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studdering running rich black smoke out tailpipe

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91dsmeclipse

15+ Year Contributor
184
0
Mar 22, 2004
Siloam Springs, Arkansas
my car wont rev past 4,000 rpms in neutral and if i step on it a little bit it studders and spits black smoke out of the tail pipe the same as being in neutral i checked all sensors only 2 things i couldnot test is the maf and the fuel pressure regulator has any one had this problem before
 
^^ditto ;)

Is there anything significant that you did/noticed prior to this problem?
How did you check your sensors, with a datalogger/scantool?

Black smoke = rich AFR. Either your loosing metered air or it's gone into "safe" mode due to a failed sensor / MAS :dsm:
 
i tested everything with a digital voltmeter i pulled my plugs and they have carbon deposits on them all black the plugs are 4 months old, i dont have any boost leaks did a boost leak test a week ago and i had alot of leaks i fixed them all and still the same thing i even replaced my turbo becuz the compressor housing was leaking air.also i noticed that the stock boost gauge is totally of ill be at 0 boost on my aftermarket and the stock one wll be very close to 14 psi. well yesterday i was curious so i unpluged my mas and it reved right up it runs like shit with no mas but it reved all te way up do u think the mas is bad?
 
one thing i did kinda significant was put in a narrowband a/f gauge but that was a couple of weeks ago before the problem happened but just when this started happening it would only do it when the car was cold and once it fully warmed up it was fine but now it does it all the time
 
one thing i did kinda significant was put in a narrowband a/f gauge but that was a couple of weeks ago before the problem happened but just when this started happening it would only do it when the car was cold and once it fully warmed up it was fine but now it does it all the time



ps i used a multimeter not a voltmeter i went by the haynes manual what the values where
 
Try disconnecting disconnecting the (-) battery cable and then unplugging the MAS and clean the terminals (coat with a bit of dielectric tune up grease).

Reconnect the MAS and (-) battery cable after ~15mins (to ensure the ECU is reset) and see if still a problem.

If this doesn't help may want to pick up a datalogger (~$30 on eBay) to read any CELs the ECU is throwing. It also may even be the ECU itself, which you can check by removing the cover and looking for acid damage/shorts on the circuit board, or if smells like rotten eggs/sulfur :dsm:
 
so it might not be the mas even tho i disconnected it and everything is fine i dont have any codes on my computer i checked already with my analog voltmeter mly computer is fine it was one of the first things i checked and i already took my mas apart and cleaned all the contacts really good i didt disconnect my battery tho so i will trythat today
 
i just disconnected the battery for 15 min and reconnected it no luck same thing

i was wondering could it be my fuel pressure regulator or no?
 
91dsmeclipse said:
i was wondering could it be my fuel pressure regulator or no?
Anything is possible with DSMs, though would not expect your car to behave that way in neutral (no load/boost) if the FPR went bad. On that subject though, there is an FPR module on the firewall that takes a vac/boost line from the intake and then routes to the FPR. Try "cutting" this module out of the equation by routing a vac line directly from the FPR to the intake port. FYI.. all this module does is cut the vac/boost signal to the FPR on startup to boost fuel pressure for easier starts. With an aftermarket pump it is unnecessary to have and only creates a possible boost leak.

Also I have to ask, is your BOV outlet reouted back to your intake?

Couple other thoughts:
- More intake leaks (pressure test compressor inlet to min 16psi)
- MAS is bad (may want to source a friends locally to test)
- Compression test
- Plug wires bad (make sure boots are not cracked/arcing)
- Fuel filter bad (replace if age unknown)
- CAS bad/installed 180deg out
- EGR valve bad (blockoff plates can be made free)
- Base timing/cam timing (a separated crank pulley can affect both).

Hope this helps :dsm:
 
Where are those boost and compression tests?

What kind of spark plugs are you using?
Any CEL? What are they?
How's the O2 sensor?
How are the caps in the ECU (I doubt this is the problem, but it's a good thing to check).
I want to see the results of the boost leak test and BOV routing before anything else.
20 psi for a minimum of 30 seconds. Use soapy water to pin point leaks.
 
i did a boost leak test a week ago when this first happened i had a lot of leaks intercooler pipes,throttle body elbow compressor housing(which i bought a new turbo) their are no boost leaks its holds at 15 psi . i changed the fuel filter still no difference i checked the return line from the fuel pressure regulator for blockage no blockage,i checked the tps,cas,ecu, i checked the egr valve i checked that selenoid on the firewall that controls the fuel pressure regulator according to the haynes manuel by applying 12v to it to see you it holds vac and it does. the o2 sensor is good i checked it.there are no cel's i am recirculating the stock bov. i am running ngk plugs and wires (oem) the only thing that i could possibly think is the mass airflow sensor but im confused wouldt my car throw a check engine light?

its also pretty weird my stock boost gauge in the dash is really off by alot ill be at 0 psi and my aftermarket and the stock boost would read around 14 psi(all the way up) and as soon as i start boostin to like 5 psi in 2nd gear the stock boost gauge will go all the way up and it will start studdering but when im in 5th gear ill be at full boost like 11 psi and it will start studdering at 4000 rpm

i dont have anyone around here with turbo 1g i know that i can barrow a mas to use ill have to go buy one
 
Re-do your boost leak test at 20 psi. Make sure it holds it for at least 30 seconds.
What kind of plugs, NGK's don't tell me enough. What are they gapped to?
Have you checked the ECU for leaky caps?
 
91dsmeclipse said:
the only thing that i could possibly think is the mass airflow sensor but im confused wouldt my car throw a check engine light?

its also pretty weird my stock boost gauge in the dash is really off by alot ill be at 0 psi and my aftermarket and the stock boost would read around 14 psi(all the way up) and as soon as i start boostin to like 5 psi in 2nd gear the stock boost gauge will go all the way up and it will start studdering but when im in 5th gear ill be at full boost like 11 psi and it will start studdering at 4000 rpm

i dont have anyone around here with turbo 1g i know that i can barrow a mas to use ill have to go buy one
Another thought, are there any obstructions either pre-MAS or post MAS? I had a similar problem once when the rubber adaptor "collar" on the compressor inlet stuck inside my intake pipe. When I reinstalled the intake the collar twised and partially blocked the compressor inlet.

An obstruction pre-MAS could also have the same effect :dsm:
 
ill do a boost leak at 20 psi when i get a chance im using the v-groove ngk i dont know the number but i do know they are for a stock setup i have them gaped at .028 i did the spark plugs and wires 3 months ago and i did take them out to see if thats the problem and they are black(carbon = rich mixture) i took the intake out a couple of times and the rubber insert is always on the compressor housing obstructing nothing.
 
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