91 burb runs terrible in reverse

[Jawzjeep]

I've been picking through the big issues on my Suburban and now I'm down to the smaller ones.

My issue is when I drop it into reverse and give it any gas it bucks and snorts like it's running on less cylinders. Its fine sitting in reverse while I'm waiting to back out. It only acts up when I start giving it gas. It seems to back up the best when I give it larger amounts of gas and don't feather it at all. When feathering it feels like it shakes. It doesn't stall but feels like it might. Zero issues in forward gears.

Anybody had anything kind of short when you put it into gear? I had a carbed K10 that when I dropped it in gear would die because the distributor connection would break free slightly due to wires being too tight and engine twist.

91 burb, 350tbi 700r4 with lots of new parts like fuel pump, clean tank, fuel filter, ICM, MAP, cap, wires, CTS, egr solenoid and valve.

 

[squaredeal91]

I wonder if the AIC / IAC acting up only on reverse? And How is the kickdown cable adjustment.
@NickTransmissions any thoughts buddy?

 

[gmbellew]

Do the volts drop in reverse, like the reverse lights or something has a wiring issue?

Otherwise I think you will be trying to track down a wiring issue like you suggested.

An OBD1 Bluetooth reader and ALDLDroid will let you watch all the sensors and computer stuff to help diagnose....

 

[NickTransmissions]

I've been picking through the big issues on my Suburban and now I'm down to the smaller ones.

My issue is when I drop it into reverse and give it any gas it bucks and snorts like it's running on less cylinders. Its fine sitting in reverse while I'm waiting to back out. It only acts up when I start giving it gas. It seems to back up the best when I give it larger amounts of gas and don't feather it at all. When feathering it feels like it shakes. It doesn't stall but feels like it might. Zero issues in forward gears.

Anybody had anything kind of short when you put it into gear? I had a carbed K10 that when I dropped it in gear would die because the distributor connection would break free slightly due to wires being too tight and engine twist.

91 burb, 350tbi 700r4 with lots of new parts like fuel pump, clean tank, fuel filter, ICM, MAP, cap, wires, CTS, egr solenoid and valve.

On a level grade with no vehicles or anything else behind you, throw it in reverse, keep foot off gas pedal. It should move in reverse on its own without any throttle input. If it doesnt or slips, the trans needs to come out.

ETA: If you suspect a short to ground where the electrical system is grounding itself on the transmission, put key on engine off, leave driver side door open so dome light is illuminated then start running through the gears with the engine off. Watch the dome light as you shift from reverse to neutral, neutral to drive and so forth.

If the dome light flickers during those range transitions from R to N and N to D4, etc you have a short thats grounding itself to the transmission's shift linkage

 

[Jawzjeep]

I got a chance to check off a few things.

On flat ground dropping into reverse with no throttle it starts to rolls back fine. Engine loads like normal. As soon as I give it tiny throttle it stutters, like plugs not all firing. No pops or backfire. I give it heavy throttle stabs in reverse and its less noticeable.

I don't have a dome light but taking it through the gears with just the key on and my other lights on yielded no results.

For full clearity I was dealing with a code 34 map sensor issue in another thread. Seemed to fix the 34 but nothing changed with the reverse issue.

When it decides to stop pouring I'll crawl under it and have peek at the backup lights and shift linkage. Thanks for the pointers

 

[Jawzjeep]

I did a bunch of looking and wire wiggling. Didn't find anything that stood out. I did however find a couple spark plugs were oil fouled dealing with other issues. That was the miss I was feeling. Cleaned the plugs and it stopped acting weird in reverse.

I can't say if it was the wire wiggle or if it was the plugs but since they were clearly fouled I gotta think that fixed it.

If/when the reverse issue comes back I'll check clean or swap the plugs and report back.

 

[bucket]

That kinda makes sense about the plugs. Reverse gear is much taller than first gear, which would put more load on the engine for the same amount of RPM, compared to first gear.

 

[Jawzjeep]

Some may know but I started a thread about a map sensor issue. As I've been making my way figuring out the issues I found that when I unplugged my EGR the burb ran normal and alleviated all of the stuttering at low throttle application in reverse. Before unplugging the EGR it was starting to do the same thing and forward gears. There's more to figure out like why it's being opened at such a small amount of throttle input but I at least wanted to state something here if anyone had the same issue.