corypowell1234

i have a very stange issue involving a 1998 jeep grand cherokee the problem im having is its throwing a code the code is a cylinder 5 misfire i tested the compression and it said that cyl # 5 has 75 psi i know thats bad i was wondering if it was a burnt valve its firing on that cly but the plug is wet and black some one please help thanks

tinytrax78

time for a leakdown test

corypowell1234

true ill try that thanks

corypowell1234

i just wanted to post an update i redid the compression test 150 psi ? lol but the distributor is brand new so i think the timing is off not sure though

Hatsuwr

Well, misfire means you either don't have ignition, a good fuel/air mixture, or proper compression. You say it is still firing, and is intermittent?

That you got a new distributor recently makes me thing it's ignition. Make sure the distributor is clean and the contacts in the cap are secure and undamaged. Double check that both ends of the spark plug wire are clean and secure, and that the wire is undamaged. Check the plug gap and make sure it is clean. Maybe just get a cheap new plug to rule that out.

If it wasn't intermittent, I'd say check that your injector is working at all. Nice trick for that is to put a screwdriver tip against the injector while the engine is running and put your ear up to the handle of the screwdriver. You can hear it clicking when it opens up. You can check the performance of the injectors by removing the fuel rail with the injectors still on. Pressurize the line and manually trigger the injectors to observe the spray pattern. Obviously make sure there are no ignition sources nearby.

Any reason for the inconsistent compression test? Repeat the test - first do a normal test, making sure the the cylinder is dry. If your reading is at all low, repeat the test, but put about a teaspoon of engine oil into the cylinder first. If the pressure increases then you've probably got leakage in the cylinder wall. If it doesn't, you've probably got a valve issue. Do that leakdown test too.

Double check air delivery. Air filter and throttle body controls (idle air control, throttle position sensor, and MAP sensor).


That's where I'd start!

corypowell1234

UPDATE i took the cyl # 5 injector and moved it to cyl #2 and now the misfire is on CYL# 2 so bad injector i would like to thank everyone who helped and i will come here if i have anymore issues

corypowell1234

there is one more thing i have a question about, the temp is it soupposed to run at 210

Hatsuwr

Now might be a good time to get upgraded injectors!
I bought a set from these guys: https://www.ebay.com/itm/281391348769
They were awesome. One injector looked a bit off for some reason - I don't remember what it was, but it probably would have worked fine. I asked them about it and they just sent a new one out, no questions.
The engine responds and sounds better, and there was a jump of 1-2 mpg (if the built in gauge is to be trusted.) Lots of disagreement whether this is due to the new injectors being a better design than the old (4 vs 1 hole), or if it's just due to getting rid of the old, clogged, degraded ones. I personally think it's a bit of both.

And 210º is a bit high for regular driving, but not a cause for much concern by itself. Wouldn't be too surprised if it was lowered after getting new injectors and better combustion.

dave1123

The engine should operate between 195* and 210* for maximum efficiency. Above and below that, the PCM has a hard time controlling mixtures. I wouldn't worry unless it starts running above 220*

Hatsuwr

Any thoughts on where in that range is preferable?

dave1123

Anywhere in that range is normal. The thermostat should hold 195* as a bottom end and the electric fan in my WJ cuts on high at 210*. That's only a range of 15* and hoping for anything closer is daydreaming.

Hatsuwr

Give me a week or two for parts to arrive and I'll see if I can get closer!

corypowell1234

well i know 1 injector is like 41.99 and thats all i feel like paying for this jeep for right now but there are two brands and they are the same price there is a BWD injector and a STD injector which one is the best? and can i clean the injector and make it work again ?

00t444e

You can get 6 12 hole injectors for $100 or so.

corypowell1234

where ebay and why does the amount of holes matter is it for more gas flow im new to EFI i love CARBS