Laser Base hesitates/stalls/bucking when warm

[mmountain]

I just bought my first DSM! http://www.dsmtuners.com/forums/welcome-forum-member-intros/463392-hello-all-new-dsm.html proud of that fact, but need some help with it. I see that a lot of people with turbo engines have the bucking/stalling/hiccupping problem and everyone always tells them to check for boost leak, but I don't have a turbo so what could be happening.

Its a 90 Laser Base, 5 speed, Big Hole in the flex pipe (SO DANG LOUD), the car is bone stock though and I'm the second owner.

When my car gets warm the CEL comes on (everytime I try to jump the terminals to check the computer it doesn't work) and then under heavier acceleration (3500+ RPM) the car acts like its stalling/losing power/bucking. I have changed the plugs and wires, put in NGK plugs and oreilly's premier wires. the engine idles better, but the problem isn't gone. The previous owner told me that it started this before he had the timing belt and water pump changed last November.

Also if anyone knows why my headlights would work on lo but cut out on hi that would help to.

Thanks for any help.

 

[Operate]

Those symptoms are very similiar to when the capacitors leack on the circuit board of the engine ecu. Just as a precautionary check with owning any 1g DSM removing the engine ecu behind the dash and opening the case to inspect the capacitors is a very good idea.

This happened to me on my 2nd DSM it had the EXACT symptoms, the capacitors were just starting to fail and created strange symptoms.

There re 4 10mm bolts that hold it in place I believe, and thre connectors to the ecu. After it is removed there are 4 phillips screws that hold the top ontop the ecu. you should be able to identify the two capacitors and inspect them for leakage, it is usually obvious. but also there is a "fishy" smell associated with the leaking capacitors.

 

[mmountain]

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Can you tell me what I'm lookin at? I ran the # MD128658 and it came up to 1g 1.8L FWD AT. Is the problem that this ecm is for an auto? I don't know how to look at the circuit board itself and figure out anything.

 

[DSM1G90]

Sounds like a fuel filter needs to be changed. You're running out of fuel when you get up to those high RPM's.

Could also be that your ECU, being an AUTO ECU simply isn't configured correctly for the 5sp Federal setup that you have due the driver setup on the momboard can't talk to the tranny.

You need this ECU for the 4G37 Manual Federal (D21A is the chassis model which is the FWD NT chassis):

MD159561 1G DSM 1.8L NA FWD D21A MT E2T33674M/A E854 6/90-5/94 FEDERAL

 

[Mischif]

Ecu looks to be in great shape. Also for the 1.8, it doesn't matter if you use an auto or manual ecu. Its the TCU that handles the communication between the ecu and the transmission. I've converted 2 1.8 autos to manual and never had to touch the ecu. Also have used the ecu from an auto in a manual with no ill effects. Since your cel comes on once the car is up to temp i would guess that maybe the coolant temp sensor is acting up or possibly the o2 sensor. Which could very well cause your issue. However since your unable to pull the codes from the ecu thats just a shot in the dark. I would try again to pull the codes from the ecu. Make sure your connecting to the right pins. If you can manage to pull the codes you will find your problem.

 

[DSM1G90]

Only diff between the two ECUS of Federal and Calif, is the one resistor inside that the Calif uses to communicate with the EGR temp sensor-installed on cars driven in Calif.

Take the resistor out and you got a Federal ECU.

EGR temp sensors loves to go out and you will get a CEL when the EGR temp sensor fails. Take the resistor out off the momboard of the ECU and this problem will never come up again.

When doing codes, use an analog (needle type) VOM where one can see the swings of the needle to record the slow long swings and the fast short ones. VFAQ has the listing of the codes and the instructions on how to pull codes from the OBI connector, and read the instructions on how to read these codes from the swings of the needle.

 

[mmountain]

Since your cel comes on once the car is up to temp i would guess that maybe the coolant temp sensor is acting up or possibly the o2 sensor. Which could very well cause your issue.

Could the hole in the exhaust before the o2 sensor be part of the problem by any chance? The ecm trying to adjust a faulty reading?

 

[Mischif]

Could the hole in the exhaust before the o2 sensor be part of the problem by any chance? The ecm trying to adjust a faulty reading?

You have a hole in your manifold? If the hole is after the o2 sensor in the pipes then it wont affect it just sound annoying. Now if the manifold is leaking then that would cause the car to run richer then it should. It would have to be a really big hole for it to make the car run so rich that it sputters.

 

[mmountain]

You have a hole in your manifold? If the hole is after the o2 sensor in the pipes then it wont affect it just sound annoying. Now if the manifold is leaking then that would cause the car to run richer then it should. It would have to be a really big hole for it to make the car run so rich that it sputters.

There's only one in these cars? my last couple cars had both upstream and downstream o2 sensors. Sorry you can ignore my last post then.

 

[DSM1G90]

It's the 2G line that uses two, O2 sensors.

1g's only had the one in the EXH manifold- a non heated variety.

 

[mmountain]

Well, I just got a job a O'reilly so hopefully the car won't be limping too much longer, I'll keep this post updated on what I do and whether or not it works. thank you for all the input.

 

[mmountain]

The starter is out, so It will be a little while til I can fix the hesitation/bucking issue. I think I'd take a difficult oil filter over a difficultly placed starter...ugh.

 

[mmountain]

Got the starter put in, Changed the fuel filter, which didn't fix anything, changed the thermostat cause I had a leak at the housing and it was cheap for me anyway. My cooling fans aren't engaging, I jumped the relay and they came on, so I'm going to guess its the Thermo switch as the relay is brand new.

the symptom feels like a I have a rev limiter at 2k RPM now when the car is warm only, its more consistent in the last couple weeks than it was initially.

 

[mmountain]

However since your unable to pull the codes from the ecu thats just a shot in the dark. I would try again to pull the codes from the ecu. Make sure your connecting to the right pins. If you can manage to pull the codes you will find your problem.

I got a code 15, which is the idle speed control motor sensor. My Haynes says that one possible issue to throw that code would be the Throttle Position Sensor TPS, which I then hooked the ol multimeter up to pins 2&3 and found that it is not producing the wide range that the manual calls for, its starting at 1.5 and is about .6 off from the top, which I can't remember off the top of my head. pins 1&2 are reading a .54.... do I need a new tps or does this one need adjusting? the TPS on the car looks to be only a few years old, if that matters.

 

[Mischif]

I got a code 15, which is the idle speed control motor sensor. My Haynes says that one possible issue to throw that code would be the Throttle Position Sensor TPS, which I then hooked the ol multimeter up to pins 2&3 and found that it is not producing the wide range that the manual calls for, its starting at 1.5 and is about .6 off from the top, which I can't remember off the top of my head. pins 1&2 are reading a .54.... do I need a new tps or does this one need adjusting? the TPS on the car looks to be only a few years old, if that matters.

Off the top of my head i can't remember which pins are what. I know the tps has a ground, a constant 5v power supply and then the signal wire. How i always test it is ground the multi meter on the body or something and then see which pin gives out the constant 5v power supply. Once that checks out i find the pin that gives out .51-.54v at closed throttle. Then i leaving the multimeter connected to the signal wire i open the throttle plate all the way. You should get now get a 5v reading from the signal wire. However i've found that they rarely give off the full 5v, its more around 4.8x-4.9x. Even when logging using mmcd with the tps adjusted right the ecu only sees a max of about 86-95% throttle. This doesn't cause an issue tho. Also make sure and test the signal wire from the tps at the ecu end of the harness to eliminate any chances of bad wiring somewhere in the length of the wiring.

Also you can unbolt the idle speed controller from the throttle body and just ziptie it out of the way leaving it plugged into the harness.

You say pins 2 and 3 gives you 1.6v. So im assuming pin 3 would be the constant power supply. Which if your getting 1.6 volts, and it varies then that very well could be your problem. When your testing, are you just jumping the pins with the harness still plugged in, or are you testing just the harness itself?

That .54v from pins 1 and 2 sounds about right if pin one is the signal wire. As long as thats the case then the tps itself is adjusted correctly.

 

[mmountain]

Off the top of my head i can't remember which pins are what. I know the tps has a ground, a constant 5v power supply and then the signal wire. How i always test it is ground the multi meter on the body or something and then see which pin gives out the constant 5v power supply. Once that checks out i find the pin that gives out .51-.54v at closed throttle. Then i leaving the multimeter connected to the signal wire i open the throttle plate all the way. You should get now get a 5v reading from the signal wire. However i've found that they rarely give off the full 5v, its more around 4.8x-4.9x. Even when logging using mmcd with the tps adjusted right the ecu only sees a max of about 86-95% throttle. This doesn't cause an issue tho. Also make sure and test the signal wire from the tps at the ecu end of the harness to eliminate any chances of bad wiring somewhere in the length of the wiring.

Also you can unbolt the idle speed controller from the throttle body and just ziptie it out of the way leaving it plugged into the harness.

You say pins 2 and 3 gives you 1.6v. So im assuming pin 3 would be the constant power supply. Which if your getting 1.6 volts, and it varies then that very well could be your problem. When your testing, are you just jumping the pins with the harness still plugged in, or are you testing just the harness itself?

That .54v from pins 1 and 2 sounds about right if pin one is the signal wire. As long as thats the case then the tps itself is adjusted correctly.

I tested it at the harness, the reason I kind of figured that the problem was in the TPS is because in the last month my idle RPM has risen from around 1300 to about 1800 today. The throttle wire is tight.

could it be the Idle Speed Controller causing my engine to cut out above 2k RPM? to fix that would I just need a new throttle body? I can't find the ISC anywhere.

 

[Mischif]

No, the idle speed controller only effects the idle. It has a little metal rod on the end that pushes the throttle plate open to keep the idle at the same spot whenever you turn on the a/c or the fans kick on. Its not really needed however.

It sounds to me like either there is a problem with the ecu and its not supplying the sensor with the correct 5volt constant power, or there is a short in that wire somewhere. For the tps that is.

 

[mmountain]

So I need to check the 5v constant wire back to the source? where does it run to? The ECU looked good when I pulled it last time, I think the pictures were on this thread.

 

[Mischif]

Not sure what pin on the ecu provides the power for that sensor. I have a spare harness laying around. I'll rip it apart and see which pin it goes to and check and see if it feeds power to any other sensors. I'll let you know what i find out.

 

[mmountain]

Thank you, it is really awesome to be part of a community that will help so much!!

 

[Mischif]

Okay the tps, the bigger plug on the idle speed control motor, and maf sensor all share the same 5volt green wire with red strip. This wire goes into the ecu through 2 pins. Its going to be the bigger of the 3 connectors. The two wires are on the flat side of the plug, the side that does not have the release button. With the flat side up, going from left to right its going to be the second wire and also the last wire. Also they are the only green with red stripe wires on that side.

So with this information, do a few tests. First tho a little note. The big plug for the idle speed controller has two green wires with a red stripe. The correct one that you want to test is going to be the one with a green wire with black stripe next to it. Also the maf pigtail has a green with orange stripe wire that may look red or the green with red stripe wire may look orange if they are faded, so make sure you test the correct one on that too. Now for each one of these pigtails, the green with red stripe should be putting out a constant 5volts with the key in the on position.

Now i already think i know your problem. Since your ecu is giving a code 15 for the idle speed motor i think that sensor may be faulty and shorting out on the inside back feeding your constant 5 volt power green with red stripe power wire. Leave all the sensors plugged in, remove the tps plug and hook up the multimeter to the green/ red strip wiire. Once its hooked up disconnect the big plug from your idle speed controller. If my guess is right as soon as you disconnect the idle speed controller plug you should be now getting the correct 5 volts.

If none of this works disconnect the 3 sensors then test the 2 pins at the ecu and see if they are putting out 5v.

 

[Blu92]

Not sure what the problem is, but my ecu looked fine and my knock sensor kept going off. I did the sniff test and the ecu smelled like bad fish. I replaced the capacitors and it went away.

 

[mmountain]

Now i already think i know your problem. Since your ecu is giving a code 15 for the idle speed motor i think that sensor may be faulty and shorting out on the inside back feeding your constant 5 volt power green with red stripe power wire. Leave all the sensors plugged in, remove the tps plug and hook up the multimeter to the green/ red strip wiire. Once its hooked up disconnect the big plug from your idle speed controller. If my guess is right as soon as you disconnect the idle speed controller plug you should be now getting the correct 5 volts.

Mischif, You. Are. Amazing. As soon as I unplugged the plug it straightened right out. But now how do I fix the ISM sensor? or just fix the problem?

 

[Mischif]

You need to get a different one, there's no repairing that one. You should be able to leave it unplugged for now and drive without issues until you find a better replacement. Unplugging it will cause you to throw a cel, but since you already are throwing one it wont make a difference. Have you already tried driving it to see if the hesitation is gone?

 

[mmountain]

I surely did....This car absolutely blows my mind. this was the first time I was able to really let it unwind. Its like the quickness of my old accord with the fun-to-driveness of my CRX....But better than both, I drove it for about 20 minutes with the sensor unplugged and not a single issue.

any idea where I can find a new sensor? It doesn't even come up on my catalog screen at O'reilly...