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Discussion Starter · #1 ·
I've been trowing money at this problem for some time now and well i'm stumped and just about broke! Started after hg was replaced, loud knocking ended up being stuck lifter, replaced that and now my engine has low vac. constant misfire at idle, timming is good checked and rechecked with timing light, it bounces around alot cause of missfire but it still checks out. i've replaced vacume lines with silicone ones, replaced IAC, replaced ecu, replaced tps, replaced injectors, spark plugs and wires, tried changing out my maf but someone sold me a bad one, for 15 bucks I wont bitch to much, so how else can I be sure my MAF is good, It feels like i have a rev limitter at 5k rpm's checked for boost leaks and fixed them, on a side note, when I pressure test the car, only 10psi because of stock bov there is a bubling noise but, its not from the coolant it sounds more like it's coming from the engine, my guess air is making it to the oil pan??? is that even possible? bad turbo seals? IDK but possibly related, my car has pretty much always ran pig rich and recently started pulling timing really bad as soon as it sees any boost, so knock sensor is also on my list of things that are possibly bad. One more question before I let you guys work your magic and diagnose my car trough the web, what are the simptoms of bent valves? ok I think that's it, and like I said in the title if you can help me solve this i'll happily send over a 6 pack (your choice)
MODS 3" exhaust turbo back
14b turbo
550 injectors
intake thats probably it, i'm boosting 10psi and getting the crappiest gas millage you could emagine 02 sensor also been changed less that 8 months ago. Thanks for reading.
 

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Take out the plugs and look down into the cylinders to see the tops of the pistons. (You may have to use a flashlight. First check your plugs to see if you see a tint of green on the electrode (coolant) than when checking on the piston tops, look to see which one, if any, is super clean. That would also show a HG leak.

Now you said that you checked timing but that is not enough. I say remove the timing belt covers and re check the timing belt, to see that its aligned. If its off than you vac would be off as well. I rule out a vacuuum leak cause you said you fixed the boost leaks.

Also warm up the car real good and then do a compression test. This may show you if you have a problem with holding compression which could show you if you have a fualty valve in that cylinder or a HG leak.

Also what car is this problem on?
 

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Discussion Starter · #4 · (Edited)
Yeah i've done a compression test and they are all circa 150. I'll take a look at the pistons later today, I actually already removed the timing belt cover and made sure it was all alligned, it was, since day one i've been trying to blame the timing but, everytime i check it it's good:dunno: I'm going to replace the fuel pump and the coolant temp. sensor because i've crossed out just about everything else in the trouble shooting section of the haynes book. I forgot to post this little clue, when I hold the accelerator at just under 2k rpm's it has major idle surge. Oh yeah leak down tester is on order so i'll place the results when it gets here. Thanks for the help so far
 

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You could also check the IAC motor. When I first rebuilt my engine and started it, it idled like crap. Vacuum was not right. Could not figure it out. Than I turned on the ac by mistake and noticed that my rpms dropped to 550-600. That made me realize that my IAC was shot. It was working before the car went down 3 months earlier.
 

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Discussion Starter · #7 ·
[QUOTEWhen I first rebuilt my engine and started it, it idled like crap. Vacuum was not right. Could not figure it out. Than I turned on the ac by mistake and noticed that my rpms dropped to 550-600.][/QUOTE]
Hey that sounds familiar, my idle drops a couple hundred everytime I turn on the a/c (even though my a/c's no good now in 110+ weather :() But I just replaced the IAC, I guess I should check it anyway.
I just got back from lunch and i'm getting a p0170 code: fuel trim bank 1???
thats the second time i get this code last time it kind of just went away, anyone now if this is related?
 

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Discussion Starter · #9 ·
I actualy don't have any tuning software or wideband, I was waiting till I started upping the boost to get dsmlink, but would that be causing a problem? The car has prety much ran pig rich all its life way before the 550's also.
 

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Your ECU is tuned to have 450's at most, but since you've got an auto, I think they are 300something or other. Not sure exactly on the auto specs. ANYWAY, that is surely causing some problems. And if its not the direct cause, then its no helping AT ALL. The ECU doesn't know you've got 550's, so its a bit confused right now.
I assume you did the boost leak test after the 550's were installed? I'm guessing when you first started having problems, you had a boost leak. Or you had one, and didn't realize the problem, or the problem wasn't that bad. You, or previous owner, may have installed the 550's without knowing that you've got a boost leak. When you replaced the vacuum lines, you probably fixed the leak, now you've got to deal with the bigger injectors.

I ASSUMED quite a bit here, but this is the easiest, most likely solution to whats going on. It makes sense, if you think about it.

I could be wrong about the leak, then you fixing it, but I'll guarantee your ECU is confused as all hell as to why your injectors are running differently than stock. DSMlink is great, but throw on *some* way of checking your tune. You won't waste money if you throw on a wideband, as you'll probably want one in the long-run anyway.
 

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If I was you, I would just get a hold of the stock injectors and fix it to run stock. That way the ECU can have a chance to show you the problem. You need to see what your engine is doing so a Datalogger is a tool you should consider.
Slapping on 550's with no way to control them is the first mistake.
 

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The CEL is probably from running so rich and having such negative fuel trims. A bad egr will mess with your vacuum and can make your car run poorly so it might be worth checking to see if that is working properly. When you changed the HG did you get the head resurfaced and at least check the block to make sure it's straight or get it decked? Cracks are another potential problem since the car was overheated. If coolant got to the rings they could be damaged. It's good you ordered the leakdown tester, it will make it easier to track down your problem.
Another thought is that the misfire will give you crappy vac so it could have to do with that, such as a crappy coil, intermitent cam angle sensor, bad ignition module or just a rich misfire condition.
I would check the rich misfire condition first because, like you said the car ran rich for a long time and would have adapted to it. When the HG was changed the ecu would have been reset to factory settings so it would run poorly. If you have them throw the stock injectors back in and see if that helps.
Also keep in mind running the car rich like that will ruin your new o2 sensor and damage your cat. A plugged cat will give you a car that lacks power and eventualy wont run properly. So you gotta get some sort of tune on it soon even if its just an safc or you will probably start having other problems soon enough. Not to metion fouling plugs and carbon deposits.
 

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Discussion Starter · #14 ·
Cool I appreciate all the help guys. But it's kind of going in a different direction than I was expecting, the car ran crappy before the 550's, ran rich before the headgasket failure and with the stock 450's, I really want to get this fixed and I never really considered a tune would help out but I might have to spend 100.00 to get it tuned at a dyno. I have a pocket logger and will post a log later on but it's also really hard right now to do a pull cause of it hitting something like a rev limiter at 4700rpm's and it pulling my timing *atleast I think it is* ignition goes down to 4 when boost kicks in. Anybody now how to get the log of the palm and onto the computer? Again thanks for all the help.
 

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Discussion Starter · #15 ·
A bad egr will mess with your vacuum and can make your car run poorly so it might be worth checking to see if that is working properly
I vacume tested the egr and it held vacuume but i'm going to try blocking it off maybe it will make it better

When you changed the HG did you get the head resurfaced and at least check the block to make sure it's straight or get it decked?
Yeah it was taken to a shop and was checked for cracks and warps but it checked out, even had a valve job done.

Another thought is that the misfire will give you crappy vac so it could have to do with that, such as a crappy coil, intermitent cam angle sensor, bad ignition module or just a rich misfire condition.
I would check the rich misfire condition first because, like you said the car ran rich for a long time and would have adapted to it.
Thats actually the direction I was trying to head but like I said I've trown tons of money at this thing, replacing parts, with no luck. The only good thing that really came from all this is that I got to upgrade a couple things like my injectors, but now you guys are telling me that it was a bad Idea, but i'll check into it a little more and work on getting some kind of tune.
 

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For any upgrade to be successful, you have to start with a well running engine. That way you can pinpoint the problem easier. Taking it to a Dyno and spending $100 is not going to help you without a way to modify the airflow signal, therefore controlling your injectors.

You are going at it all wrong.

EDIT
Look the rich problem can be corrected by modifying the airflow signal. In order to do that you need an SAFC. If the car was running rich before the 550's than what you could have done is look at your fuel trims on the logger. On WOT you could have logged O2 bank 1 to see if you say 1.00 which means pig rich.
There are much simpler ways you could have went at trying to figure out the rich problem.
 

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You did not state in the begining that you had a logger so that sheds new light. Since airflow is used by the ECU to calculate its fuel, and you stated that the car ran rich even with 450's, that you could assume that the airflow is already modified. To modify the airflow without a SAFC or link, you can do it right at the Mass sensor. Theres a screw on the bottom that is supposed to be sealed with factory silicone. If this has been touched, than the airflow the ECU sees would probably be different than what it is suppose to see, therefore making your car run rich at idle and at a load.

You have a logger....Use it. Look at your fuel trims. On a 98 you only have +17% or -17% correction from the ECU. You want the LTFT's to be as close to 0% as possible.
 

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To get to the bottom of this we have to first figure out the cause of the symptoms. It has to be either air, spark or fuel. I would get a spark tester and test the spark since it actualy simulates the conditions the spark plug is under.
Now as you said you are not sure if the maf is good or bad so we can't condem it just yet but it is possible. So you should get a reading from you logger
If the car is running rich before the up grade then it could be a feul pressure regulator. To test simply unplug the vacuum line to it and if the idle changes then the fpr is good if it stays the same then it is stuck. A bad ect could cause an overly rich condition and the big injectors just make it worse., if you have a multimeter it is a simple test, one side should have 5v the other should have between 2 and 4 depending on the vehicals temp.
It might be helpful if you could post your o2 readings. I would think the misfires are probably picking up on the knock sensor and that is probably why you are losing timing. And I belive the poor vacuum is just from the misfire condition. I know it sounds dumb but check basic things like the plug wire order.
 

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Discussion Starter · #19 ·
I know it sounds dumb but check basic things like the plug wire order.
At this point nothing sounds dumb and i'm willing to try just about anything, I got home a couple hours ago so i'm still waiting for the car to cool off enough so I can replace the ect sensor, then i'll try unpluging the fpr.

I would get a spark tester and test the spark since it actualy simulates the conditions the spark plug is under.
I'd never heard of a spark plug tester, but it sounds like a good one to add to my collection.

I would think the misfires are probably picking up on the knock sensor and that is probably why you are losing timing. And I belive the poor vacuum is just from the misfire condition.
That makes a ton of sense, fixing the missfire is proving elusive though, the only thing I haven't changed are the coils, wires and plugs are pretty new.
 

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Discussion Starter · #20 ·
For any upgrade to be successful, you have to start with a well running engine
I agree with you 100%

Taking it to a Dyno and spending $100 is not going to help you without a way to modify the airflow signal, therefore controlling your injectors
I was kind of hoping they could help with tuning :(

You are going at it all wrong
I know, I know. The 550's were actualy to try and solve the missfire problem (i was hoping for a faulty injector) also I didn't know you could mess with the
airflow without an aftermarket part, so i'm going to give that a shot. I've never seen the screw so it probably still has the plug in it.

You have a logger....Use it.
I'm doing the best I can with my limited logging abilities, but i'll read up more on how to properly play with a logger.

Thanks for all the help guys and I guess I'm going to have to send a couple thank you gifts out. But keep em coming. I'm gonna go try some/all of the things suggested and i'll post up results later tonight.
 
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