before I launch into this issue, I'll give a little back story. My friend and I picked up an 89 bird in fairly good shape a few months back with a cracked 2.8 block, which had been stripped down to the heads, complete with a trunk full of intake parts for 800 bucks (we didn't know the block was cracked at the time, nasty surprise later). After discovering the crack, we pulled the dead 2.8 and a mechanic friend of mine found me a fresh pull from wrecked a 94 camaro with only 50k original miles for only 500 bucks - good deal around here, complete with 1 year warranty. so we grabbed the engine and set to work swapping everything over according to the legendary 3.4 swap boogie.

All went off without a hitch (minus that stupid innie coolant plug in the rear of the head for the fan switch - we ended up needing an oxy torch and a pipe fitter's plug remover to get it loose). Now we've got the engine mounted, trans bolted up, and to the best of my knowledge, everything else properly connected. The engine is running like crap, though. My own 92 bird has been an invaluable resource as a working display model whenever I couldn't figure out how something bolted up on the 89, but the only exception is the differences to the vacuum systems of the two are too great for the 92 3.1's system to save me. The first time I tried to crank up the frankenstein 2.8-3.4, it backfired through the intake. I adjusted the distributor a bit, and the second time I cranked it up, it started and immediately died. The third time, it revved up to about 3,000 RPMs, and then died again, throwing code 33 (MAF sensor).

After reading some other posts related to code 33, I decided to unplug the MAF and give it another go. Sure enough, this time she fired up and held her own, but idled very rough, popping through the intake and fluctuating between 500 and 1500 rpms. I checked the timing with a gun, and it seems to be hoovering between 8 and 10 degrees, so I know my timing is fairly dead on. I don't know where to start troubleshooting next, though. I know code 33 doesn't necessarily mean bad MAF, and can be triggered by a vac leak, so I don't want to go spending money on another one I might not be able to return. I know out of everything we've assembled, the vac system is my only concern. My vacuum routing is a bit of a mess, since the only info I have on the 2.8's vac system is a confusing old scan out of a service manual. The 89 doesn't even have a routing decal on the hood. Since the old 2.8 was already disassembled when I got the car, I don't have very much to go on, and I was hoping some of you guys could shed some light on it for me.

Right now, these things I'm pretty sure are correct: I've got the port coming out of the back of the upper intake capped on one side, and straight to the brake booster on the other side. The port on the lower intake, that's right below that one, is T'd off, one to the driver's side valve cover, and up to the front, where it connects to a round black thing I don't know the name of. That black thing also connects to the passenger's side valve cover, and to the side of the intake plenum in front of the throttle. All of this piping/tubing is perfectly spaced and fits fine, so I'm almost certain it's connected properly, fits tightly, and doesn't leak.

Where things really start to get hairy are at the two hard plastic lines coming out of the front of the throttle body. I'm left with those two, two rubber hoses coming from my front left fender, and single hoses coming from my fuel pressure regulator, one from the top of the egr valve, one from the air pump/smog pump, one running from a small square box with a 4 pin electrical connector, one from the alien space craft with the throttle cable that I believe to be the cruise control (we've just thrown this one aside, since we don't care about the cruise control) and two from a small cylinder mounted by the egr valve. Right now my friend swears he's read the diagram and that he's connected this conglomeration properly based on the one diagram we have, but I'm banking on some mismatch causing my rough idle/dying engine condition. I've checked all the lines as he has them set, and they are all tight and do not seem to be leaking.

So, sorry for such a long post, but how do you think I should proceed? Is it worth replacing the MAF? Could someone with a complete 2.8 clarify the routing of the smaller vac lines for me? Any advice would be much appreciated.

 

With a code 33, the vacuum lines aren't relevant. Code 33 actually means HIGH flow through the MAF, not low (code 34). Examine the film inside the sensor and check for problems with the signal wires. The film inside the sensor should be perfectly flat and the sensor needs to be replaced if it's not.

I'll try to upload my vac hose routing sticker pic up on Photobucket in a bit here and post a link so you can access it, since the TGO system won't let me repost it (since I posted it the last time like 3 years ago or so).

 

Thanks... That'd be a big help. I really need to just break down and buy the factory manual for the 89, but so far, the 92 FSM I have for the other car has been good enough to get me by. I'll check the MAF this weekend (car is in a friend's equipment storage 25 miles away right now, as my community assoc. will have unregistered vehicles towed). I thought popping noises and rough idle were generally indicative of a vac leak. Is the default maf value that the computer uses when I unplug the cable simply causing the computer to run it too lean and cause these symptoms?

Rockauto has a reman'd MAF on closeout for $35 that looks awfully tempting compared to the delco at ~$95... ever heard of "kemparts"? If I see any ripples on the MAF film, I'll probably order it. Are there any other testing procedures for the MAF if there isn't any visible rippling?

 

A word of warning: DO NOT GET A REMAN MAF! They are not built the same as an AC/Delco MAF, and they fail pretty quick. The elbow required on your Bird does not fit right and breaks upon installation (I've had 2 now and BOTH broke upon installation). There is a seller on eBay that is still selling AC/Delco MAF sensors for $50 plus shipping... Her name is beckysbids on there.

As for the link, I hope it works: http://s988.photobucket.com/albums/a...onssticker.jpg The sticker may differ from yours slightly, but it will give you a good idea of where things hook up.

:edit: The only other accurate ways to test the MAF are to either use a scantool and read the sensor's output or to hook up a DMM with frequency capability to the signal and ground wires.