Fresh upper end, terrible idle, error code 33
#1
Fresh upper end, terrible idle, error code 33
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
The plugs are black, but they fire. The engine ran rich before I tore it apart.
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.
Last edited by MarkE; 06-23-2016 at 09:10 PM. Reason: Video formatting
#3
Re: Fresh upper end, terrible idle, error code 33
@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 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.
#4
Re: Fresh upper end, terrible idle, error code 33
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?
#5
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Car: 1988 Iroc vert black
Engine: 305 TPI
Re: Fresh upper end, terrible idle, error code 33
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.
#6
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Re: Fresh upper end, terrible idle, error code 33
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.
Last edited by red rock; 06-24-2016 at 10:55 PM.
#7
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Car: 91 G92 Z28
Engine: 305 TPI
Transmission: T5
Axle/Gears: 342
Re: Fresh upper end, terrible idle, error code 33
Also, did you check the grounding wires that go to the back of the heads? These are sometimes overlooked after pulling/re-installing heads.
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#8
Re: Fresh upper end, terrible idle, error code 33
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.
Thanks!
#9
Re: Fresh upper end, terrible idle, error 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.
Also, did you check the grounding wires that go to the back of the heads? These are sometimes overlooked after pulling/re-installing heads.
Thank you!
#11
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Car: 91 G92 Z28
Engine: 305 TPI
Transmission: T5
Axle/Gears: 342
Re: Fresh upper end, terrible idle, error code 33
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.
#12
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Car: 91 G92 Z28
Engine: 305 TPI
Transmission: T5
Axle/Gears: 342
Re: Fresh upper end, terrible idle, error code 33
actually, there is probably one in the intake that does that. You may want to check that though.
#13
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Re: Fresh upper end, terrible idle, error code 33
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.
#14
Re: Fresh upper end, terrible idle, error code 33
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.
#15
Re: Fresh upper end, terrible idle, error code 33
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.
Thanks!
#17
Re: Fresh upper end, terrible idle, error code 33
I'm puzzled about the Error code 33.
Here are a few listing of the conditions that cause an Error Code 33:
Turbo Regal
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?
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?
#18
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Re: Fresh upper end, terrible idle, error code 33
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?
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