tractor_boy
New Member
- Joined
- Feb 17, 2009
- Messages
- 24
- Reaction score
- 0
- Points
- 0
- Vehicle Year
- 93
- Make / Model
- Ford
- Transmission
- Manual
Hey guys I'm getting pretty frustrated with my truck. It's a 93 4.0 with 140,000 miles.
I just did a complete tuneup at 110,000 and now it's acting up. When I am accelerating the engine seems to misfire. It's not a real consistent misfire, and happens on average it feels like twice per second. The engine temperature, rpm, gear I'm in, or throttle position seem to make no difference at all. No pinging or knocking noise, just the stumbling symptom. It feels almost as if the clutch is just slipping for a bit and then quickly grabbing again. I know that isn't the case (it had a new Valeo clutch 20,000 miles ago), but it might help to describe what's going on.
So I pulled all the spark plugs and they are all very clean and good condition and very little variation in appearance from cylinder to cylinder. I checked all the wires with my ohmmeter and they're good. Thought maybe the coil pack might be getting weak so I swapped it off my 94 4.0 ranger, no difference.
Changed the air filter, cleaned the MAF, no difference.
Fuel injectors were rebuilt at 120,000. I changed fuel filter and checked fuel pressure afterward. It was roughly 5 psi below spec both at idle and at full throttle, so I dropped the tank and put a new high flow pump assembly in. Absolutely no difference as far as the stumbling, but my fuel pressure is back up where it should be now.
Then I was driving today and the check engine light would come on at random times, and then finally stayed on. Shut the key off and the light is gone when you turn it back on.
I plugged it into the $3000 genesys scan tool at the shop where I work and found no background computer codes.
Then I put the tool in datastream mode to look at all the sensor values and noticed a long-term fuel trim of -6% on bank 1, 0% on bank 2. All other values were well within spec and seemed very reasonable. Figured that might mean a bad 02 sensor, so I bought the sensors and replaced tonight. NO DIFFERENCE!!!
I am tearing my hair out and am becoming ashamed that I call myself a mechanic at a shop whose specialty is none other than driveability and diagnosis- but at least it's my own vehicle and not another customer's.
Please help me guys if anyone has had similar problems or has any ideas, I'm willing to try pretty much anything at this point!
Thanks
Chris
I just did a complete tuneup at 110,000 and now it's acting up. When I am accelerating the engine seems to misfire. It's not a real consistent misfire, and happens on average it feels like twice per second. The engine temperature, rpm, gear I'm in, or throttle position seem to make no difference at all. No pinging or knocking noise, just the stumbling symptom. It feels almost as if the clutch is just slipping for a bit and then quickly grabbing again. I know that isn't the case (it had a new Valeo clutch 20,000 miles ago), but it might help to describe what's going on.
So I pulled all the spark plugs and they are all very clean and good condition and very little variation in appearance from cylinder to cylinder. I checked all the wires with my ohmmeter and they're good. Thought maybe the coil pack might be getting weak so I swapped it off my 94 4.0 ranger, no difference.
Changed the air filter, cleaned the MAF, no difference.
Fuel injectors were rebuilt at 120,000. I changed fuel filter and checked fuel pressure afterward. It was roughly 5 psi below spec both at idle and at full throttle, so I dropped the tank and put a new high flow pump assembly in. Absolutely no difference as far as the stumbling, but my fuel pressure is back up where it should be now.
Then I was driving today and the check engine light would come on at random times, and then finally stayed on. Shut the key off and the light is gone when you turn it back on.
I plugged it into the $3000 genesys scan tool at the shop where I work and found no background computer codes.
Then I put the tool in datastream mode to look at all the sensor values and noticed a long-term fuel trim of -6% on bank 1, 0% on bank 2. All other values were well within spec and seemed very reasonable. Figured that might mean a bad 02 sensor, so I bought the sensors and replaced tonight. NO DIFFERENCE!!!
I am tearing my hair out and am becoming ashamed that I call myself a mechanic at a shop whose specialty is none other than driveability and diagnosis- but at least it's my own vehicle and not another customer's.
Please help me guys if anyone has had similar problems or has any ideas, I'm willing to try pretty much anything at this point!
Thanks
Chris