Kevin Phillips

New to the forum but not new to working on my car, audizine was my go to forum but I can’t seem to have a good discussion / guidance
snapped my timing belt a year ago and had to have the head rebuilt.

completely stock car except for boost gauge and a aftermarket tip

1. Was heading from Las Vegas to California when coolant temp gauge went to cold/0 within 5 minutes it went to The middle again.
within 20miles my car starting sounding like a slight misfire and has a vibration when going 80mph
I slowed down to 70mph went away.

eventually I got a code for fuel too rich.
when I got back I checked my fuel trims and there were -20%+ on my long term.

1. I replaced all 4 coil packs and copper plugs gapped at .028
2. Replaced maf
3. ecs tuning coil pack harness repair kit
4. fixed a tiny leak on manifold to turbo ( both machined flat and new gasket. No leaks now)
5. Fuel injector harness repair
6. cts sensor harness repaired and new sensor from autozone( possibly my problem right here)
7. new fuel filter
8. Replaced the upstream 02 sensor from a junkyard car.

At this point I’m frustrated and I deleted the section jet pump that connects from manifold to brake booster.

8. Really checked my vacuum lines, even I was getting 18-20 hg

9. boost leak showed I had 3 injector cups cracked, replaced those and in the process stripped 1 of the bolts that bolted down the fuel rail.

here’s the weird part after #5 the car was running good and my fuel trims were okay.
On step #5 I swapped my cts sensor for a known broken one, it was broken where the coolant gauge wouldn’t read but I never had a problem with fuel trims, actually drove like that for months before swapping to a new cts sensor.

so I thought I fixed it and went to swap a new aftermarket cts from autozone
and now I’m running super lean under part throttle.
like short term is anywhere from -3% to +15%
I under anything within 10% is in spec But there’s

1.now way I should be having this bad of fluctuations right?
2. I guess it possible the machine shop did a **** job and I have low compression across all 4?
3. My fuel pump is supplying enough pressure?
5. I have a vacuum leak somewhere causing these crazy fluctuations?

my maf readings are 4.5-5.5 at idle
vacuum at idle is 18-20hg
my short term fuel trims at idle are anywhere from -9% to +11%
I reset the fuel trims couple days ago and in the time I went 4miles my fuel trims went to -11% and then today when I test drove it 5miles from ltft went from -11% to 0% then went I got home I let it idle and that’s when I noticed the short term fuel trim was anywhere from -9% to +11%

can someone please drop some knowledge on me and point me in the right direction?

turbo510

Your story is perplexing; though it sounds like during the process you found and corrected some issues. For the compression, borrow a gauge set and find what it is, although I doubt low compression causes these symptoms. Fuel pressure fluctuating might be it, which means you would need to get a ~100 PSI gauge (I suggest a cheap oil pressure gauge) and tap into the fuel rail hose (be careful that your setup can't blow apart under pressure)! A MAF that is intermittent, or CTS might do this too, and you could use VCDS to plot those sensors to see how they behave. Naturally the temp sensor should be stable and reasonable, the MAF should remain steady at a steady cruise. A vacuum leak big enough to throw off your fuel trims would be big enough to hear, in my opinion.