I had the intake plenum off today to do a knock sensor job, as well as cleaning of the intake, throttle body and AAC valve. Now that I have it all back together, it won't start.

I'm thinking I must have either missed an electrical connector or my AAC valve is giving me trouble. Before I reinstalled the AAC valve, I turned the screw in all the way, then out 1.5 turns. When trying to get it to go, I turned it out further, which hasn't helped.

Should I try backing out the screw on the AAC valve further? What else should I look for?

3 1/2 turns is a good starting point for the AAC adjustment. Is the engine flooded by chance? Try holding the gas pedal to the floor for 30 seconds while cranking.

My Q started hard after cleaning everything when I had it torn down for the injector replacement. Inspite of my efforts to pack the runners with paper towels to catch any brake parts cleaner that ran down the runner walls, enough got by to flood it a little. Try starting the car with the accelerator pedal floored as Mike suggests.

I also seem to remember Q45Tech mentioning that it's possible to cross-connect a couple of the connectors on the right side of the plenum near the injector subharness and knock sensor subharness, so double check those as well.

Good Luck!

Heath

It turns out the problem was in a somewhat unexpected place.

I pulled the #2 plug, it smelled of gas a bit, but there was spark. Fuel pressure was fine, I could feel the hoses pressurize when the engine was cranking.

I checked the injector resistance at the harness and I couldn't get a reading off any of the injectors. I checked #1 and #2 at the injector and they were both fine. I checked continuity between the harness connector and the #1, #1 and #8 connectors and there was continuity, so I knew the under plenum injector harness was good. I knew at this point the problem was between the battery and the injector harness, since you have to check resistance between the positive post on the battery and the hanress connector. It turned out that the main 25A fuse for the fuel injectors was bad. I don't know what made it pop, but I replaced it and the car is running fine now.

Unfortunately I'm not completely finished. The idle is a bit high and I can hear a hissing noise from the plenum area, so I'm going to have to go hunting for vacuum leaks. At this point I am just glad to have the plenum back on and the car running again. As I found out the hard way: Removing a VH45DE plenum and doing knock sensors is probably the 5th circle of automotive hell.

how were your hoses? in my experience, 94+ hoses seem to hold up a lot better than 90-93

was this the first time the plenum has been off to your knowledge?

All the hoses were in great shape. Nothing cracked or brittle at all.

I'm not sure if this was the first time the plenum was off or not. All the hose clamps were OEM and the angles that some of them were at made me wonder if I was the first in there. The maintenance history from the PO has a receipt for a fuel induction system cleaning from a couple years ago, I don't know if they take the plenum off to do that or not.

I know I wasn't the first into the throttle body. After I took off the elbow piece that mounts before the throttle body, I noticed a wire sticking out of the hose that bypasses the TCS throttle plate. I pulled on it and I found a wire bottle brush wedged inside the hose. :eek

I'm guessing the brush has been in there for years, so any damage that could have been done because of how it got there has already been done long ago. I do notice that my TCS seems to work better. Before, when the TCS kicked in, the engine would lose a lot of power and the car would crawl forward. Yesterday, when I was trying it in the rain, the tires would start to break, power would be reduced briefly, but it wouldn't bog the engine down like before.

That little wire brush is supposed to be in there... It acts like a filter for the PCV gasses, so they dont get inside the TCS motor and things like that.

I thought the same thing the first time I saw that brush in a car I was parting out... never noticed it on my Q, but I guess it was because I hadn't ripped that particular hose hose apart.

Heath