to expand...

yeah the fuel pressure is off the charts. I do feel vac on the fpr hose when it is pulled while the vehicle is running.

changed fpr and filter, nothing changed. truck seems to be idling high and surging not missing would be a better description. unplugged the tps and nothing happened, kind of makes me wonder.

You might want to pop off the cover on the ECM case and look in there to see if you have capacitors that are leaking all over the circuit board and eating away the traces from the CPU to all of the other components.

This is usually the number one reason behind problems that have no apparent cause and weird stuff that just happens.

If the ECM is original then it's well within the time frame for this to happen.



If circuit board looks ok I'd say maybe the fuel pump is going out.

Thanks for the tips. Will be spending lots of time in the garage this weekend. Will update on any changes.

blocked return?

If you still have the stock return type fuel system the return line may be blocked resulting in high fuel pressure. You might try disconnecting the return line from the FPR and see if you can blow air thru the return line.

i tried getting close enough to the return line to blow through it, even tried with a vac pump but there is no way to get to it with my size and the amount of lift lol

swapped tps, iac, cleaned maf, reset computer, still same thing. below are some horribly videos. you can see/hear the surging. im holding a secret as to why i need this thing fixed so soon, should be able to tell you guys in a couple days.

https://www.youtube.com/watch?v=eGQEPbfqes0

https://www.youtube.com/watch?v=y35v07t9tYI

private videos

I tried to watch the videos but both were marked private.
I read thru your entire Registry and found no mention of modifications to the fuel system. That means you have a return type fuel system. The max fuel pump pressure is 65 psi. The rail pressure should be 30 to 45 psi with the vacuum hose attached and 40 to 50 psi with the vacuum hose detached. The only way there could be 65 psi on the rail is if the FPR is defective or the return line is blocked. If you can't connect a hose to the return line at the FPR to blow thru you might leave the return line disconnected and then disconnect the end at the tank and blow thru that end.

Got up a couple blocks and beached myself across the top of the engine and blew thru the return. I could hear myself making bubbles on the other end.

Recheck fuel rail pressure

Since the return line is not blocked and you have a new FPR I'm beginning to question the accuracy of your fuel pressure readings at the fuel rail. No fuel in the vacuum line indicates a good FPR diaphragm. No or very little vacuum to the FPR at idle would result in high fuel pressure. I suggest that you repeat the fuel rail pressure checks with the engine idling and the vacuum hose to the FPR connected and disconnected. If there is very little difference in the pressure readings then either the new FPR is defective or your engine vacuum is very weak at idle.

I second the another tester for fuel rail pressure, its very high with times two the normal pressure.

I thought I would bring up the idea of the converters being at the end of their expected life cycle. Any thought to this?

I was able to borrow an EECIV scanner, did KOEO and KOER scans and was able to watch some live data. One thing that we thought was strange was the O2 sensor voltage, jumping between .03 and .80. Searching the forum now for that and other normal value ranges.

Had a memory code for IAT above max voltage, we did have it unplugged saturday night while the engine was running, live data voltage of 2.9

TPS voltage looked normal, it is brand new
O2 .03-.80, the .03 seems a little low after reading Glacier's fantastic thread
timing advance ranged between 21 and 24 degrees
injector pulse 2.2

I am in no way remotely good at diagnosing engine problems, especially on these odler models. Big thanks to all who are helping me.