Engine engine bogs down over 2500 rpm

[Taterbug23]

I've had this 1996 3.8 mustang since 1997. Recently it sit for alittle over a year due to body damage.
Acouple weeks ago I charged the battery and took it for a spin. I added some 93 octane fuel to help with the older gas. It ran okay but when I parked it, it was very hard to crank back up. I tested the fuel pressure and it was only getting 20PSI. So I replaced the fuel pump. It's now getting 30-35 PSI and no problems cranking/running.
I let it idle for an hour (trying to get some of the old gas out) and it never cut off.
I've noticed that when i 1st take off everything seems fine. After maybe 5 minutes of driving, if I try to accelerate (maybe peddle 1/2 way down) and get to 2500 rpm it starts to bog down. Then once that's happened it bogs down every time I press peddle. Making climbing a hill impossible.
Although if I pull to the side of the road after this bogging happens..turn car off then immediately start the car back up, I can accelerate hard with no problems at all.

Before I replaced the fuel pump OBD2 was throwing codes both banks were lean. No codes are currently present.
Things I've done
Replaced fuel pump now get 30-35PSI
Checked fuel filter (by the way the filter will not click in place, no matter how hard I push. It does have the white clips on the lines and it isn't leaking)
Checked air filter
Cleaned MAF sensor and throttle body
Replaced fuel pressure regulator
Changed oil
Checked throttle position sensor
Drove car with MAF disconnected

Please does anyone have any ideas?

 

[OneSick99GT]

A lean condition means too much air being read by the oxygen sensors. The upstream oxygen sensor is on the ps side exhuast above the collector. You probably have a bad gasket or seal allowing air to enter the motor after the throttle body. This would provide the lean condition and throw a code if its severe enough. What is happening when you throttle the gas more fuel is supplied. Too much air and the upstream oxygen sensor tells the pcm to cut fuel. This provides a no power situation, stumbling, lack of power, ect. It can also cause all sort of idle issues. Your gaskets shrink when they heat up. When the motor is cold, right after start it creates a strong vacuum seal, but as the motor heats up the seals shrink allowing that extra air in your motor. Check for a vacuum leak or have a shop do a leak down test after the car is warmed up. Its worth the 200 dollars to save you the time looking for it so you can either fix it yourself or have a shop do it. Sounds like a bad gasket or seals.

 

[Taterbug23]

One slick thanks so much for the reply.
I forgot to mention that I have checked for a vacuum leak. Not sure if it's a fail proof way, but I sprayed carb cleaner around then entire upper engine area while the car was running. No increase in engine speed was noticed.
Although I think I'm going to focus more on the a vacuum leak, because what you are saying makes perfect since.

 

[OneSick99GT]

I've had the exact problem before. There are a couple more things you can check that it could be but with the lean condition code I'm almost positive its a vacuum leak somewhere.

Other things to check:
-Battery Tested
-Alternator Tested
-pcv valve
-Use a stethoscope to check each injector. Stethoscopes are super cheap and work really well at troubleshooting the injectors and spark plugs. Not to mention weird engine noises.

This should help getting the issue resolved with the info I provided. I would highly suggest getting your battery and altenator tested since it sat for an extended amount of time. A car that sits also wreaks havok on seals and gaskets since they dry up and begin to crack, which is probably why your having issues.

 

[wmburns]

+1 on taking steps to rule out a vacuum leak.

If this were my car, I would check the ODB2 mode6 misfire data making note of which cylinders are misfiring. Are all cylinders misfiring? Or only some?

Is your fuel pressure regular intake vacuum reference line connected and leak free? At idle does the fuel pressure jump to 40 PSI if the intake vacuum reference line is disconnected?

What have you done to rule out excessive EGR flow?

Have you considered having the fuel injectors cleaned and flow tested? If so, consider an injector cleaning and flow test service such as InjectorRX.com.

Do you have an ODB2 scanner? If you did it might totally change how you go about trouble shooting this issue.

ForScan ODB2 scanner w ELM327 USB

ForScan ODB2 scanner w ELM327 USB

While working on your car have you ever wanted: to find an ODB2 operational PID value (say fuel pressure or MAF)? How about graph a PID value over time? Or compare multiple PID's over time? Access a bi-directional PCM control such as test a...

www.stangnet.com

 

[Taterbug23]

Thanks for the responses. I REALLY appreciate it!
So I changed out the fuel injectors today, still the same problem.

At idle the fuel pressure does jump to 40 PSI if I disconnect the hose ontop of the fuel regulator.

I have a cheap 3D printer and printed out some adapters to do a smoke test. (pictures enclosed in case someone else stumbles on this thread and needs a cheap smoke tester idea)

This video shows when I had the system pressurized from the brake booster side. No smoke is seen. At the end of the video it shows me taking the ducktape off and the smoke coming out. I also attached the hole to this adapter and pushed the smoke the other way...no smoke escaped.

View: https://youtu.be/mbHytUVv0YQ


I have a obd2 scanner and the free version of forscan. I'm not seeing any engine codes.

Once again I took the mustang for a spin after installing the fuel injectors. It ran fine for a few minutes, although once it bogged during acceleration It would no-longer accelerate. Every time I would pull to the side of the road...turn ignition off...start right back up (not even waiting 2 seconds) then take off and everything is fine to accelerate for a few minutes. Then all the repeats until I'm able to limp it home.

 

[wmburns]

It sounds like you can reproduce this problem at will.

What have you done to ensure that the battery and alternator is in tip shape?

Howto perform charging system voltage drop test

Howto perform charging system voltage drop test

To anyone else reading any of my posts I usually include the line: Today's cars simply will not run right without a strong battery and charging system! Cut corners here at your own risk I'm a big believer in starting with the basics. As such I...

www.stangnet.com

Since you have the ForeScan software consider monitoring:

• RPM
• TPS voltage
• MAF
• ECT & IAT
• EGR Flow (DPFE)
• EVAP flow (purge flow).
• Open/closed loop
• timing advance
• Long term Fuel trims (LTFT) bank 1 and 2.
• engine load

While driving. What you are looking for is WHICH PID's change when the problem occurs. If the problem happens as easily as you have suggested it might only be necessary to monitor a few PIDs while driving.

For the temperature sensors (ECT=Engine coolant temperature, IAT=Input air temperature), double check the values are "reasonable". An easy way to check while the motor is stone cold. The sensors should read close to local outside air temperature.

Have you looked at the ODB2 Mode6 data? Especially interested in the misfire by cylinder data.

 

[Taterbug23]

Well I didn't consider this could be a battery problem. I had the battery tested and was told it was on its way out, but did barley hold a charge. I didn't want to drop $100 for a battery and the car sit again for months. I'll take the battery out again and have it tested again.
As for the forscan suggestions. All I've done so far is program keys for my F150 and check codes on the Mustang. Ive got a good bit to learn on that software.

 

[Taterbug23]

Also being that I can leave the car running for 1.5 hours parked without any problems narrow down anything? I did that when I thought the problem might be bad gas.

 

[OneSick99GT]

I'm leaning towards a bad battery and weak alternator. Could be bad connections with the battery or alternator. Check the grounds on both and make sure the wires are clean and shiny on both the battery and alternator positive and negative terminals.

 

[Taterbug23]

Battery and alternator tested good.
I threw up some random gages on torque today the short term fuel trip seemed to move alot. The - 15.6 is when it was running fine and the 32.8 is when it wasn't

 

[wmburns]

At 150-165 the motor is way too COLD. Or there's air trapped inside the motor (air will make the ECT read low). The stock T-stat is 192 degrees F. The cold motor will affect the open/closed loop operation. This will also affect the PCM"s target air fuel ratio. The PCM needs an accurate engine and outside air temperature.

If you are not using the Ford stock T-stat, go back to the stock T-stat temperature. Follow the V6 coolant refilling procedure EXACTLY. The motor temperature should be at least 190 degrees just idling in your driveway.

V6 coolant refilling procedure:

1998 mustang irregular rpm's showing hot

98 mustang was overheating, jerking, running rough and just not sounding healthty. New wires, plugs,thermostat, Air Filter you name it has been replaced along with a radiator, hoses and battery within the past two months. Once the tune up was completed it jerked a little then ran fine for 10...

www.allfordmustangs.com

In general. IF the fuel trims shoot up (adding fuel) when the RPM's are about 2500 this means that the motor is starving for fuel. But before you can make that assumption it's important to VERIFY that the O2 sensors are actually providing good data. IE. do they switch in response to change in mixture? One quick test for this is to monitor the O2 sensor voltage (or graph). Create a vacuum leak. Do both O2 sensors shoot lean? Does the O2 sensor go back to switching lean/rich when the vacuum leak is restored?

When you know that the O2 sensors are functioning, start by looking at the long term fuel trims (LTFT). The short term fuel trims change too fast to look at general trends. Use the STFT's when trying to zero in on the problem. Compare the LTFT's at idle. Then raise the RPM's and hold steady. What do the LTFT's do?

The key is to figure out WHY the fuel trims are changing sooooooooooo much. Possible causes:

• The MAF flow suddenly changes
• The O2 sensors suddenly switch lean/rich or rich/lean
• EVAP VMV opening allowing a vacuum leak or a Vacuum leak that comes/goes.
• The fuel pressure suddenly changes. Given the fact this car has a mechanically fuel pressure regulator, IMO this is less likely.
• Clogged fuel injectors.

Have you looked at the ODB2 mode6 misfire data? This is a very powerful tool to see if there's a problem tied to specific cylinders.

 

[Taterbug23]

I am using the stock t-stat.
Now that you mention it the engine temperature gage stays pegged out, even when the engine is off. I figured this was just a gage problem, as I can take the radiator cap off and it's clearly not overheating.

I checked the o2 sensor voltage today. The dial constantly sweep back and forth between 0 and 0.7. When I created a vacuum leak the voltage dropped and stayed at zero. Once I removed the vacuum leak the dial sweep stsrted back. I didn't get time to proceed to the others.
I have unplugged the MAF and drove while it was unplugged. The car still bogged after a few minutes.
I have a new fuel regulator on it.
The fuel injectors were changed out Saturday.
As for the 2nd part of the fuel trim test. If I am parked, I can rev the engine to what ever rpm, with no problems. It's only when driving a few minutes and I get over 2500 rpm then it starts to bogg. Then once it boggs it won't run right (even if I pull off the road and let it idle rough) Although with a quick key cycle everything is restored and I can resume any rpm for a few minutes.
I haven't looked at the ODB2 Mode6 data, I still have to figure out how to do that.

 

[Taterbug23]

Enclosed is my obd2 Mode6 results

 

[OneSick99GT]

Battery and alternator tested good.
I threw up some random gages on torque today the short term fuel trip seemed to move alot. The - 15.6 is when it was running fine and the 32.8 is when it wasn't

It can only be a few things.

You said battery was on its way out in a previous paragraph when it was tested. A weak battery will cause that condition.
Fuel pump going out.
An injector not properly firing causing the oxygen sensor to read more air than fuel.
Its fuel related if in fact both battery and altenator are good.

 

[OneSick99GT]

Do you have any check engine light codes? And did you replace the coils at same time injectors were changed. For some reason it wants to enter limp mode until you power down the car. This seems more like a tune issue or PCM issue.

 

[Taterbug23]

It can only be a few things.

You said battery was on its way out in a previous paragraph when it was tested. A weak battery will cause that condition.
Fuel pump going out.
An injector not properly firing causing the oxygen sensor to read more air than fuel. I didn't change out the coil pack yet.
Its fuel related if in fact both battery and altenator are good.

Once I had it tested and was told the battery was going out and doubted it would hold a charge. They charged for me and said it may be okay. I took to another shop last week and they stated the battery and alternator were fine.
New fuel pump
No check engine lights
Not sure what all can cause a injector to not properly fire, although they are new.

I had a friend come over that works at a local ford place. He ran their scanner on it and said 02 sensors and everything else looked okay. He re-flashed the computer and we took it for a test drive with the scanner still attached. (1st we let it idle for around 10 minutes and nothing appeared wrong) When We took it for a test drive once again after a few minutes it started bogging under acceleration. He checked the computer and he stated the purge valve appeared to be looking weird. So I ordered a purge valve and IAC, and plan on hopefully giving them a try towards the end of next week when they arrive.

 

[wmburns]

We took it for a test drive once again after a few minutes it started bogging under acceleration. He checked the computer and he stated the purge valve appeared to be looking weird

If seems to me that if the EVAP system is the suspected leak source that the problem is going to be a vacuum leak between the EVAP purge solenoid and the gas tank.

Why guess? Simply block off the EVAP purge line at the throttle body (low tech method). IF the problem goes away you will know on the right track. Blocking off the EVAP line may cause a different EVAP code to come up but it's OK (trouble shooting).

The higher tech method as mentioned before is to monitor the EVAP purge solenoid to see IF it's commanded open at the time. Also monitor the EVAP purge flow PID to see if it changes.

My experience tells me that the purge flow sensor fail at a very high rate. I could see a case that IF the EVAP purge flow sensor is sending bad information to the PCM that the PCM will open the EVAP solenoid more than it should. I would recommend replacing the purge flow sensor for pure diagnostic reasons anytime an EVAP problem is suspected. Plus it not an expensive part.

If asking for an WAG. To me the odds favor a vacuum leak in the line between the EVAP purge solenoid and the gas tank. Given the fact that the car had some body damage would make sense. Especially if the collision damage is on the front right side where the charcoal canister is located.

 

[Taterbug23]

The Collision was on the drivers side rear panel, where the fuel shut off is.

Before you posted this message I ordered EGR vacuum soleniod, IAC control valve and canister purge solenoid.
The EGR vacuum already came in, it wasn't that. Waiting on the other 2, they were all pretty cheap parts

 

[Taterbug23]

If seems to me that if the EVAP system is the suspected leak source that the problem is going to be a vacuum leak between the EVAP purge solenoid and the gas tank.

Why guess? Simply block off the EVAP purge line at the throttle body (low tech method). IF the problem goes away you will know on the right track. Blocking off the EVAP line may cause a different EVAP code to come up but it's OK (trouble shooting).

The higher tech method as mentioned before is to monitor the EVAP purge solenoid to see IF it's commanded open at the time. Also monitor the EVAP purge flow PID to see if it changes.

My experience tells me that the purge flow sensor fail at a very high rate. I could see a case that IF the EVAP purge flow sensor is sending bad information to the PCM that the PCM will open the EVAP solenoid more than it should. I would recommend replacing the purge flow sensor for pure diagnostic reasons anytime an EVAP problem is suspected. Plus it not an expensive part.

If asking for an WAG. To me the odds favor a vacuum leak in the line between the EVAP purge solenoid and the gas tank. Given the fact that the car had some body damage would make sense. Especially if the collision damage is on the front right side where the charcoal canister is located.

Which hose are you recommending blocking off? The red 1? Even though I'm still getting the same results...I really feel like you are getting me close.