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See my previous posts in this discussion. After it warms up and I shift into neutral and come to a stop rpms drop below idle. Also, hesitation. ISC passed multimeter tests. Asked above if both brown and black isc were metal as I have a plastic black one installed new 5000 miles ago and was told that the heat can destroy them quicker.
Did you do the IAC test (resistance) after the car has been running a while?
Heat does strange things to bad electronics...

Bob.
 

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did you also have hesitation during acceleration that was solved by this? or anything noticeable in the drive?

I haven't had time to work on the car/test anything yet, hoping within the next week here I'll make some time to at least try the TPS sensor swap.
My car didn't have any issues with a bad TPS sensor, it was out of spec, and caused a CEL. However, I had a friend with a 94 RT/TT that ran terrible with a bad TPS sensor. In order for him to drive home safely, I gave him my broken TPS sensor that triggered CEL, and it was a huge improvement over his.
 

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Discussion Starter · #103 ·
My car didn't have any issues with a bad TPS sensor, it was out of spec, and caused a CEL. However, I had a friend with a 94 RT/TT that ran terrible with a bad TPS sensor. In order for him to drive home safely, I gave him my broken TPS sensor that triggered CEL, and it was a huge improvement over his.
hm while strange, that is definitely encouraging to hear for mine.. lol thanks!
 

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1991 VR4
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See my previous posts in this discussion. After it warms up and I shift into neutral and come to a stop rpms drop below idle. Also, hesitation. ISC passed multimeter tests. Asked above if both brown and black isc were metal as I have a plastic black one installed new 5000 miles ago and was told that the heat can destroy them quicker.
I just skimmed through this log. Not much i could infer really... Strangely, when the idle dips, the AFR goes either lean OR rich and not consistently one way or the other... Also, when the idle dips sometimes it looks like the NBO2s and the WBO2 are reading opposite, assuming fp/rp are the NBs and wbscaled is the WB.
 

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ThinkFastLookAliveDieHard
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Ok, so I got crafty and turned off STFT in chrome so it runs in open loop all the time. When it idles it doesn't want to stall, but it sounds like idle surge and goes up and down between 650 and 812 (Idle is set at 700. Thoughts? Does this rule out exhaust leak?
 

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Have you traced wiring? There very well could be a broken wire somewhere in the harness. A real pain in the ass but once you eliminate the possible causes, what remains, however impossible must be the cause.

jrhorne knows a lot about open and closed loop. What systems are used in closed loop and what isn't? What ever is left should be the cause.

I had a friend right after high school, a vietnam vet. He was a big Mustang guy. Changed out the cam in his 66 302. Nice lift and duration. The car ran like absolute shit afterwards. I mean come on, we were changing cams like underwear back then. Takes a couple hours, tops. Backfires, bucking, stalling. Would sit there and idle just fine and as soon as you touched the gas, it would die. Poor Mike actually couldn't eat or sleep he was so upset, "Dammit, I spent 2 years shooting people in a jungle and a stupid car is worse!"

He went through everything, plug order, distributor off a tooth, ignition timing, changed out the distributor sensors, changed the fuel pump. Guy worked on it for a week trying to figure it out.

Well, I just so happened to be doing a lot of work on my car at the time related to vacuum issues. A vacuum gauge can diagnose just about anything if you know how to read them. So I throw one on his Mustang.

"Mike, you've got a vacuum leak"

Turned out to be loose nuts on the carb he forgot to tighten up. Ran fine, we went out, got in a race, he missed 3rd. Again.

Anyways, the moral is assume the lotus posiition, grab a beer and hook up a vacuum gauge.
 

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Ok, so I got crafty and turned off STFT in chrome so it runs in open loop all the time. When it idles it doesn't want to stall, but it sounds like idle surge and goes up and down between 650 and 812 (Idle is set at 700. Thoughts? Does this rule out exhaust leak?
Capture a short log when the issue occurs. Idle surge is most often a vacuum leak. I assume you have pressure tested? What's your idle AFR while in open loop? Is the AFR 'surging' as well while in open loop?

Also if you are truly in open loop, unplugging both NBO2s should do nothing, so i would confirm that is the case.
 

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ThinkFastLookAliveDieHard
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Just FYI I resolved this a couple weeks ago. I replaced my stock airbox with an FIPK and swapped my stock 27 year old BOV with an EVO 9 one. So far so good.
 

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Just FYI I resolved this a couple weeks ago. I replaced my stock airbox with an FIPK and swapped my stock 27 year old BOV with an EVO 9 one. So far so good.
Yeah, that open airflow and new BOV made my car nice and happy too. Love the psssssh sound.
 

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Discussion Starter · #112 ·
Just FYI I resolved this a couple weeks ago. I replaced my stock airbox with an FIPK and swapped my stock 27 year old BOV with an EVO 9 one. So far so good.
that's awesome, happy for ya. I'm just starting to get back at mine again. I have a new throttle position sensor to test, and going to redo a pressure test since I haven't done one for quite awhile and have removed/replaced the plenum doing plugs/wires so I guess I should start back with the basics. Injector flow test/cleaning I think is my next plan though if needed...
I replaced my airbox with a filter last season, sounds nice but I wasn't expecting that to fix anything. Didn't think about the BOV though...For yours how did you know the stock one was faulty? or just replaced and had good results?
 

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ThinkFastLookAliveDieHard
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that's awesome, happy for ya. I'm just starting to get back at mine again. I have a new throttle position sensor to test, and going to redo a pressure test since I haven't done one for quite awhile and have removed/replaced the plenum doing plugs/wires so I guess I should start back with the basics. Injector flow test/cleaning I think is my next plan though if needed...
I replaced my airbox with a filter last season, sounds nice but I wasn't expecting that to fix anything. Didn't think about the BOV though...For yours how did you know the stock one was faulty? or just replaced and had good results?
I kept trying to find a solution all over the internet and finally read somewhere that the symptoms where consistent with an open BOV when using stock MAF. Recirc. BOV must be leaking I figured. Did FIPK just because stock airbox had no give (I have a Dejon Y pipe which has different dimensions than a stock y pipe and messes with the bubble location) and figured maybe that was causing a small leak also? I had fuel, I had spark, fuel trims were within 5%, I didn't have an exhaust leak and my ECU is Chrome (No cap leaks).

I drove it Sunday after adjusting fuel trims (MAF VE in Chrome) for the FIPK and with HKS EVC IV at 1 bar (14.7 psi), it's a blast.
 

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Discussion Starter · #114 ·
I kept trying to find a solution all over the internet and finally read somewhere that the symptoms where consistent with an open BOV when using stock MAF. Recirc. BOV must be leaking I figured. Did FIPK just because stock airbox had no give (I have a Dejon Y pipe which has different dimensions than a stock y pipe and messes with the bubble location) and figured maybe that was causing a small leak also? I had fuel, I had spark, fuel trims were within 5%, I didn't have an exhaust leak and my ECU is Chrome (No cap leaks).

I drove it Sunday after adjusting fuel trims (MAF VE in Chrome) for the FIPK and with HKS EVC IV at 1 bar (14.7 psi), it's a blast.
That is awesome, finally nice to see someone's issues resolved!! I'll definitely pressure test mine again (hopefully on the weekend here), and look into replacing my BOV too (at least it's another good option anyway. I also have a cone filter and Chrome ECU.. didn't really think about having to adjust fuel trims though... Is this required considering I'm still using the stock MAF and injectors etc...?
I've been planning on getting BlackStealth's LEDBC (to go with the rest of the stuff I have from him), but decided not to blow more money until I've at least got the car running smoothly. Boost control, and freeing up the exhaust - test pipe/pre cat gutting and possibly downpipe are hopefully soon to follow:)I was researching the BOV options a bit already since your post... where did you pick up you evo9mr if you don't mind me asking?
 

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Discussion Starter · #115 ·
Just read into the MAF EV from here: http://chromedecu.org/?page_id=879 Interesting stuff. I'm new to any of this though so only trying to understand the basics, and still curious to hear your thoughts/ personal methods used on your tune. I also haven't even gotten my wideband sensor yet, which of course goes along with the LEDBC plan.. but yea.
 

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ThinkFastLookAliveDieHard
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Yes, you want to do it to get fuel trims within +/-5% of 0. This means when the ECU switches to open loop, it will use the AFR map correctly (you won't run lean or rich). Fuel trims wander outside +/-5% of 0 when engines age, cats are removed, injectors get old, etc.
 

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Discussion Starter · #117 ·

Yes, you want to do it to get fuel trims within +/-5% of 0. This means when the ECU switches to open loop, it will use the AFR map correctly (you won't run lean or rich). Fuel trims wander outside +/-5% of 0 when engines age, cats are removed, injectors get old, etc.
hmmm ok I guess I should definitely start getting into this.. I don't have the flashtool yet so that'll be added to my list. I tested my TPS this weekend, again to make sure and it seems ok. Didn't drive around with the new one swapped in though to be extra sure though yet.
SO new order of to do list: Boost test again (check BOV?), Injectors flow/tested/cleaned, wideband (likely install into a testpipe), LEDBC, flashtool, tune fuel trims. I think that makes sense? Maybe I'll try swapping coilpacks too at some point.
 

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ThinkFastLookAliveDieHard
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What do you mean you don't have the flash tool? Do you have a conversation harness and a 98/99 ecu (Could be real or could be a clone) or a plug and play chrome ecu (A 93 ecu converted to flash ecu)?
 

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Discussion Starter · #119 ·
What do you mean you don't have the flash tool? Do you have a conversation harness and a 98/99 ecu (Could be real or could be a clone) or a plug and play chrome ecu (A 93 ecu converted to flash ecu)?
I have a new Chrome ECU. Just haven't picked up the tactrix device as tuning wasn't initially my priority (just wanted to replaced my ECU because that seemed to be a problem, though I realize I probably should have just gotten it at the same time).
Where did you find your new BOV if you don't mind me asking? I didn't get to redoing the pressure test last weekend, so plan to fit that in this weekend and will pay closer attention to the BOV area now too.
 

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ThinkFastLookAliveDieHard
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Its just an OEM EVO 9 or 10 BOV (Can't remember which; the vacuum port points down when installed). You can probably find a used one on Ebay or in the forums. With yours being a 5 speed, it should be plug and play. With my 6 speed, a couple black zip ties and a few tries got it out of the way of my shifter counterweight were necessary.
 
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