ejin4499 Posted May 20, 2011 Share Posted May 20, 2011 The truck has a horrible lope to the idle. When I step on the gas the check engine light comes on. When I let go of the gas the light goes out. Pulled the codes I got a 12 and 35. I looked up what the codes mean but I'm a little unsure of how to proceed. Anyone run into this before? Link to comment Share on other sites More sharing options...
Towncivilian Posted May 20, 2011 Share Posted May 20, 2011 Bad MAF wiring? That's just a guess pulled outta my butt, I don't even know what those codes mean. Inspect the MAF wiring closely for fraying or other damage. Maybe tighten ground screws too. Link to comment Share on other sites More sharing options...
MY1PATH Posted May 20, 2011 Share Posted May 20, 2011 I looked up what the codes mean but I'm a little unsure of how to proceed. And what do they mean? or do we have to look them up too before we help you? It kinda sounds like an egr issue but I'd know more if I memorized what all the codes mean.... Link to comment Share on other sites More sharing options...
Precise1 Posted May 20, 2011 Share Posted May 20, 2011 12 Air Flow Meter/Mass Air Flow Sensor.35 Exhaust Gas Temperature Sensor. And what do they mean? or do we have to look them up too before we help you? It would help if you list them... No I have not heard of that combination, but I suspect you have some significant MAF sensor wiring issues. I'd address that first and then clear the codes to see if the other even shows again. I recommend you download the FSM (pinned in the Garage section) for the specific pin/troubleshooting information. B Link to comment Share on other sites More sharing options...
ejin4499 Posted May 20, 2011 Author Share Posted May 20, 2011 It would help if you list them... No I have not heard of that combination, but I suspect you have some significant MAF sensor wiring issues. I'd address that first and then clear the codes to see if the other even shows again. I recommend you download the FSM (pinned in the Garage section) for the specific pin/troubleshooting information. B Sorry I didn't post those I meant to come back and add that later. I got distracted by dinner and the kids. Thank you for your help. Link to comment Share on other sites More sharing options...
MY1PATH Posted May 20, 2011 Share Posted May 20, 2011 (edited) Its all good. Check out your MAF Check the wires at the plug, they are a common failure point. unscrew the maf from the housing and gently wipe the wires on the inside with an alcohol q-tip... 35 goes with my EGR theroy. CA models come equiped with an EGT sensor to monitor the condition of the EGR valve and verify is operation. If It's leaking enough it will disrupt your idle and when you accelerate its supposed to remain closed Hence the light because the sensor is reading hot under acceleration. My solution for that code was to install a egr block off plate and a Federal ECU. That stops the EGR from leaking (or even working) and the Fed ECU has no EGT sensor code to throw when it doesn't work. You'll need a 27mm or 1_1/16" wrench if you want to change it out. Edited May 20, 2011 by MY1PATH Link to comment Share on other sites More sharing options...
ejin4499 Posted May 21, 2011 Author Share Posted May 21, 2011 Update So the error codes were caused by a bad ground connection. When I put my intake manifold back on I didn't tighten them down good enough (they are the two wires that are bolted to the front of intake manifold that come off the main wireing harness) The horrible lope was at least partialy caused by my o2 sensor. Disconnected it, started up, idled way better. It still has a little lope to it but I think the egr valve is getting stuck open a little bit so its sucking in some exhaust on idle. When I give it a little gas it evens out. Anyone know where the idle speed adjustment screw on the Iac valve is supposed to be set? Half way in half way out? Also how does that interact with the idle speed adjuster on the back of the ecm? When I adjust either of these it doesn't seem to make any difference. I also have an exhaust leak that I think may be contributing to the lope issue. Will consult FSM for more idle hunting/lope info. Cheers Link to comment Share on other sites More sharing options...
sewebster Posted May 21, 2011 Share Posted May 21, 2011 (edited) The idle screw on the IAC body is supposed to be set per the FSM procedure which is: idles at 700 rpm with the AAC valve harness disconnected. On mine that means the screw is backed all the way out, so there is no additional constriction inside from the screw. When you plug the connector back in the idle increases to 750 rpm. I don't think my truck (91) has an idle adjust on the ecu? Or am I blind.... hmm. Also, the FSM has a diagnostic for "unstable idle" but on my truck I did all that and my idle still isn't perfect. It could be that these trucks just aren't the best idlers. Mechanically my engine should be really good, and I've replaced basically all the sensors, but there are still a lot of "old" things in that engine bay... Edited May 21, 2011 by sewebster Link to comment Share on other sites More sharing options...
adamzan Posted May 22, 2011 Share Posted May 22, 2011 Also, the FSM has a diagnostic for "unstable idle" but on my truck I did all that and my idle still isn't perfect. It could be that these trucks just aren't the best idlers. Mechanically my engine should be really good, and I've replaced basically all the sensors, but there are still a lot of "old" things in that engine bay... Don't think that is very true since I have two wd21's that have a perfect smooth 750 idle. Something else is amiss. Link to comment Share on other sites More sharing options...
sewebster Posted May 22, 2011 Share Posted May 22, 2011 Don't think that is very true since I have two wd21's that have a perfect smooth 750 idle. Something else is amiss. can be hard to track down though! actually my truck has been good recently so I won't worry unless I have a problem again. Link to comment Share on other sites More sharing options...
ejin4499 Posted May 22, 2011 Author Share Posted May 22, 2011 The idle screw on the IAC body is supposed to be set per the FSM procedure which is: idles at 700 rpm with the AAC valve harness disconnected. On mine that means the screw is backed all the way out, so there is no additional constriction inside from the screw. When you plug the connector back in the idle increases to 750 rpm. I don't think my truck (91) has an idle adjust on the ecu? Or am I blind.... hmm. Also, the FSM has a diagnostic for "unstable idle" but on my truck I did all that and my idle still isn't perfect. It could be that these trucks just aren't the best idlers. Mechanically my engine should be really good, and I've replaced basically all the sensors, but there are still a lot of "old" things in that engine bay... Thanks I'll see if I can find the section you are referencing. My tach is all jacked up so I don't quite know where my rpms are. I'm just kinda guessing based on ear. I'm thinking about getting a replacement tach as it seems like everyone has trouble with the oem ones. Link to comment Share on other sites More sharing options...
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