Spyder 97 GST Spyder P0300 and Jumpy Tachometer.

[ZubUchiha]

Hey y’all, I Just got a 97 gst spyder and it has a p0300 code. I changed the spark plugs and the check engine didn’t come on but halfway of driving it back home, check engine came back on and it started misfiring. When I start to accelerate it would feel as if the clutch was slipping, and the entire car would start to rumble and shake hard, but this would only happen sometimes. Another problem is that when I accelerate the rpms fluctuate up and down like it’s lagging as it’s going up, but when it’s in neutral, it goes up and down smoothly. The temperature gauge would also start to go up slowly past the halfway mark. Another question I have is when the car is idling in neutral and not moving, the rpm’s will drop below the normal range the car will vibrate as if it’s about to stall, any reason why this would be? My reader only shows this code and none other. Any help would be appreciated.

 

[Jk's97DSM]

Can you post some pics of your engine bay?
It can be anything and anything without knowing a little more.
How low is the voltage? Quality parts are key to maintaining these cars. A Denso, OEM or rebuilt (from a legitimate shop) alternator is the only alternators I’d ever put on anything. Voltage irregularities cause so many issues.

 

[ZubUchiha]

Can you post some pics of your engine bay?
It can be anything and anything without knowing a little more.
How low is the voltage? Quality parts are key to maintaining these cars. A Denso, OEM or rebuilt (from a legitimate shop) alternator is the only alternators I’d ever put on anything. Voltage irregularities cause so many issues.

Here’s the engine bay picture, I’ve checked everything multiple times.

After renewing my grounds from battery to chassis and battery to starter, the car wouldn’t turn on and our alternator went out. We just put in another alternator, a Duralast one from autozone and the car is able to run. Voltage on the battery is almost 14 as well as the alternator. Car still has jumpy tachometer (performance is not affected when tach is jumpy/bouncy) and still has a random misfire.

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[mitsubishikid]

Do a compression test and a leakdown test won't hurt to have the engine health checked.

I know you tested injectors but did you clean them and have them inspected to make sure they are not clogged or stuck open, also are you running the egr valve, it activates when the engine is under load and that could be sticking causing a misfire might need a cleaning, and look for exhaust leaks, an old worn lazy o2 sensor could be telling the car to dump more fuel, just a few things i would be looking for.

 

[ZubUchiha]

Do a compression test and a leakdown test won't hurt to have the engine health checked.

I know you tested injectors but did you clean them and have them inspected to make sure they are not clogged or stuck open, also are you running the egr valve, it activates when the engine is under load and that could be sticking causing a misfire might need a cleaning, and look for exhaust leaks, an old worn lazy o2 sensor could be telling the car to dump more fuel, just a few things i would be looking for.

I apologize I forgot to mention a compression test. We did a compression test and got 180 on all 4 cylinders, I updated the post as well. I got the injectors tested by a professional who has all the machines and tools to see whether it needs to be cleaned or not. Only slight noticeable difference was a 10 sec run on the test machine on one of the injectors, but it’s not enough to make a difference. Next I’m going to focus on the O2 sensors. My obd on my phone shows that the O2 sensor and O2 heater sensor has not passed.

 

[ryan4269]

Ensure the ground from firewall to intake manifold is good, hard to see but is it on a plastic bracket? Try relocating or putting beneath the bracket. That ground is crucial in my experience

 

[Jk's97DSM]

Do you have codes?

 

[Justin DuBois]

Has the ECU circut board been inspected?

 

[chrysler kid]

Your battery ground loops around and goes to the firewall?

There should be another ground cable going from the starter bolt on the transmission to the negative post, and a ground wire from the negative post to the chassis on the firewall

So youre missing the starter ground cable.

My car had a similar problem, basically in boost the coil would over power the ground cable on the intake manifold and cause a misfire so bad the car would shut itself off

 

[ZubUchiha]

Sorry yall, was going to reply, but on the 7th, a bad driver hit me and messed up my car. Havent touched the car until now. I am currently trying to fix up the suspension. Unfortunately I never got around to fixing the misfire because of this issue, but because I am going to fix it soon, I want a headstart on this issue to finally fix this dsm once and for all.

Ensure the ground from firewall to intake manifold is good, hard to see but is it on a plastic bracket? Try relocating or putting beneath the bracket. That ground is crucial in my experience

I redid the whole ground wire, it's hooked up to the firewall, and not on any plastic. The car is bone stock (except for ic pipes and bov) so I know the ground you're speaking of and it has always been there. It's just connected to a bolt and the bracket is hooked up to the intake just be held up. Could this cause any kind of issue? Thanks.

Do you have codes?

Yes, one code only. P0300.

Has the ECU circut board been inspected?

No, the ECU circuit board has never been inspected. This car is bone stock a part from the IC pipes and bov so it's never been touched. When I first got the car it has the P0300 code but the engine bay was completely stock, I did all the colorful things.

Your battery ground loops around and goes to the firewall?

There should be another ground cable going from the starter bolt on the transmission to the negative post, and a ground wire from the negative post to the chassis on the firewall

So youre missing the starter ground cable.

My car had a similar problem, basically in boost the coil would over power the ground cable on the intake manifold and cause a misfire so bad the car would shut itself off

Sorry, not quite sure what you mean. The ground should be connected to the firewall. And the other wire goes to the starter, but I will check again when I go home this weekend from school. I definitely have the starter ground cable because the car can be started with the key.

So, are you saying the thin ground cable on the intake manifold is causing this issue?

For my car, it misfires only in gear and under load that's more than 10%. And when underload over 10%, the rpms fluctuate heavily and jump/dance around.

 

[Dericsh]

Sorry to hear that someone hit your car, but I’m glad you’re able to have it repaired and move forward to solve this issue.

It was mentioned earlier in the thread, Did you try blocking off the EGR valve?

 

[ZubUchiha]

Sorry to hear that someone hit your car, but I’m glad you’re able to have it repaired and move forward to solve this issue.

It was mentioned earlier in the thread, Did you try blocking off the EGR valve?

I have not tried blocking off the EGR valve. I did take it off and gave it a good cleaning with carb cleaner and reattached it with its gasket. What is the point of the EGR valve and what purpose does blocking it off have?

 

[Dericsh]

Read thru this whole linked thread for the answers to those questions, but this post in particular is the reason I suggest that it’s worth a try to test a block off plate, it can be home made, just to test. Your valve could be partially sticking open causing your issue.

https://www.dsmtuners.com/threads/egr-valve.376683/#post-152326540

 

[ZubUchiha]

Read thru this whole linked thread for the answers to those questions, but this post in particular is the reason I suggest that it’s worth a try to test a block off plate, it can be home made, just to test. Your valve could be partially sticking open causing your issue.

https://www.dsmtuners.com/threads/egr-valve.376683/#post-152326540

Okay, awesome. Thank you, I will do this when I fix up the suspension. Where do i get the sheet of metal from?

 

[Dericsh]

Okay, awesome. Thank you, I will do this when I fix up the suspension. Where do i get the sheet of metal from?

I’m sure you could find something to work with at any hardware store.

I’ve not done this to a DSM, but a trick I learned back in the day at the Honda training center was to just take a regular business card and slide it between the valve and gasket just to temporarily block the passages to eliminate or confirm the EGR valve as the cause of the drivability issue.

 

[ZubUchiha]

I’m sure you could find something to work with at any hardware store.

I’ve not done this to a DSM, but a trick I learned back in the day at the Honda training center was to just take a regular business card and slide it between the valve and gasket just to temporarily block the passages to eliminate or confirm the EGR valve as the cause of the drivability issue.

Thanks man, sounds like a plan. But could this really be causing a misfire and rpm fluctuations? With my luck, I doubt it's something this small causing such a big issue. Another thing I recall from January was that the car has always emitted a very strong exhaust gas. I tried using an exhaust detector but couldn't pinpoint where it's coming from, but the light goes off when it is near the lower part of the intake manifold.

 

[Dericsh]

Thanks man, sounds like a plan. But could this really be causing a misfire and rpm fluctuations? With my luck, I doubt it's something this small causing such a big issue. Another thing I recall from January was that the car has always emitted a very strong exhaust gas. I tried using an exhaust detector but couldn't pinpoint where it's coming from, but the light goes off when it is near the lower part of the intake manifold.

It’s tough to say, but it’s easy enough to eliminate. Focus on one thing at a time. You’ve had other suggestions for things that need to be repaired or inspected. Low voltage from low quality alternators and 30 year old ECUs that can have leaking capacitors that can cause all sorts of various electrical problems.

 

[ZubUchiha]

It’s tough to say, but it’s easy enough to eliminate. Focus on one thing at a time. You’ve had other suggestions for things that need to be repaired or inspected. Low voltage from low quality alternators and 30 year old ECUs that can have leaking capacitors that can cause all sorts of various electrical problems.

I replaced the alternators many times by the way. The voltage regulator kept failing. I replaced the one it had when I got it, but then replaced it three more times in very short time because it kept failing. At first I thought it was the alternator itself, but now I am not sure what's causing the voltage regulator to fail. I also replaced the battery but the problem persists.

 

[chrysler kid]

The main issue i have seen with these cars and grounding isnt from the starter, its from the ignition coil on the intake manifold over powering the ground and causing misfires.

Your battery ground cable only has one wire on it, the cable itself in your car is just the negative post hooked to the firewall. The ground should have the cable from the starter hooked to it. This could also explain your issue with cooking alternators if the engine isnt grounded properly.

It has been my opinion that these cars had marginal grounding from the engineering and the ignition coil puts out alot of power on the metal intake manifold. To be more specific I feel the engine should have one more ground at the front of the bay to the chassis, regardless it appears your ground cable to the starter bolt isnt hooked properly

 

[ZubUchiha]

The main issue i have seen with these cars and grounding isnt from the starter, its from the ignition coil on the intake manifold over powering the ground and causing misfires.

Your battery ground cable only has one wire on it, the cable itself in your car is just the negative post hooked to the firewall. The ground should have the cable from the starter hooked to it. This could also explain your issue with cooking alternators if the engine isnt grounded properly.

It has been my opinion that these cars had marginal grounding from the engineering and the ignition coil puts out alot of power on the metal intake manifold. To be more specific I feel the engine should have one more ground at the front of the bay to the chassis, regardless it appears your ground cable to the starter bolt isnt hooked properly

Hi,
Like I told the other person, it may look like there is one cable, but I think there are two cables there instead. I haven't looked at the battery post in a while, but when I get a picture, I will send it here, but I am pretty sure there are two cables, one to the firewall, and the other to the starter. And I redid those ground cables because the alternator kept getting cooked. The previous wires were bad.

 

[Mello]

Sorry but I'm with @chrysler kid on your battery's power ground.

Both my 2G DSMs battery positive have three wires, 2 white (maybe 3 gauge) for the distribution block (fuse box) & the main, large black positive wire (maybe 0 gauge) going to the starter solenoid. My battery negative has the black large ground wire (again, maybe 0 gauge) connected to the starter mounting bolt that's on the tranny bellhousing. Also, my negative battery clamp has an addition ground strap attached to it with a bolt that connects to the firewall.

I don't see any of this in your engine bay picture.

 

[ZubUchiha]

Sorry but I'm with @chrysler kid on your battery's power ground.

Both my 2G DSMs battery positive have three wires, 2 white (maybe 3 gauge) for the distribution block (fuse box) & the main, large black positive wire (maybe 0 gauge) going to the starter solenoid. My battery negative has the black large ground wire (again, maybe 0 gauge) connected to the starter mounting bolt that's on the tranny bellhousing. Also, my negative battery clamp has an addition ground strap attached to it with a bolt that connects to the firewall.

I don't see any of this in your engine bay picture.

Sorry, I will get that picture as soon as I can.

 

[ZubUchiha]

I was able to get a picture, here it is. You can see the ground has its own cable attached to the terminal, and the terminal has its own wire attached to the starter post

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[aaronth777]

I agree with everyone else that this seems like an electrical issue with the random misfires but only under load and it affects the tach. How are you measuring the voltage? Are you only measuring it when it's sitting still? I'm wondering if the alternator isn't sensing the increased electrical load and isn't upping the voltage to compensate. When did the misfires and tach issues begin? Did they happen after doing car work like redoing the grounds or just randomly one day started having issues?

As far as voltage regulators failing, I've been through that myself with 3 alternators in a year. I found that the Duralast remanufactured alternators were junk and the voltage regulators would give out very quickly. I ended up getting the Duralast Gold new alternator and I've been fine ever since. I don't know about Ultima but if it's remanufactured then I'd suspect that could be an issue. Keep in mind that the alternator is grounded through the metal to metal contact on the pivot bolt, so the ground goes through the engine block. Make sure those metal surfaces are clean where the alternator bolts to the engine, and that there's a good solid ground from the engine to the battery. Also when you're under load and the tach is jumping, do the lights also dim (like the headlights or interior lights)? That would be a dead giveaway that you're having a voltage issue and can focus on that.

 

[chrysler kid]

I was able to get a picture, here it is. You can see the ground has its own cable attached to the terminal, and the terminal has its own wire attached to the starter post

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Under the intake manifold and attached to the transmission bolt that connects the transmission to the engine block there is a cable, from the transmission bolt, there is suppose to be a wire that is suppose to go to the negative battery terminal.

Your car is missing that cable

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[ZubUchiha]

I agree with everyone else that this seems like an electrical issue with the random misfires but only under load and it affects the tach. How are you measuring the voltage? Are you only measuring it when it's sitting still? I'm wondering if the alternator isn't sensing the increased electrical load and isn't upping the voltage to compensate. When did the misfires and tach issues begin? Did they happen after doing car work like redoing the grounds or just randomly one day started having issues?

As far as voltage regulators failing, I've been through that myself with 3 alternators in a year. I found that the Duralast remanufactured alternators were junk and the voltage regulators would give out very quickly. I ended up getting the Duralast Gold new alternator and I've been fine ever since. I don't know about Ultima but if it's remanufactured then I'd suspect that could be an issue. Keep in mind that the alternator is grounded through the metal to metal contact on the pivot bolt, so the ground goes through the engine block. Make sure those metal surfaces are clean where the alternator bolts to the engine, and that there's a good solid ground from the engine to the battery. Also when you're under load and the tach is jumping, do the lights also dim (like the headlights or interior lights)? That would be a dead giveaway that you're having a voltage issue and can focus on that.

Hello,

Measured voltage using a multi meter at the battery. Not sure how to measure it while driving it. I do have a fm transmitter that displays voltage when i plug it in, so it gives a low reading. The misfires and tach issues were there when I bought the car.

The lights do dim and flicker when i turn on a turning signal etc.