Its been 2 and a half months, but my 2003 MC-S is back to running. Started right up after some fuel-less cranking to get the oil moving. Been checking things, running it a bit, etc. Noticed the exhaust manifold was red hot after running ~5 minutes.

Looking for suggestions on what to check . I just reset the ECU, but haven't tested that yet. I also just checked spark plug wires and the order seems correct. It is not running rough.

The work that I just did - I pulled the engine to repair a bad big end bearing. Crank was worn below limits - so replaced all that (crank, bearings), too. Cam was worn as well, so it got a new stock cam (and lifters).

Sent the supercharger in for rebuild while it was off the car. It also got a new PCV valve and hose, new "cold" plugs. It has a 15% pulley and the DT bypass valve and a CAI. Had the injectors cleaned and flow tested - they were all doing well.

Thanks,

David

 

Cat slagged up?

 

I agree the cat may be plugged. On an older car with simple electronics, I'd wonder about retarded timing. The manifold would get really hot as would the coolant. Don't know about what really controls timing on an R53.

 

Thanks. Will get my hands on an exhaust pressure tester and see what it says. $750 for a new cat is too much to just start switching out parts...

 

No engine light on? When I had a cracked intercooler boot, it ran lean enough to make the stock manifold glow cherry red and that was just from idling in the parking.

 

No check engine light. I did replace the intercooler boots and just checked that they are well seated.

Since there is no mixture screw, I was also wondering what would fool the ECM into a lean condition - it seems the TMAP and MAP sensor are used to calculate the air charge and set the fuel flow and timing. Perhaps this is a sign one of those went bad?

 

check the vacuum lines, I had the same thing and it was the one under the intercooler.

 

Do you mean the vacuum line going from the PCV valve to the push-to-connect fitting on the supercharger?

 

There is s vac line to a fuel psi regulator near the fuel rail....under the ic...

 

That's the one I had a problem with.

 

Seems like it, but I want to start by saying I haven't been getting into the magic brownies.

Hooked up a scangauge and it reports -10 psi boost (negative boost). Switched units to show absolute manifold pressure and sure enough, it is reporting 4 to 5 psi (absolute) pressure in the manifold, from idle to 3000 rpm. I didn't rev it faster as I am trying to keep it from getting too stressed/hot.

So... This is with a brand new MAP and T-MAP sensor. I'm guessing the reading is real and I am somehow getting serious vacuum in the intake. Any ideas how ? I will try to duplicate the measurement tomorrow with a mechanical vacuum gauge just to be sure...

 

I replaced the fuel regulator today and those two small vacuum lines under the IC. Fuel regulator fell into pieces as I was removing it. Hoses seemed fine. Also cleared the ECU the best I could. Not sure any of that mattered.

 

Seems polite to finish the story.

I'm still getting vacuum levels of boost (negative boost), but the diagnostic part of the bentley manual shows an example of 2/3 atmosphere of vacuum at idle, so I guess mine falls in the same range. I never would have guessed that a car with forced induction would have so much manifold vacuum at idle.

Anyway, I did replace the MAP sensor, T-MAP sensor, fuel pressure regulator and the vacuum hoses. The regulator was the only part that looked suspect, but it could have broken in the process of removing it. Discovered the injector o-rings were torn when I removed the fuel rail, so that could have been a source of intake leak.

I did test the Cat pressure (inserted special pressure gauge into pre-cat O2 sensor hole) and got less than 0.5 psi up to 3000 rpm, so think the Cat is OK.

I have AutoEnginuity software (use it on my other cars, too) and it can clear all the engine adaptations, so did that. Also did the reset process from the dash.

Exhaust temperatures at idle are now in the 300C-400C range.

So far so good... Thanks for all the suggestions.

 

I just went through this this week. I had crazy idle and over 1200 deg. exhaust temps. I could see it glowing after only a few minutes of idling. I knew I had an air leak in the intake system. I could put my hand over the throttle body and it would not effect the running of the car nor could I feel any suction. I hope this helps you. I also have to say a big thanks to Chad and Nick from Detroit Tuned for giving me some of the these great tips for getting this sorted out. Outstand customer service. They will have my business in the future. Get yourself a cheap fog machine from party city and adapt it to your throttle body and smoke test it. I found a massive leak at the end of the intercooler veins. I also had major leak around throttle body to sc tube at the sc snout and vac tubes not pushed in all the way. Siliconed the tube to sc with the old seal and put on another used intercooler. Retested with no leaks. I hope this helps you.

 

Thanks!

The fog machine rig sounds really useful for this sort of troubleshooting. Can you describe more how you set it up or post a picture? Was it tee'd into the intake or did all the air flow through the fog machine? What size fog machine?

 

Its the 400 watt machine at Party City for $29. I just used some stuff I had laying around. But I put a 1/4" brass hose nipple that threaded into the plastic housing at the fog outlet. Cut the top off of a spray can and drilled the top of it out to fit another 1/4" brass hose nipple and connected the two with some 1/4" hose. I was able to fit the can top in place of the air intake elbow on my car with after market intake. If you don't have that just tape it to your throttle body. Very simple. I would have never found these issues otherwise. You must do this. You will be amazed. You could also adapt it to you vacuum side of the motor as well. I haven't done this yet. Good Luck

 

Great. I can rig something like that up.

Curious about one thing though - did you run the engine like that or just use the machine to pressurize the intake and check for leaks with the engine off?

 

Update. COMPLETELY FIXED!!!! I got the car back together and it would start but not idle. after trying everything imaginable including resetting the ecu at least a dozen times. What I had to do was pull the pvc tube off and it would idle. I let it idle like that for a while to learn the smaller air leak. Then I slowly put the pvc hose back on letting it adjust to the reduced vac leak and stayed idling. I then had to let it idle for a while like that. After about 10 mins of idling I shut it off. It now restarts and idles perfect every time. EGTs are now around 650 deg. Best $50 I have ever spent. Good Luck..

 

Thanks for the good word Dave, glad to see everything is fixed and the car is running as it should!!

Should you need any help in the future you know where to find us!