Please Help with Sputtering C4
Thread Starter
6th Gear
Joined: Apr 2004
Posts: 6
Likes: 0
From: San Francisco CA
Please Help with Sputtering C4
Guys, I'm having a problem with my '87 roadster 4+3 that I hope you can help with. I have a new cat-back exhaust, but other than that, the car is stock with less than 50,000 miles. The problem is that the car will be driving along fine, and then it will suddenly stutter and the "Check Engine" light will come on - then, if I give the car some gas, it will stutter badly and continue to run poorly.
I changed the Mass Airflow Sensor, and it didn't seem to help the problem. I then changed the pigtail, with my thought being that the connection to the MAS was faulty - this didn't help, either. The only thing that seems to make the problem go away is if I pull over and turn the engine off and leave it off for about a minute - it will then run better for a while until it stutters, the "Check Engine" light comes on again, and I have to go through the same routine.
Any ideas on what the problem might be? Thanks.
I changed the Mass Airflow Sensor, and it didn't seem to help the problem. I then changed the pigtail, with my thought being that the connection to the MAS was faulty - this didn't help, either. The only thing that seems to make the problem go away is if I pull over and turn the engine off and leave it off for about a minute - it will then run better for a while until it stutters, the "Check Engine" light comes on again, and I have to go through the same routine.
Any ideas on what the problem might be? Thanks.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Re: Please Help with Sputtering C4 (Niner Fan)
without knowing the code, I am betting fuel filter or pump.
to check the code, you take a paperclip and jump pins A & B. turn ON the car, but DO NOT START IT!!!! That will set the computer into diag mode.
The SES light will flash:
<flash> pause <flash><flash>
<flash> pause <flash><flash>
<flash> pause <flash><flash>
thats a code 12. It means you are in the computer.
then the error code will flash - 5 times... so for a code 33 (MAF) it will flash
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
If there is another code, it will flash 12, then the next code. if no more codes are stored, it will simply flash the only code, again.
Report back to us what the codes say. :thumbs:
oh, if the MAF was bad, you will have to clear the code. Disconnect the battery and wait 1 minute. Reconnect, codes cleared.
[Modified by bogus, 2:34 PM 4/19/2004]
to check the code, you take a paperclip and jump pins A & B. turn ON the car, but DO NOT START IT!!!! That will set the computer into diag mode.
The SES light will flash:
<flash> pause <flash><flash>
<flash> pause <flash><flash>
<flash> pause <flash><flash>
thats a code 12. It means you are in the computer.
then the error code will flash - 5 times... so for a code 33 (MAF) it will flash
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
<flash><flash><flash> pause <flash><flash><flash> Long pause
If there is another code, it will flash 12, then the next code. if no more codes are stored, it will simply flash the only code, again.
Report back to us what the codes say. :thumbs:
oh, if the MAF was bad, you will have to clear the code. Disconnect the battery and wait 1 minute. Reconnect, codes cleared.
[Modified by bogus, 2:34 PM 4/19/2004]
Racer
Joined: Apr 2003
Posts: 371
Likes: 0
From: Kingsport TN
Re: Please Help with Sputtering C4 (Niner Fan)
This has been a problem with mine for the last several months. I have also changed the MAF, Maf relays, O2 sensor, TPS, AIT, fuel filter. It leaves no codes for me. If I find the problem I'll let you know, you do the same...PLEEEZE. I have the Dr. coming this week. I thrown all the money at it that I'm going to. Time for a PRO. Let you know.. If you want an idea of the frustration check previous post in my sig.
Racer
Joined: Feb 2004
Posts: 265
Likes: 1
From: Irwindale Ca
Re: Please Help with Sputtering C4 (Niner Fan)
It sounds like the PROM or ECM. My brothers vette did the same thing, it turned out to be the ECM computer. You must pull the codes. If you pull a ECM code, It might be the PROM chip in the ECM. When the auto parts sells you the ECM they dont give you a new PROM chip. You have to use your own. If your computer codes a ECM code, I would change the PROM out of the ECM first, Then if that doesnt help, change out the ECM. You will have a extra PROM for future trouble shooting. ECM is usually the last thing you will replace but if your computer is telling you that that is the problem then its probably the problem. Good luck :smash:
Thread Starter
6th Gear
Joined: Apr 2004
Posts: 6
Likes: 0
From: San Francisco CA
Re: Please Help with Sputtering C4 (Niner Fan)
O.k., I used the paperclip technique to get the codes, and it threw the following THREE codes: 33, 34, and 51.
Can anyone tell me what this means? Thanks for your help.
Can anyone tell me what this means? Thanks for your help.
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Thread Starter
6th Gear
Joined: Apr 2004
Posts: 6
Likes: 0
From: San Francisco CA
Re: Please Help with Sputtering C4 (Niner Fan)
I regularly disconnect the battery, so that doesn't help the problem. I do have a hypertech chip that I installed over 10 years ago - the chip is the one that allows a 160 degree thermostat. I think the code 51 means that I have a bad ECM/EPROM. If I replace the EPROM though, I'd have to get one that is compatible with my 160 thermostat. Where exactly is the ECM located? Any ideas on what the next step should be? Thanks.
Advanced
Joined: Dec 2003
Posts: 75
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From: Lenexa KS
Re: Please Help with Sputtering C4 (Niner Fan)
33 is MAF Sensor (High Voltage)
34 is MAF Sensor (Low Voltage)
51 is PROM Error
Looks like either your ECU or PROM (or both) are bad.
Since you can turn it off and wait a few minutes and it starts running ok again for a while, it sounds like all is ok as long as it's in open loop. The problems start when it goes closed loop.
I'd stick the hypercrap PROM in (temporarily) and see if that fixes it. If not, try to borrow an ECU and swap it in.
The ECU is located behind the hush panel on the passenger side. Not too diffucult to get to.
Why do you regularly disconnect your battery? That could be what lunched the ECU if that is indeed the problem.
34 is MAF Sensor (Low Voltage)
51 is PROM Error
Looks like either your ECU or PROM (or both) are bad.
Since you can turn it off and wait a few minutes and it starts running ok again for a while, it sounds like all is ok as long as it's in open loop. The problems start when it goes closed loop.
I'd stick the hypercrap PROM in (temporarily) and see if that fixes it. If not, try to borrow an ECU and swap it in.
The ECU is located behind the hush panel on the passenger side. Not too diffucult to get to.
Why do you regularly disconnect your battery? That could be what lunched the ECU if that is indeed the problem.
Thread Starter
6th Gear
Joined: Apr 2004
Posts: 6
Likes: 0
From: San Francisco CA
Re: Please Help with Sputtering C4 (Niner Fan)
I have a slow drain on the battery somewhere in the system, and I don't drive the car everyday, so I disconnect it when I leave it for more than a few days. Any suggestions on other PROMs that would work with the 160 thermostat (I don't really want to have to swap out the thermostat with a new chip, as well)?
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Re: Please Help with Sputtering C4 (Niner Fan)
If it were my car.
I would 1st replace the MAF power and Burnoff relays as they are cheap and eventually go anyways so if you haven't yet I would do it.
If that did not clear things up I would purchase a new ECM, you can always return it soon if that doesn't fix it.
I would 1st replace the MAF power and Burnoff relays as they are cheap and eventually go anyways so if you haven't yet I would do it.
If that did not clear things up I would purchase a new ECM, you can always return it soon if that doesn't fix it.
Advanced
Joined: Dec 2003
Posts: 75
Likes: 0
From: Lenexa KS
Re: Please Help with Sputtering C4 (Niner Fan)
You don't have to swap the thermostat to put the 160 degree chip in temporarily. Your cooling fan will run more than it should but that won't hurt anything during a temporary swap.
Good thought about the relays Scorp.
Good thought about the relays Scorp.
