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Engine Running Rough After Head Replacement

91_427

Well-known member
Joined
Apr 2, 2012
Messages
101
Location
South Jersey
Several months ago I removed the engine/trans/subframe assembly in order to replace the head. The head needed to be replaced because I broke 3 exhaust manifold studs in the process of trying to replace a cracked exhaust manifold. I was able to extract two of the three studs, but my extractor bit snapped while attempting to remove the last broken stud. In the process of trying to remove the extractor I destroyed any chance of using a helicoil to repair that stud hole. I purchased a recast head from ebay without cams, springs, lifters, or rockers. I transferred all the necessary components from the stock head to the new head. (I only "eyeballed" the CAS, so I know that needs adjustment.) Since I had to replace the head I replaced the water pump and timing belt as well. (I followed the vfaq article on timing belt replacement to the "T" including using the Mitsubishi tools recommended for the job, and making sure the front and rear balance shaft were in the correct orientation. I spun the crank two full revolutions to check my timing marks, and I did this several times with everything lining up properly each time. Therefore, I don't think my timing belt is off even by a tooth.) Anyways, I reassembled the car (I numbered and took pictures of all the connectors that I disconnected, and bagged and labeled hardware as it came off.)

*****TL;DR**** Removed engine/trans/subframe, replaced head and timing belt.

When I tried to start it the first time it cranked very slowly and difficultly. After an hour of diagnosis I traced the problem to the water pump pulley bolts being too long because the captured washers had worn away to nothing. This resulted in the tips of the bolts getting caught on the water pump itself. After installing shorter bolts in the water pump pulley, I was able to get the car running, but there are several things wrong with how it is running:
1)Very rough vibration at lower rpm's (under 2000 rpm, but the lower the rpm the worse the shake)
2)Will not idle on its own
3)During further diagnosis there are times when the engine will not get above 600-700 rpm regardless of how much throttle is applied. The dash boost gauge maxes out during this.
4)Other times during diagnosis the engine will jump in rpm's with no additional throttle input.
5)Car doesn't sound or feel like it is running on all cylinders, but I have no way to keep the car running and check if all cylinders are functioning.

Here's what I've checked so far:
1)Fuel pressure is at 40 psi at low rpm's.
2)All couplers are tight and connected.
3)All connectors are plugged in.
4)All spark plugs are firing.

Things that might be relevant:
1)Coolant temperature wiring was damaged from previous owner. I attempted to repair the wiring (several wires broken entirely). After several wiring combinations I was able to get the instrument panel coolant gauge to display correctly, but when I look at the temperature in ECMlink it says-20 degrees, but this wasn't an issue with how the vehicle performed before changing heads.
2)I'm using ECMlink.
3)EGR and IAC have been removed and blocked off.
4)Boost is turned all the way down with Hallman Pro MBC.
5)Vehicle does have all poly motor mounts and transmission mount.
6)I'm using larger injectors (650's?) because it didn't come with any injectors from previous owner.
7)Yes, I'm fully aware that i need to dial in ignition timing with the CAS, but I can't do that until I have an assistant to help keep the car running. I'm skeptical about setting ignition timing while it cant even idle...

So, does anyone have any suggestions, comments, or insults that might help me out?
 

Fish

Well-known member
Joined
Nov 12, 2012
Messages
206
Location
Idaho Falls, ID
Incorrect ignition timing can cause some crazy things to happen. I would try to set that before doing anything else. Also was the replacement head new or used? Was it checked out by a machine shop?
 

AllanL

Well-known member
Joined
Aug 4, 2008
Messages
294
Location
NV
were the plug wires connected to their corresponding coil posts correctly?

1-4 on one coil
2-3 on another coil
 

thomcasey

Well-known member
Joined
Sep 24, 2014
Messages
907
Location
Indianapolis, IN
Have you input the correct settings for the injectors (in Link)? You indicated that they are "650's?", leaving us to assume that they are new to the car and therefor Link is not configured for them. You need the correct information for those injectors or you may never get an idle that is good enough to set the timing, especially since you cannot properly set the timing with the throttle being held open by someone.

Get your injectors setup correctly, set your CAS to dead center (just center the studs in the slots) and get it up to operating temp and see if you can then ground out the plug and set the timing with a timing light. This should get you to a better running car
 

transparentdsm

Well-known member
Joined
Jul 27, 2011
Messages
3,690
Location
Cherry Hill, NJ
^ this, with things configured properly you should be able to start the car and it should idle on its own so you can adjust the CAS. ive rebuild a lot of cylinder heads for these cars and ive always been able to set ignition timing by myself. i actually just did my cam shaft not to long ago and after reinstalling i had to readjust the CAS. Also a good thing to do would be to check the CAS to make sure it isn't 180* off, make sure you have your spark plug wire order correct as well.
 

91_427

Well-known member
Joined
Apr 2, 2012
Messages
101
Location
South Jersey
Thanks for the suggestions/questions. I'll try to address them all.


Fish
The replacement head was new, but to be more specific it was an OEM recast purchased on Ebay. I didn't have it checked out by a shop since it was an OEM recast and everything looked fine to me. In hind sight I probably should have had the head checked anyways.


AllanL
The plug wires are going to the correct coils for the corresponding cylinder.


thomcasey
I just checked my ECMlink settings and injectors. The injectors are indeed FIC 650's, and they were in the car when it was running previously. Sorry for the confusion in my previous posts regarding the "650's?". I couldn't remember off the top of my head what the injectors were. Since you seem knowledgeable of link, do you think my improper wiring causing the incorrect engine coolant temperature reading could be causing the motor to run too rich? I believe there's a section in link for adjusting fuel tables based on vehicle temperature (which I assume link is getting from the engine coolant temperature reading).


transparentdsm
I've read in a few threads on dsmtuner that a vehicle will not run at all if the CAS is 180* off. Is that true, or complete bs? I don't have time to fiddle with it today, but I'll try to get to it tomorrow.
click
The second post is the one that mentions if the CAS is out 180* then the car won't start at all.


**********
Is it possible that a boost/vacuum leak could be causing it to run this horribly? I checked all my couplers and used new intake gaskets when I reassembled everything.
Would a compression test help verify that the head is good?

Thanks again everyone for your input!

Edit for sentence structure
 
Last edited:

tektic

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Joined
Dec 19, 2012
Messages
1,497
Location
ronkonkoma, ny
I didn't read all that... sorry. I can offer a possible solution to your exhaust stud problem.

VW sells a stud for their timing components that is 8my on one side and 10my on the other. If you think you can tap the head for 10 mm you could probably save that head.
 

Fish

Well-known member
Joined
Nov 12, 2012
Messages
206
Location
Idaho Falls, ID
The replacement head is probably not the issue, I was just curious. You said the boost gauge is maxed out, is this an actual mechanical gauge or the digital one in the cluster? I thought I remembered reading that people with link can use that to read engine knock instead of boost.

But anyway to me it sounds like your ignition timing is severely off or you've got a large vacuum leak. If it's a vacuum leak big enough to cause a rough running or stalling engine it should show up in the o2 sensor reading. Anything below 450 milli volts is lean and anything above is rich. Usually something that bad will read very low such as 20 milli volts. Hope this helps.
 
Last edited:

thomcasey

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Joined
Sep 24, 2014
Messages
907
Location
Indianapolis, IN
Yes, it can cause you to be too rich. Better to fix the temp/wiring issue than mess with fuel tables
 

91_427

Well-known member
Joined
Apr 2, 2012
Messages
101
Location
South Jersey
tektic
Thanks for the input, but I replaced the head and now I have a no idle issue.

Fish
The boost gauge is just the stock one that comes in the instrument cluster. I rotated the CAS 180* and started the car. The car ran, but a little worse than before so I rotated it again and centered the CAS on the studs. Car still runs rough and won't idle at all. Every third or fourth start once warm it will hold an idle at 500-550 rpm even though my ECMlink setting is for 1000 rpm. Anyways, I double checked my fuel trim settings and then looked at the front O2 readings which fluctuated between 600-900 millivolts. Would a boost leak cause it to run rich or lean? I always thought it would run rich because some of the air that the gm maf is calculating for is never reaching the cylinders. So less air than what is calculated is reaching the cylinder, therefore causing the air-fuel ratio would be richer. That's how I've always looked at it.

thomcasey
Thanks for the input Thom. That will be the next thing I work on, but I'm curious how I was able to run and idle with the incorrect wiring before I replaced the head.
 

Fish

Well-known member
Joined
Nov 12, 2012
Messages
206
Location
Idaho Falls, ID
At idle it would not be a boost leak but a vacuum leak and would cause a lean condition. The negative pressure would be sucking extra air into the engine. If you were at a high load/ high boost then you would have positive pressure in the intake and air would be pushed out of the leaking spot causing a rich condition. If your o2 sensor is reading 600-900 millivolts then you are running rich but not horribly rich. It's fairly normal to run a little rich with a cold engine.

Now you should be looking at the coolant temp issue like the others have suggested. It's possible that the coolant temp sensor could be causing your issue. You should also take a few minutes to look over everything you've done and sort of double check yourself. Make sure everything is hooked up correct and you didn't forget anything. Did you stuff a rag in the exhaust to keep metal shavings and other things out? Stupid crap like that. Let us know what you find.
 
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