8

First time I looked at this the A/C compressor clutch wasn't engaging. Long story short: the high side pressure switch on the back of the compressor was unplugged. Noted that the engine was shaking (like it was misfiring) as I was watching them add refrigerant.

The next day I get the call asking me to look at why the van wouldn't accelerate was misfiring etc...

They had replaced the engine prior, the old one had head gasket problems as I was told. I was also told they compression tested the engine and all the numbers were roughly equal though they couldn't find the numbers they had written down. The intake gaskets are new and plugs and wires are new.

Thinking that the exhaust may have been plugged they disconnected both banks after the manifold, it still won't accelerate. They also tried with the MAF unplugged as well, more of the same.

Pulled whatever codes they had in the computer.

P0102
P0171
P0174
P0175

This makes sense with the exhaust and MAF being unplugged. Though the P0175 may need to be looked at further once they hook the exhaust system back up.


Cleared the codes and let it idle while looking at misfire monitors.

On start up cylinders 1 & 8 showed around 80 misfire counts each. Then the misfire cycles stop for no apparent reason... At least this gives me a place to start.


A capture of engine PIDS on a hot start. Engine MAP is high at idle, suggesting low engine vacuum.

enter image description here

I didn't have a vacuum gauge or transducer with me (I want a WPS500...) so I asked if they had one. Of course they couldn't find one, so I'll leave that for later.


After a few seconds of idling The check engine light comes on with a P0200 Injector Control Fault.

I decided to focus on cylinder #1 as it was the easiest to access and I didn't have anything in the way of hand tools.

This is a capture of the bank 1 ignition and injectors at idle.

Trace 1 (Yellow) is the number one coil trigger.
Trace 2 (Green) is the number one injector trigger.
Trace 4 (Red) is the amperage reading taken at the ENG1 fuse. This powers all the bank 1 injectors and coils.

enter image description here

This doesn't look right...


So I suspect that the engine has multiple issues.

Low engine vacuum according to the MAP sensor reading. Maybe a restricted MAP sensor port? Maybe, but I doubt it the range is too good on the PID capture. Bad MAP sensor? Another maybe. Leaking Intake? I'm pretty sure it is. There was a hissing sound but I couldn't nail down the source. I asked them to smoke test it when the engine was cold and get back to me. Valve timing? Another maybe. The P0175 may be related.

The P0200 code. Honestly I need more time with this one, why would the injector be firing so early? The timing looks off too. I think the harness connections may not be in the right spot. Or there's something wrong with the harness.

Ideas? Comments? I'll be taking another look at it tomorrow probably.

  • I think I see what you're talking about ... one question with the injector firing at the same time as the coil ... could there be a cross (short circuit) in the wiring there? Why would the injector fire at the same time as the coil, and then be doing it out of time (an extra injector pulse is what it looks like to me). Maybe I'm off base on this ... It darn sure doesn't look right, though. You'd expect it to be more rhythmic in whats going on. – Pᴀᴜʟsᴛᴇʀ2 Jul 24 '16 at 21:53
  • @Pᴀᴜʟsᴛᴇʀ2 the yellow trace is the coil trigger. but you're right the injector trigger is firing twice for #5 and not on #1. or it's super delayed for some reason. I think I'll take a look at the cam and crank signals as well next time. – Ben Jul 24 '16 at 21:58
  • Stellar job with the level of detail in the question Ben, thanks for sharing! – Zaid Jul 25 '16 at 2:05
3
+50

Make sure the cam and crank signals are good. Also check the reluctor for the crank and cam sensor.

  • 1
    CMP and CKP waveform and correlation was good on this. No obvious dropouts in the signal. Backprobed at the PCM. – Ben Oct 24 '16 at 21:43
  • Has this problem existed since the new engine was installed? And if so is there any updates for the ecm/pcm? Also double check that the reluctors are in the correct position and that they aren't spinning on the shaft or anything and that all the reluctor notches are there and that the key way isn't broke on the cam and cranks where applicable. – Derek Oct 28 '16 at 0:35
  • I couldn't get a straight answer out of the owner or mechanic. According to the owner the problem started after the engine was installed. But the mechanic told me that the problem existed before the engine was swapped. Unfortunately while I did do the cam crank correlation I never saved it to disk. As to the PCM I did search for TSBs regarding the generated codes and PCM calibration. Nothing obvious came up. I recommended they replace the PCM and have it updated to the latest calibration since I didn't find anything wrong the the wiring harness. – Ben Oct 28 '16 at 0:52
  • Back story on the old engine. A stud on the manifold was broken and someone drilled the stud and managed to drill into the water jacket and that's why the engine was replaced. – Ben Oct 28 '16 at 0:55
  • If the condition truly was there in the old engine and is the same condition I would suspect the pcm. If the old engine over heated from the head issue and it was bad enough, then as you stated the harness could be melted somewhere and causing signal interference. – Derek Oct 28 '16 at 1:03

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