Need help with Snap On Modis Data

[78TurboMali]

I have a stock 87 T that runs rough when im at a light and it throws a SES light gives me a code 31 overboost failure and a code 44 lean exhaust. I have a oxygen sensor ordered from Kirban. Just wondering if you guys have any further info on the data files, Any info would help.

 

[TurboDave]

Well, the most obvious thing that jumps off the page is the BLM of 150.. The ECM is adding a LOT of fuel to compensate for a lean condition.
Now, what causes a very high BLM? Usually the culprit is a vacuum leak, or in some cases a pre turbo exhaust leak.
Could it also be a faulty O2 sensor? Well....possible but not usually.

 

[dennisL]

I agree with Dave in that you are way too lean and you need to determine where the extra air is coming from. I'm not sure why you're seeing a Code 31 though because this would never occur at idle. It was either a fluke or caused by sun spots. In any case, ignore it and start checking your vacuum lines.

 

[78TurboMali]

The code 31 i assume comes when im in boost because the ses comes on when i get into boost and it stays on. The 44 for the lean exhaust comes on when im stopped at a light, the car will start to run rough and smell rich and then the ses will come on but will turn off once i get on the throttle to take off. I think the car only runs lean at idle?..... I received my o2 in the mail yesterday so i will put that in today and also start replacing my vacuum hoses because a lot of them are pretty brittle. Not sure what to look into for the Overboost / solenoid failure

 

[trbojo]

o2 millivolts are 161...lean...poss bad o2 causing ecm to add fuel(high blm's) ...no vacuum leak(iac counts 23) with vacumm leak iac usually goes to 0(not adding air)....overboost...need to start looking at boost control....

 

[trbojo]

I agree with Dave in that you are way too lean and you need to determine where the extra air is coming from. I'm not sure why you're seeing a Code 31 though because this would never occur at idle. It was either a fluke or caused by sun spots. In any case, ignore it and start checking your vacuum lines.

lean could also be not enough fuel also......

 

[78TurboMali]

Replaced the 02 sensor today with a fresh Denso and still have the same issue! I am going to check the fuel pressure tomorrow and change the fuel filter, i think the filter is still the stock original.

 

[CGASTON]

I have a stock 87 T that runs rough when im at a light and it throws a SES light gives me a code 31 overboost failure and a code 44 lean exhaust. I have a oxygen sensor ordered from Kirban. Just wondering if you guys have any further info on the data files, Any info would help.

After our conversation tonight and looking at these logs, I have to say a couple of things. Your IAC and TPS are in good shape. Now this will all change once you get the vacuum leak fixed. Indicators of you having a vacuum leak: look at your idle RPMs (they should be around 800-850), your O2 are really low (this is because you are running extremely lean, causing the ECM to add more fuel and return cause the engine temps to run high. The hotter the motor, the leaner as well). This car is 25 yr old. As so is the fuel pressure regulator. You regulator could be going bad. I highly suggest a new fuel pressure regulator so you can set your fuel to 43 (vacuum off) and this will help your lean issue a bit. I would also go to a bit colder plug. I would run a R43TS@.35 gap. Since you just changed your head gaskets, check your intake for a vacuum leak (we discussed this). Change your vacuum lines since they are all brittle. Get yourself a scanmaster w/PL and aftermarket tach. Also we talked about unplugging you vacuum to the boost solenoid and run a line from your compressor housing to the actuator. See if the clears the code. Also contact Eric Marshall of TurboTweak and get yourself a chip for stock car. You will notice a big change once everything is up to par. Let me know how things are and going. You will get it!!

 

[trbojo]

After our conversation tonight and looking at these logs, I have to say a couple of things. Your IAC and TPS are in good shape. Now this will all change once you get the vacuum leak fixed. Indicators of you having a vacuum leak: look at your idle RPMs (they should be around 800-850), your O2 are really low (this is because you are running extremely lean, causing the ECM to add more fuel and return cause the engine temps to run high. The hotter the motor, the leaner as well). This car is 25 yr old. As so is the fuel pressure regulator. You regulator could be going bad. I highly suggest a new fuel pressure regulator so you can set your fuel to 43 (vacuum off) and this will help your lean issue a bit. I would also go to a bit colder plug. I would run a R43TS@.35 gap. Since you just changed your head gaskets, check your intake for a vacuum leak (we discussed this). Change your vacuum lines since they are all brittle. Get yourself a scanmaster w/PL and aftermarket tach. Also we talked about unplugging you vacuum to the boost solenoid and run a line from your compressor housing to the actuator. See if the clears the code. Also contact Eric Marshall of TurboTweak and get yourself a chip for stock car. You will notice a big change once everything is up to par. Let me know how things are and going. You will get it!!

i still have to disagree with the vacuum leak...iac's would be at zero....much like having an overadjusted throttle blade letting too much air in, the iac counts would be zero...seems like a fuel issue....

 

[trbojo]

the computer uses the iac to control IDLE speed by openening or closing the iac to add or remove AIR...if there was a vaccuum leak (AIR) then his iac counts would be at or close to zero(NO AIR)....i believe they were 23 which is right on target...actually thinking about this now, this could be a MAF issue....i pulled the screens out of my MAF the other week to check another issue, and my blm's went from 128, up to the 140's.......

 

[CGASTON]

i still have to disagree with the vacuum leak...iac's would be at zero....much like having an overadjusted throttle blade letting too much air in, the iac counts would be zero...seems like a fuel issue....

Well then, how do you explain the higher idle RPMs if it us a fuel problem. Read the whole thread before trying to shoot someone down. Secondly, I spoke with him for about an hour on the phone. There is more to play here. He never mention that when car is warm and when he puts it into gear, the car runs very rough like it is going to die. SIGN of vacuum. This is a bone stock car, so when he puts it into gear, the car shouldn't want to stubble and want to die. Now if he a had a bigger cam (224/224 or higher) I could see that. Also since he just replaced the head gaskets, there is a great chance that chance that his intake/plenum could still be leaking.
Lastly, I look at things at all angles. I have been around these cars and racing them since I was in high school (1990). So I do know a little.

I really appreciate your incite, but would rather it be addressed more as a suggestion rather than a blast. That is the problem around here and why newbies are scared to ask questions or say something. The are scared that someone is going to make fun of them or call them out.

So lets help this guy instead of trying to look like the guy with the biggest TURBO!!

 

[CGASTON]

the computer uses the iac to control IDLE speed by openening or closing the iac to add or remove AIR...if there was a vaccuum leak (AIR) then his iac counts would be at or close to zero(NO AIR)....i believe they were 23 which is right on target...actually thinking about this now, this could be a MAF issue....i pulled the screens out of my MAF the other week to check another issue, and my blm's went from 128, up to the 140's.......

Now I forgot about the MAF screen.... Thanks for that incite. But that still doesn't answer the 1000rpm idle and 102v O2. I am starting to think it is a combination of the two. Now I have had IAC run at 70v and at 0v and TPS .42v and the car ran just fine. However it didnt have the throttle response that it should. So I did some playing around and got it back to where it should be!!

 

[trbojo]

Well then, how do you explain the higher idle RPMs if it us a fuel problem. Read the whole thread before trying to shoot someone down. Secondly, I spoke with him for about an hour on the phone. There is more to play here. He never mention that when car is warm and when he puts it into gear, the car runs very rough like it is going to die. SIGN of vacuum. This is a bone stock car, so when he puts it into gear, the car shouldn't want to stubble and want to die. Now if he a had a bigger cam (224/224 or higher) I could see that. Also since he just replaced the head gaskets, there is a great chance that chance that his intake/plenum could still be leaking.
Lastly, I look at things at all angles. I have been around these cars and racing them since I was in high school (1990). So I do know a little.

I really appreciate your incite, but would rather it be addressed more as a suggestion rather than a blast. That is the problem around here and why newbies are scared to ask questions or say something. The are scared that someone is going to make fun of them or call them out.

So lets help this guy instead of trying to look like the guy with the biggest TURBO!!

i didn't think disagreeing with something was a blast....i graduated tech school in '86 and have worked mostly on GM ever since. GM specialized electronics trained...i was trying to not get him too far off from what I saw..... MAF will give him all the symptoms he has, including high/surging/stumbling idle....go pull a vaccum line off an otherwise good running Buick and see what happens to the Iac counts.......then go pull a Maf screen out and see what happens....

 

[trbojo]

and Maf issue could cause a lean condition too.....letting more MASS AIR into the engine, or the computer getting the impression that it is, while the computer can only make up with so much fuel....thus the blm's pegged at 150..

 

[rbarragan]

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[mikestertwo]

and Maf issue could cause a lean condition too.....letting more MASS AIR into the engine, or the computer getting the impression that it is, while the computer can only make up with so much fuel....thus the blm's pegged at 150..

I'm thinking MAF on this one also. He did mention it smelled rich yet the BLM is pegged at 150. The computer is compensating for a bad reading from something. My money is on the MAF

 

[78TurboMali]

I just checked fuel pressure and im at 44lbs with the vacuum off. And i let it run until it started running rough and threw the ses light on (like it always dose at the stop lights) and fuel pressure stayed at 44lbs (with the vacuum off still)

 

[78TurboMali]

i just went out and checked again and with the vacuum line on at idle its showing 38#'s and when it starts to run rough and the ses light comes on it jumps up to 40#'s. so the computer is adding 2#'s when i gets the fault code?

 

[78TurboMali]

Gaston has been a huge help through this and has been dealing with me over the phone and coaching me! I checked the fuel pressure today and a few other things that Gaston suggested. I ended up narrowing down the location of an air leak and with Gastons help and a little carb cleaner i found that the front of the plenum is leaking!! It has a leak straight across the front from end to end! I tried to snug it down but the leak is still there. I will order a new plenum gasket tomorrow and change it out once i receive the new one. I will keep you guys posted, see if we finally found the gremlin! i sure hope so!

 

[CGASTON]

i just went out and checked again and with the vacuum line on at idle its showing 38#'s and when it starts to run rough and the ses light comes on it jumps up to 40#'s. so the computer is adding 2#'s when i gets the fault code?

Now, add what you have found after you checked the MAF and fuel pressure. How about the vacuum leak in front of plenum.