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Of course, it’s got the 4.3 (vin W) with automatic transmission and it’s rear wheel drive. I started out chasing a power loss problem on this van. It got a tune up in Colorado on its way to Wisconsin which I’m told helped dramatically, but did not solve all the power loss problems. My test drive felt a little sluggish and it felt like the engine hesitating almost in a cyclic fashion. I have two codes stored; 0032 EGR and 0045 system rich. The codes themselves really get no more specific than that. I first looked at fuel trims and O2 PID’s. It’s got the block learn and integrator numbers for fuel trims which I don’t remember so well, but did notice they were both more apt to return closer to 128 with some steady light throttle. As I recall, 128 is the sweet spot. The O2 sensor signal was cycling, but it wasn’t pegging much higher than 350mV. With a steady throttle, I could get hi/lo cycling much closer to normal between 100mV & occasionally up to 800mV. I could at least observe 700-750mV fairly consistently on the peaks as it cycled.
This led me to ignore the rich code and look for a vacuum leak instead. I smoked the intake and found smoke pouring out in the throttle body area and it’s a lousy place to get a visual confirmation of exactly where. I expected some smoke to leak through just for the shaft of the throttle blade, but the volume did appear to be too much for a shaft leak. There also looked like there could be other leaks behind the throttle body, but once again, it was still in an area where I just couldn’t visually verify sources. I quit worrying some with the vacuum leak once I realized there was no MAF sensor on this van. It’s strictly a speed density system.
I abandoned the vacuum leak for a while and moved my focus onto the EGR code. I commanded the EGR open with a Tech2 and got no actual response from the EGR. I tested power and ground for the solenoid only, ignoring the position sensor circuits. Battery voltage was present on both the power and ground side of the solenoid. I pulled the EGR out and applied a power and ground to it. The pintle opens every time I close the circuit. I plugged the EGR back in later and confirmed by scan tool that the sensor circuit is working. It showed .7 volts closed and 4.7 volts with the pintle wide open. When I came back to the van this morning, I found the PCM and tested the EGR control wire directly at the PCM pin. With the EGR off, I still had battery voltage getting all the way to the PCM. I commanded the EGR to open, I still had no response and the circuit maintained battery voltage. This is where I condemned the PCM as it looked like the driver wasn’t grounding the circuit when it should.
The new PCM solved nothing. Something particular about this PCM is that it’s got a removable PROM memory chip. I transferred the chip to the new PCM and made sure the tabs locked onto the chip. The PCM I got was a Cardone remanufactured unit. That’s a brand that’s been consistently disappointing for me and I still felt good about my diagnosis, so I ordered another PCM. I moved the PROM chip again and installed the next PCM and I still couldn’t command the EGR open.
I tapped in an alternate ground using my test leads with back probes as the new ground with no change in command ability. I reread my circuit diagram to ensure I could safely ground the EGR manually with a jumper wire. I grounded the circuit and could open the EGR every time I did such. (Just so you know, all testing was done by back probing the circuit. No pins are damaged or pulled out of their socket on the PCM connector.) I also did my voltage drop testing the same time I was manually closing the circuit. It would consistently drop all but 100mV. While that’s a tad high, it’s still been good enough to continually open that valve when I want it open so I’m not going to concern myself with it. As much as I felt it was stupid at this point, I wiggle tested my harness looking for that battery voltage to drop out at the PCM. I also tested primary power and grounds to the PCM and they’re fine too. Battery voltage is available at the power side with 16mV on the ground wires.
I should also mention that I did testing with both the original EGR valve and a new one at various stages. Neither valve made a difference for any test performed and both operate normally on a live circuit.
Long story short, my circuit integrity up to the PCM is just fine. My EGR valve is just fine. Three PCM’s are not grounding the EGR circuit and I have no idea why. The only thing left that I can’t account for is that PROM chip. I wouldn’t know how to test it and can’t see why I’d need to considering that the EGR driver circuit is the only part being affected.
I’m not the least bit concerned about any possible vacuum leaks at this point. I might come back to it later, but the EGR issue, right now, has my full attention. Any thoughts?
Thanks in advance.
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This is very far off, but something I ran into this week on a Mitsu is coming to mind. I had problem where the hazard light and horn did not answerback when the car was locked using the key fob. Mitsu’s version of a BCM, the ETACS, made all those decisions internally and so I replaced it but it didn’t fix it. I had figured it would be a more than even Mitsu would bother to have in the programming, but I had thought that maybe there is a circuit that the ETACS is looking at (the same way any OBD2 PCM looks at a component to know to generate a circuit code) that looks wrong so it won’t perform the answerback. I was wrong and found a broken wire in a door harness that was not telling the ETACS that a door lock actuator had successfully moved into the lock position. Because it wasn’t seeing that door lock, it was not answering back with the lights/horn that the car had been locked. In hindsight, it makes all the sense in the world, it’s just surprising how smart they make these modules sometimes.
Like I said, this is very far off, but sometimes computers will look at things you wouldn’t think of as part of their logic process.
As so often seems to happen with performance diagnosis it seems mechanical has been overlooked. In fact, you found what seems to be some substantial vacuum leaks that could certainly contribute to a performance issue. If the mix isn’t right, the power won’t be either. I would turn your attention back to those vacuum leaks and also do a compression test just to see what kind of shape the engine is in. Once again if the engine isn’t in good shape, it won’t be able to perform properly. More info on this here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
Lastly don’t rule out low system voltage. It can reek havoc on the electrical system and as a result it won’t perform correctly.
http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems
Good luck and keep us posted.
[quote=”EricTheCarGuy” post=137337]As so often seems to happen with performance diagnosis it seems mechanical has been overlooked.[/quote]
I wouldn’t say that. In writing the long post that I did, I wanted to be thorough about what I knew. But, at the end of it all, there was only one part of the diagnosis I wanted to focus on for the sake of this post and that was the EGR problem.
As it turns out, I was my own problem on that one. I had enough stuff apart with the vacuum leak testing that I decided to try commanding the EGR without the engine running. What I didn’t know, at the time, was that the PCM will ignore the scan tool commands unless it sees an RPM signal. I wouldn’t have suspected that I needed to pay attention to that detail since the Tech2 gives you EGR position PID’s while in the actuator tests. With or without the engine running, the pintle can still move and the position sensor can still see it. (Just so you know, I’ve otherwise always tested EGR’s with engine running where bidirectional controls were available.)
There’s a quote that goes, “You must learn from the mistakes of others. You’ll never live long enough to make them all yourself.” So there’s one of my mistakes. Don’t let it be one of your mistakes.
I did return to the vacuum leak diagnosis and smoked the intake again. I had the boss in at the back side of the engine with better eyes, better lighting, and a better mirror. He found a small piece of rubber tubing leaking a little for the PCV piping. The IAT sensor was very capable of leaking smoke with the electrical connector unplugged. The intake bellows boot had been on & off a couple times, so we found some smoke where it mates to the throttle body. Turns out I didn’t tighten the clamp well enough the last time I put the boot back on. Once we got that out of the way, all that was really left was the same leakage through the throttle blade shaft. When I initially smoked the intake, I was fairly blind to what was going on at the left side of the throttle body. The boss got a better view of it than I could.
This one has been an in-betweener diagnosis, so I’ll probably get to keep testing a little here and there between other jobs, but I’ll keep you posted as I learn stuff.
I took that Astro out for another test drive to see what I missed and did so without carpet on the dog house this time and I heard the engine tell a much different story. I could hear the engine loading up on itself and what I first thought was a cyclic hesitation was anything but cyclic. Pulling the doghouse altogether made it even more apparent that I wildly missed what should have been an easy diagnosis. Once I got a better ear for what the engine was saying, I was able to diagnose it as a restricted catalytic converter. The guy that owns the van is going to try a snake oil in the gas tank to clean it out. In the meantime, we’ve got a new cat on the shelf waiting for when it doesn’t work.
Yeah, it sounds like it was a bona-fide whoopin’ alright. I’ve got a Volvo S60 Turbo 5cyl AWD doing some wacky stuff that makes the car undriveable. Nonetheless, it’s a in-betweener kind of thing that’s seems to be blossoming with Volvoisms. You know how it is. If you’re good, you end up getting these kinds of headaches. I’m thinking now of the time I fixed a GM tranny that was in a Volvo S60, oh the things they do….
I got a new job a couple weeks ago that I really really like and one of the reasons why is because the boss said something to this effect: “We don’t speak Volvo here.” 😀 He’s not fond of anything European either and will often defer to other shops that specialize in euro cars depending on what it needs. I’d actually like to see a few VeeDub’s from time to time so I can finally justify buying all those damn triple square sockets.
It would be cool to hear about that Volvo once you get it sorted out.
That Volvo is definitely a horror story in the making. I’ll send you a PM whenever that gets resolved.
Quick funny story: A few years ago I interviewed at the local Volvo/Jag dealer to be a Volvo tech, or so I thought. The Volvo shop there is a beautifully clean and nice fishbowl-type setup like I dream of working in, but with barely enough room in a bay for my tools. I wrote them my first official resume, went through multiple interviews, then finally was accepted as a friggin’ JAGUAR tech at the end of the last interview. They had told me the Jag techs all get a guarantee because the whole job is warranty work that grossly underpays . I was like “uuhhh”, but was still of going with it during that surreal moment and asked to see the Jag shop I’d be moving into. They, of course were offering me something ‘greater’ than Volvo. It was a crazy small windowless magazine of a shop and I couldn’t fit half of my tools in the corner they pointed to (they didn’t my amount of tools). I had to blow that whole deal off right there, after all that effort.
After my first interview I didn’t hear from them, and thought maybe I wasn’t their cup of tea. Turns out they lost my application or something. The shop foreman who was in my first interview showed up at my work (he remembered where worked) to tell me that they wanted a 2nd interview. They send a tech to get me back in there, and then It’s such a shady deal I have to opt out in the end. Something is whack with these luxury dealers, but I haven’t been around long enough to understand it yet.
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