1987 GL10 single port fuel injected

Non turbo

Automatic

2wd

55K original miles

 

I changed the MAF sensor a few days ago (due to non starting). When I got the car started I noticed it was idling rough and even stalled when I put it in gear. So I pulled all the plug wires one at a time (engine running) and when I pull cylinders 2,3 and 4 the engine runs worse. But when I pull #1 wire the engine has no change. So I changed the #1 plug, wires, distributor cap and rotor and pulled #1... still dead. I took the #1 wire off, put the old plug in the end of the wire and ran a jumper wire from the old plug to the new plug (still in the engine) and the old plug (exposed) fires the plug consistantly.

I took the new plug out of the engine and the cylinder has good compression... Which tells me there is fuel issue, but with the single point fuel injection why would it feed all the cylinders except #1????

 

When in park it idles around 700-800 rpm. In drive it idles around 500-600.

 

Any ideas why the #1 cylinder is not firing or why the engine is suddonly running rough?

 

Thanks

Frank T

 

 

 

id say the missfire would be number 1 as to why its running rough.

 

leaky intake gaskets can kill a cylindar and weaken the others, and of course if your vavles aren't opening correctly you can have compression but no intake charge as well. 

 

the SPFI still pulses fuel, but i dont know if it pulses for each cylindar individually or if it just pulses at a rate for the RPM's.

 

I dont really know off hand what is the most likely, but i would probably check the intake gaskets

+1 on the valves. I had that same problem on my car(carbed) i took the valve covers off and adjusted the valves. Problem solved.

Had the same problem once. In my case the problem turned out to be a small broken vacuum line that was attached to the intake manifold runner that fed the dead 
cylinder. 

87 GL-10 would be mpfi with 4 injectors. maybe your car is an 86? 

+1 on the valves. I had that same problem on my car(carbed) i took the valve covers off and adjusted the valves. Problem solved.

 

Ea82 engines do not have adjustable vavles

87 GL-10 would be mpfi with 4 injectors. maybe your car is an 86? 

 

Nope.  Non-turbo MPFI was dropped for the GL-10 in 87.  All 2wd non-turbo cars that year are SPFI  (excluding XT)

 

86 2wd non-turbo GL-10 would also be SPFI

 

85  2wd Non-turbo GL-10 would be MPFI

85 4wd Non-turbo GL-10 would be carbed

 

He's got an SPFI car.

 

My suggestion would be to do a leakdown, not just a compression check.  Burnt or hung up valve can still show pretty good compression.

I found a very small vacuum hose disconnected on the same side as the #1 cylinder!!!

I Hooked it up and it smoothed out the idle. Why this was acting like the #1 cylinder not firing??? Im assuming it was pulling vacuum from near the #1 cylinder///

Im just glad it was something simple.

Thanks for everyone's input!!

Edited July 15, 201312 yr by Frank T

Glad you got it figured out. Good to know theres no adjustment on the valves and kinda weird also

 

I found a very small vacuum hose disconnected on the same side as the #1 cylinder!!!

I Hooked it up and it smoothed out the idle. Why this was acting like the #1 cylinder not firing??? Im assuming it was pulling vacuum from near the #1 cylinder///

Im just glad it was something simple.

Thanks for everyone's input!!

 

Because #1 was not firing.

Vacuum leak leaned out the mixture for #1 to the point of incumbustibility

  

Because #1 was not firing.

Vacuum leak leaned out the mixture for #1 to the point of incumbustibility

these engines aren't very powerful anyway. when even a small vacuum leak can feel like a cyl's not firing.

post a pic o the vacuum hose... for the future problems....

stuck injector try a differnt one have seen them stick faily often