J30 Engine Bogging Down During Stops

[VimyJ]

Jeez, I hope this isn't one of those "little problems". When I come to a stop the engine bogs down to 400 rpm for a few seconds and then goes back up to a normal 650 rpm as I idle in gear. It feels like the torque converter isn't disengaging. I checked the transmission fluid (Mobil One) level is fine and still looks like new. Does this sound serious? Man, I sure hope it's not.

I have checked the service manual and the symptom is described and relates to the throttle position sensor (TPS). When the "soft closed throttle position switch" is malfunctining the "hard closed throttle position switch" begins to function. Does this sound familiar to anyone? I'm going to go out and f*** around with it and see if anything is amiss.

[Mayhem_J30]

I had a similar problem that seemed to be easily remedied with a good TB cleaning.The TPS sounds like it could just as well be the problem.Also the IACV might be a culprit.Last thought, the EGR valve might be sticking open. Let's hope not as it looks like it's VERY difficult to get to.

[VimyJ]

Well, so much for effing around with stuff. I gave the throttle body a good cleaning (I had been feeling a little "stickiness" upon start up). I used a tooth brush and a good amount of cleaner on both sides and wiped the throttle bodies out as far as I could reach. Clean as a whistle. No change in the bogging.

Then I took the TPS off and inspected it. There is an adjustable slider on it so I effed around with that for a bit. If you slide it too far down the slot the idle increases quite a bit. I adjusted it so that a normal idle speed was indicated on the tach and took her for a spin. She's still bogging down, boys, but not all the time. I called a local Nissan dealer for the part and the good news is that it only costs $44. I'll order from Lisle.

Once again, I had to convince the Nissan parts guy that the J has the same engine as the 300ZXna. Once again, these guys didn't carry the part. Not many 300zx around here it seems.

Next step is to check the electrical connection of the TPS if I can figure out how to unclip it. The wires look good going into it. I'm not to concerned because there is a failsafe mode that the TPS reverts to but I want my luxury ride back!:mad:

[VimyJ]

Tomorrow I 'm going to try a transmission self diagnostic. Looking through the service manual, there are few things that might be causing this bogging.

[Mayhem_J30]

i hope you're not paying full dealer price from the nissan parts guy. ouch!

[VimyJ]

i hope you're not paying full dealer price from the nissan parts guy. ouch!

No,no,no. I get my parts from one of "our" suppliers.

[VimyJ]

Well, something interesting from adjusting the TPS. The not so smooth cold shift from 1st to 2nd gear is gone! However, the shift from 2nd to 3rd feels more mushy. Interesting. I will adjust it back a little and see if I can get a compromise. The bogging problem still persists, unfortunately. I am heading out to do the transmission self diagnostic right now. Will let you know how it goes.

BTW, I went out to a local tire chain "Discount Tires" and they are selling a stock size Yokohama YK420 all season, H rated, 93 load, non-directional, 60,000 mile tread wear tire for $82. I checked Tire Rack for comparison and they don't seem to carry it. The guy said they had been selling it for a year. Anyone heard of this tire before?

[Mayhem_J30]

BTW, I went out to a local tire chain "Discount Tires" and they are selling a stock size Yokohama YK420 all season, H rated, 93 load, non-directional, 60,000 mile tread wear tire for $82. I checked Tire Rack for comparison and they don't seem to carry it. The guy said they had been selling it for a year. Anyone heard of this tire before?

with that kind of tread wear and that price they might not be a quality tire. but will probably last as long as advertised at the sacrifice of performance.

keep us updated on the idle problem!

[maxnix]

I believe this is a Dicount only tire made especially for them.

AZHitman has something like them on his Q on 97 rims. Maybe he'll chime in.

[VimyJ]

OK. I performed the self diagostic. Looks like a long pulse on no. 12, "Engine control circuit between A/T control unit and ECM (ECCS control module) is short circuited or disconnected." (However, there is a hestitation between 11 flash and the 12th longer pulse and then the flashes repeat the order again. I'm assuming that this is normal.) The manual then says "Go to engine control circuit check." Flip, flip, flip....to page AT-52.

OK, where is the connector between the A/T "control unit terminal" and ECCS control unit terminal? I have an elcheapo circuit testor. If I can find the connector, will this testor be sufficient to test for continuity? Electrics have never been a strong suit of mine but it's time to learn. Suggestions? Tips? Thanks. Man, I hope this isn't one of those "little problems". Yikes!

[VimyJ]

I haven't attempted to locate the connections yet but there does seem to be a link to to the TPS. A couple of weeks age while cleaning the throttle body, I let the throttle snap shut a couple of times while holding it open near the cable connections at the front of the motor. The TPS is made of pretty light plastic and I probably damaged it.

[VimyJ]

Well, I seem to be on my own with this problem. I checked out the Z32 site and got on their chat area and described the symptoms to them. They think that the problem is most likely a leaky intake. This would cause problems with the MAF sensor or it could be the MAF itself. They don't think that it could be the TPS as hardly anyone has ever heard of them going bad or causing the symptom I described. The J is running great otherwise.

[VimyJ]

Gas mileage is way down. I did a cursory check of the intake system for leaks. No obvious connection problems. Vacuum lines seem to be intact as well. Will have to teach myself how to check the MAF system. I will also try to perform as self diagnostic just for yucks. The transmission trouble code "12" is also bothering me a little. I wonder if that code could be connected to a MAF problem. I'll have to try trial and error method until I'm forced to take the car to a tech. Thankfully, Z32 guys are quite helpful, though. However, they say the NICO site sucks.

[VimyJ]

Sure is nice not to have anyone offer advice or tips. I love being a member of a board that shows no interest in a member's travails. :rolleyes

I think I may have solved the bogging problem. I cleaned the MAF connection and the problem seems to have dissappeared. However, the idle is lower than it used to be. I adjusted the TPS but couldn't get to ~800 rpm in idle. Wish that I had never touched it in the first place. It would jump to 1100-1200 rpm when I very delicately tried to move it. Out of gear it is idling @ 650 and in gear it's ~600. I also can't seem to squeeze my circuit tester probes into the harnesses. Is there a flatter probe design used for this purpose (he asked himself)? Getting able and practical advice from the Z32 board including a performance mod that seems to make a lot of sense. I wonder if any of the J guys on this forum have tried it? (He asked himself again)

[juiceman]

I have been following you but being I am in a perdicament myself and newer I cannot supply info. I do feel for you though

I think from what I remeber is that the idle is adjusted via the IAC. Q45tech stated to another q owner that your turn IAC screw clockwise to stop and then back 3.5 turns but do not know if this applies to the J.

I adjusted my Idle using this screw and it is right on now. Had to do it after a good induction service which left the idle too high.

I hope this helps.

BTW I got my new transmission mount and now see that mine is crapped out. I am replacing this weekend. Figure this might solve some or all of my vibration problems.

[VimyJ]

Thanks for the response. I suppose I am just grousing a little because, if I had a Q, guys would've been all over this problem like a busted chain guide. We, unfortunately, lost Prof. Mike who would give his sound opinions regarding the J30. My problem doesn't seem like it should be that difficult to diagnose for someone really familiar with these cars. The J is a fairly rare bird and now we J owners don't have an expert backing us up. Such is life. I'll probably be spending more time at the Z32 site for drivetrain info. I guess I was lucky in that I had never had a mechanical glitch that wasn't responded to expertly on this site. But, in this case, the silence has been deafening. I am still wondering why my idle is now so low after this MAF episode. I'll obviously have to go elsewhere for an answer or opinion on that matter. "Infiniti Online Mechanic"? Not if you have an Infiniti J30.

[DAEDALUS]

I've been following the thread as well, hoping for the best. My lack of knowledge is not a measure of my lack of support. Yeah, if it was a Q there would be more responses, but maybe too many. I don't think there is enough info to narrow it down, or maybe there is more than 1 problem, complicating the troubleshooting. Wish I could help, and I hope you let us know when you figure it out.

[Mayhem_J30]

Vimy, i think the J should be idling in the 700's. so you're close. i also use Z source info for the J. i think the best is http://www.twinturbo.net huge wealth of info there.

[VimyJ]

Cleaning the MAF harness conections seems to have done the trick. The engine doesn't bog anymore. Happy days are here again. However, there is one curious thing occuring now.

Today was windy and rainy in Chicago land. The J is motoring along nicely with the engine still idling low but I figure I'll let the ECU relearn for a couple of days and failing that disconnect the battery for 15 minutes to reset the the ECU to the default factory settings (if that doesn't work, I'll adjust the idle screw). The windows start foggong up so I switch on the defrost button to clear the windshield. I come to a stop at the next light and notice that the engine is idling at a perfect 650 rpm. "Nice", I think to myself, "The ECU is learning very quickly." The by the time I get to the next light the windows are clear so as I sit there I switch off the derfrost. The rpm drops back down to ~450! "Hmmm", I think, "The AC must be sending a signal to the ECU to keep the rpms up. Interesting."

I normally drive around with the climate control in "Econ" mode. To test what is going on, I leave the temperature at the same setting but switch to "Auto" mode. The AC shouldn't be activated becuase the temperture outside is low enough that the heater will be going not the AC. The J is idling at 650. I turn switch to "Econ" and the rpm drops to 450 again. "Very curious.", I say to myself. Hit Auto again and the rpm goes back to 650. Weird. I'll leave it like this for a couple of days and see what the ECU comes up with.

[Eswift]

whats the performance mod you're talking about? ive seen 6 throttle bodies and carbon fibre intake on a VG30DE, and it works great in the euro-spec E36 M3....i can find pictures if anyone is interested. i would help you Vimyj about the idle problem, but i dont know what to do off hand, and my service manual is 135 miles away

[VimyJ]

whats the performance mod you're talking about? ive seen 6 throttle bodies and carbon fibre intake on a VG30DE, and it works great in the euro-spec E36 M3....i can find pictures if anyone is interested. i would help you Vimyj about the idle problem, but i dont know what to do off hand, and my service manual is 135 miles away

The mod has something to do with the butterfly valves in the throttle body. Check out the "Butterfly" thread in the Infiniti general area.

[Q451990]

Sounds to me like the ECU is using the AAC (IAC) valve up when you turn the A/C on. Even though it's cold the A/C compressor runs in low mode even when it's cold to eliminate humidity (at least on the Q). Try unpluging the AAC valve at idle (with the car warmed up) - then set the idle to the desired range with it unpluged. This should set your base idle. Then plug it back in. The idle should rise momentary and then drop back down.

Adjusting the TPS has nothing to do with the idle... the switch communicates with the ECU/TCU for shift points. You may want to have someone with Consult reset the TPS, and check the IAC/AAC as well.

I know this will make you happy, but this is all based on Q experience... hopefully it helps.

Heath

[VimyJ]

Many thanks for the insight, Heath. It's been tough getting an experienced wrencher's thoughts around here lately. I would imagine that the basic principles of Nissan engine management apply to both the J and the Q alike.

[Mayhem_J30]

how corroded were your tps harness connectors? I went through and cleaned all the connectors I could find and they all looked new!unhooking the battery will not reset the ECU. Unfortunately the J's ECU is a PITA to get to. But you have to do the reset procedure with the switch on the back of the ecu. Do a search for retrieving ecu codes or ecu reset and I've posted instructions somewhere.

Heath, I thought about the IAC, but I was under the impression that it only was in use before the vehicle is properly warmed up. But maybe it's malfunctioning so that could be the problem. I could stand to be educated on this device.

Vimy, I made an appointment at the dealer for the 6th of Jan! They must really be booked. So it'll be a while before I report back results.

[VimyJ]

how corroded were your tps harness connectors? I went through and cleaned all the connectors I could find and they all looked new!unhooking the battery will not reset the ECU. Unfortunately the J's ECU is a PITA to get to. But you have to do the reset procedure with the switch on the back of the ecu. Do a search for retrieving ecu codes or ecu reset and I've posted instructions somewhere.

Heath, I thought about the IAC, but I was under the impression that it only was in use before the vehicle is properly warmed up. But maybe it's malfunctioning so that could be the problem. I could stand to be educated on this device.

Vimy, I made an appointment at the dealer for the 6th of Jan! They must really be booked. So it'll be a while before I report back results.

I only worked on the MAF connections. You know, the connections didn't seem to be corroded at all but I cleaned them nonetheless and the bogging problem stopped. I still have the low idle problem I described but the phenomenom of the idle suddenly popping back up to greater than normal levels disappeared after the cleaning. They probably hadn't been cleaned in 7 years and even slight oxidation could have been messing the voltages up.

I was under the impression that disconnecting the battery for 15 minutes would reset the ECU. At least that is what the Z32 guys told me.

The ECU is totally a PITA to get to. A guy on Z32.org has a device that, if I understand it right, hooks up the the ECU and lets you read the codes in comfort. Might be something to check into more closely.

One thing is for sure, the backlog at the dealer isn't being created by J30s.

[Eswift]

yeah you can get something to plug into the consult port to read the error codes and to read sensor variables, hasnt been confirmed to work on the J30.

[Eswift]

i just cant wait until the Zemulator comes out, then i will be able to supercharge this heifer.

You guys that have done exhuasts on the J30, did you just buy the mufflers and have a reputable shop weld em in, or what? i assume they only used aluminized piping, its hard to find a place that does stainless, and forget mandrel bent. Im looking into this exhaust thing because several of the welds on my exhaust are rusting through, and i want a plan of action ready for when the time comes. im thinking replace cats with catco cats, borla mufflers, and no resonator. i believe someone said that the stillen headers dont fit. Is this a myth, or did someone actually try it? its a shame its so hard to adopt the Z32 engine aftermarket the the J30, im really itching for 500bhp.

[VimyJ]

The same low idle problem exists so I will attempt to adjust it.

I checked the voltage for the TPS. I am not sure if my meter is sensitive enough to register .4-.5 volts so I can't be sure the reading is up to spec. I am only messing with this thing because I'm trying to return it to its original position. I cleaned the connections for it as well. However, the TPS doesn't seem quite right somehow. Further checks are in order.

Checked the voltage for the MAF sensor and it reads low but within specs with the engine idling.

I've got a bit of a bug and the garage is cold so this stuff just isn't as much fun as it usually is.

[Mayhem_J30]

Vimy,How's that J doing? Did your gas mileage improve? If not you might wanna check the O2 sensors. Start with looking for excessive soot buildup on the exhaust. They'll usually make the motor run excessively rich when going bad.

[VimyJ]

Vimy,How's that J doing? Did your gas mileage improve? If not you might wanna check the O2 sensors. Start with looking for excessive soot buildup on the exhaust. They'll usually make the motor run excessively rich when going bad.

The J is doing pretty well. The idle is still a little low but not too bad. I think I've gotten the TPS back to its original position. I will check the O2 sensors when I get back from my little road trip in the beauty. The mission? Palm trees and salt water.