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 RTM Racing
Please Support STM Tuned

1G car sputters, hitting fuel cut, backfires when sputtering.

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.

xander123

Probationary Member
22
3
May 29, 2021
Edmonton, AB_Canada
I just got my car running again, old spark plug wires were 8mm but they were worn so I replaced them with a spare set. Before this the car ran as normal, but the new set is only 7mm, and those and spark plugs are the only things I've changed.

Yesterday at WOT, car hit a super aggressive fuel cut in first gear, so I pulled over to make sure all sensors and everything were connected. I tried again to see if I was overboosting but I was only hitting about 10psi, when normally I’m at about 12.5. The car also sputtered, seemed like it was struggling to burn the fuel maybe? When it stopped sputtering it backfired about 4 times.

So I’m thinking maybe my spark plugs or the wires are causing something? My exhaust is also leaky so I was wondering if my o2 sensor would be reading wrong and then causing the ECU to do something?

1990 tsi
gm maf
550 injectors
small 16g
 
Last edited by a moderator:
Check plug gap and make sure wires are in the correct order. Ecu ignores O2 sensor feedback in open loop.

What plugs did you get?
I got ngk iridiums, the old owner had copper plugs gapped at .023. I have mine gapped at .025, because the car ran on .028 fine.

The wire order should be right, unless the order is different from 2g to 1g. I got my spare wires out of my 2g and just put all the wires in the same order.

I've been told that iridiums arent too good for DSMs and that they like copper ones more, so I have a spare set of coppers that I’m going to install today but I’m worried to run the car as it is right now
 
Last edited by a moderator:
I have had issues with plug wires "cross talking" and also shorting out to the underside of the hood. I found that issue accidentally one day when I left a shop rag on the top of the valve cover and the issue went away. A NEW set of plug wires fixed it.
Start it at night and mist some water over the wires. If you see arcing then replace the wires.
 
If you hit fuel cut, you KNOW it. Fuel cut is not a sputtering. It’s a big BANG!! Also, 10psi on a s16g is more airflow than a 14b at 10psi. Are you running a MAFT or DSMLINK with that GM MAF?

Also, it’s easier to hit fuel cut when the temps get colder. What are your settings on the MAFT?
 
If he has ECMLink, he can set the fuel cut but only up to a certain point. I didn't know about that feature and just stumbled across it one day. Just FYI
 
This is nothing subtle like spark plug gap or a difference between iridium and copper. It's wrong wire order, one or more pushed back into the sleeve and not really connected, bad wire insulation -- the 'mist' trick is a good one and should find that -- or something else that just showed up like a jumped tooth on the timing belt.

Backfires are fuel burning in the exhaust system because it didn't burn in the cylinder. Like -- one or more cylinders are not firing at least some of the time.

For what it's worth these cars came with plastic supports/separators for the spark wires. These not only keep the wires apart and in the right order, they prevent them resting on metal -- touching metal is asking for trouble as the wires age. I'm guessing that the plastic separators crumble after a decade or two and are then thrown away but they are a good thing if you can find them.

Edit: I spent quite a while last month chasing down part numbers for those separators so I could order them:

MD121633 Clamp spark plug wires (White nylon, 3 notches, use 3)
MD300098 Clamp spark plug wires (metal bracket/black nylon, guides 2 wires, use 1)
MD190974 Clamp spark plug wires (Black nylon, guides 4 wires out of valve cover, use 1)

So that's a total of five guides of three types.

You must be logged in to view this image or video.


'amayama.com' claims to be able to supply them from overseas. I didn't have any luck in U.S.

Should work on any 4g63 engine. Cost with shipping is about $30 from amayama.
 
Last edited by a moderator:
I just got my car running again, old spark plug wires were 8mm but they were worn so I replaced them with a spare set. Before this the car ran as normal, but the new set is only 7mm, and those and spark plugs are the only things I've changed.

NGK plug wires for the 1g are 7mm blue silicone, and they've been working fine on my car for a long time. They are good quality and have well made boots over the plugs. I don't even have a wire holder like what waltah mentioned but I did wrap the wires with self-fusing silicone tape in one small area where they contact metal.
For plugs, Lucas English told me to use BPR7ES NGK plugs gapped at .020" but then when I looked later at what they had actually put in the car, they were NGK BPR7EIX Iridium IX spark plugs (stock number 4055) and they've been fine. Those particular iridiums don't have anything exotic for the side electrode. It is just a single side electrode made from a fairly conventional alloy and you can adjust it for gap as long as you don't push on the center electrode at all with your tool. It is only the center electrode that is exotic.

I guess you aren't logging with anything? If you were it would be good to know what your MAF Hz is at the point where this problem happens.
 
If you hit fuel cut, you KNOW it. Fuel cut is not a sputtering. It’s a big BANG!! Also, 10psi on a s16g is more airflow than a 14b at 10psi. Are you running a MAFT or DSMLINK with that GM MAF?

Also, it’s easier to hit fuel cut when the temps get colder. What are your settings on the MAFT?
it was definitely fuel cut, sorry I meant to say I experienced BOTH fuel cut and sputtering, my fuel cut hit very hard and it felt as if I had slammed on the brakes. I’m running a gm maf right now, I’m not too sure what it’s tuned on. I never touched it, but previous owner tuned it and said it ran perfect. my car actually ran better in -30° C than it is now at -5°

NGK plug wires for the 1g are 7mm blue silicone, and they've been working fine on my car for a long time. They are good quality and have well made boots over the plugs. I don't even have a wire holder like what waltah mentioned but I did wrap the wires with self-fusing silicone tape in one small area where they contact metal.
For plugs, Lucas English told me to use BPR7ES NGK plugs gapped at .020" but then when I looked later at what they had actually put in the car, they were NGK BPR7EIX Iridium IX spark plugs (stock number 4055) and they've been fine. Those particular iridiums don't have anything exotic for the side electrode. It is just a single side electrode made from a fairly conventional alloy and you can adjust it for gap as long as you don't push on the center electrode at all with your tool. It is only the center electrode that is exotic.

I guess you aren't logging with anything? If you were it would be good to know what your MAF Hz is at the point where this problem happens.
yeah those are the wires I’m using right now, but the boot on it is an angle and so none of the wires are sitting very nicely. the old 8mm wires came straight out. and not sure what you mean by logging, but my afr is really good 90% of the time - 10.8 at WOT and 13.5 at cruising. my boost seems fine most of the time, and oil pressure and coolant are perfect. thinking of taking all the intake and intercooler piping off and checking those? could my problems come from a major boost leak?
 
If he has ECMLink, he can set the fuel cut but only up to a certain point. I didn't know about that feature and just stumbled across it one day. Just FYI
Marty, what do you mean fuel cut can only be set up to a certain point?

it was definitely fuel cut, sorry I meant to say I experienced BOTH fuel cut and sputtering, my fuel cut hit very hard and it felt as if I had slammed on the brakes. I’m running a gm maf right now, I’m not too sure what it’s tuned on. I never touched it, but previous owner tuned it and said it ran perfect. my car actually ran better in -30° C than it is now at -5°
You need to take the cover off the translator box and see what the settings are. Then compare those settings to what the instructions manual recommend, which you should be able to find online somewhere
 
the boot on it is an angle and so none of the wires are sitting very nicely.

None of the wires are sitting very nicely? Well that sounds like something is damaged, or you have the wrong wires.
Here's what the NGK wires should look like and other info like part number and the length of each wire:

You must be logged in to view this image or video.
 
One of the members on here was reproducing the plug wire separators from 3d printing. I run the Iridium NGK plugs myself as a suggestion from John Shepard, I have been running them for several years now with no problems.
 
not sure what you mean by logging, but my afr is really good 90% of the time - 10.8 at WOT and 13.5 at cruising.

Logging, I'll show you a screen shot from the logger that I was using in 2008, when my car was more stock than yours is now. This type of log is nice to look at because everything is practically self explanatory. Each engine parameter is labeled for what it is and scaled properly, and shown separately instead of all thrown together like a pile of noodles.
I mentioned MAF Hz above. In this log MAF HZ is called MAS Frequency, and you can see that I was approaching 2000 Hz here at about 610.5 seconds where the cursor is. That's fuel cut territory.

So after this I switched to a 3 inch GM MAF. Still the 1g stock ECU will call a fuel cut at somewhere around 2000 hz. So I had to do more stuff. Which you can see in my old profile which was for my car up through 2015. With ECMLink there would be a different way to do this I think, like Marty mentioned above.

Anyway I don't know if this is your problem but this is why I asked if you could log MAF Hz. It's pretty well defined where fuel cut happens frequency wise.
The plug wires could be your problem if they don't fit right or are damaged. But seems to me that would cause bad running most of the time, or all the time, rather than something like a fuel cut event.

You must be logged in to view this image or video.
 
Last edited:
None of the wires are sitting very nicely? Well that sounds like something is damaged, or you have the wrong wires.
Here's what the NGK wires should look like and other info like part number and the length of each wire:

You must be logged in to view this image or video.
these are the wires I had before, except 8mm. the ones I have on the car are from a 2g, I think thats why they have a bend. I’m looking into getting new wires before running the car again
 
The NGK wires for the 2g are about 3 inches shorter than the wires for the 1g. So they might not lay right. I don't know I've never tried it. But if your coil pack is in the regular stock position, I'd want the 1g wires. Maybe that's the problem.
Here's what STM says about using 2g wires on a 1g: "These can be used with the 1G DSM/GVR4 if you've moved your coil pack."
 
The NGK wires for the 2g are about 3 inches shorter than the wires for the 1g. So they might not lay right. I don't know I've never tried it. But if your coil pack is in the regular stock position, I'd want the 1g wires. Maybe that's the problem.
Here's what STM says about using 2g wires on a 1g: "These can be used with the 1G DSM/GVR4 if you've moved your coil pack."
Backwards sir. 2g are longer. The coil pack sits farther back
 
Backwards sir. 2g are longer. The coil pack sits farther back

Ok, but that would mean JNZ, STM, Extreme PSI, and MAP all have it backwards.
On the MAP page for the NGK 1g wires (ME64) they say you can use them on the 95-99 Eclipse where they are 6 -7 inches longer than stock.
On the JNZ page for the NGK 2g wires (ME77) they say "Helpful hint: for 2G owners running a SMIM with a relocated coil pack, use 1G wires for the extra length".
 
Ok, but that would mean JNZ, STM, Extreme PSI, and MAP all have it backwards.
On the MAP page for the NGK 1g wires (ME64) they say you can use them on the 95-99 Eclipse where they are 6 -7 inches longer than stock.
On the JNZ page for the NGK 2g wires (ME77) they say "Helpful hint: for 2G owners running a SMIM with a relocated coil pack, use 1G wires for the extra length".
Well just shoot me. Chalk it up to one of my many senior moments.
You are correct. 2g is shorter. Thank you for the correction.
 
Get anywhere else with this? I am having a very similar issue. Running 2g ngk plug wires on my 1g. Idle and running is nicer with the iridium plugs.

I may try to gap them smaller I don't remember what my current gap is but it's super large on the iridium plugs. Swapping between some non iridium and back the iridium idles nicer. (they suggest the iridium plugs take less voltage to achieve better spark)

Below 5k rpm no issues at all, above cut out happens.

My issues could be
Coil pack
Plugs / wires
Fuel pressure regulation issue
Boost leak?

I don't have link on my 1g so this makes testing things more interesting /mostly part swapping.
 
Get anywhere else with this? I am having a very similar issue. Running 2g ngk plug wires on my 1g. Idle and running is nicer with the iridium plugs.

I may try to gap them smaller I don't remember what my current gap is but it's super large on the iridium plugs. Swapping between some non iridium and back the iridium idles nicer. (they suggest the iridium plugs take less voltage to achieve better spark)

Below 5k rpm no issues at all, above cut out happens.

My issues could be
Coil pack
Plugs / wires
Fuel pressure regulation issue
Boost leak?

I don't have link on my 1g so this makes testing things more interesting /mostly part swapping.

I ordered 1g wires online, hoping that it will fix something. I still may have a boost leak though.

I did find one problem but I doubt it’s yours, I had a really thick wire leading to my fuel pump and it shorted on something. Instead of the fuse blowing it just melted the fuseholder and started smoking. Fixing that solved my rough start and I think my fuel cut too.

I have a .025 gap on my iridiums and it seems to run fine with that. I definitely think the 2g wires shouldn’t be run, but I’m not an expert. I just dont like how they sit in the 1g.

I'll let you know if the proper wires help at all, but I think a large part of my problem was that melted fuse. I also don't have DSMLink or anything that will give me much detail on the car.

Could you be overboosting? Mine was weird cause it would hit fuel cut at a lower boost than i've been running
 
Last edited by a moderator:
Well just shoot me. Chalk it up to one of my many senior moments.
You are correct. 2g is shorter. Thank you for the correction.
Paul,

No shame in it, my friend--at least in my mind.

It's become more and more common where I get a question, say to myself, "Hmmm..I need to figure this out" then do some Google-Fu to find the answer in one of my posts from 15-20 years ago. I think I've forgotten about 50% of what I've learned over the last 25 years of working on this platform.

The body/motivation aspect is even worse. I *dread* having to swap a clutch in one of my cars at this point, but remember driving two hours after getting out of work, swapping a clutch in a garage that had no lift and limited tools, and getting back on the road home in an hour and 1/2.

We older guys need to start collecting info on modifying Rascals so that we're prepped for what's coming next.

You must be logged in to view this image or video.
 
You need to start stocking aftermarket parts for the "Rascals" Josh! ROFL
 
I ordered 1g wires online, hoping that it will fix something. I still may have a boost leak though, I did find one problem but I doubt it’s yours. I had a really thick wire leading to my fuel pump, and it shorted on something. instead of the fuse blowing it just melted the fuseholder and started smoking, solved my rough start, and I think my fuel cut too. I have a .025 gap on my iridiums, and it seems to run fine with that. I definitely think the 2g wires shouldn’t be run, but I’m not an expert. I just dont like how they sit in the 1g. ill let you know if the proper wires help at all, but I think a large part of my problem was that melted fuse. I also dont have dsmlink or anything that will give me much detail on the car. could you be overboosting? mine was weird cause itd hit fuel cut at a lower boost than ive been running

Well that sounds promising. I mean for solving what seems like a lack of fuel issue. If that wire and fuseholder were the cause of it, good deal. Must have been that the wiring could still handle small currents but then would conk or just have too much resistance for when current demand goes high like it does when fuel pressure goes high.
 
Last edited:
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