Severe engine hesitation - Please help
01-02-2016, 02:04 PM
#1
Junior Member
Thread Starter
Join Date: Mar 2015
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Severe engine hesitation - Please help
Hey all,
I've got a 1995 F-150 with a 5.0L 302 and a 5 speed.
I've been experiencing some engine performance problems. I've got a hesitation, mostly at lower RPM's. The problem is intermittent, but has been occurring more often as time goes on. The hesitation feels like I'm hitting a strong headwind or almost as though the hulk has grabbed the tailgate of the truck and does not want me to move. lol. It will struggle to even hold a speed. Sometimes i need to downshift just to maintain the speed limit. The odd part is that once I've accelerated into the high RPM range (probably around 3000) the hesitation immediately stops and the truck kicks me back in the seat and takes off. The problem doesn't seem to be related to engine temperature. It hesitates all the way from cold to hot.
Other days, however, the truck will run just fine from start to finish.
The truck also idles a bit weird. It will at times randomly rev up and down and up and down and up and down and i have to get in and slap the accelerator all the way to the floor and back and then it will usually idle correctly when the rpm's come back down. not to mention, anytime i rev the engine or push the clutch after accelerating, say for instance to shift, the rpms will hang really high for a few seconds and then very slowly fall back down towards idle. I can't imagine that's normal.
I've been getting between 7 and 13 MPG which seems a little low to me. Tends to average around 11.
I ran the OBD trouble codes:
KOEO (Key on Engine off)
332- Insufficient EGR flow
565- Canister purge circuit failure
172- HEGO sensor circuit indicates system lean (right side)
173- HEGO sensor circuit indicates system rich (right side)
KOER (Key on Engine running)
116- ECT out of self test range 0.3 to3.7 volts
172- HEGO sensor circuit indicates system lean (right side)
332- Insufficient EGR flow
538- Invalid Cylinder balance test due to throttle movement
I dont understand how i'm running lean and rich at the same time. I thought it might be a fuel pressure problem so i put a gauge on it.
KOEO - 38psi (Should be between 35 and 45)
KOER -30psi (should be between 30 and 40)
If i pull the vaccum line off of the Fuel Pressure Regulator the pressure shoots all the way up the 40psi and as soon as i plug it in, it drops to 30psi.
I had somebody suggest to me that the PCM might be bad since it threw code 538 when the throttle was not touched. I have no idea how to test a PCM and i dont want to spend that kind of money without knowing its bad.
I wanted to test the EGR system so i removed and cleaned the EGR as well the intake where it attaches. It did not appear very dirty and seems to function correctly so I moved to the EGR Valve Position Sensor. I first went to test the 5v voltage at the connector and only had 3.8 volts. I'm not sure what would cause that other than maybe a bad EEC? It was much to cold out to continue testing the sensor so I will finish that testing later.
Here are all the parts that have been replaced over the last year (that i remember at least)
-Distributor, cap, and rotor
-Plugs and wires
-coil
-MAP sensor
-All vacuum lines were swapped out due to the factory plastic ones cracking
-PCV valve
-and of course regular oil changes, air filter.
Please help me fix my truck.
Thank you!
I've got a 1995 F-150 with a 5.0L 302 and a 5 speed.
I've been experiencing some engine performance problems. I've got a hesitation, mostly at lower RPM's. The problem is intermittent, but has been occurring more often as time goes on. The hesitation feels like I'm hitting a strong headwind or almost as though the hulk has grabbed the tailgate of the truck and does not want me to move. lol. It will struggle to even hold a speed. Sometimes i need to downshift just to maintain the speed limit. The odd part is that once I've accelerated into the high RPM range (probably around 3000) the hesitation immediately stops and the truck kicks me back in the seat and takes off. The problem doesn't seem to be related to engine temperature. It hesitates all the way from cold to hot.
Other days, however, the truck will run just fine from start to finish.
The truck also idles a bit weird. It will at times randomly rev up and down and up and down and up and down and i have to get in and slap the accelerator all the way to the floor and back and then it will usually idle correctly when the rpm's come back down. not to mention, anytime i rev the engine or push the clutch after accelerating, say for instance to shift, the rpms will hang really high for a few seconds and then very slowly fall back down towards idle. I can't imagine that's normal.
I've been getting between 7 and 13 MPG which seems a little low to me. Tends to average around 11.
I ran the OBD trouble codes:
KOEO (Key on Engine off)
332- Insufficient EGR flow
565- Canister purge circuit failure
172- HEGO sensor circuit indicates system lean (right side)
173- HEGO sensor circuit indicates system rich (right side)
KOER (Key on Engine running)
116- ECT out of self test range 0.3 to3.7 volts
172- HEGO sensor circuit indicates system lean (right side)
332- Insufficient EGR flow
538- Invalid Cylinder balance test due to throttle movement
I dont understand how i'm running lean and rich at the same time. I thought it might be a fuel pressure problem so i put a gauge on it.
KOEO - 38psi (Should be between 35 and 45)
KOER -30psi (should be between 30 and 40)
If i pull the vaccum line off of the Fuel Pressure Regulator the pressure shoots all the way up the 40psi and as soon as i plug it in, it drops to 30psi.
I had somebody suggest to me that the PCM might be bad since it threw code 538 when the throttle was not touched. I have no idea how to test a PCM and i dont want to spend that kind of money without knowing its bad.
I wanted to test the EGR system so i removed and cleaned the EGR as well the intake where it attaches. It did not appear very dirty and seems to function correctly so I moved to the EGR Valve Position Sensor. I first went to test the 5v voltage at the connector and only had 3.8 volts. I'm not sure what would cause that other than maybe a bad EEC? It was much to cold out to continue testing the sensor so I will finish that testing later.
Here are all the parts that have been replaced over the last year (that i remember at least)
-Distributor, cap, and rotor
-Plugs and wires
-coil
-MAP sensor
-All vacuum lines were swapped out due to the factory plastic ones cracking
-PCV valve
-and of course regular oil changes, air filter.
Please help me fix my truck.
Thank you!
01-02-2016, 03:09 PM
#2
Its probably not happening at the same time. See if you can find a scanner that can pull the freeze frame data and I'll bet you're getting those different readings at different RPM/load.
It sounds like there are multiple problems, and they may be interacting. It sounds like the EGR system isn't detecting sufficient exhaust gas flow. It sounds like maybe the throttle position sensor is getting intermittent. It also sounds like the PCM thinks the temperature sensor has failed.
I'd verify that the EGR isn't constantly leaking exhaust into the intake, then ignore it since it doesn't matter at idle. The throttle position sensor should be fairly easy to get to and test, so I'd do a sweep test and make sure it's voltage changes smoothly with throttle position -- let it snap closed a few times and see if it always returns to the same voltage. The coolant temp sensor is the other thing I'd focus on -- unless, of course, it really is -40F where you live right now
Might be a sensor wire or ground issue, might be a bad sensor.
If you're not as strong on diagnosis as you'd like, you might check out some of the videos on youtube. I'm partial to scannerdanner's ones because I really like his approach to the problems.
It sounds like there are multiple problems, and they may be interacting. It sounds like the EGR system isn't detecting sufficient exhaust gas flow. It sounds like maybe the throttle position sensor is getting intermittent. It also sounds like the PCM thinks the temperature sensor has failed.
I'd verify that the EGR isn't constantly leaking exhaust into the intake, then ignore it since it doesn't matter at idle. The throttle position sensor should be fairly easy to get to and test, so I'd do a sweep test and make sure it's voltage changes smoothly with throttle position -- let it snap closed a few times and see if it always returns to the same voltage. The coolant temp sensor is the other thing I'd focus on -- unless, of course, it really is -40F where you live right now
Might be a sensor wire or ground issue, might be a bad sensor.If you're not as strong on diagnosis as you'd like, you might check out some of the videos on youtube. I'm partial to scannerdanner's ones because I really like his approach to the problems.
