1fz-fe Misfire/stumbles in when put into gear!

[Dudemanslick]

I have a 1993 LC , after the parts cannon, the truck seems to idle FiNe when in park and even rev up smooth, but as soon as I put the truck in drive/reverse etc. It stumbles and hiccups, almost dies. Parts replaced are:
Dizzy
Dizzy cap
Button
Plug wires
Plugs
Coil pack
Fuel filter+reg. + pump
Cleaned injectors
Grounds are fine..
I'm down to the ignitor (as it supposed to send a high voltage signal to the coil pack)... can somebody point me in the right direction...?

 

[cruiserdan]

Ive got the back 2, but the ones right off the engine have been blocked off, they never caused any issues other than stinky exhuast

There are no "Back two" only two just in front of the cats, in the front exhaust pipes.

 

[ppc]

Must be referring to the two ports on the exhaust manifold for the PAIR system.

 

[Dudemanslick]

Must be referring to the two ports on the exhaust manifold for the PAIR system.

Yes , sorry im unsure, don't know too much about these trucks

 

[landtank]

Sounds like a problem with the engine harness when the engine torques under load

 

[cruiserdan]

Sounds like a problem with the engine harness when the engine torques under load

Probably by the EGR pipe.

 

[landtank]

Probably by the EGR pipe.

most likely, the other spot is at the firewall. While idling smooth I'd grab onto the harness and move it about to see is there is a reaction.

 

[Old Nick]

I would also check that your TPS and IACV are in spec and working properly (I've been beating a dead horse with that advice... lol... because it solved the problems the rig was having... which were very much like yours).

While you are checking/replacing vacuum lines and the intake hoses... pull the throttle body. Clean it thoroughly and go through the FSM tests for the the TPS and IACV.

I had the same problems with my wife's rig... (which is now reliable...). Admittedly, this rig had been neglected for a LONG time, when I bought it. TPS was bad and the IACV was gummed up terribly (later model 95-97 IACVs work on 93-94 80s).

One last thing... is your check engine light on when you turn the key to the on position? If not... check all fusible links (and replace the ones in the engine bay fuse box... and while you are in there, put a new EFI relay in). Also inspect the main link final link, at the battery. It's a cheap part. If it looks ratty, change it out, and buy an extra for your glovebox.

Factory timing is 3 degrees, but I've read all around Mud that timing as high as 9 degrees is ok. I'm running mine at 3.

 

[Mat Jadamec]

Since the PAIR system seems to be out make sure the vacuum line on the front of the head is plugged. I took mine out and put the O2' sensors in the manifolds (much better position if you ask me).

All three times I had this symptom on my '94 it was something simple and the change was night and day. First it was a cracked intake tube, then it was vacuum lines (the metal ones, corroded) for the EGR, and then the O2 sensors (the ECU was right that time). I've done the ignition parts cannon and rebuilt fuel system tank to fuel rail, valve cover gasket, PVC, vacuum hoses, and charcoal canister and never really noticed a difference from that work. I put a heat shield on the harness next to the EGR about 10 years ago. My check engine light has been on 95% of the time since and when I bought it 2006.

Right now I have to keep off the gas to avoid speeding...

 

[Dudemanslick]

Update : just replaced iacv, tps and EFI relay,not much change, the trucks runs great when the revs get past about 2k rpm...below that the truck is still struggling bad, sprayed ether around intake again but there are no leaks.
If I attempt to blip the throttle, it's an immediate misfire..., but if I ease the pedal it will take rpm smoothly...., leaning towards buying another ECU!

 

[Old Nick]

Update : just replaced iacv, tps and EFI relay,not much change, the trucks runs great when the revs get past about 2k rpm...below that the truck is still struggling bad, sprayed ether around intake again but there are no leaks.
If I attempt to blip the throttle, it's an immediate misfire..., but if I ease the pedal it will take rpm smoothly...., leaning towards buying another ECU!

Man, that is a bummer. Where simple stuff in concerned: Is your idle at 650rpm or thereabouts? Have you checked the tension on your throttle cable?

 

[Fj80oregon]

What IACV did you use to replace it?

 

[Dudemanslick]

Man, that is a bummer. Where simple stuff in concerned: Is your idle at 650rpm or thereabouts? Have you checked the tension on your throttle cable?

Funny you asked about idle, it's sitting at about 1500rpm...but the cable is fully slacked...I can't get it any lower, also noted that with the ac on the idle does not change...i

 

[Dudemanslick]

What IACV did you use to replace it?

I just bought a cheap one, maybe 60$ , im running out funds for this head scratcher..it made a noticeable difference...the idle is very smooth now, but it wont take throttle at a normal pace...if I let it stumble a second with my foot on the pedal it clears up...

 

[Dudemanslick]

Man, that is a bummer. Where simple stuff in concerned: Is your idle at 650rpm or thereabouts? Have you checked the tension on your throttle cable?

When i put the shifter into gear or reverse the idle is at 650-800...but with, what sounds like misfire..

 

[Old Nick]

Funny you asked about idle, it's sitting at about 1500rpm...but the cable is fully slacked...I can't get it any lower, also noted that with the ac on the idle does not change...i

If you have a timing light, hook it up and check your timing.

I'm guessing your timing is too advanced. The throttle cable being slack and the timing being off.. I'm betting those are the causes of your stumbling and high idle.

Did you pull the distributor while you were servicing your truck? If so, it could have gone back in a "tooth off", making the timing too high. If you didn't pull it, the po might have and re-installed it incorrectly.

 

[Dudemanslick]

When i put the shifter into gear or reverse the idle is at 650-800...but with, what sounds like misfire..

If you have a timing light, hook it up and check your timing.

I'm guessing your timing is too advanced. The throttle cable being slack and the timing being off.. I'm betting those are the causes of your stumbling and high idle.

Did you pull the distributor while you were servicing your truck? If so, it could have gone back in a "tooth off", making the timing too high. If you didn't pull it, the po might have and re-installed it incorrectly.

Yes I did pull it, so I just used the distributor to set it right at 3 with timing light, the idle lowered to about 1200..., you may be onto something, i followed the photos I found online to adjust the distributor, but like you said I may still be a tooth off

 

[Dudemanslick]

If you have a timing light, hook it up and check your timing.

I'm guessing your timing is too advanced. The throttle cable being slack and the timing being off.. I'm betting those are the causes of your stumbling and high idle.

Did you pull the distributor while you were servicing your truck? If so, it could have gone back in a "tooth off", making the timing too high. If you didn't pull it, the po might have and re-installed it incorrectly.

Here's what we got at tdc now

 

[Dudemanslick]

If you have a timing light, hook it up and check your timing.

I'm guessing your timing is too advanced. The throttle cable being slack and the timing being off.. I'm betting those are the causes of your stumbling and high idle.

Did you pull the distributor while you were servicing your truck? If so, it could have gone back in a "tooth off", making the timing too high. If you didn't pull it, the po might have and re-installed it incorrectly.

The amount of time between the piston stopping and going back down is long. Are you supposed to set the dizzy when the crank mark is at 3?

 

[Old Nick]

The amount of time between the piston stopping and going back down is long. Are you supposed to set the dizzy when the crank mark is at 3?

 

[Old Nick]

Have you downloaded the factory service manual? If not, go to the resources at the top of the page. It’s located there for free.