Engine Stumbles After Approx 10 Miles Driven

[dwilson80]

Hello all, I hope everyone had a great Christmas and has a fun and safe new year. Ok, I recently had to do a head gasket kit on my stock 94 Explorer XLT v-6 w/ auto transmission. The engine was replaced by Ford (crate motor) about 60k miles ago and tranny has approx. 80k on it. She starts and idles great but after driving her about 10 miles (or until gets to operating temp) she starts acting like she's starving for gas or air, she stumbles horribly and stalls out if I don't give her some gas. When I 1st finished the job she idled like crap and figured out the idle air control valve was bad, I replaced the IAC valve and that's where I'm at now with issue of stumbling at operating temp. I did some other work on her while she was apart/down. I installed a new Delphi fuel pump & sending unit, new fuel filter, valve stem seals, fuel injectors professionally cleaned, cylinder head bolts, cooling fan, thermostat, coolant, idle air control valve, transmission fluid and filter change, air filter and a new water pump. I was able to clean the good majority of engine parts with the machine at my brothers shop while they were apart. If anyone has some thoughts where to start next or has dealt with a issue similar to this one I appreciate any help. I'm headed out there shortly to go test before and after fuel filter and at different temps to check filter and new pump/sending unit. Thanks in advance and have a GREAT NEW YEAR!!!

 

[2stroke]

Did you have the head pressure tested and milled? I would start with a compression test. Make sure to take all the spark plugs out when you do it. I would then do a fuel pressure test.

 

[dwilson80]

Thanks for the response, no I did not have them tested or milled. Was trying to watch how much money in this repair was being spent since 60k ago paid Ford $5800.00 fro RR with a brand new crate motor. I've gotta either rent a fuel pressure tester or borrow one, that is now on my list of things to try/check out. Thanks again!!

 

[Rhett]

How many miles are on the O2 sensors? I have seen those cause poor running once the truck was up to temp.

 

[natenkiki2004]

Thanks for the response, no I did not have them tested or milled. Was trying to watch how much money in this repair was being spent since 60k ago paid Ford $5800.00 fro RR with a brand new crate motor. I've gotta either rent a fuel pressure tester or borrow one, that is now on my list of things to try/check out. Thanks again!!

x2 on the fuel pressure.

I don't want to sound negative or harp on you but doing a head gasket job without having the heads looked over is pretty much a waste of time and money. There can be a minor crack that you can't see and it will open and spread with heat cycles. You might be lucky but it's a possibility to consider.

 

[dwilson80]

@ Rhett....they are original, I hadn't even thought of those causing a issue once at operating temp.....thx for the response

@ natenkiki2004.... no worries, I get it. I wish $$ wasn't an issue and I would've had/done a lot more to her. My fingers are crossed (lol) that's the issue, one good sign is there is still NO choco milk in my engine and hope it stays that way....thx for the response

 

[natenkiki2004]

The upside to my negative post is that you have a 1994 and Ford put an even newer engine in so the heads are most likely some of the better ones that Ford made.

 

[Centaurious]

Due to the fact that it runs good when cold and bad when warm I don't think your problem is fuel related. That is not to say it might not be fuel control related...

Check your codes, clear them and check again after running until warm, this may give clues.

My suspicion is that you have either an emission or sensor related problem. areas to check include MAF, Temp sensor for the computer, DPFE sensor, pipe and hoses, ICM, coil pack. Things that are affected by heat, can go bad when heated, or indicate when heated.

Good Luck

 

[malohnes]

Due to the fact that it runs good when cold and bad when warm I don't think your problem is fuel related. That is not to say it might not be fuel control related...

Check your codes, clear them and check again after running until warm, this may give clues.

My suspicion is that you have either an emission or sensor related problem. areas to check include MAF, Temp sensor for the computer, DPFE sensor, pipe and hoses, ICM, coil pack. Things that are affected by heat, can go bad when heated, or indicate when heated.

Good Luck

Coolant temp - 2 wire unit, O2 sensor, dirty MAS and EGR system seem the likely culprits to me.

 

[Rhett]

The reason I said O2s was because their signals are dependent on the truck's temperature (open loop vs. closed loop), and you're only getting the stumble when hot.

Also look at the Fuel Pressure Regulator.

There's a lot to look at but I agree with the others it sure sounds fuel-related to me.

 

[2stroke]

I understand not having money to spend, I would still look at it as a possibility. To compression test all cylinders might take 30 minutes to an hour, but its time well spent. In the future, you can also have the heads tested with a straight edge. If you have a mechanic buddy, they probably can do it. Dealerships send them in no matter what. The tolerance for a head is about .003 from corner to corner.

I would then test fuel pressure after the engine is warm. This will tell you if you have a failing fuel pump, bad FPR or other problem with the fuel system.

If it snaps right up to the recommended pressure (something like 30-40 psi), then I would do a KOER test. This will almost certainly give you a direction to look.

If all else fails, do all the basic maintenance. Spark plugs, wires, air filter, clean the MAF, clean the IAC, replace fuel filter, etc.

 

[dwilson80]

back at it again

thank you all for your thoughts and help. I had to stop for a few days. Anyways so my brother came over with his nifty little computer thing and ran some diagnostic tests. At 1st (cold) it threw all sorts of codes...111 (pass), 122 (tps voltage), 157 MAF(low or grounded), 158(short to power), 176(O2 left side), 178(O2 right side) and 543 fault in fuel circuit. After we got her up to temp and cleared codes the only one that popped was the fuel circuit one, last night I RR the new/old Delphi pump and finished the rear brakes and I'm taking her on the maiden voyage again today....wish me luck
What are your guys thoughts on why there would be so many voltage issues, it just seems weird to me that multiple sensors are throwing same kind of issue?

 

[2stroke]

I hope it works out, but I think you are wasting time without a compression and fuel pressure test.

 

[Centaurious]

With the information added by the codes I would suggest:
Reading the battery voltage across the terminals with the engine off.
Read the battery voltage from the positive terminal to the Body of the Explorer.
Read the battery voltage from the positive terminal to the Engine.
Read the battery voltage across the terminals with the engine running.

First test shows battery charge, should be around 12.6
Second lets you know the condition of the battery ground to frame to body path, should not be much voltage drop.
Third checks the ground path to the engine, should not be much voltage drop.
Fourth checks the charging system, should be 13 volts to 14 volts.

These are simple tests and not a full diagnostic, they will give areas of further testing.

Battery Cables are a known trouble on these older explorers with bad connections or corrosion running for feet inside the cables. Having the battery circuit in good condition is the foundation of any other electrical diagnostic work.

Best of luck

 

[dwilson80]

update

so she drives a lot better at temp but still lopes a little after to temp and also engine light turns on and off. I did the voltage tests and everything checked out, another crap thing.... she gave me all of 79 miles for a 1/2 tank of gas. tested the ignition coil- primary all 3 at .6 (in range) secondary @ 14.42-14.65 (above-should be 6.5-11.5 per Haynes) and tried testing the TPS sensor but couldn't get it to do anything (prob operator error). Will have to replace O2's next for sure and get TPS and MAF tested/replaced if needed. Any other thoughts to the low mpg? Thanks again to everyone and I'm glad I did the voltage test because was wondering if was a ground issue...thank you for the detailed procedure- Centaurious

 

[natenkiki2004]

The coil test sheet I have shows a secondary of 11-17k of being acceptable. I don't know where it's values are from but I would trust it more than Haynes.

A faulty TPS usually gives issues in the throttle range. Like at 3/4 throttle, it would drop out and give you less RPM and bog. Press it more and it would come back. If you don't have that kind of behavior, I'd let it slide for now but try to get it tested.

 

[FR-425]

Sounds like a wiring problem to me.

I would be carefully checking the engine harnesses.

Could also be the PCM not outputting the proper 5v reference voltage.

The best place to test is the MAF. There are three wires Ground, signal and reference.

With the key on engine off you can check for the 5v reference at the MAF.

 

[FR-425]

OOOHHHh wait

BROKEN GROUND STRAP!

Located on passenger side from right cylinder head down to the frame.

 

[dwilson80]

@natenkiki2004 & FR-425

morning, thanks for the response. I haven't noticed any throttle issues so far so will move on to next thing and get TPS tested. I tried testing the MAF yesterday but wasn't having any luck following instructions from the Haynes manual (possibly/probably operator error...lol) and will def check out that ground strap you spoke about on right side. What's the best procedure to accurately test the MAF? Thanks again everyone for your help!!! She's getting there

 

[Rhett]

morning, thanks for the response. I haven't noticed any throttle issues so far so will move on to next thing and get TPS tested. I tried testing the MAF yesterday but wasn't having any luck following instructions from the Haynes manual (possibly/probably operator error...lol) and will def check out that ground strap you spoke about on right side. What's the best procedure to accurately test the MAF? Thanks again everyone for your help!!! She's getting there

I'm still thinkin FPR and/or O2s.