Intermittent engine "stutter" - Ford Explorer

[grey26]

Was able to drive my truck around today on my lunch break. Drove it for about 40 minutes before capturing this data. The coolant stayed around 170 degrees the whole time once it warmed up...seems kind of low? I've noticed over the last year or so, since I had someone flush my radiator, the needle doesn't ever seem to move above that temp. In any case, here's a pic of the data. 20 secs of idle, 20 secs of 1500 RPM, 20 secs of 2500 RPM with engine warm:

 

[grey26]

IMHO, If you have over 100,000 miles on the pump I'd rather change it at my leisure then have it leave me sit or cause problems.

Most pumps last much longer then that but if that vehicle was owned by the type that always drives on fumes, that is very hard on a fuel pump. To me it is $100 peace of mind.

But to answer your question, I have no idea how to test since I have never needed to using the technique above. But the lean codes tell me it's a fuel problem.

Just checked local Ford dealer...they want $600 for a fuel pump (Motorcraft)! Where are you finding them for $100?

 

[SWIGIN]

Anywhere but a dealer.

And they sell it as a drop in unit already mounted to the sending unit. I'm talking just a fuel pump not the whole assembly.

From Google.
http://www.jcwhitney.com/replacement-direct-fit-fuel-pump-brand-new/p3038551.jcwx?skuId=1201081&TID=bngpla&origin={adtype}&VSID=d50361y1998j1&98FoExRep1037377

I mean $100 was a high number I just threw out there but a stock replacement pump should be under $60. I buy mine at NAPA and they come with all new hoses, clamps, plugs, seals, ect.

 

[grey26]

SWIGIN, thanks for the explanation. I didn't realize I had the option to replace just the pump itself...you just saved me a bunch of money in the future if/when the times comes to replace the pump and I appreciate that!

 

[grey26]

We can all guess at this. Lets get some real numbers.

I would like to know fuel trims (LT AND ST) at:
1) Idle
2) 1500 RPM
3) 2500 RPM

96eb96, just wondering if you had a chance to look at this info (Posted on March 31) and, if so, what your thoughts were?

 

[96eb96]

96eb96, just wondering if you had a chance to look at this info (Posted on March 31) and, if so, what your thoughts were?

Sorry I didn't see this earlier. Fuel trims are under 10ish and unremarkable so that is definitely ok. Vacuum leaks are likely eliminated, you can double check at cold start too to for sure. The different RPM bands check for vacuum leaks. For example, if you had 20 at idle and 5 at 1500RPM, you know there is a vacuum leak. If it was high at 2500 RPM, that could be a bad fuel pump and the PCM is trying to compensate.

Like to see your BARO parameter. Should be around 159Hz at sea level. This will tell me if your maf is working and if there are no exhaust or other issues. Getting lean on both sides could be a failing MAF. BARO indirectly computes air pressure (altitude sensitive) based on all the sensors in the engine and total volumetric air flow..

This is a smoking gun for your MAF:

At first, it was just the occasional stumble/stutter when accelerating ....

My truck also runs a bit cool, not sure if that really affects anything, as long as you are in closed loop.

You may also be able to get fuel pressure as a PID, not sure.

Intermittent problems are very hard to diagnose. Once you have that BAFX tool you may be able to get torque lite or another app to read the freeze frame data. Freeze frame data is important because it lets you know conditions of the code(cold, idle, high speed, etc).

 

[96eb96]

There is also a snap throttle test you can do to test your MAF. Basically you hit the throttle hard and watch MAF V. I think it has to go above 4 volts. I don't like suggesting it because it is a bit hard on the engine, but mechanics do it.

Try cleaning the MAF first, there are special chemicals for it.

 

[grey26]

96eb96, thanks for the reply. I checked my BAFX (using the paid Torque app) and it doesn't do freeze frame data, fuel pressure, or BARO. Torque has fuel pressure and BARO listed but when it's connected to my vehicle it's greyed out as an unavailable option. Would that be a limitation of my vehicle's PCM?

Fuel trims are under 10ish and unremarkable so that is definitely ok. Vacuum leaks are likely eliminated, you can double check at cold start too to for sure. The different RPM bands check for vacuum leaks. For example, if you had 20 at idle and 5 at 1500RPM, you know there is a vacuum leak. If it was high at 2500 RPM, that could be a bad fuel pump and the PCM is trying to compensate.

I've been logging results with the BAFX device almost daily. I've actually noticed that at idle, the LTFT's are elevated (around 10, +/- 1%) and as soon as I accelerate and raise the RPM's, the LTFT's drop considerably and stay low until I stop and the engine returns to idle at which time the LTFT's go back up to the 9-11% range. When I graph the results, RPMS and LTFT are almost mirror opposites. When RPM's are high, LTFT is low and vice versa. Also, just FYI, I replaced the ignition coil pack a few days ago as the original one tested outside of the range my Haynes manual specified. The new coil pack tested just slightly better than the original one and once I read threads/posts from others indicating their coil pack tested outside the range and that it appeared to be normal, I opted to just keep the new one installed. It was only $40 and the old one was 17 years old.

Like to see your BARO parameter. Should be around 159Hz at sea level. This will tell me if your maf is working and if there are no exhaust or other issues.

Since I'm not able to pull the BARO reading, is there another way you would recommend testing the MAF? I did a test with a multimeter a couple of years ago and although I don't remember the specifics of the test, the results I obtained indicated the MAF was fine according to the testing procedure I found online at the time.
I do clean the MAF every 5,000 miles when the oil is changed and just cleaned it last week when I hit 160K.

This weekend I'm going to clean the IAC and take a closer look at all of the vacuum hoses. I'm also saving up all of my errands for Saturday so I can gather more info from the BAFX while the engine is warm and has been running for a bit. I'll also grab LTFT/STFT at idle, 1500, and 2500 RPMs again.

When it comes to freeze frame data, is that stored in memory and only cleared when the CEL is cleared? If so, I'll make sure nobody clears the CEL like the mechanic did a few weeks ago before I'm able to obtain the freeze frame data.

 

[Spuddy]

Get FORscan demo for Android (free). It'll pull BARO.

https://play.google.com/store/apps/details?id=com.astech.forscandemo

I haven't tried the full version (FORscan Lite) for Android yet. The laptop version is outstanding, free and highly recommended.

 

[grey26]

Get FORscan demo for Android (free). It'll pull BARO.

Thanks for the heads up, Spuddy! I'll definitely give FORscan a shot this weekend.

 

[96eb96]

96eb96, thanks for the reply. I checked my BAFX (using the paid Torque app) and it doesn't do freeze frame data, fuel pressure, or BARO. Torque has fuel pressure and BARO listed but when it's connected to my vehicle it's greyed out as an unavailable option. Would that be a limitation of my vehicle's PCM?



I've been logging results with the BAFX device almost daily. I've actually noticed that at idle, the LTFT's are elevated (around 10, +/- 1%) and as soon as I accelerate and raise the RPM's, the LTFT's drop considerably and stay low until I stop and the engine returns to idle at which time the LTFT's go back up to the 9-11% range. When I graph the results, RPMS and LTFT are almost mirror opposites. When RPM's are high, LTFT is low and vice versa. Also, just FYI, I replaced the ignition coil pack a few days ago as the original one tested outside of the range my Haynes manual specified. The new coil pack tested just slightly better than the original one and once I read threads/posts from others indicating their coil pack tested outside the range and that it appeared to be normal, I opted to just keep the new one installed. It was only $40 and the old one was 17 years old.



Since I'm not able to pull the BARO reading, is there another way you would recommend testing the MAF? I did a test with a multimeter a couple of years ago and although I don't remember the specifics of the test, the results I obtained indicated the MAF was fine according to the testing procedure I found online at the time.
I do clean the MAF every 5,000 miles when the oil is changed and just cleaned it last week when I hit 160K.

This weekend I'm going to clean the IAC and take a closer look at all of the vacuum hoses. I'm also saving up all of my errands for Saturday so I can gather more info from the BAFX while the engine is warm and has been running for a bit. I'll also grab LTFT/STFT at idle, 1500, and 2500 RPMs again.

When it comes to freeze frame data, is that stored in memory and only cleared when the CEL is cleared? If so, I'll make sure nobody clears the CEL like the mechanic did a few weeks ago before I'm able to obtain the freeze frame data.

Coil pack is a good idea to change at this point. Some Explorer PCMs don't report OBD stream data, I'm not sure what years though. You may have a small vac leak but 10 is definitely in the calibration zone. Should not cause major issues.

Here Scanner Danner tests an explorer MAF. In this case it is totally shot, but usually you can clean them. Tap on the sensor like he does to see if anything changes.

 

[grey26]

Like to see your BARO parameter. Should be around 159Hz at sea level.

Downloaded FORScan (thanks again for the recommendation, Spuddy!) and have checked the BARO 5 different times:
154 Hz, 158 Hz, 159 Hz, 159 Hz, and 158 Hz. From a chart I found online, those are all acceptable readings for Dallas, TX which is about 430ish feet above sea level. But I guess since it's a very intermittent problem...happening only once or twice a year, the MAF would probably read fine 99% of the time?

I clean the MAF every 5,000 miles when I change the oil and just cleaned it last weekend about 8 or 9 days ago. I've recently read an online article that mentioned an oiled aftermarket air filter could cause oil to get on the MAF sensor and make it malfunction. I do have a K&N air filter...I don't believe I've mentioned that before. But if it was oil from the MAF getting on it, wouldn't the oil stay on the sensor and cause it to malfunction more than once or twice a year? I'll have to check my records to see when I purchased the K&N and compare it to when I first started having the engine stutter problem to see if the problem started after installing the K&N. I'm pretty sure I've had the air filter for at least 2 years and I've only oiled it once. I'll post that info once I can look it up.

As far as testing the MAF using the instruction in the video, I'll have to see if the Torque app has those PID's. Perhaps it's time I purchase the FORScan app for Android. Unfortunately, I couldn't get the bluetooth BAFX device to pair up with my laptop.

 

[SWIGIN]

The MAF oil problem is only if you over oil your air filter. I have had a K&N on my 94 Stang since 2001 and it has never oiled the MAF unit.

 

[grey26]

The MAF oil problem is only if you over oil your air filter. I have had a K&N on my 94 Stang since 2001 and it has never oiled the MAF unit.

I checked and I purchased the K&N about 4 or 5 months after the problem started happening so I think we can safely rule out the K&N as the cause of this problem. I just wanted to give you guys as much info as possible so you knew the whole situation while making recommendations, etc.

Tap on the sensor like he does to see if anything changes.

I was able to get my BAFX to connect to my laptop after upgrading to Windows 10. FORScan seems to be working fine. I'll do a little more testing on the MAF this weekend and will report back. If anyone would like any more info now that i have FORScan functioning, let me know.

 

[grey26]

Sorry guys, things have been a bit crazy for me lately and I haven't had much time to do some more t'shooting. I'm heading out of town on vacation for a few weeks so this will have to wait until I get back.