88 Corvette idle problems could be MAF?
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From: Ocean City Maryland
88 Corvette idle problems could be MAF?
Recently I replaced the intake gasket because I had a leak on the rear of the intake. I put everything back together and while I marked the bottom of the distributor and the top of the intake so I could put it back in properly, Duhh, I had the intake cleaned and of course the mark was no longer there. I adjusted TDC and set the Distributor and it started but would not stay idling. I replaced a bad Rotor cap and Rotor, I check the TPS and made sure
I had 054. I checked all the Vacuum hoses, and the fuel pressure is running about 42 psi of so. I also replaced the CTS and the IAC while I was in the process and cleaned up the EGR. While troubleshooting I disconnected the MAF and it started and idled well, but of course I had a code. I pulled it back up and the problem came back. Could it be the MAF Relay? Any help would be appreciated.
I had 054. I checked all the Vacuum hoses, and the fuel pressure is running about 42 psi of so. I also replaced the CTS and the IAC while I was in the process and cleaned up the EGR. While troubleshooting I disconnected the MAF and it started and idled well, but of course I had a code. I pulled it back up and the problem came back. Could it be the MAF Relay? Any help would be appreciated.
Last edited by senorv47; Jun 22, 2014 at 04:04 PM.
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From: Ocean City Maryland
tomorrow. Thank you for your reply, every little bit helps.
Melting Slicks
Joined: Jan 2014
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From: Lunenburg MA
If the MAF was OK before you changed the gasket, chances are it's OK now. Odds are much more likely it's something you touched. Did you set the base idle after you changed the IAC? If you set the timing without disconnecting the advance wire, it's probably way off. Vacuum at idle?
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From: Ocean City Maryland
If the MAF was OK before you changed the gasket, chances are it's OK now. Odds are much more likely it's something you touched. Did you set the base idle after you changed the IAC? If you set the timing without disconnecting the advance wire, it's probably way off. Vacuum at idle?
Instructor
Joined: Oct 2002
Posts: 218
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From: Durham NC
Recently I replaced the intake gasket because I had a leak on the rear of the intake. I put everything back together and while I marked the bottom of the distributor and the top of the intake so I could put it back in properly, Duhh, I had the intake cleaned and of course the mark was no longer there. I adjusted TDC and set the Distributor and it started but would not stay idling. I replaced a bad Rotor cap and Rotor, I check the TPS and made sure
I had 054. I checked all the Vacuum hoses, and the fuel pressure is running about 42 psi of so. I also replaced the CTS and the IAC while I was in the process and cleaned up the EGR. While troubleshooting I disconnected the MAF and it started and idled well, but of course I had a code. I pulled it back up and the problem came back. Could it be the MAF Relay? Any help would be appreciated.
I had 054. I checked all the Vacuum hoses, and the fuel pressure is running about 42 psi of so. I also replaced the CTS and the IAC while I was in the process and cleaned up the EGR. While troubleshooting I disconnected the MAF and it started and idled well, but of course I had a code. I pulled it back up and the problem came back. Could it be the MAF Relay? Any help would be appreciated.
WOW !!!!!!!!!!!! I did the same job you did last October and had the exact same situation when I tried to start the engine. After much frustration, etc., I found out it was the MAF sensor. I replaced this and the car ran great. Even after replacing the MAF, I had a few issues since I tried "forcing" the car to run. It was running extremely rich and "soot" was covering the plugs as well as the air temp sensor in the plenum. It took a bit of time to figure all this out, but once I cleaned all this up, the car runs good.
I should say that at the time this happened, I only removed and re-installed the distributor. Similar situation to you but, I did not remove the intake that time. When I removed the intake earlier this year, this is when I discovered the sooty air intake sensor. Before cleaning this, the car ran good, but not as good as after cleaning the sensor. Closely check your MAF sensor.
Last edited by J H; Jun 26, 2014 at 06:17 PM. Reason: Correction
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WOW !!!!!!!!!!!! I did the same job you did last October and had the exact same situation when I tried to start the engine. After much frustration, etc., I found out it was the MAF sensor. I replaced this and the car ran great. Even after replacing the MAF, I had a few issues since I tried "forcing" the car to run. It was running extremely rich and "soot" was covering the plugs as well as the air temp sensor in the plenum. It took a bit of time to figure all this out, but once I cleaned all this up, the car runs good.
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From: Ocean City Maryland
UPDATE: Changed out the Burn off and Power Relays and still the same issues, so I guess I am down to the MAF. The new MAF should be here next week so I will provide and update then. Everyone have a great 4th of July!!!
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New MAF received, now getting the dreaded code 33!! Ran down the checklist for code 33 and all tested good. Contacted the company about possible bad MAF and they were kind enough to send me another, but guess what still code 33!! Could not be two bad MAF's? I have swapped out the relays, checked all the connections and wires, TPS setting and still CODE 33 (I did reset the PCM every time) Anybody have and advice?
Burning Brakes
Joined: May 2002
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From: Collegeville PA
I used to have a Black 87 w/red interior that had the same problems you are having. I took it to every shop around and finally took it to a shop called Corvette Paramedics in NJ. They replaced everything in the circuit (MAF, sensors, etc...) checked all the wiring, the whole 9 yards. About a day later BOOM same problem came back, code 33 again, etc... At that point I gave up and sold it.
It's a frustrating feeling. Good luck!
It's a frustrating feeling. Good luck!
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From: Ocean City Maryland
I used to have a Black 87 w/red interior that had the same problems you are having. I took it to every shop around and finally took it to a shop called Corvette Paramedics in NJ. They replaced everything in the circuit (MAF, sensors, etc...) checked all the wiring, the whole 9 yards. About a day later BOOM same problem came back, code 33 again, etc... At that point I gave up and sold it.
It's a frustrating feeling. Good luck!
It's a frustrating feeling. Good luck!
Anyone have more input please? I could use the help
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I will post my results when I change it out.
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If the MAF was OK before you changed the gasket, chances are it's OK now. Odds are much more likely it's something you touched. Did you set the base idle after you changed the IAC? If you set the timing without disconnecting the advance wire, it's probably way off. Vacuum at idle?
- to the OP, SLOW DOWN, TAKE A DEEP BREATH!!! sounds like you're just throwing a bunch of parts at the it without fully analyzing issue. first of all, are you 100% positive you have the distributor indexed correctly, and all spark plug wires installed in the correct firing order?
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- to the OP, SLOW DOWN, TAKE A DEEP BREATH!!! sounds like you're just throwing a bunch of parts at the it without fully analyzing issue. first of all, are you 100% positive you have the distributor indexed correctly, and all spark plug wires installed in the correct firing order? 1. All spark plug wires installed in the correct firing order.
2. TPS set to 0.54. Initially could not set timing because it would not idle with old MAF installed (no code at this point due to idle issue).
3. Set timing and minimum idle in limp home mode (only way it would idle)
4. Found purple and blue wire insulation stripped back (could have shorted) and used electrical tape to cover.
5. Received and installed new MAF. Car started idled and after 10-20 second threw code 33.
6. Reset PCM and installed old MAF and car would not idle again.
7. Re installed new MAF and got code 33 again.
8. Performed code 33 testing procedure from FSM and test results pointed to bad MAF.
9. Reset PCM. Replaced MAF Power Relay and MAF Burn off relay. still code 33.
10. Contacted auto place that sold me the MAF and they replaced it with a new one.
11. Reset PCM and installed new MAF and got code 33 again.
This is where I am currently. Did I miss a step? Not sure what I did wrong?
Team Owner
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From: SE NY
Cruise-In II Veteran
Sounds like tossing parts w/o having detailed analysis data.
From the FSM Code 33 is set when ECM has seen flow >45 gm/sec (>2.2 V) for 1second when:
-engine is first started
or
-TPS < 1/4 throttle & RPM <2,000rpm.
Since it takes 10-20 sec for the code 33 to be set, sounds like the 2nd case is the one on which to focus.
It would be very helpful to have a monitor tool to show what values the ECM is seeing when the code 33 is set.
From the FSM Code 33 is set when ECM has seen flow >45 gm/sec (>2.2 V) for 1second when:
-engine is first started
or
-TPS < 1/4 throttle & RPM <2,000rpm.
Since it takes 10-20 sec for the code 33 to be set, sounds like the 2nd case is the one on which to focus.
It would be very helpful to have a monitor tool to show what values the ECM is seeing when the code 33 is set.
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Joined: Nov 2006
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From: Ocean City Maryland
Sounds like tossing parts w/o having detailed analysis data.
From the FSM Code 33 is set when ECM has seen flow >45 gm/sec (>2.2 V) for 1second when:
-engine is first started
or
-TPS < 1/4 throttle & RPM <2,000rpm.
Since it takes 10-20 sec for the code 33 to be set, sounds like the 2nd case is the one on which to focus.
It would be very helpful to have a monitor tool to show what values the ECM is seeing when the code 33 is set.
From the FSM Code 33 is set when ECM has seen flow >45 gm/sec (>2.2 V) for 1second when:
-engine is first started
or
-TPS < 1/4 throttle & RPM <2,000rpm.
Since it takes 10-20 sec for the code 33 to be set, sounds like the 2nd case is the one on which to focus.
It would be very helpful to have a monitor tool to show what values the ECM is seeing when the code 33 is set.
By the way I was wrong code sets after 3 seconds
Last edited by senorv47; Jul 21, 2014 at 11:01 AM.
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1. All spark plug wires installed in the correct firing order.
2. TPS set to 0.54. Initially could not set timing because it would not idle with old MAF installed (no code at this point due to idle issue).
3. Set timing and minimum idle in limp home mode (only way it would idle)
4. Found purple and blue wire insulation stripped back (could have shorted) and used electrical tape to cover.
5. Received and installed new MAF. Car started idled and after 10-20 second threw code 33.
6. Reset PCM and installed old MAF and car would not idle again.
7. Re installed new MAF and got code 33 again.
8. Performed code 33 testing procedure from FSM and test results pointed to bad MAF.
9. Reset PCM. Replaced MAF Power Relay and MAF Burn off relay. still code 33.
10. Contacted auto place that sold me the MAF and they replaced it with a new one.
11. Reset PCM and installed new MAF and got code 33 again.
This is where I am currently. Did I miss a step? Not sure what I did wrong?
2. TPS set to 0.54. Initially could not set timing because it would not idle with old MAF installed (no code at this point due to idle issue).
3. Set timing and minimum idle in limp home mode (only way it would idle)
4. Found purple and blue wire insulation stripped back (could have shorted) and used electrical tape to cover.
5. Received and installed new MAF. Car started idled and after 10-20 second threw code 33.
6. Reset PCM and installed old MAF and car would not idle again.
7. Re installed new MAF and got code 33 again.
8. Performed code 33 testing procedure from FSM and test results pointed to bad MAF.
9. Reset PCM. Replaced MAF Power Relay and MAF Burn off relay. still code 33.
10. Contacted auto place that sold me the MAF and they replaced it with a new one.
11. Reset PCM and installed new MAF and got code 33 again.
This is where I am currently. Did I miss a step? Not sure what I did wrong?