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Idles like crap after hard stop in reverse?

K

KaiserMan

NAXJA Forum User
Location
Huntington MA
I was pretty pissed off (still am) at the Jeep (for other reasons then in this post). I had it parked in front of the garage and floored it reverse (not stupid high RPM's but I was probably doing 12mph) and gave the brakes (ABS) a good stomp when I wanted to stop.

Right after that it started to idle like crap and vibrate. It will idle at 1K fine for 20-30 seconds then idle very rough ranging from the first mark on the tach to the third (I'm assuming this is 250 RPM's and 750 RPM's).

It smooths out at high idle goes down the road okay, but not like it used to.

This is a 90 4.0/Auto.

Either it gets fixed this weekend or it's up for sale, or on fire.

Any help is appreciated.

I'm leaing toward fire right now.
 
Tune up would be a good start and my solve the problem..

Another thing comes to mind , if you were low on gas. going that fast may pool the gas away from the pump to cause air in the system.

Just a thought

Nick
 
I have about 1/4 tank of gas. Would filling it up purge thre air?

I Just ordered up Ecklin cap and rotor, delco plugs, belden 7mm wires and a fuel filter to the tune of $87. So much for buying the NP205 for my 63 this week....

It also seems to be running richer now. I'm getting a gassy smell out the pipe.
 
Check all wires for integrity. Slamming on things like this can cause the torque to move your engine around a bit and if your motor mounts are weak wires can get pinched.
 
goodburbon said:
Check all wires for integrity. Slamming on things like this can cause the torque to move your engine around a bit and if your motor mounts are weak wires can get pinched.
Click to expand...

And vacuum hoses, too.
 
Well the tune up made it idle better, not as it should (still drops but not half as much as before). It felt like it had a slight miss before, and it's pretty obvious at the tailpipe now.

All of my PCV vac hoses (all three sections) are new, any other hoses I should look at?

Could it be a clogged injector?
 
Could be. Best way to find out is to unplug them one by one as the jeep is idling. If you unplug one and the idle does not change, there is likely your culprit.
 
I'll give that a try, thanks. I was thinking maybe I kicked up some sediment in the tank.

Stuff like this kind of stumps me on newer vehicles. This is the first thing I've owned with a computer and more then three or so sensors.
 
Okay, dumb question. How do you unlug them? They don't seem to just pull off.

Also, I noticed that the first injector (#1 cyl I'm assuming) is leaking a bit. The bottom side of it was damp with fuel. Would this cause a miss?
 
yes that could very well be the problem. just hit the parts store and get a bag of rings, its only a few bucks. try that and see where it gets you, its worth a try since its leaking anyway.
 
I was readig a bit oabout the rings. Do they go inbetween teh metal and plastic part of the injector?

I just fired the Jeep back up and I don't see it leaking now, and the miss seems to be gone? I was also to lazy to close the hood so I just pulled the negative cable on the battery (so the under hood light didn't drain down teh batt.) if that makes a difference.

Also, the parts store lists fuel injector o-rings ($8.99) and a fuel injector seal kit ($6.99). What's the differance?
 
KaiserMan said:
I was readig a bit oabout the rings. Do they go inbetween teh metal and plastic part of the injector?

I just fired the Jeep back up and I don't see it leaking now, and the miss seems to be gone? I was also to lazy to close the hood so I just pulled the negative cable on the battery (so the under hood light didn't drain down teh batt.) if that makes a difference.

Also, the parts store lists fuel injector o-rings ($8.99) and a fuel injector seal kit ($6.99). What's the differance?
Click to expand...

did the battery unplug happen before the rough idle?

Mine always run rough after i pull the iod or unplug the batt.
btw instead of pulling the battery cable there is a fuse labeled iod in the fuse box under the hood of most cars it stands for "ignition off drain" should stop the lights from coming on.
 
Rough idle before the unplug. I just took it for a drive. Idle surges a bit, better though. Still can't get the injector to leak again, and the miss seems to have gone away. Just getting a bit of an extra puff now and then from the tail pipe. I really have no idea what is going on.

I am going to pick up an o-ring seal kit tonight though.
 
I'd go ahead and grab some o-rings for those injectors....may end up with that fire you wanted if you let it go too long.
 
Just got back from advanced with the rings. Do I oil these or anything before putting them on?

Also got a new gas cap, muold locking one (with no key) is a pos. Figured it can't hurt.
 
Well I decided to hold off on teh rings for now. Looks like it's enough of a pain in the butt to get to the rail that I might as well replace the injectors. I'll be picking up some of the 19lb 5.0 refurbished injectors off ebay.

I'll update when I get them in.
 
KaiserMan said:
Well I decided to hold off on teh rings for now. Looks like it's enough of a pain in the butt to get to the rail that I might as well replace the injectors. I'll be picking up some of the 19lb 5.0 refurbished injectors off ebay.

I'll update when I get them in.
Click to expand...

let me know how they worked out. thats my next step on my 88 to get it to run right all the time !!!
 
It is easy to change those injectors.

There are four bolts holding the fuel rail to the manifold. Remove them. Then there is a "block and bracket" where the vacuum line assemblies attach to the manifold at the front of the engine, loosen the vacuum assemblies and remove the nut holding the bracket.

Use a pry bar to lift against the injectors' bodies and gently pull up on the fuel rail, work from back to rear a couple of times and they should all pull free from the manifold. Unplug the injectors, you have to slightly displace the wire locks, then twist and pull them free from the fuel rail.

You can use Petroleum jelly to lube the top and bottom seal of each injector, then start them a little into the rail, then align them all with the manifold and push them into the manifold. Now put the nut, bracket, vacuum assembly, and the four bolts back and tighten everything. Now the last steps--use a pry bar to gently push against the injector body and make sure it is fully seated into the fuel rail, then reattach the wiring harness, set the wire locks, and you are done.
 
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