I'm still getting the P0108 code after replacing both my up and downstream MAP sensors (not concurrently). I'm currently running the stock bypass vale + VGS. Could the VGS be causing this?

I've searched around and aside from the MAP sensors, the only other thing that could be causing this problem is the bypass valve. The spring tension seems good. Could the diaphragm be going bad too?

As a possibly related aside, I've noticed that the engine idles roughly for a few seconds when running while cold, then goes away.

Thanks in advance for the help.

- edit -

The part numbers for the MAP sensors correspond to their proper positions on the intake track. xx-xx-648 on the intake manifold, and xx-xx-679 as the upstream MAP next to the airbox.

 

I think I had the same code and same issue of diminished power. And it was right after I replaced my intercooler boots. It wasn't immediately noticed, and loss of power was felt while on the highway during acelleration up thru top gears. I had an onboard Scangauge II and code was read. I drove it another 10 miles to the shop I was going to anyways and we figured it out.

One on the pass side. The bottom of it where I couldn't see had slid off the horn side. Once it was buttoned up correctly the issue and code was gone.

 

had same issue, my boots were worn. replaced boots good to go.

 

The boots, huh? Interesting. I remember loosening the boot clamps in preparation for running the VGS line, but found a way to run the line without removing the intercooler.

Would the boots wear out at 80k miles? Seems a little premature to me ... I'll check it out, though. Thanks, guys.

 

Look for cracking in the "bubble" (or bulge) that is in the middle of each intercooler boot, both on the inside and the outside. You could have also gotten one of them misaligned underneath the clamps. I've done that a few times with as much as I have taken my intercooler off and on.

 

I've never taken the intercooler off, but I guess that doesn't mean the previous owner didn't ...

I checked it yesterday using the dish soap/water sprayer method for finding leaks, and I didn't find any. The clamps were a *little* loose, so I put in a quarter turn or so to each one. The flange on the "exit" boot from the intercooler didn't sit exactly flush on the intake manifold "horn", and I'm seeing a little bit of oil on the bottom of the supercharger horn and "entrance" boot (from the PCV valve, I take it).

I'm also having some difficulty believing ALTA's product literature about their silicone boots being better than OEM ... Anyone go with OE instead of Alta when their boots go out?

I do all my car work in my father's garage ~40 miles away. On the drive home, I didn't get an SES light. Tightening the clamps appears to have solved it, but I'm still a little skeptical. I kept it around 3k RPM throughout the drive home (70 MPH = driving like a grandma on I55). I don't drive my car much during the weekdays, so I guess I'll find out next weekend!

 

If you are using an OEM or GP intercooler, stick with the OEM boots. This is per Way at Way Motor Works. I just replaced mine when I bought my GP IC back in May 2011. He can probably shed some additional light if you go with any other configuration. It ends up being a tradeoff. The silicone boots last longer, but you will have a harder time getting the clamps to properly close down on the ends.

Keep us posted if you have any more issues with the boots. Yeah, I understand what you mean about having to tighten on them, but even the OEM ones need a little TLC just to make sure they are properly sealed off.

 

Welllllllllllllllllllll ....

It seems as though that did not fix the problem. Downshifting to 5th to pass a Pious driver hypermiling in the fast lane gave me an SES light.

I'm starting to think the intercooler horn boots are leaking, as everyone is suggesting. I tried using the tried-and-true method of a spray bottle with water and dish soap to look for leaks, but it is much more effective to have everything pressurized.

Is there a way to do a boost leak test? I figured I'd do it like every other FI'd car I have owned. Boost leak tester made up of a PVC pipe cap and a tire schrader valve clamped to the end of the throttle body hose going to the airbox. ... But then again, there's that electronically actuated throttle body in the way ...

 

I may have found the problem. My crank pulley is wobbling intermittently. Woo hoo. ==;;

Ordered a new, standard size Fluid Damper pulley from Amazon for $240 shipped! Car's gotta be parked for a week now, though ...

 

I like the color of the silicon boots. Had a red Alta set and a few black M7's. You just need to remove them every so often to check the inside of the sleeves for cracking.

Running OEM boots right now.

 

Time will tell, but anything under such stress containing "fluid" would have me looking for leaking fluids all the time.....much like the engine mounts and such.

I would have opted for the Craven 0% myself and saved the extra $$ for other mods.

I changed my IC Boots first time at 80K miles.....I am at 133+ now. Ran a set of Alta's for a while now back to a new set of OEM's.

They are constantly stretching and blowing up under pressure. Over time like a balloon constantly inflated and deflated, they may not have cracks, but become weak.....Since it sounds like your IC is full of oil varnish, I would suggest an Intercooler cleaning with Red can of CRC brake cleaner. ( Will end up using most of the can btw ) and then getting new OEM IC Couplers.

 

Ehhh ... I didn't want to run the risk of running an un-damped pulley. I know it's somewhat of a controversial topic here. Jan of the Kingdom of RMW recommended the PRW pulley, so I went with that one, only I got it $50 cheaper from Amazon with free two day shipping.

Good call on the cleaning of the intercooler. Now that I spent all of my monthly "mods/parts budget" on this damn pulley, however, I'll have to wait for my next paycheck 'til I can order the OE boots.

I remember when I first cleaned out the intercooler on my '92 Talon TSi, I removed a quarter quart of oil! I will probably end up putting a coat of black radiator paint on it as well. ... And a catch-can.

So many weekend projects with this car ... Lynne's making my DSM look pretty reliable right now. I didn't have to replace the harmonic balancer/crank pulley 'til I hit 130k miles. I'd say they don't make 'em like they used to (my old-n-sold '92 Honda Accord LX with 222,xxx on the odometer comes to mind), but my colleagues accuse me of being more 62 than 26.

 

I just started the car this morning to play "musical cars" in my parents' driveway.

Right away, my car impersonated an occupy wall street protester by chattering it's head off and smoking without going anywhere. That pulley is in a bad way. I'm surprised it made the ~40 mile drive down to the suburbs without failing.

 

Well, it's back ...

I replaced the OE pulley/damper with a PRW unit, and installed a Mini Madness CAI while I was at it. Car was down for two weeks while I attended to other things begging for attention in life.

So, third gear pull onto the highway, and *bing* goes the Service light ...

I feel like I'm just throwing money at my car again ... It was fine when I was in undergrad (and living at my parents'), but pretty soon I'm going to have to go back to a Top Ramen dinner every night, if I keep replacing parts!

The only thing I have left to check out is the intercooler boots, but I am skeptical, to say the least ... How can those boots be leaking at 80k miles?!

 

I Have had aP0107 come up on My 2005 Jcw Changed Map And TMap sensors and detroit tuned bpv and still get code on ocassion. When I clean Air filter Which is a Itg foam problem seems to go away. Will clean it every 10,000 miles and hop the lights stay off.

 

Filter's been cleaned and reoiled ... I also blew off some of the excess oil on the filter. Luckily my parents' neighbor was generous and paid me $200 to replace his brake pads over the weekend, so I guess I'll order OEM boots next ...

 

The saga continues. ...

The intercooler boots were leaking (oil seeping out through the bottom, one of the "ears" on the cool side had been crushed by one of the clamps as well) and deformed. I replaced both of them with OE factory-fresh boots after soaking the intercooler core in de-greaser to get the oil blowby from the PCV valve out of the inside and dried it thoroughly before reassembly.

I noticed a slight increase in power, and a slight improvement in MPG (approx. 2 MPG during my last fill-up: back to 30 on the highway, woo-hoo!) but I'm still getting that God-forsaken SES light!!! It goes away after approx. 3-4 engine start/stop cycles, but promptly returns at WOT above 4,000 RPM in 4th, 5th, and 6th gears.

My friendly neighborhood O'Reilly's parts counter guy and I are on a first-name basis at this point: I'm now known as "Mr. P0108."

I'm at my wit's end at this point. If it's not the MAP, T-MAP, crank pulley, serpentine belt, intercooler clamps or intercooler boots, what in the name of all-that-is-good-and-holy could be causing that light to come on?! I will check my intercooler boots for the fourth time to see if they have slipped off the horn or intercooler ... But I doubt that's causing it.

Could it be the VGS? My next course of action will be to remove the "Vacuum Gain System" and revert back to stock. I'll deal with the yo-yo until I can afford a DT bypass valve.

 

When you replaced the sensors, they are not the same. The upstream is a Cooper part & downstream is an S part. Some think they are the same part.
Just a thought.....

 

Correct. I replaced the sensors accordingly. Per my original post: xx-xx-648 on the intake manifold, and xx-xx-679 as the upstream MAP next to the airbox.

After a bit of research on these forums, I've come across several possibilities for the SES light problem:

1. Melted cat (unlikely, checked cat ~10000 miles ago)
2. OEM manifold/precat restriction in exhaust: trips SES by not getting exhaust gasses out quickly enough (likely?)
3. Throttle body/throttle body harness damaged (likely?)
4. Dirty MAP/T-MAP sensors (unlikely; new [ as of ~8000 miles ago] parts)
5. Harness short (likely?)

Whatever it is, I doubt it's something that "usually" causes an overboost code.

As an aside, I noticed my car still yo-yos under very light throttle under 3,000 RPM while driving around town. ... I have a SprintBooster, so that may be causing it.

 

You're lucky the crank pulley failed at home. Mine gave up the ghost 150 miles away.

If you're yo-yoing... I'd replace the BPV. Either with a new OEM or DT - I like the DT, but not everyone does.

Other possibilities - loose hose somewhere around the VGS setup, mis-piped VGS, cracked fuel pressure regulator hard vacuum line (under the IC), other vacuum leak.

But these vacuum / boost leaks can be frustrating. I've wrestled with several over the past 106K miles.

 

Spring tension is still tight, though. What else on a BPV would fail?

 

If it's yo-yoing, the spring tension isn't "that" tight. :-)
Which is what the DT BPV does... uses a heavier spring so the BPV slams shut except when until heavy vacuum.

Otherwise, there's probably nothing wrong with your BPV... if there were, it wouldn't be boosting at all. The car drives like a justacooper with a non functional BPV. No boost.

 

Check the T-MAP harness - the radiator seal on my car rubbed thru mine, it took days to find it the wires were under the heat shrink, shorted.
Just a thought.............

 

Good point. I'll look into the BPV after I track down some possible sources of boost leaks. Guess I'll have to pull the intercooler off again ... Thank God that's a 10 minute job.

I suppose after millions of oscillations, the BPV spring tension can weaken. I've just been checking it by pushing on the actuator arm and seeing if it snaps back, and it has, every time I've checked it.

I'm still confused, though. If the BPV is held shut by boost under WOT (as opposed to a diverter valve in turbocharged cars), then how would a weakened spring in the BPV cause an overboost code? Does the BPV open above a certain boost threshold? If so, I can see how a weak spring (which has to fight the pressure generated by the supercharger) may cause the BPV to not open at all.

... I've read up on the DT BPV before, the only thing keeping me from buying one is the decreased MPG. I'm going to be putting a lot more miles on the car in the forseeable future (judicial internship in my home county, can be as far as 40 miles, one way), so if a stock replacement BPV and the VGS wil fix the yo-yo'ing, then I'll go with that route.

 

The T-MAP is the sensor on the intake manifold, towards the front of the car, correct?

I may do that real quick as I happened to steal a garage bay from my mother.