|11-14-2012 11:16 AM|
Help me or shoot me...hesitation above 1200 RPM
2001 Ford Focus ZX3, S2, 2.0 Dual overhead cam
My issue started about 2 weeks ago. I was on my way home from work, ran into the gas station for some milk, and when I get in the car to start it it just cranked for several seconds before it finally started up. No issues for a week after this. Then last Tuesday on my home from work when I would pass a vehicle on the highway and it would start to surge and hesitate. I ended up missing my exit and had to do some city driving (about 30mph) the rest of the way home. While going 25-30mph up hill, it felt as though my car was falling on it's face. Once it got level I was going smooth again. So I pulled it in the garage and checked for DTC and fuel trim.
What I found at the time was no DTC's but fuel trim was at +24(lean). I monitored the vehicle's engine data saw that my rear 02 sensor wasn't giving me any reading. So I swapped my fuel pressure relay(per another forum post), replaced the 02 sensor, PCV, ignition coil connector (wires were damaged where they went into the connector), DPFE sensor (because of posts I saw on the forums), fuel filter and drained the tank got a few gallons from the gas station (in case it was bad fuel). After replacement , my rear 02 now gives me a reading, I have the same fuel trim reading(+24), and my fuel pressure is reading the same (30-35psi on my pressure gauge, 36-40 on the scan tool through the sensor). I continued checking for external vacuum leaks - none found. I did replace the tube behind the intake (connects to PCV, the tube really soft) and the tube from the valve cover to intake (just to change).
Also, before I forget, I did test drive it after replacing the first set of components (prior to changing the vacuum lines) and it drove like crap. Anything about 1200rpm it feels/sounds like the converter is clogged or I have a huge exhaust leak near the engine where it would suck in air through the exhaust.
So, I disconnected (and damaged) the egr tubing at the exhaust side and put my blow gun to it. Under light throttle/pressure with the blow gun I can hear it leaking into the intake. So, I deleted the egr to retest. Fuel trim numbers are now perfect at idle, they fluctuate between -2 and +4. So I think, ha I fixed it.....WRONG. I lower the car and pull it out of garage and I can feel that same severe hesitation on light acceleration (anywhere above 1200RPM) and fuel trim when it is running rough is again in the 20's (lean). So I pull the car back on the lift, apply a rod to the brakes (for light to moderate brake pressure), and put the car in gear. The car accelerates smoothly (up to around 2500rpm) and is going at about 60mph. I checked for exhaust back pressure, at idle it bounces pretty good but is in spec on the gauge. I increase the rpm and it stays right at 0 the hole time (makes me think cat isn't clogged). But at the dealer we would just disconnect the cat and take it for a run, so I did the same. Popped the cat loose after the flex and pulled it out - no difference, in the driveway or going down the street anywhere near or above 1200RPM it falls flat on it's face. After letting the vehicle idle in the driveway for about 2 hours I did have a history P1233 and yes I have searched forums and the web for that code and have ran as many tests that I came across related to that code.
By this time I have already checked plugs (look normal), checked for spark (all cylinders look the same), TP sensor operation and MAF sensor operation (using scan tool), checked injectors for operation at different rpm (using stethescope), checked injector operation doing a balance test (all injectors drop from about 45-46psi to 15-17psi), I checked compression (I'm at or above 150 on all cylinders), and checked plug wires for resistance ( I have the livewire plugs) the all read between 250-550ohm depending on length (you can see some arcing points where the plug wires over lay each other). Checked my original factory plug wires for resistance they are all between 2.5kohm-5.5kohm.
I swapped out the screamin' demon coil pack and my aftermarket wires with the vehicles original - no change. By this time I also redrained the tank, and pulled the pump (I saw the posts about the fuel pump extended warranty, which mine expired a year ago). I already have the new redesigned pump, but the strainer/pump sock looks like crap. So they don't just sell the stainer kit, so I bought a new NAPA fuel pump and retested - NO CHANGE...
Now, we are about up to date. This last part was done last night and my brother was here to rev it up in gear for me while it was on the lift and I am starting to get it to fail there as well (hearing the occasional back fire as well). Clearly I don't expect anyone to be able to fix it through the forum for me, but clearly there is something I am missing or forgetting to check and that is where all of you come into play. Below is a list of some other things that I recall testing and then below that is a list of the mods that have been done and resent repairs.
IAC: spec is 6-14 ohms (I'm getting 10.7 ohms)
Injectors: spec is 13.7-15.2 ohms (I'm getting 17.2/17.1/17.2/17.2 and I'm getting .1 across my leads, so average at injectors is right at 17ohms)
Injector Balance: 45-46 peak, dropping to 15-17 on all for
Compression: about 150-153 on all 4
TP: Normal flucation with voltage/percentage as the pedal is depressed (much like myself at this point)
MAF: normal fluctuation with throttle change
Plug Wires/Aftermarket: 250ohm-550ohm depending on length
Factory Wires: 2.5kohm-5.5kohm depending on length
Fuel pressure on my gauge/new pump:
Key on Engine off: 45psi
Fuel Pressure old pump:
Key on Engine off: 40psi
Fuel Pressure with scan tool:
Running: 40psi - average
STFT at idle: Near 0
LTFT at idle: Near 0
LTFT on throttle/when hesitation is present: above 20 (lean)
Battery Supply/Key on Engine off: 12V
Battery Leaving/Key on Engine off: 12V
Signal Voltage w/ key on engine off: Fluctuating between .3-8v
Parts Changed for this Issue:
Removed tune from vehicle and reset to factory (I have since moved back to the tune since it made no change)
Rear 02 Sensor
EGR Delete (fixed fuel trim levels at idle, but not drive-ability issue)
Plug Wires and Coil (swapped back to original/factory)
Installed electric vacuum pump to brake booster and sealed off engine vacuum line (vacuum to booster was only at 15 psi and braking was weak, now vacuum to booster is near/at 20psi and I can lock up my brakes).
---I did disconnect the fuse to this pump in case the electrical draw causing this issue, but no change.
I did recently change the battery and removed my underdrive pulley and reinstalled the factory pulley - I did this because I am no longer on home dispatch and have to drive my vehicle about 31 miles each way to work.
New timing belt and tensioner about 1.5 years ago
INJEN Inake (not cold air)
Crower Stage 1 Cams
Livewire wire set/Screamin' Demon Coil Pack
OBX race head and MBRP 2.25" catback exhaust
--Modified exhaust to install cat (about 5 years ago)
SVT Brake Kit
Anyway questions or info would help, right now I'm just grasping for anything. And for those of you who took the time to read through this book I've just written, THANK YOU...