cdf43

1987 cherokee 4.0 motor. 5speed.

So what's happening is it will idle just fine. But when I put it into gear and give it a little gas like normal it will sputter bog out and die. Sometimes it will start right back up. Sometimes it will crank and crank and not start right away.

So I parked it for a few months because I didn't have the time or money.

But now winter is approaching and I need to get it fixed before it snows.

So the battery was completely dead from sitting for a few months. I put it on a trickle charger and got it to start.

Drove it around the block about 7-10 times and it didn't act up at all.

I know it's gonna act up sooner or later and I need to start tearing into it.

I haven't started to diagnose it yet. Where should I start. I know the spark plugs are good and the O2 sensor is about 3 years old.

caged

does it do it only when it's hot?
check the catalytic converter. it could be plugged. tap it with a rubber mallet to see if the honeycombe internals has come apart. you can check with a backpressure gauge, but you would have to remove the upstream O2 sensor, which depending on age of it, can be a pita to get out, then to get it or a new one back in without changing the engine pipe.

rusty_bucket

Fuel Pressure?

Turbo X_J

1. If the battery is that far gone it should be replaced first.
2. Check fuel pressure with a gauge you can borrow from Vatozone.
Then,

Waaaaaaay too much work, try this:

Here's a simple do it yourself (DIY) test that can be performed to see if your CAT convertor is clogged or if you have excessive exhaust system backpressure or restriction:

Tools needed: vacuum gauge, tee connector

Connect a standard engine vacuum gage into a vacuum port off the intake system. You can tee off the fuel pressure regulator or purge valve lines located on the engine.

Start engine and maintain rpms at 2000 - 2500 rpm.

Watch vacuum gauge and reading should stabilize and stay steady.

If vacuum reading starts dropping or decreasing, it indicates either a clogged CAT convertor or restriction/backpressure in the exhaust system.

cdf43

It does it hot or cold.

I'll try to check the Cat.

cdf43

Any other ideas? Besides the cat and fuel pressure. Which I will check next week. Gotta get it down to my shop.

ehall

Fuel pump or coil / ignition module

cdf43

So now I can't get it to act up. Must be an intermediate issue. Which is gonna make it harder to trouble shoot

DFlintstone

Might have been a fluke. My renix was bogging under throttle and backfiring out the intake. Long story but it turned out to be one of the wires to the lower sensors grounding. Unfortunately I don't know which it was, but that condition may be caused by being lean, which the temp sensor could maybe do. ( I don't think the 02 has that range).

Sometime when it won't start, giggle those wires....

cdf43

I started it today. Got it up to operating temp. And it wouldn't act up. Sprayed around for a vacuum leak. Didn't find one.

Tested the TPS. It was out of adjustment a little (0.6v) so I adjusted it to 0.8v and according to the test procedure it's fine. When I started it again the idle jumped way up. Like 5k rpm. Shut it off. Waited a couple mins and started back up and idled normally.

cdf43

Might also be worth pointing out my radiator is plugged up. It's gotten hot. But not enough to do any major damage.

cruiser54

Of the tips in my signature below, how many have you completed?

cdf43

I'm using mobile. Can't see signatures.

cruiser54

https://www.cherokeeforum.com/f51/cr...x-tips-153657/

DFlintstone

These dam "smart things just **** me off! Youngsters, there waz a day when we could communicate.
Here ya go. Maybe look for an app or something so you get the full window.

https://www.cherokeeforum.com/f51/cruiser54s-mostly-renix-tips-153657/



Anyone getting Cruisers response for a Rienx problem is a lucky one. Unfortunately, this bogging and popping back seems to be a pretty sticky issue. Ruling out the basics, (1-5) for you is an excellent start. Checking fuel pressure is free. 29 with the vac line on the regulator and about 10 less with it off.