I need some help.

Here's a video of a scanner hooked up to the car.
I went through the upper end of an 1989 Iroc TPI 5.7. It's throwing an error code 33, backfires, surges at idle, stumbles when the throttle is brought off idle, and sounds like it has a wild cam. The car is not complete/drivable yet.

Here's what I've done:
Fresh stock 083 mild ported heads, Howards 180235-12 cam and 98213 springs, new distributor (ebay), coil, cap, rotor, wires, plugs, cam chain, GM fuel pump, and fuel filter. I bench tested the injectors, and they sprayed. They do not leak. They ohm out consistent and within spec (forgot the value).

The ECM is stock.

To fix the error code 33, I've

• bought a new MAF sensor. It reads 14 gm/sec in my posted video.
• went through the Cartech error code 33 troubleshooting flow chart. I found and repaired a broken ground wire to the MAF connector. Solenoids check out OK.
• plated off the EGR valve
• replaced the fuel regulator
• tested the fuel pression (~40psi @ idle)
• replaced the runner gaskets (twice)
• reset the IAC. The solenoid works.
• adjusted the TPS
• I can't find a vacuum leak

The plugs are black, but they fire. The engine ran rich before I tore it apart.

 

Have you tried a vacuum gauge or tried spraying carb cleaner around all the gaskets on the intake and also the throttle body butterfly? Usually a code 33 is a vacuum leak.

 

@redrock, thanks for the post! I sprayed carb cleaner around all of the runner gaskets, the outside of the throttle body, around the intake manifold, and there was no change in RPM. It idles at about 10 inches of vacuum. With a quick rev, the gauge goes to 20 inches. I also tried blocking off the brake booster hose.

I sprayed through the butterfly, and the RPMs did go up. I don't believe the plates should necessarily be fully closed though. I did adjust the IAC, but I can't get it run well enough to put it in gear to set plate position per this document.

 

I can't find the other end of this connector. It's a single green wire coming out of the Y in the loom on the drivers side near the firewall. Does anyone know what it goes to?

 

Just a stab in the dark but maybe 02 sensor? Also, instead of carb cleaner an unlit propane torch is also good for checking leaks; it will also cause idle to surge.

 

I meant to say throttle body shaft. Sorry. Also, it's very common to get the bottom runner gasket on backwards. The ones that mate up to the intake manifold. But if you sprayed them and no change then you possibly have them right. What is your base timing set at? You may also try adjusting the idle up to 1000rpm, and the readjust your TPS. One more thing, you can raise the TPS up to .60-.65 sometime that eliminates a code 33.

 

The single green wire coming out of the harness on the drivers side firewall on my car goes to the coolant temp sensor between the 1&3 cylinders. Is yours plugged in?

Also, did you check the grounding wires that go to the back of the heads? These are sometimes overlooked after pulling/re-installing heads.

 

I checked the timing, and it's 6* BTDC with the EST disconnected. When I disconnected the EST wire, the car didn't surge at idle. It still idled poorly, and it stumbles like crazy when I move the throttle plates off idle.

Thanks!

 

The temp sensor makes sense. Someone installed an aftermarket temperature sensor that connects directly to a gauge. I did double-check the ground wires that connect to the back of the heads.

Thank you!

 

I know this may sound redundant, but have you checked and double checked your spark plug wire firing order? What kind of rockers and what lash setting did you do.

 

You may want to hook that back up so it's going through the ECM. That sensor does more than just feed the guage information. I'm pretty sureh the coolant sensor in these cars helps regulate idle.

 

actually, there is probably one in the intake that does that. You may want to check that though.

 

That green wire goes to the coolant temp sending unit which only sends the temp to the gauge. the coolant temp sensor in the front of the intake manifold is what relates coolant temperature to the ECM. I would tape off the intake and blow cigar smoke into various vacuum hoses to confirm there's no vacuum leaks and then go over every sensor.

 

Yep, I've checked the firing order multiple times. The rotor is pointing towards #1 when #1 is firing at TDC. It has stock rockers and I adjusted them 1/4 turn after they stopped clacking.

 

The temp sensor in the front of the intake is hooked up, and the scanner shows a reasonable coolant temperature. So what you're saying makes sense. That's a good idea with the smoke. I'll need to find a smoke source that doesn't make me ill though

Thanks!

 

You can probably buy a hand pump siphon and stick the end of a cigar in one end and the other end into the vacuum lines and do it that way so you don't have to smoke the cigar

 

I'm puzzled about the Error code 33.

Here are a few listing of the conditions that cause an Error Code 33:
Turbo Regal

• no Code 21 or 22 (TPS Error) present, and
• the air flow reported is > 40 grams per second, and
• TPS indicates < 10% throttle position, and
• the engine speed is 1400 RPM or less, and
• the above conditions exist for over 5 seconds.

SuperChevy
is set when the computer sees a high mass air reading at low engine speeds. In other words, there appears to be more airflow through the MAF sensor than the engine can physically breathe at a specific throttle and rpm.

I've been through this flowchart, and all conditions check out up to the point of replacing the ecu. I have my doubts that the ecu is bad. The kicker is that the scanner is showing 14 gm/sec. The gm/sec go up to 17 gm/sec or so when I bump the throttle. It seems like the MAF sensor is working, and it's well below 40 gm/sec listed on several sites. When I pull the MAF off to the side, the scanner shows 5 gm/sec, and the error code 33 still comes on.

I'm missing something.

I found this post , and these symptoms are very similar to what I'm experiencing. The injector base pulse width (BPW) in my video shoots up to 8mS at idle and the engine then almost dies. When the idle stabilizes, the BPW is 3.3mS. I wonder if there is too much fuel at idle causing the bad idle and backfires through the runners. There is no mention of an error code in this post. Do I have several things going on here?

 

FYI, here is a new post, https://www.thirdgen.org/forums/tpi/...moke-test.html also is the vacuum port on the bottom of your throttle body connected?