BigTodd

OK, I have a code 33 popping up about 4 minutes into driving my 88 vert. I have replaced the burn off relay and power relay, replaced the ECM and tried a known good MAF. Still get the code 33. The car goes into the limp mode and run's like crud.

I can let it sit for about 20 minutes and start it back up again and it run's fine (No SES) for about 4 minutes, then SES goes on and starts running bad. What else coule it be?? I have seen several other problems that have caused this, but I can't find them on the search anymore. Please help...

Pete K

It is a long shot but check the condition of the spark plug wires. A leaking wire or a poorly routed wire can generate an rf signal that can cause the code. Also rare is the oil pressure sending unit can cause this. Both rarely happen but it sound like you covered the obvious stuff.

skateparkdave

Code 33 is definetly a MAF related issue in 85-89 and a MAP issue in 84 and 90-93 Being that you've replaced the relays and ECM and tried a working MAF I would really look close at intake system for air and vacuume leaks if you haven't already.

65Z01

Check the TPS sensor reading at base idle (450rpm) and at WOT position.

Also check the connectors; you might clean them with TV tuner cleaner.

If it still is a problem and you don't have a GM Service Manual, pick up a copy of "Chevy TPI Fuel Injection Swapper's Guide" by John Baechtel for full trouble shooting tables on trouble codes for your '88.

jackdaroofer

Might pay to invest in an easy lonk or other Scanner. This can help you refine your problem areas and not wind up replacing a lot of expensive parts with no positive results . I know, been there, done that

If you have a scanner, check your Idle Air Control counts. I had a very similar problem and it turned out to be the IAC motor. GM manual minimises this part as part of the problem, but I found my counts were all over the lot even at speed. When I pulled the IAC, it was way out of adjustment and full of carbon.

Installed a new one and car runs great at all speeds. Problems with the IAC can cause problems at all operating speeds

BigTodd

OK, The spark plug wires are new accell 8.5mm, NGK TR55 plugs new, Fuel Injectors new, (Ford Motorsport) Cap rotor, and coil new. As you can see I have been doing a face lift on the engine. It had a bad hesitation problem that boiled down to the ECM not reading the TPS correctly (It would max out at 1.8 v when the TPS was giving 4.7 volts). I have also removed the screens and cleaned the MAF with non residue contact cleaner (Did not help)..

The car ran great for about 2 months then the code 33 started out of the blue, I do have 89,000+ miles on her, so I thought could be the relays, or the MAF.

I will check for vacume leaks, but how drastic would they have to be to set the code?

Does anyone have the wiring diagram of the 88 MAF circuit to trace the voltages, wiring and ground.

What is the best price I can get for scan software for my laptop, It turbo link a good software to use?? Great help so far, please keep the suggestion coming...

88_vette

You cleaned the MAF wire? This, from my personal experience which is a lot with these. Means you have just killed that MAF. Meaning you can't trust it as a good unit now. That wire is very very sensetive, and I don't think they can be tuched in anyway. Someone back me up on this??

Yes a scan tool would be great however expensive to get up and going. Worth getting if you plan to work on it yourself a lot.

The TPS start at something like .450-.6Volts (I've seen them set this high). THen climb up to around 5 volts. You may not hit 5 volts, but your WOT will have kicked in by that time anyway.

You cut the screens out? Did you do this cleaning and screen cutting before you used it to test the MAF?? Both are things that can cause a MAF to go bad.

You need to see if the ECM is getting the signal fro the MAF. It is not uncommon for the plug to have become loss and not make contact well enough to support the current. This is were a scan tool would help. It would show your grams per second reading from the MAF if you are in fact getting them.

A vac leak will cause unsensored air to enter the engine thus making it go crazy because it has extra air it doesn't know what to do with. The O2 sensor and MAF kinda work together, and against each other. ONe tell the engine how much air goes in the other tells how much leaves. Of course the ECM is try to make both happy. Like two timing. HAHA.

Check the wiring, and I know it's not fun or easy, but you have to do it. Because if it's wiring it doesn't matter how much you replace in parts the wires are still the same. Which means the problem is still there.

Also check the fuse. Make sure it's making good contact and clean. I had my Alt. stop working because the fuse wasn't making good contact.

BigTodd

Thanks 88_Vette, I popped the screens out with the retainer to clean the wire. used non residue contact cleaner, then put the screens back on. I used electronic microtip stick pads and very gently cleaned the wire. No stress or tention was put on the wire. Anyway I borrowed an exact match known good MAF off my buddies 88 and still got the same result.

Makes sense about the vacum leak, O2 vs MAF, I need a to get a scanner hooked up and see what it says.

88espo

undefinedchange the tps along with the two relays and should clear code

TheStef

Hi,

I think my input might help you a lot, I also have an 88 and had a code 33, 2 weeks ago. My service engine light would turn on 10 or 15 second's after turning on the car.

It turned out I had a bad MAF sensor in my case, but I read the trouble shooting steps, and it could be A LOT of stuff. MAF, burn off relays, ECM, all included, but it could also be the wiring.

I'll send you the PDF trouble shooting document by email, its very easy to follow and all you need is a test light and a Ohm meter/voltmeter.

Good luck

Ps: The document I'll send you is very easy to follow.

TheStef

Can't seem to find your email ... post me or instant message me your email and I'll send you the trouble shooting steps.

TrueBlue ChevyDude

I had trhis same problem on my 88, went through all the logic charts, pulled my hair out, no solution...

What finally solved theproblem was playing around with the TPS setting. I had it smack dab in the middle of the suggested range (.54 I think), and it had the exact same symptoms that you describe. I had minor intake modifications and true dual long tube header exhaust.

I reset the TPS down to thebottom end of the acceptable range (.48 or so) and VOILA! no more problems.

I guess at .54 volts closed throttle the math just didn't add up for the computer. It figured that there should be more airflow than there actually was for .54 volts. Changed it to .48, and ran like the wind. I made sure that at full throttle the TPS was still reporting full throttle, and it was, read over 4 volts.... alls well

BigTodd

Thanks Stef and Trueblue. I will try the TPS reset, and I have sent Stef my email address. This is really helpful, and I wil try most everything. This is my wife's car and she let's me know about it everytime I drive my 02 coupe.

Any other feedback would be helpful.

BigTodd

Went through the trouble shooting procedure sent by Stef (Thanks again) and everything checked out. Took it for a drive and the code 33 set again.

Decided to check my TPS once again, Hooked it up to the VOM and noticed I did not see any voltage change on the TPS when I went from Idle position to WOT, Hmmmmm, Got my old TPS out and tried it, .54 to 4.89, Went back to the newer TPS and still nothing. Swapped them out and went for a drive, No code 33. Also the tranny seemed to be shifting better, I think the TPS send info to the ECM to set shift points.

I figure if the TPS was dropping to 0 and the MAF had air moving through it it could set the code 33 "High excessive grams of air" because the car thought it was at idle or lower. Well that's my theory until it the code pops back up again. Fingers crossed.

DKOV

Where is the MAF?

I can't find mine

Scott

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flyersfan1088

What year is your car? If it's 84-89, it's the big piece that sits between the throttle body and the accordion duct.

DKOV

1990 and nope... notta

I have the butterflies, the accordian tube and then the K&N FIPK. That's it.

Scott

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flyersfan1088

1990 is speed density. You can look all day and you will never find a MAF

skateparkdave

Yep, our 90's have speed density with a MAP (manifold absolute pressure) sensor and no MAF (mass air flow) sensor.

Big Todd, I know I have MAP and you have MAF but did you ever look close for vacuume and air leaks in and around manifold?.. as they will throw TPS and ECM off. If the MAF or MAP sends ECM a high pressure or high flow signal then the ECM will substitute a fixed value for either and use TPS to control fuel delivery. Vacuume is very important and all lines and fittings should be in good shape and tight.

Duf

Could you send me the same document, please?