bad idle

[Can1991Ram]

My truck is starting to not idle. If I put it in neutral at a light and hold it at 1500 it will be fine. If I leave it in gear it misfires and then sputters as I take off. It has to Rev up to clean out.
It reminds me of my old drag car loading up and runs better after snapping the throttle to clean it out.

I have no idea how a fuel injected engine would do that. The idle sometimes cycle up snd down too.

It only seems to happen in closed loop.

Amy ideas?

[Merrill]

When was your last full tuneup?

[Can1991Ram]

its all new

[Version6]

sounds like bad spark, my 88 was doing similar and I just changed the plugs (today actually) the old ones were looking pretty old/fouled

[Merrill]

Did you do all of it or did you just replace only a few things?

[camoit]

Have you looked for vacuum leeks? The hoses are nearly 30 years old so they do come apart. Also check for stretched timing belt. If you have never changed it. Do it now before you get stranded along the road.

[Can1991Ram]

Wires. .cap ..rotor..new timing belt...plugs

I'm changing the fuel filter tonight. .

[Merrill]

The only other probable issue (other than fuel filter) is the TPS. If it's worn out, or out of adjustment, it will act like that. A fuel filter will definitely do what you are describing if it is clogged though.

[Can1991Ram]

Ok...I have checked the tps and it is within spec..I was thinking egr too but haven't checked it.

Now today it drove great...and I have done nothing to it

[Can1991Ram]

Well I swear the filter must have been original and some of the fuel that came out of the filter looked kinda brown at first.
The truck got pep now and actually pulls past 4000 now

[GoodApollo]

Look at the Idle air control valve (IAC) on the throttle body. this is most likely your problem if not part of it. The coils in the stepper motor go out and give you bad idle and eventual burn up your ECU, been there. Is the IAC brown or black?

fallow this video on how to test the IAC:
https://youtu.be/KibYz21IMA0
It is the same testing procedure for all Mitsubishis up until about 2000.

This is where you can buy a new quality IAC motor that is improved and reliable on the cheap:
http://www.ninjaperformance.com/mitsubishi-3000gtstealth-isciac-p-21601.html?osCsid=90120f1554d3ee7c998e12c33664589c

[GoodApollo]

Please let me know if this works for you.

[Can1991Ram]

I will check this out next!!!

[Can1991Ram]

It started misfiring in gear at stop.lights again today.

[Can1991Ram]

The idle is cycling up and down...I think your right..The idle control.
It's the black one.

[pennyman1]

it can also be the ECM - bad caps can cause this.

[Can1991Ram]

http://www.ebay.com/bhp/mitsubishi-lancer-idle-control-valve

Are they all the same?

I can't find the part number to cross over to another brand.

[Merrill]

They're not all the same.

The jumpy/bouncy idle is usually caused by the TPS not responding correctly, or the ECU not knowing when the throttle is closed.

[Can1991Ram]

I can't get an IAC in canada for this truck.

If I hop over the border to Autozone would anyone have a part number?

The O'rielly's website give me a throttle speed valve not the IAC when I go on their site.

I have found a few numbers but not sure. Any suggestions

[Can1991Ram]

I now see that the whole thing is a unit md614351....
It has 2 plugs were all the replacements I've found have only one and the plugs don't match at all.

I'm at a loss of what you could get at auto zone that could have replaced this....

[Fordubishi]

I found this for a 1900 Ram50 http://www.rockauto.com/catalog/moreinfo.php?pk=1002430&cc=1096411&jnid=600&jpid=6 its a 2 plug and you should be able to get it ordered from Canadian tire. I would order it from Rockauto as it will be 1/3rd the price even with exchange and shipping.

[Can1991Ram]

Holy crap...with exchange that's about $500 can.

[BradMph]

Wouldn't be better to take the ECM out and check it for burnt caps or bad solder points before you spend all that money and it isn't the problem. It sure could be the problem and they are also easy to pull out, but if it isn't and you spend that cash, you will be kicking yourself even harder when your wallet is empty. Perhaps even try one from another truck if available before pouring out that kind of money.

[Can1991Ram]

Good idea..
I have noticed that idle has improved since the fuel filter change and 4 containers of fuel injector cleaner run through the tank.

The idle seems much less iratic.

The tps and the motor sensor and servo checked in spec last night with the multimeter so I'm headed to the ecu

[GoodApollo]

I am glad you fallowed the video I linked above and checked the coils on the IAC and did not just replace it.

If you need a ECU rebuild send it to AV Pro, they do work for aerospace and have an excellent reputation along with a life time warranty for $190.00, or take your chances on eBay...

http://www.avproecm.com/

http://www.avproecm.com/mitsubishi.htm

[Can1991Ram]

I'm thinking the ECM has been replaced... I looked at it tonight in the truck and it has "ram 50" written on the front of it..

I'm assuming the factory did not write on the cases... they would have just scanned the code on the side.

I was sad to see it wasn't an Eprom unit :(

The big question is... how the heck do you get it out????

[GoodApollo]

With lots of busted knuckles! :shrug:

[Can1991Ram]

I was thinking of these guys for the repair and install an Eprom for tuning...

http://www.ecmtuning.com/

[GoodApollo]

I run 3000gt's and in the past DSMs... ecmtuning is good but expensive, and a lengthy turn around and down time. AVpro repairs and ships out same day they receive your unit.

[Can1991Ram]

OK... and I'm thinking that maybe I should find another ecm to send to them so my truck won't be down.

[pennyman1]

if it is written ram 50 on it - it was most likely a jy pull, not a rebuilt one.

[Can1991Ram]

i agree... so the first one probably had bad caps

time to look for another ecm

[Can1991Ram]

Well...just got done emailing back and forth with ecu tuning.com.
He said he isn't interested in the N/A part of the market and said he is not interested in looking at ram 50 ecms.

Well that sucks as I would like to have the tuneability.

So it looks like I'm sending my ecu to other repair shops.

[Can1991Ram]

Will a 1995 ECM work in my 1991? I found a good deal on one...

[GoodApollo]

told ya ecmtuning was not the best choice for our platform. If you want tunning, when its all said and done its best to just go with AEM ECU for tuning. Dont waste your time with chrome or piggy back units.

[Can1991Ram]

Well the air filter was pretty much blocked so I put a fresh one in...now the bad fire at idle and the up and down idle came back.
Maybe it's a fluke that it's at the same time but for the last while the truck has run great.
I'm gonna swap in the new o2 sensor tomorrow morning and maybe clean the maf sensor.
I better get another ecu

Will and ecu from a 94 work. ?

[GoodApollo]

You have to match the part numbers... As long as the part numbers match it is probably a safe bet.

[Can1991Ram]

The reason I want the 94 is it is the first year for the eprom in the ecu. That can be socketed for a rewriteable eprom.

[finalfighter]

the ecms from 1993-1996 will work but there is one wire that needs to be switched on the harness going into the ecm and its the maf reset signal wire. 1991-1992 ecms have this located differently than the 1993-1996. i put a 1994 harness in my truck and used a 1992 ecm. you have to move the reset switch or it will throw a code.

also make sure you look up the part number from those ones on ebay. they mismatch sometimes. the only difference from 1991-1992 and 1993-1996 is that maf reset switch wire.

some side info though, in 1993 the mighty max/d50 got a hybrid 7 bolt motor. i say hybrid because it uses the internals of a 7 bolt (crank and rods) but has the same deck as a 1g dsm. same bore, stroke, hp and compression specs as the 6 bolt motors found from 1990-1992.5 mighty max/d50 trucks. the heads are slightly different in regards to valve stem seals. the 1993+ use a bigger valve seal than 6 bolt head but other than that they are identical.

[finalfighter]

oh and the lower front timing cover is different along with the passenger side balance shaft belt idler being smaller than the 6 bolt. the front engine cover is slightly different too.

[Can1991Ram]

I noticed that there is lot of soot in my tailpipe of the truck.
Isn't that from erupting too fat?

[finalfighter]

ok so i got some pictures to show you what i mean about how you can use any ecm from 1991-1996 on your truck.
14755
so if you have a 1993-1996 harness like the one shown and you want to use a 1991-1992 ecm just move that wire over. this is on the center plug going into the ecm btw.

also here is an image of a 1991-1992 harness, its not real clear but if you look close enough you will see what i mean
14756
I have personally tested both styles of ecms on both 6bolt and 7bolt motors and they work fine on both.

So now the secret is out that you dont have to spend $115+ on a 1991-1992 when you can get the 1993+ ecms for 45 bucks on ebay.

A Side note: the 1991-1992 ecm in my opinion has a slightly better idle than the 1993+ ecms and that goes with when its paired with either 6 or 7 bolt motors. the 1993+ works great though. either ecm is good for smog in cal. ive use both combos sense ive had my trucks.

I might as well add this info for those poor folks who have the 1990 mighty max like myself.

the 1990 mighty max has the same wiring going to the 1g style MAF as the 2g style mighty max MAF. You can simply cut the pigtail off a 1991-1996 mighty max maf and splice it into your harness. the wire coating is even the same between the two. the one thing that the 1990 mighty max does not have is the MAF Reset wire. You will need to grab this wire when converting your 1990 to use a 1991-1996 style MAF and ecm. YOU CANNOT USE THE 1990 ECM WITH THE 1991-1996 MAF. so if you do this be safe and create a duel connector like this.
14757
this way you can swap between MAFS and ECMS latter if you want.

Another side note for 1990 guys. this year came with different injectors than the 1991-1996 mighty max trucks. they are the same flow and cc but have a different part number and are specific to this year. This may sound far fetched but i have also tried the 1991-1996 ecms with them and they work fine. i did notice a tad bit more fuel consumption like going from 23mpg to 22mpg. nothing big and i did do smog like this.

I Hop[e this helps you and answers all your questions. I Love this site and love these trucks.

[Can1991Ram]

This is awesome info.
I wish I could grab the ecu out if a 1991 eagle talon I found on the wrecking yard.
I'm assuming it would be really different?

[finalfighter]

oh god here i go again. the ecms out of the 1991-1993 eagle talon, Plymouth laser, eclipse, and gallant with a 1.8l sohc 8 valve motors with a distributor will run in our trucks. i have also tried this Just for the hell of it. the one issue i found is that the engine will surge when coasting to a stop when paired with the automatic. i have converted mine to a Manuel and have not tried it on it on it. The 1990 1.5l hyundai elentra ecm will even run in the trucks but surging issues to. I was trying to see if any other ecm paired with the truck would give me a better advance. this was before i found out about injectors and ecm tuning differences. sense then i have got a degree in diesel tech and done tons of more research.


be safe and use the info i provided above and get yourself one of the cheaper 1993+ ecms before everyone finds this info out and they are gone!

[Can1991Ram]

Any idea what would make the tail pipe full of soot?

[noahwins]

Rich condition.

[Can1991Ram]

I understand that part...I'm wondering why it would run rich

[finalfighter]

sense your ecm has writing on the case it mighty be a rebuild. i have seen rebuilt ecms in these trucks that were the wrong one for the truck. someone shipped the ecm for rebuild and got the wrong one back. about 1 in every 3 trucks i went threw were like this. yes it worked but it was not the proper ecm. like i said earlier with the 1.8 and 1.5 ecm, it my run in the truck but that does not mean its proper.

also if your maf sensor is bad this would cause it (should throw a code), or if your ecm was rebuilt with the wrong caps.

to remove the ecm you need to pull the kick panel off on the passenger side. then remove the mpi relay. after that move it aside and disconnect the three plugs going into the ecm and remove the two bolts holding it in. Now This is were it gets tricky, you need topull the harness toward the driver side while wiggling the ecm down and slightly towards you. you may have to reach up and move the harness from as far as you can reach it to the right to make room. you wont hurt anything so keep at it if it gives you trouble. i might make a video of the process if it becomes impossible.

once you have the ecm out go ahead and open it up and post a pic of the inside and the case. i can identify if its the right ecm for the truck. also look over the caps and smell it for any burnt electronics.

[Can1991Ram]

I will give it a try. A video would make a great sticky.
I went looking at newer ecms and I think they read the post here cause the cheapest was still over a hundred bucks for a core.
I would like an eprom 94 signified with an E in the bottom lower right of the sticker. Non eprom have an M in the lower right of the sticker

[Can1991Ram]

I cleaned the MAF and wow...it seems to have helped the idle and part throttle performance...
So far putting a new air filter..cleaning the maf , changing rge fuel filter and changing the O2 sensor is really helping this truck

[finalfighter]

holly ***, just looked upped the 1993+ ecms on line and ya, they all went up in price except this one

http://www.ebay.com/itm/94-95-MITSUBISHI-MIGHTY-MAX-PCM-ECU-ECM-ENGINE-COMPUTER-CONTROL-UNIT-MD302265-/321511108167?fits=Model%3AMighty+Max&hash=item4adb8e2e47&vxp=mtr

its not mine so i hope i am not breaking any rules by posting it. i would be a little weary in that its bot rebuilt.

[finalfighter]

what plug wires did you buy for your truck? also check the coil to see if its gone bad, i had this happen to me. you can get them cheep. clean all the ground cables.

[Can1991Ram]

I haven't done wires and cap yet...or plugs... any suggestions
I have found that it will pass cars easier and will now Rev to 4950 before it stops pulling.
I was thinking about swapping coils too..but one thing at a time so I can get results from individual change.
It reminds me of when I won my drag racing championship. ..if you make one change at a time you can always go back if one makes it eorse