Engine sporadically sputtering/hesitating/chugging

[KEVSTER]

1995 F150 5.0 Automatic

Engine sporadically sputtering/hesitating/chugging under accelration and/or uphill

I did a tuneup (plugs, wires, coil, cap, & rotor) about 6 weeks ago. Afterwards it ran like a champ. Then about two weeks later, it starts acting all wierd like it starved of fuel or something. Sometimes it runs fine, sometimes it does all this chugging. Sometimes while it's doing this chugging thing it'll stop and just start humming along like normal.

Things i've already done: Removed, inspected, & cleaned EGR Valve, Cleaned MAF, Clean Throttle body, Replaced Fuel Filter, Reinspected everything i did during the tuneup, Dumped two cans of Sea Foam in a tank of Premium gas (no change), pulled codes and only got 111(system OK).

I'm wondering if it's related to the tuneup? Seems odd that it ran fine for two weeks and then this. I've read a lot about crossfire on these engines between the plug wires if not properly routed. Any thoughts on that? I don't think it's the fuel pump as there are two of them (duel tanks) and can't see them both going bad at the same time.

I do have a bad temp sensor i'm going to replace soon, but it was bad before this started. Besides, i think these engines have two: one to the gauge and one to the PCM.

Starting to wonder if it's one of the injectors or the O2 Sensor but i don't want to keep throwing $$$ at it till i figure out what's wrong.

Thanks in advance for any help. It's driveable but it's really annoying.

[DaggumTruck]

Hello KEVSTER,
I wish I had a solution for you. My truck is doing the EXACT same thing as you describe. See my post here for all the parts I changed out with no luck:
viewtopic.php?t=106530

It has been recommended to me to check fuel pressure and sniff out vacuum leaks anywhere there are vacuum lines as well as intake assembly gasgets. I'm buying a fuel pressure testing gauge and vacuum gauge this afternoon and giving it a shot. I pulled EEC-IV ODB-I code 172, but was told to rule out other things first before swapping out the O2 sensor.

I also heard about dual fuel tanks and a recall that was done on bad fuel tank check valves, not sure if this applies to you though, it may have just been for the 1993 models: https://www.ford-trucks.com/forums/1043 ... -f150.html

Hope this helps a bit.

[kg5ie]

Crossfire is an issue. Check to assure wires are routed per the diagram under the hood. If the sticker is gone, you can find the routing guide posted here.

[KEVSTER]

KG5ie - Thanks. I do still have the sticker and have checked and rechecked it several times.

Daggum - I feel your pain. I found this thread that may be of help viewtopic.php?t=106080

[KEVSTER]

KG5ie - If it were crossfire, wouldn't it happen consistently and wouldn't i be hearing the engine backfire as certain cylinders would be firing when the exhaust valve was open? I'm just trying to eliminate this as a possibility. Thanks.

[Steve83]

First: what intake system does the truck have?



Second: put that & all the truck's other details in a signature so they show with every post. Read this whole caption:



Third: read this caption:

[KEVSTER]

Steve - I have the lower right intake, 5.0 maf. I did read that notice about the wire routing and I don't think that's my issue.

I did run the KOER test this afternoon. Got back 412 and 538. From what I've read these point to an issue with the IAC or the TPS.

Thoughts?

[Steve83]

I think you should test your IAC & TPS.



If they're OK, keep testing things.



Use either a mechanic's stethoscope with the probe removed or 3' of garden hose to listen around the idling engine for vacuum & exhaust leaks. Make sure the battery terminals are CLEAN:

[DaggumTruck]

I wish I had seen this post last night!! Steve, your caption about TPS and the "posidrive" screws would have kept me from screwing myself, I stripped both of those stupid things!!

[KEVSTER]

Thanks Steve. i'm planning on whipping out the multimeter soon and testing both.

[KEVSTER]

OK so i checked out my TPS and IAC this weekend. Everything appears to check out nice. TPS voltage steadily increases as i open the throttle and within specified parameters. IAC checks out too. I took it off and cleaned it, though.

It appears that the kid at o'reilly's didn't do the KOER test right when i had them hook their scanner up to it. From my first post i was getting 412 and 538. 538 indicates that the throttle wasn't WOT (wide open throttle) during the test. This is odd becasue we certainly did do a WOT during the test. Over the weekend i did the KOER myself with a paper clip. The key is WHEN you do the WOT, which i'm guessing we didn't do right while we were at O'reilly's. Long story short: during my KOER at home i did the WOT at the right time and i got a 111 (system pass) code in return. So now i'm pretty confident that those 412/538 codes were not really pointing to anything.

So where do i go from here? Truck still behaves as indicated earlier, but now i have no codes to point me in a direction. I'm going to do a full vacuum system check next, just to be sure that there isn't any leaks. Steve83 mentions checking other sensors. I got under and looked at the O2 sensor. From what i've read you've got to get the everything warmed up nice and hot before you can troubleshoot the O2 sensor. Is that right? I don't see how i can get under there and do that without burning the $#!t out of myself. I did notice that a little bit of oil had dripped down onto the top of the electrical connector for the O2 sensor. Think that could be causing issues with the sensor? Thanks

[KEVSTER]

Steve83 - Not that i'm doubting you, but why did you suggest making sure my terminals are clean? how could that be causing my issue? Thanks

[DaggumTruck]

Steve83 - Not that i'm doubting you, but why did you suggest making sure my terminals are clean? how could that be causing my issue? Thanks

He likely recommended it to reduce possible electrical noise/interference and/or ensure you have a good solid ground going to the chassis. Both could affect the ECM. Digital electronics are super prone to error from electrical noise/instability. The ECM should be well taken care of regarding filtering, but you can never be sure, it's just an easy thing to remove from the equation.

Of course here in Atlanta the weather has been wonderful the past week/week and a half, so the truck has been running great , but not helpful for diagnostics. Be sure you check out your fuel pressure too, along with vacuum. I've had both gauges in place for the last week studying their readings each day to establish a baseline. Fuel pump is on the suspect list since I have to turn the key on and off a few times just to build up the initial pressure needed to start the engine. I'm just hoping that when the truck does decide to sputter & hesitate that the fuel pressure gauge will show something of interest.

[jcfacf4706]

check your iat sensor on the intake (passenger side one 6th cylinder bank) before you spend the money on changing it, unplug it and drive it around for a day or two. if the problem stops while unplugged then you may want to replace this sensor, but you may have a false result if you have a large exhaust leak such as a cracked manifold or blown out manifold gasket. i had the same problem with my truck, this did the trick for me. really threw me through a loop. hope i could help sorry if not.

[starfury27]

I have the same problem as KEVSTER and DAGGUM. I have replaced the plugs, wires cap rotor and fuel filter. Fuel pressure test was normal. Can not reach the injectors to perform a NOID test. Tried running injector cleaner thru the tanks 4 times with no change. Have not had an ODB 1 done yet. Have eliminated the cross fire theory. Any ideas that I have not tried? I am new to this forum and this site so if I have forgotten anything that may be useful information, please let me know.

[Evan_P]

Pulling codes is the next step. Its easy to do and only requires a paper clip or jumper wire. Click this and read its caption a few times to test your system properly.


*Courtesy of Steve83

Report back with your results.

[older]

My daughters truck 1986 f150 200k miles was acting like it was running out of fuel when the temperature rose into the 90s. Couldn't find any solid information, so I want to get good information out there. This truck has two tanks. Started with fuel filter on frame and fuel filter on tank switching valve, 1hr and 10 dollars,no luck. For those who do not know, this truck has 3 fuel pumps and 4 fuel filters. Replaced high pressure pump on the frame about 30 to 40 dollars and 1 hour job. This made the symptoms worse with the truck. Replaced the rear tank pump because it's gage did not work. About 4hr job and 80 dollars. When running on the rear tank with the new fuel pump the truck now ran fine. The center tank still acted like it was running out of fuel. So, replaced the center tank fuel pump. 2hr job and 80 dollars. Truck now runs fine and both fuel pump gages work. So about $210 and 8hrs of labor. The owner of the garage told me that it could get expensive at $90 a shop hour, would have been around a thousand dollars. There are no specialized tools required to do this job. You can disconnect fuel lines with a screwdriver.
Long story short all of the pumps were getting old at the same time. The hotter it got the worse the pumps worked. This was evident when I put on the new High pressure pump on and the low pressure pumps in the fuel tanks could not provide enough fuel to keep up with it.

[Steve83]

Steve - I have the lower right intake, 5.0 maf.
...
Thoughts?

Same as I thought before: I think you should PUT IT IN YOUR SIGNATURE & profile so it shows with each post.

I did run the KOER test this afternoon.

It appears that the kid at o'reilly's didn't do the KOER test right...

First, it was YOU; then it was someone else who did the test. Don't let an underpaid burger-flipper work on your truck, especially when you have access to all the info to DIY.

So where do i go from here?

Back to the previous posts, and continue reading. And don't hesitate to recheck ALL your previous work.

I'm going to do a full vacuum system check next, just to be sure that there isn't any leaks.

That's a step in the right direction. Even if you find no leaks, that's useful info.

I don't see how i can get under there and do that without burning the $#!t out of myself.

Then don't. Every sensor's wiring goes to the EEC. Pick it up anywhere in the engine bay and pierce-probe it.

https://www.amazon.com/dp/B000K1FXXS/

You can do the same thing with stickpins if you're VERY careful not to ground them, or to pierce 2 wires with 1 pin, or let the pins touch each other.

...a little bit of oil had dripped down onto the top of the electrical connector for the O2 sensor. Think that could be causing issues with the sensor?

No.

Steve83 - Not that i'm doubting you...

If you weren't doubting me, you'd have checked them already.

...making sure my terminals are clean? how could that be causing my issue?

Your engine runs well sometimes. That means that, when it runs badly, it's likely NOT a mechanical fault because mechanical faults don't usually self-correct even once; much less, repeatedly. So that means it's most likely an electrical/electronic fault. Everything electrical on the truck is subject to battery voltage fluctuations, and battery terminals are known to corrode on ALL batteries on all vehicles of all makes/models/years. Any time an electrical fault is suspected, CHECK the battery terminals by REMOVING, cleaning, & tightening them.

Fuel pump is on the suspect list since I have to turn the key on and off a few times just to build up the initial pressure needed to start the engine.

That actually points to the FDM internal valves & diaphragms - not the pump motor. Read this caption & the NEXT few:



It could also be the FPR:

'95 F-150 XLT. 4.9L inline 6

We assume it's an F150 because you're posting on this BBS, and we know that the 4.9 is an I6, so you can delete both of those.

4 Speed manual with Overdrive

What vehicle did that trans come out of, and why was it swapped into a '95 F150? What was the truck's ORIGINAL trans? If you don't know, read my first post in this thread.

158K original miles

We assume that they're original, and that any number that high refers to miles, so it's enough to say "158K." Use that space to tell us things we DON'T know & can't guess about the truck.

My daughters truck 1986 F150...

Almost nothing about that truck is relevant to the topic of this thread. It's good that you fixed it, but the trucks under discussion are vastly different.

[UproarinSonoran]

Steve83,

You seem extremely knowledgeable, whereas I am just a weather guy. So here goes.

2002 F150 5.4L 183k.

The problem is bucking when RPMs are below 1500. It used to only happen in OD, now I've noticed it also occurs in 3rd. Truck runs nearly perfect at all other times. the "nearly" is that it does have some hiccups in idle, and it idles at 600 RPMs.

Another concern is that the vehicle does not shift OUT of OD when I am trying to maintain a cruise (say 50-55mph) and simply holding steady on the accelerator when encountering a hill. Thus, when the RPMs dip even to well below 1500 (as low as 1000-1100) the vehicle REMAINS in OD and bucks hard until I either regain the sense to turn off the OD or jam the accelerator down to downshift and RPMs return to ~2000.

I am no mechanic and will likely rely 100% on a professional to diagnose and/or treat. I just thought I should ask your opinion before venturing into the maniacally-hand-wringing mechanic.

-Uproarin

[Steve83]

That's even farther off-topic for this thread, and off-topic for this forum. You should post in the '97-04 forum, where they're more familiar with modular engines. I'm familiar with smallblocks.