Car finally tries to start, but no tach and terrible bucking/misfiring

hulakai

Registered User
Hey all,

New symptom with an 89 5 speed that sat for a LONG time.

Replacing the injectors got it to fire after running all the other no-start tests several times and finding nothing amiss.

However, it bucks and backfires and runs terribly (and not for very long) when I start it. I suspected Cam Sensor initially but it RUNS THE SAME WITH OR WITHOUT IT THE CAM SENSOR plugged in. Also, THERE'S NO MOVEMENT OF THE TACH at all.

I left the battery on charge last night because it was getting low and I know voltage is critical, and this afternoon I was planning to remount the DIS with fresh paste (I had it off during the initial troubleshooting) and perhaps change the cam sensor to one I have that I know is good....but shouldn't these cars run (not optimally) without a cam sensor at all?

I could sure use some more tips from the more experienced.

Thanks

K
 
Well, think about it.

If it runs the same with or without the cam sensor plugged in, and there's no tach (which is derived from the cam sensor), then it makes good sense that it's the cam sensor circuit (cam sensor, connectors, wiring, or PCM circuitry related thereunto.)

Does it not?

RwP
 
Sounds like perhaps you changed the plug wires around while trouble shooting? Double check the wires at the coil and trace to each plug.

The back row goes (left to right from front of the engine) 1-2-3
Front row goes (left to right from front) 5-6-4 .. note it is NOT 6-5-4
 
Hey all,

New symptom with an 89 5 speed that sat for a LONG time.

Replacing the injectors got it to fire after running all the other no-start tests several times and finding nothing amiss.

However, it bucks and backfires and runs terribly (and not for very long) when I start it. I suspected Cam Sensor initially but it RUNS THE SAME WITH OR WITHOUT IT THE CAM SENSOR plugged in. Also, THERE'S NO MOVEMENT OF THE TACH at all.

I left the battery on charge last night because it was getting low and I know voltage is critical, and this afternoon I was planning to remount the DIS with fresh paste (I had it off during the initial troubleshooting) and perhaps change the cam sensor to one I have that I know is good....but shouldn't these cars run (not optimally) without a cam sensor at all?

I could sure use some more tips from the more experienced.

Thanks

K

My car literally just did this exact same thing today. I’ve had the bucking but today was the first day I lost the tach signal
 
Well, think about it.

If it runs the same with or without the cam sensor plugged in, and there's no tach (which is derived from the cam sensor), then it makes good sense that it's the cam sensor circuit (cam sensor, connectors, wiring, or PCM circuitry related thereunto.)

Does it not?

RwP


Ummmm, my understanding is that the car does not need the cam sensor to run. The ECM has a timing table in memory that it will use if the cam sensor isn't talking to it. So if it was the cam sensor wouldn't it at least start and idle with it unplugged.

Am I mistaken?
 
Sounds like perhaps you changed the plug wires around while trouble shooting? Double check the wires at the coil and trace to each plug.

The back row goes (left to right from front of the engine) 1-2-3
Front row goes (left to right from front) 5-6-4 .. note it is NOT 6-5-4


I am such an idiot. You're probably right that the plug wires are wrong. That is EXACTLY what it find like....ie wrong firing order. I was so fixated on the 5-6 misprint in the Haynes manual that everyone warns about that I forgot that 4 goes on the 6th post not the 4th. I'm almost positive I've got it 123465 instead of 123564.

Been staring at this engine for too long. Thanks very much for snapping me out of my stupidity.

K
 
Swapping wires isn’t going to make your tach not work. Is the problem intermittent or is it every time, if it’s plug wires it will do it every time but like I said that’s not going to make your tach not work. Mine is doing it intermittently so tells me it’s some kind of connection or electrical item going wrong. Plug wire misfires don’t go away.
 
So....changed the wires for 4, 5 and 6 today (564) and it still won't run. It WANTS to run, but won't and STILL sounds like it's a timing issue.

I agree, the tach issue is separate, I just didn't know where the tach pulls it's signal from. Crank sensor? Ignition?
 
So....changed the wires for 4, 5 and 6 today (564) and it still won't run. It WANTS to run, but won't and STILL sounds like it's a timing issue. I agree, the tach issue is separate, I just didn't know where the tach pulls it's signal from. Crank sensor? Ignition?

So the yellow up arrow, on the dash, goes out when you're cranking, but you have a dead tach?

Humor me, and try it with the cam sensor unplugged 1 more time. Give it about 3-4 tries, and about 4 seconds each try.
 
So the yellow up arrow, on the dash, goes out when you're cranking, but you have a dead tach?

Humor me, and try it with the cam sensor unplugged 1 more time. Give it about 3-4 tries, and about 4 seconds each try.


Ok....I disconnected the cam sensor. It starts (sometimes 2-3 tries) but won't stay running UNLESS I CONSTANTLY PUMP THE GAS. It won't idle or run steady at any rpm, and the tach is still dead.
I had suspected vacuum issues but I resealed all the tubes and checked the vacuum lines and I THINK all the lines are good and in the right place but I admit I'm not 100% sure. Is there a map of all the vacuum lines here on the site?

So no tach, cam sensor disconnected, and will only run smoothly if I'm pumping the gas. If it was a carb I would describe it as only running on the accelerator pump gas.

I should add that I'm seeing 20lbs of vacuum when I let off the throttle, but again it won't run at a steady rpm no matter what rpm that is.

Help?
 
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Ok....I disconnected the cam sensor. It starts (sometimes 2-3 tries) but won't stay running UNLESS I CONSTANTLY PUMP THE GAS. It won't idle or run steady at any rpm, and the tach is still dead.
OK, you can plug it back in.. still strange you don't have a tach signal.. DIS is new also, right?

I had suspected vacuum issues but I resealed all the tubes and checked the vacuum lines and I THINK all the lines are good and in the right place but I admit I'm not 100% sure. Is there a map of all the vacuum lines here on the site?
There's a vacuum line diagram on the frame. You might try capping off some of them at the intake just to eliminate a batch of lines.. inspect carefully around all those vacc lines with a flashlight, especially just behind and beneath the throttle body. Does the car have EGR? Anywhere a vacc line connects to any port on the intake.. try capping that off.. don't worry about what that line does for now, just see if it fixes anything.
 
Ok...checked the vacuum lines for the umpteenth time and all looks fine. Pretty sure its not vacuum anyway since it runs super rough at all rpm and won't hold a steady rpm at any throttle.

Plugged cam sensor in and now it starts every time but again, it only stays running if you pump the throttle continuously. So I'm thinking cam sensor is ok.

Tried a known good DIS. No change.

Tried a known good ECM. No change.

No upshift light, but also no tach (could be simple electrical problem...fuel gauge isn't working either).

Fuel delivery related? Whatever the ECM does when detecting throttle increase (ie accelerator circuit) is working but that's it. Consistent speed simply won't work. It sputters and shakes like mad when it runs, but revs right up when giving it lots of gas. Is it reasonable to start ruling out ignition?

Two codes are appearing. 19 (CID Sensor failure) and 96 (Fuel pump secondary circuit failure). Not sure but those codes seem more like an effect rather than a cause. I've never understood 96. It seems to come and go with other issues.

So frustrating.

What are the symptoms of a bad fuel pressure regulator?
 
OK, you can plug it back in.. still strange you don't have a tach signal.. DIS is new also, right?

There's a vacuum line diagram on the frame. You might try capping off some of them at the intake just to eliminate a batch of lines.. inspect carefully around all those vacc lines with a flashlight, especially just behind and beneath the throttle body. Does the car have EGR? Anywhere a vacc line connects to any port on the intake.. try capping that off.. don't worry about what that line does for now, just see if it fixes anything.


Yes it does have egr
 
Make sure the balancer isn't broken. Check to see if the bolt in the center is still there and that balancer doesn't wobble.
 
Being I'm dealing with a similar issue, I just read my factory service manual, and it gets that tach signal initially from the crank sensor, it is then relayed to the tach via the DIS module.

I'm honestly unsure if these cars have this or not, but coming from a general automotive knowledge aspect perhaps an idle air control or idle air issue, basically if the engine cannot get sufficient airflow to idle it will die and will stay running once you crack the throttle cause it gets air. I would maybe see what's up with that crank sensor though for the dead tach issue. I'm putting a new DIS module in mine tomorrow.
 
Does anyone know if the crank sensor is an 'all of nothing' type of part? Either it works or it doesn't? Or it can work intermittently?
 
The CRANK sensor is a all or nothing component (GO/NO GO) in most cases. The exception would be bad connection and or chaff wires.


What is the condition of the DIS harness? Do you see any chaffing of harness and or connector of the CAM or CRANK sensor next the supercharger belt? Check the connector pins for indication of corrosion. Clean if necessary. Add die electric grease.


IF the car has not run over and extended period of time fuel system maintenance is required. Old contaminated fuel could cause the injectors to stick again. Did you drain all the old fuel from the tank? Did you add a strong fuel system cleaner with the new fuel? Did you replace the fuel filter prior to start? The bucking and misfiring (after checking emission/ignition components) is typical of a stagnate car in storage with contaminated fuel. Is fuel pressure (key on engine off) within limits? If so and as mention before if the emission/ignition and vacuum connections are good I would do the following.



With new fuel (approx 3 gallons) in an empty tank and a new fuel filter add 3 bottles/ containers of fuel system cleaner. Start car. Hold throttle until RPM are 1500 for 3 minutes. Return throttle to idle. Repeat 3-5 times. If it still wants to shut off repeat the procedure but hold RPM to 2000 and then to 2500. This should clear out enough contaminates in the fuel pump sock, fuel lines and fuel injector (basket) filters. Shut down and replace the fuel filter. Do start again. It should idle. It should be a little rough until the first road runs.
 
The CRANK sensor is a all or nothing component (GO/NO GO) in most cases. The exception would be bad connection and or chaff wires.


What is the condition of the DIS harness? Do you see any chaffing of harness and or connector of the CAM or CRANK sensor next the supercharger belt? Check the connector pins for indication of corrosion. Clean if necessary. Add die electric grease.


IF the car has not run over and extended period of time fuel system maintenance is required. Old contaminated fuel could cause the injectors to stick again. Did you drain all the old fuel from the tank? Did you add a strong fuel system cleaner with the new fuel? Did you replace the fuel filter prior to start? The bucking and misfiring (after checking emission/ignition components) is typical of a stagnate car in storage with contaminated fuel. Is fuel pressure (key on engine off) within limits? If so and as mention before if the emission/ignition and vacuum connections are good I would do the following.



With new fuel (approx 3 gallons) in an empty tank and a new fuel filter add 3 bottles/ containers of fuel system cleaner. Start car. Hold throttle until RPM are 1500 for 3 minutes. Return throttle to idle. Repeat 3-5 times. If it still wants to shut off repeat the procedure but hold RPM to 2000 and then to 2500. This should clear out enough contaminates in the fuel pump sock, fuel lines and fuel injector (basket) filters. Shut down and replace the fuel filter. Do start again. It should idle. It should be a little rough until the first road runs.


First thing I did was drain the tank and wipe it out clean, put in a new pump, blew out the lines and changed the filter. Since then I've changed the injectors and replaced the fuel filter again.

The car will not hold ANY rpm steadily to run it as you suggest. It will only run if I'm constantly adjusting the throttle up and down. It's not just an idle issue.

The bucking has stopped, but it won't run at a steady throttle position....it will start losing power and sputter until it dies from ANY rpm if I don't work the throttle. It WILL start up again immediately though.

It's as if it has a massive vacuum leak but it still gets 20 inches of vacuum on the gauge when letting off the throttle, and the supercharger bypass valve is working perfectly.

So weird.
 
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It's as if it has a massive vacuum leak but it still gets 20 inches of vacuum on the gauge when letting off the throttle, and the supercharger bypass valve is working perfectly.

So weird.
Thats what I'm thinking as well. I think you just haven't found it yet. If you can, try doing a smoke test. That seems to be the best way. Do a search here to find out various techniques people have come up with to do that. Some are as simple as using a cigar.
 
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