RB20 dies when warm. PLEASE HELP

[smellslikerubber]

i posted this in small questions thread but got no response. i figured this would get more attention. yes i have searched and searched for a solution to my problem. been chasing this issue for about 2 months now.

I have a 91 240sx with an rb20 swap. Haven't had it long so im in the process of working out all the small odds an ends from previous owner. Car runs great, a bit rich but I think its due to the timing be a bit off which I plan to fix in the next week or so..but anyways more often than not the car will just die once the motor gets hot. Or after about 10-15min of driving. (Previous owner informed me of problem and said he had tried almost everything. I call BS) i thought it randomly occurred but noticed that it does it mostly when i start and drive it for the first time that day. sometimes it Wont do it for a day or two but then it comes right back. Idle or 60mph it just dies. No sputter or kick. dies as if i turned the key off. when this happens it kicks on the check engine light. i noticed that once the motor cools the light goes off and then it starts right up and drives away. no i havent hooked up to a scanner yet, having trouble finding one for the older OBD1 port. it used to take 10-30min before it would restart but i found that letting the fans run it takes about 8min (yes i timed it) Searched here for the answer when I first got the car and was told to try coolant temp Sensor which I did(bought from Nissan) i thought that had done the trick!..But it still happens. im trying to give all the information i have and know. Any ideas? Im willing to try anything. Trying to get car ready for track season

also previous owner said it has a Z32 MAF. Could it have went bad? If so where is a good place to get one? I know they can be pricey

could i be loosing spark? making it something ignition related?

also have Z32 ecu. i have made sure it was not getting hot in its current location.

Thanks for the help

[Slo_240sx]

Find a way to pull the code. That is what you need to do first..

But by experience, it could be a bad coolant temp sensor or 02 sensor.

[nissandrift!]

MAFS could be bad. Try switching to a known good one. Also double check that the MAFS was wired correctly.

[OutToWinPAHC]

Im leaning ignitor heating up and cutting spark

[smellslikerubber]

Well i just changed the coolant temp sensor a week ago so i dont think its that. Ill probably try the O2 sensor. Just today I think i found somewhere where I live that can run the code.

Ill check the MAFS wiring. Where could I get a replacement?

so would I just move the ignitor to a place away from heat? Somewhere I read that a bad distribitor could cause a similar problem to this.

[OutToWinPAHC]

you mean a CAS? Not likely they are optical, but the igniter can break down with its own internal heat, happened to me before, happens to coil packs with built in coils, happened on my motorcycle before. see if you can try someone's locally.

[OnTheChip]

Im leaning ignitor heating up and cutting spark

^^^ I vote for this too.

[smellslikerubber]

you mean a CAS? Not likely they are optical, but the igniter can break down with its own internal heat, happened to me before, happens to coil packs with built in coils, happened on my motorcycle before. see if you can try someone's locally.

Cam angle sensor? The one located at the top front right side of motor?

And what do you mean by ignitor exactly?

[OnTheChip]

The "ignitor" is the power transistor pack between the ECU and ignition coils.

[OutToWinPAHC]

it is the square thing on the spark plug cover near the firewall. Has fins on it.

[smellslikerubber]

i found it. i also found a thread on the nico forum. the guy gave a part number for a ignitor replacement and retrofit kit from nissan said it cost about $140. i think im gonna look a bit more into it and order one this week

thanks for all the help. ill keep posted on how it goes and if it solves my problem

[smellslikerubber]

Okay so I installed the z32 ignitor retrofit. No luck. So that leaves me with the CAS and MAFS. While doing some more diagnosing found that car will sometimes pop start. Also seems like as the weather has gotten warmer in the past week or so the problem has gotten worse. Seems to die sooner after first starting it and instead of takeing 10-15minto restart its now 30min+. Actually waited an hour the other day and got nothing. So once again any help is very much appreciated

[bboyclo]

Okay so I installed the z32 ignitor retrofit. No luck. So that leaves me with the CAS and MAFS. While doing some more diagnosing found that car will sometimes pop start. Also seems like as the weather has gotten warmer in the past week or so the problem has gotten worse. Seems to die sooner after first starting it and instead of takeing 10-15minto restart its now 30min+. Actually waited an hour the other day and got nothing. So once again any help is very much appreciated

You ever get this sorted out? Im having the same issue ever since I switched to a reflashed ecu and z32 maf. Did you ever try changing your o2 sensor?

[smellslikerubber]

You ever get this sorted out? Im having the same issue ever since I switched to a reflashed ecu and z32 maf. Did you ever try changing your o2 sensor?

Nope still working on it. I messed with the MAF over the weekdend and I dont think thats the problem. When car is working probably I unplug MAF and try starting it. It starts n runs but quickly sputters an stalls out. When the car dies after warming and wont restart i unplugged the MAF and nothing changed. wouldnt even start up for the short time as before. So I think I can rule that out. Im leaning more towards ECU :( the guy that I bought the car from gave me an extra one. Im gonna hook it up and see what happens

havent changed the o2. But its worth a try.

[Jesuus_Maxson]

Check your knock sensor an o2 an maf .. that was my problem

Sent from my PG86100 using Tapatalk

[smellslikerubber]

im almost positive that my MAF is good. im gonna get an 02 sensor in the next few days just to try it.

knock sensor? what is that and where is it located
(im a huge noob to all of this :-/ )

also could anyone provide information how how to test CAS? ive done some searching to find it, but have not come up with any good quality instructions on how to do so.

also last night i tried plugging in the extra ECU i have. car wouldn't ever start. just cranked. im very tempted to buy another ECU and plug it in because everyday im leaning closer and closer to my problem being related to the ECU. any suggestions on doing this?

[Jesuus_Maxson]

Well on the ka mine is under the intake bro.. look it up an see if its on the sr im pretty sure yu have one

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[g14novak]

I had a similar issue 2 times. First time was from bad MAFS wiring. Second was from my fuel pump starting to crap out.

Are you running a fuel pressure regulator? If so, let the car idle for a couple minutes and see if it starts to lose fuel pressure.

[Nissanrb25240sx]

im almost positive that my MAF is good. im gonna get an 02 sensor in the next few days just to try it.

knock sensor? what is that and where is it located
(im a huge noob to all of this :-/ )

also could anyone provide information how how to test CAS? ive done some searching to find it, but have not come up with any good quality instructions on how to do so.

also last night i tried plugging in the extra ECU i have. car wouldn't ever start. just cranked. im very tempted to buy another ECU and plug it in because everyday im leaning closer and closer to my problem being related to the ECU. any suggestions on doing this?

Knock Sensors are underneath the intake manifold, one towards back of the engine and one more center, that's how it is on my rb25. Should be the same

[stilettoman]

I installed an RB20DET in my 84 RX-7 about two years ago. After a few weeks, it began to have some strange behavior, similar to what is described here, but not exactly the same. In my case, the engine will shut off, just like turning off the key, but comes back after two or three seconds. This would happen before I get out of my driveway, still cold, or it may not happen until I drive for an hour - definitely not temperature related. A few times it will just quit, but if I switch the key off and back on it resumes normal running. Occasionally I will drive for miles, run errands and it runs perfectly. I get about 28 MPG in all around driving, over 30 highway.
I have swapped in four different throttle position sensors, three cam position sensors, one MAF, two ignition modules, and one ECU. None of these have made any difference. Most of the time it runs perfectly. The O2 sensor or the temp sensor could cause rich or lean running, but should not shut off the computer. When mine cuts out, it does not stumble, comes back on smoothly, just like I turned off the key and back on. This tells me that both the ignition and the fuel are being shut off. The only code I have ever gotten is TPS.
I suspect there is a bad connection somewhere in the wiring or possibly internal to one of the connectors, and an intermittent connection is causing loss of some signal which confuses the ECU.
Details of my swap are given here:
http://www.rx7club.com/nw-rx-7-forum-33/next-project-982785/

[smellslikerubber]

No not running a fuel pressure regulator.

I plan to rewire me MAFS Because it looks like monkey did it, which tells me that half the car is probably wired the same.

stilettoman: that makes me nervous to hear! I really want to find this problem. I dont want to take the car to the track becuse I dont want it to die in the middle of a run and leave me stranded. I guess im judt gonna have to start checking all the wiring and just keep swapping parts as you did till I can hopefully fins the issue.

ran a diagnostic procedure on my ECU. Got code 55, everything ok.

[smellslikerubber]

Also my IACV is not plugged In. When it is the car wants to idle extremly high. could that be the cause of the problem

[OutToWinPAHC]

no fpr? umm start there

[stilettoman]

I have talked with several experienced JDM tuners, and they all say that the ECUs rarely do anything strange - they work until they fail, and then just quit working. I think the characteristic of shutting down when hot is pretty typical of electronic ignition modules. The first thing I would try is a different ignition module, if you have not done that.

I only got code 55 also until someone told me to do the ECU diagnostic check before turning off the key when it acts strangely. I think the later OBD2 units do a better job of storing the faults.

I thought I had a real orphan motor, but my Nissan buddy kept looking on Craigslist here in the Seattle area, and within about two months I collected all the parts listed in my previous post plus what appears to be a really nice complete RB20 turbo, for a grand total of $250. Not a bad investment, especially now that I have two RB20s.

Didn't mention it before, but I like this motor so much I bought another R32 front clip with a RB20DET and only 35,000 miles. We have grafted this entire front clip onto the firewall of a 1948 Studebaker Starlight coupe, along with a complete Skyline R33 rear suspension -----pretty sure this will be the only one. I know this is not Zilvia related, but thought it might be of interest to Nissan fans. Hope to have it running this summer.

[MarkyMark]

Bad fuel pump? Try running straight wire to the pump from your battery with a switch and fuse and a new pump, most shops have in stock 255s. Id try that.

also you mentioned that ur running a z32 ecu? Bit confused on that part. Id try a known good fuel pump

[smellslikerubber]

i believe the previous owner put a new walboro fuel pump in it. not 100% thought..i have the parts list at home. but ill still give it a try

i was wrong about the z32 ecu. its an RB20 ECU.

OuttowinPHAC: are you thinking that since i dont have a fuel pressure regulator that its loosing pressure and causing the car to die?

stilettoman:ill try running the dianstic check on the ecu once it dies...yea i love the car and the motor! just wish it would stay running!!

over the weekend i ran the car till it died. i then got out and unplugged the o2 sensor. jumped back in it and it fired up but only ran for maybe 3min. i then fucked around with the MAFS sensor and o2 sensor and after about 20min the car started and wouldnt die after that. i ran it in my drive way for about a half hour then took it for a drive and ran strong the entire time.

i dont see though how the o2 sensor could cause the car to die the way it does. bad o2 sensor usually just cause the car to run like shit correct?

[MarkyMark]

Pull out fuel pump. Check hose clamps and stuff on it.mine had a bad rubber hose that was causing fuel to not pump up to rail but just back into tank

[stilettoman]

We had a car that had been sitting and would not run, found a collapsed fuel hose that was plugged. I can't see that being temperature related. But this car runs, then suddenly dies. I can see two possibilities related to fuel:

1. An intermittent connection in the power to the fuel pump, anywhere from the ignition switch to the pump.

2. Some debris floating around in the fuel tank, occasionally blocking the inlet. We had that problem once on a motorcycle. But that would almost certainly cause the engine to stumble momentarily, then die.

[smellslikerubber]

okay im going to check all of these things over the weekend. and ill report back

although i feel like if it is a fuel issue it would sputter out and die. not just turn off like it does.

[smellslikerubber]

what are you guys opinions on it being a CAS? alot of my symptoms point to that but im also not sure and it would almost be just a guess and try if i were to replace it.