I recently purchased a 1987 350 TPI Iroc-z. A few days afterwards, the SES Light came on with a Code 33. I took it to a local shop to check the problem out and after three weeks, the problem still exists. They replaced all the relays, replaced the MAF, ECM module, and catalatic converter. Yet the problem still exists. It idles fine, but when you drive the car the SES light comes on and it begins to idle very rough. When you cut the car off and restart the car the light is off. The car does have the streetrunner Hyperteck chip in it. They also tried it with the stock chip and the light still comes on. Does anyone have any advice, I am desperate.
Thanks,

 

Check the MAF wiring closely. Use an ohmmeter to check for broken wires and bad connections. Inspect any prev repairs to the wiring if present.
Make sure the pins in the MAF connector are secure and don't slide up into the connector.

 

Check your throtle position sensor.

I was getting a maf code on mine and replacing did not change the symptoms.

Someone on here suggested the tps and that corrected the problem.

Mine idled like a ford with a bad power valve and when I drove it the ting would stumble and fall on take off unless I put the accelerator to the floor to get up to speed and moving then it was drivable but made a miserable experience. There is a faq on here I think for cheking the tps but if you dont find it send me a pm and I will get the info out of my book.

Mine never gave any tip that it was the tps, everything said maf.

 

I had a code 33 come up a couple of weeks ago, replacing the TPS did the trick for me. I had replaced it a couple of years ago with a new (cheapie) TPS, and had only put a few hundred miles on it (don't drive the car much) before I got the code 33. I replaced the TPS with a Borg Warner one and the car runs great now. Hope this helps.

 

To update you on the problem, it still exists. We have replaced everything in the MAF circuit. We have adjusted the TPS to 0.7 volts and still have the code 33. The only time we can get the car to run is when we leave the scan tool plugged and test drive it and the car runs fine. The two guys at the shop have all but lost hope on fixing the car. Does anyone have a suggestion that might help.

 

Where are you? If you were close I would put your car and mine in the driveway and compare everything and then if nothing else easter egg with the known good parts from my car. That would rule out several problems and ease the search if nothing else. Are you using the GM book for trouble shooting?
Or did you find the problem?

 

Thanks for the response. I am in Angier, North Carolina. I still have not solved the problem and I will try to get my hands on the manual you spoke of. I am going to try another mechanic in the next few weeks. I will keep you posted.

 

I've posted before the flow chart for code 33. go to post#11 and see the attachment
https://www.thirdgen.org/forums/tpi/448367-code-33-need-help.html

 

OH GOD that damn CODE! I had taht friggin' code for over 8 years and spent over two grand in computers, chips, wiring harnesses and etc. Everyone scratched their heads. I used parts from my friends car (ie, MAF TPS, IAC, etc) and nothing did it. I went on here and found a thread about relays, no one knew which was which on the firewall but I replaced both, and I NEVER had the problem again. I know you said they replaced the relays...check and make sure that accurate because they might have no replaced both the MAF relay and the "burnoff" relay...It cost me 22 friggin' buck and problem solved after years of hassle. Hope that helped and I feel for ya. I'm in Wilmington NC a lot, dont know if thats close but I'd be willing to check it out with ya when I get there the third week of July.
One more thing, when I built my new car, which is now for sale and listed in the camaros for sale section, I used a speed density system, so much easier.
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OH GOD that damn CODE! I had taht friggin' code for over 8 years and spent over two grand in computers, chips, wiring harnesses and etc. Everyone scratched their heads. I used parts from my friends car (ie, MAF TPS, IAC, etc) and nothing did it. I went on here and found a thread about relays, no one knew which was which on the firewall but I replaced both, and I NEVER had the problem again. I know you said they replaced the relays...check and make sure that accurate because they might have not replaced both the MAF relay and the "burnoff" relay...It cost me 22 friggin' bucks and problem solved after years of hassle. Hope that helped and I feel for ya. I'm in Wilmington NC a lot, dont know if thats close but I'd be willing to check it out with ya when I get there the third week of July.
One more thing, when I built my new car, which is now for sale and listed in the camaros for sale section, I used a speed density system, so much easier.

 

You guys need to learn to conduct a search on this matter BEFORE you spend $2,000!!!!! I have posted on this matter many times, do a search!

I have gone thru the same thing, but back in 1997/8. Changed a bunch of parts that did not solve the issue. There is 10 years of knowledge on 3rd gen, please use it to your advantage. I have been on many message boards dealing with cars. This 3rd gen board is the BEST!

dwgardner: How many mods are on your engine? Any well modified 350 can end up with the dreaded 33 error code. The only sure fire way to get rid of the 33 error code is via a custom Eprom chip.

FWIW, the TPS should not be set higher than 0.64V at closed throotle.

FYI: the 33 error code is set when the following 3 conditions are true at the same time:
1) engine under 2000 RPM,
2) MAF reading over 45 gms/sec, and
3) less than 25% throotle.

Look at these three conditions. When do you think these 3 conditions will be met at the same time? Having a '87 350 auto, these conditions were met on the xway when the tranny shifted to OD at around 55 to 60mph. So I learned to keep the car in 3rd (D) not OD, until I got above 60 mph, then manually move the shifter to OD. Being above 60mph insured me that I was above the 45 gm/sec MAF threshold. But this is a PITA. So I learned how to burn my own Eproms and solved this issue forever.

I will program Eproms for you if you send me your best Eprom that you like and two spare Eprom; both Eproms got to have the quartz window on the top side. This quartz window is covered with a foil sticker, Only check under the sticker for the quartz window in a dim room, do not expose to direct sunlight. You pay for all shipping and I keep the extra Eprom. I will copy the info from your used Eprom onto one of the new Eproms, and fix the error code. And ship your used Eprom and the fixed Eprom back to you. Now understand that I have old Eprom burning equipment and I burn the type for my '87 car. I have done this for a guy who drove his car from Cleveland up to me several years ago. He went away a very happy 3rd genner.

 

How does it run with the MAF unplugged?

 

I was having this problem also. The car would run good but when it warmed up idle would bog down. I replaced my maf sensor it helped some. I was talking to a guy who does work on corvette engines. I told him about bad idle and stalling. He told me to change temp sensor on intake. I did this and took car for a ride went home turned car off. Refired car and light went off and car has never run so good. It helped me out.

 

Thanks, for all the info. I will start looking at these suggestions this weekend. I will start with the relays and go from there. The only mods to the car is an airfoil, K&N filters, and a Hypertech chip. Any suggestions will be appreciated.

 

I really like net_coma's, (that must add sleep to exhaustion to calculate net), idea to look at the TPS. The first thing I noticed when bought the 85 Z28 5.0L. H.O. was how slowly it upshifted, come to think of it. CODE 33 is b.s., nothing works, even NOS Bosch mAF sensor replcmnt. Haven't installed new harness pigtail yet, but have all the symptoms: no start then starts, cuts out, dies, etc.etc.; I'm looking at his SOLUTION!

 

i had this same problem a long time ago. i also replaced the sensor and relays and checked the wiring. while watching the scan tool the grams per second on the Maf would go to 48 gps when i would take off from a stop sign and the light would come on. I learned how to burn my own chips like doc and raised the error threshold from 45gps to 55 and have never had the problem again. although i now know a lot more about how engine controlls work and in hindsight it was probbably the home made cold air intake i had. the maf was just after a 90 degree bend in the pipe and the air did not flow a cross the maf straight and skewed the readings. you may try factory paper air filters just to see if it makes a difference. especially if the gps only go over 45 by just a little. hope this helps. or if you can turn the maf sensor 90 or 180 degrees in the pipe and see if the readings change.

 

pontiacdaddy, thanks for coming in here on this post. For the others who are ignoring my post above: the 3 conditions that I posted are right out of the 1987 shop manual. You need to find a way to NOT have all three conditions at the same moment in time (like try different TPS settings), or burn an Eprom chip. It is really not hard at all.

 

Thanks for all the information. The car is still in the shop (going on three months now). I did take the stock eprom and had the treshold raised from 45 gms/sec to 75 gms/sec and it still set the Code 33. Now I am having a GM shop check it out and they can't find the problem. I have read so many different ideas on the web that I am totally confused, I really don't think there is a solution to this problem. Any additional help would be appreciated. This is my last try, otherwise the car will be sold.

 

Better to fix it, first, then sell it. Tried one reman then a new maf snsr, same numbers as orig Bosch, 85 Z 5.0L, H.O., due to endless symptoms, endless code 33's - no starts, then starts, dies at intersections, choppy performance, cut-outs, etc. Car wouldn't run with replacements! - particularly bad at idle, low speed. Both repeated nefarious code 33. Went back to orig. unit, with which at least the car would drive! Changed temp snsr. (aged; both connector and sensor plastic isolators broke on removal of harness. (off vehicle, tested 2500ohms; data calls for 3800ohms @70F/20C) Result: NO code 33 w/orig maf snsr! Car dies at idle, (too lean?), has exhaust odor, (too rich?), but drives; but code 33 still comes up w/new unit, (must be defective???), but NOT with orig. unit - although haven't driven far due to current symptoms - i.e., NO codes, (exc. code 12), at all, so far, with orig. unit! Will change maf harness, and check voltages at ecm terminals, (both ign. "on", and engine running, warmed-up), etc. Will reply further if/when successful. Good luck! ps had previously changed TPS, adjusted to perfect .54 V., but no change, just new/old swap; replaced starter - solved no start/start intermittent symptom, but not dies at low rpm/lo idle problem: finally, echo! temp sensor replacement can kill code 33, below from intmadtr3

 

every code refers to the ecm, and to all the sensors it controls; every sensor related malfunction implies misinformation being sent to the ecm, (incorrect sensor energy, generating a "code"), an there4, symptoms (of all codes) imply an unsettled performance and participation among all emissions components; can a poorlyperforming temperature sensor not influence exhaust, rpm, etc., an there4 set the maf code 33? if not proven, yet changing my temperature sensor stopped the check engine light from staying on and storing code 33. It therefore appears that, despite the previous series of code 33's, (and the "dies at idle, low rpms" symptom which persists), the reason for the repeating permanent code 33 might strongly turn out not related to the mafsensor, (code 33), but to what, (precisely described), is actually a result of temperature sensor data. That would imply the ECM read the temperature sensor indirectly, and did not attribute the coolingtemperature/data/voltage, but its results, (poor performance) to a related emissionfunction, such as air mass voltage.

 

Hope you didn't give up. I changed the temperature sensor. That eliminated the code 33. Changing the TPS, properly adjusted, (all three terminals, harness connector to TPS, jumped; adjusted to .54V.), didn't change anything. Then, I changed the maf sensor harness connector. That cleared the dying at idle problem - I don't know why that worked, since only the clasp was broken, but perhaps the positive connection provided by the new connector, clasp is a critical difference. So, the cost to solve code 33 was one temp sensor replacement and one $16.00 pigtail. (It's easier to explain the temp sensor. The orig unit tested 2400 ohms, off vehicle, room temp. That would be appropriate at 100 degrees fareinheit, not room temp, as tested - data would tell ecm the car is warm when it is actually cold, and progressively giving lower resistance, hence, higher than actual temp. readings - room temp ohms should be higher, 3800 ohms, not 2400 ohms.)

 

Well I am back with the same results. The last stop for the car was at my local GM dealership. We went back through checking all the relays, sensors, and ECM. All parts were checked and swapped with new parts. They adjusted everything to specifications and still got code 33. Then we tried a new prom with revised threshold numbers, same result Code 33. The tech said he had no idea what it would take to fix the car. Back to square one after 3 1/2 months in various shops with the same result. No one in this area has any ideas for a solution. I guess I bought a real lemon. I quess it's time to cut my losses, I will try to part the car out in the near future unless someone has any other ideas.

 

Code 33, after lengthy persistence, and repetition, no longer comes up, and all running systems cleared - the symptoms, and the problems with the car along with them, since replacing the temperature sensor and not until replacing the the harness connectors, to the temperature sensor, but also especially to the Maf sensor. 85Z28 5.0 H.0.