The Top DSM Community on the Web

For 1990-1999 Mitsubishi Eclipse, Eagle Talon, Plymouth Laser, and Galant VR-4 Owners. Log in to remove most ads.

Please Support Fuel Injector Clinic
Please Support Morrison Fabrication

Misfire, dropping idle, sputtering, intermittent loss of power, jerking, NO CEL

This site may earn a commission from merchant
affiliate links, including eBay, Amazon, and others.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Crashdot

Probationary Member
24
1
Jul 21, 2010
Honolulu, Hawaii
Hi,

I've been dealing with an annoying problem for months, and the latest condition does not throw a CEL so we're not sure what to do. I've read many threads with these symptoms, checked the service manual, and so on, but can't really afford to keep replacing things until the problem is fixed, so I want to ask if anyone knows what could cause these symptoms without triggering the check engine light.

Car: 1999 Mitsubishi Eclipse GSX ~85,000
Mods: BOV, Profec B spec II boost controller at 10psi, boost guage, hard piping, KN open air intake, front and rear strut bars

Here is the history:

01. Started with very brief losses of power off the line or while accelerating moderately ~3000rpm, really just felt like a brief bump or bogging for half a second
02. Replaced Plugs/wires
03. Added Seafoam
04. CEL triggerd immediately after seafoam indicating O2 sensor in closed loop mode
05. Used tank of treated gas, refueled and reset code
06. CELs O2 Sensor, misfire, and shift position (?), reset and just O2 sensor repeated
07. Replaced O2 sensor
08. A day or two later the car started to run with no malfunctions for a few weeks
09. Suddenly started to intermittently misfire and jerk under any acceleration such as trying to drive in a parking lot
10. CEL Misfire detected
11. Managed to get the car to a garage
12. Replaced coil packs
13. Reset CEL
14. Currently, there is intermittent drastic loss of power / jerking under acceleration and Idle dropping and misfiring every minute or so. Car is basically undriveable
16. There is No CEL being triggered

Things that have been done already:
01. Full diagnostic (no result)
02. Boost leak testing
03. Changed plugs and wires
04. Fuel injector cleaner
05. Replaced coil packs
06. Replaced faulty O2 sensor

Next steps:
01. Change fuel filter (was changed not long ago though)
02. Check fuel control valve
03. Change fuel injectors
04. Fuel pump

Basically, what I want to know is what the most likely causes could be, so I know what to replace first, avoiding items that would trigger a CEL. I don't know if there is a way to test some of the remaining potential causes, such as fuel injectors and fuel flow.

Thanks for your consideration
 
The shop insists the gap is fine (on original and replacement plugs). The service manual says these are the possibilities with the things that have been replaced indicated by *::

Ignition coil *
Spark plug *
Ignition circuit
Injector
Upstream H02S *
Compression pressure
Timing belt
Crankshaft position sensor
Air intake
Fuel pressure regulator

also

Spark plugs or wires failed *
Ignition coil failed *
Crankshaft position sensor failed
Worn piston rings
Worn valves
Head gasket failed
Cracked head
Fuel lines and filter failed
Fuel pressure regulator failed
Injectors failed
Wiring harness and connectors failed
Engine coolant temperature sensor fail
Timing belt tooth broken
EGR valve failed

Air intake is a KN open intake and was cleaned recently, so that seems unlikely. Timing belt was changed already. That's a lot of stuff to test/replace

I think they are going to try injectors next, although there are none available locally.
 
YOU need to check the gap yourself. YOU. Not a shop. Unless you absolutely trust that shop then you do the work!

It's simple. First ensure you have the right plugs. I don't remember them off the top of my head but it's been beaten to death.

If you're upgraded like me, I gap to .20 or else I get blow out. Check to ensure yours aren't more than .26 or so.

Verify that before we continue. That can easily be the problem.

Another thing I see is that you just recently cleaned the filter. That filter oil can jack with the MAF and it's readings. Ensure the MAF is clean.
 
After taking my car to various places over the years because it was running poorly, this was the shop I took it to where within about five minutes the mechanic turned to me and said "the problem is that your plugs aren't gapped correctly". All of the other places just took plugs out of the box, pre-gapped from the factory, and installed them which led to problems since I understand turbos need a smaller gap. They were also gapped inconsistently.

This is a performance/racing shop that specializes in Mitsubishi Eclipse/Evo, Subaru WRX, and also does some exotics such as Ferrari, Lotus, and Dodge Viper. They put a supercharger in my brother's Lotus Elise, for example, so I'm not worried about their competence.

The gaps for these plugs are 0.025, as I ran with this model and gap for a year with no issues, but replaced them once the misfiring started just to rule that out. After just a month, the mechanic tells me that some of the new plugs are black and covered with ash/soot, so I would be interested to know if there is something that would cause that other than defective plugs.

I'll ask the shop to check the MAF. Thanks!
 
... the mechanic tells me that some of the new plugs are black and covered with ash/soot, so I would be interested to know if there is something that would cause that other than defective plugs.

Yep. The same thing that is causing the car to run rough and lose power; you are running rich and fouling the plugs.

The most common culprit is a boost leak. Do a boost leak test (BLT) on it yourself, following the guidelines outlined here: http://www.dsmtuners.com/forums/art...-boost-leak-test-how-boostpro-net-tester.html.

Note the additional posts at the bottom of the page, and you don't have to use that particular tester. You can make your own with parts from home depot for a couple of $. Also remember to keep testing/fixing/testing until you can hold 5 psi more than your planned max boost for at least 30 seconds or more.

BTW - The plugs you should be running are NGK BPR6ES, gapped at .028" or a little less, depending on how much boost you run and the type of fuel.
 
They did a boost leak test a few weeks ago and found no problems. The plug manufacturer concurs with your recommendation, indicating that the gap may need to be reduced from what I just mentioned. The shop is putting in a set of those NGK plugs today.

Thanks
 
They did a boost leak test a few weeks ago and found no problems.

Yeah, you mentioned that. So here is what I think you should do:

Do a boost leak test (BLT) on it yourself, following the guidelines outlined here: http://www.dsmtuners.com/forums/art...-boost-leak-test-how-boostpro-net-tester.html.

;)

*****

Since you have a PocketLogger, post up a log and maybe we can get an idea of what is going on with the ECU.

EDIT:

Also, go through this checklist: http://www.dsmtuners.com/forums/ecm...efore-you-ask-ecmlink-dsmlink-log-advice.html

Other than the ECMLink specific points, every other step on it should be followed while troubleshooting any issue such as yours.
 
I don't have the car at the moment since it is still at the garage. I would like to know what to look for in the pocketlogger since I did some captures during malfunctions. I'm not sure how to get them out of the palm at the moment. Finally, would failing seals on the turbo cause these symptoms?

The problem seems to have been a defective spark plug, since replacing them a second time has resulted in the car running properly. Guess I'll see if the problem re-occurs in a few weeks. Thanks!
 
Last edited:
Save yourself some issue and make sure you get those plugs mentioned above. Again, if running higher boost like myself (22psi daily) then gap them smaller around .20 or so.
 
Finally, the wiring harness to the boost controller solonoid had an intermittent wire due to a break inside the shielding. To test this, it was necessary to attach a continuity meter to both sides of each contact on the wiring harness between the cabin and under the hood. One of the wires was open/bad. When the cable was moved around, the connection would come and go.

This explains the original symptom, brief/intermittant loss of power while acceerating and under boost, as the solonoid would randomly open and close independently of what the boost controller was telling it to do. This was due to vibration and g-forces, possibly because one of the times the battery was changed, someone put it on top of a section of the boost controller wiring harness. As the battery might shift slightly, it was opening or closing the intermittent wire.

Now I know that before doing 15 mechanical tests, I should check the wiring.

It is unknown if this problem caused the other failures, although I still believe imprecise gapping was a problem.

Cheers
 
So I couldn't reply to another thread because of my lack of posts. Most likely someone will tell me something about posting but I tried looking couldn't find my exact answer I have a 97 eclipse 2.0 420a non turbo once again non turbo and I was wondering what is the correct and 100% accurate gap for ngk's the book says .33-.38 but that's for RNYC champion and I don't run those so what is the actual gap thanks guys I appreciate it
 
Support Vendors who Support the DSM Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Innovation Products Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications MyMitsubishiStore.com RixRacing RockAuto RTM Racing STM Tuned

Latest posts

Build Thread Updates

Vendor Updates

Latest Classifieds

Back
Top