So I am pretty sure I have a bad vacuum leak, but I am having trouble isolating it. It is also possible I could have a different problem that presents as a vacuum leak. I am stumped on how to proceed.
The car is a 1998 Mustang GT with the 2v 4.6L. It was driving fine, but then had two problems happen at the same time. I went out for a drive and the car had no power. It could barely accelerate, and the engine felt like it was resisting going to higher RPMs almost like it was blocked or clogged. I returned home and it blew a heater hose and barfed coolant all over the driveway. I shut it off right away and the car did not overheat.
I fixed the heater hoses and ever since then the car idles terribly, almost stalls, and has a slight backfire. It will accelerate to higher RPMs without issue, however.
My code reader live data stream shows the both O2 sensors reporting a lean condition. STFT and LTFT are consistently positive.
At first, STFT read between 0.8 to 5-7% (positive) on both banks with Bank1 always being higher than bank 2. LTFT never changed and was consistently pegged at 6.3% for Bank 1 and 1.6% for Bank2. LTFT never went to zero or negative. It literally never moved from 6.3/1.6. All numbers improve when the engine accelerates up past 2000 RPM. At higher engine speed, STFT goes to alternating between -3% and +3% and LTFT drops to near zero.
The problem seems to be getting worse. The last readings I took the numbers made massive jumps:
STFT: 25-30% (both banks)
LTFT: 23.4% on bank 1, 16.4% on bank 2
After getting these readings, STFT shifted again. This time it went negative (-6.3% bank 1, -7.8% bank 2). LTFT stayed the same at positive 23.4/16.4.
At this point car is running very rough and stumbling at idle. Engine shakes badly while idling.
So far, I have removed and closely inspected all vacuum hoses. All check out with no holes, cracks, etc. I replaced the PCV valve. I tested the O2 sensors and they check out. I did a fuel pressure check and got a consistent 30 or slightly more PSI (Car has a return system so this is at spec). I sprayed some carb cleaner on hoses and gaskets with no change to idle. I did the test where you pour some water on the engine to induce a temporary gasket seal with no observed change. I tried doing a smoke test with a homemade smoke tester. It didn't work very well, but I did get some smoke flowing so it could be an intake gasket leak, but it could also just be escaped smoke from my coffee can smoke tester as it was hard to tell where it came from.
I am stumped on where to go next. It seems like it could be an intake gasket leak, but I didn't want to tear into the engine without more definitive proof. since my smoke test didn't really work. Any ideas on other tests to run, or how to do a better smoke test are appreciated.
Also, if I am missing something, or perhaps ignoring another cause of this issue, I'd appreciate other systems components to check for problems.
The car is a 1998 Mustang GT with the 2v 4.6L. It was driving fine, but then had two problems happen at the same time. I went out for a drive and the car had no power. It could barely accelerate, and the engine felt like it was resisting going to higher RPMs almost like it was blocked or clogged. I returned home and it blew a heater hose and barfed coolant all over the driveway. I shut it off right away and the car did not overheat.
I fixed the heater hoses and ever since then the car idles terribly, almost stalls, and has a slight backfire. It will accelerate to higher RPMs without issue, however.
My code reader live data stream shows the both O2 sensors reporting a lean condition. STFT and LTFT are consistently positive.
At first, STFT read between 0.8 to 5-7% (positive) on both banks with Bank1 always being higher than bank 2. LTFT never changed and was consistently pegged at 6.3% for Bank 1 and 1.6% for Bank2. LTFT never went to zero or negative. It literally never moved from 6.3/1.6. All numbers improve when the engine accelerates up past 2000 RPM. At higher engine speed, STFT goes to alternating between -3% and +3% and LTFT drops to near zero.
The problem seems to be getting worse. The last readings I took the numbers made massive jumps:
STFT: 25-30% (both banks)
LTFT: 23.4% on bank 1, 16.4% on bank 2
After getting these readings, STFT shifted again. This time it went negative (-6.3% bank 1, -7.8% bank 2). LTFT stayed the same at positive 23.4/16.4.
At this point car is running very rough and stumbling at idle. Engine shakes badly while idling.
So far, I have removed and closely inspected all vacuum hoses. All check out with no holes, cracks, etc. I replaced the PCV valve. I tested the O2 sensors and they check out. I did a fuel pressure check and got a consistent 30 or slightly more PSI (Car has a return system so this is at spec). I sprayed some carb cleaner on hoses and gaskets with no change to idle. I did the test where you pour some water on the engine to induce a temporary gasket seal with no observed change. I tried doing a smoke test with a homemade smoke tester. It didn't work very well, but I did get some smoke flowing so it could be an intake gasket leak, but it could also just be escaped smoke from my coffee can smoke tester as it was hard to tell where it came from.
I am stumped on where to go next. It seems like it could be an intake gasket leak, but I didn't want to tear into the engine without more definitive proof. since my smoke test didn't really work. Any ideas on other tests to run, or how to do a better smoke test are appreciated.
Also, if I am missing something, or perhaps ignoring another cause of this issue, I'd appreciate other systems components to check for problems.
