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AK to HI engine code every new part gets worse

SBpunk

NAXJA Forum User
Location
Enid, OK
1998 Jeep Cherokee Classic
99kish miles
4.0L

Hey everyone first post. Tried using Jeepforum.com but figured two sites are better than one.

Backstory: Bought a Jeep while I was deployed. Jeep was in Alaska had my parents go check it out and had no big issues. Belt needed to be changed and few rust holes. Parents drove around for a few weeks. Had it shipped to Hawaii. Picked it up and as soon as I started it engine code and jumping idle / boggy engine.

What I've Done: Had the code ran with a misfire on 1. Replaced spark plugs and cables gaped at .035. Put some SeaFoam in the engine and sprayed the intake out. Didn't help.

Next I changed out the fuel injectors. Reset the computer and problems got worse. Old fuel injectors were shot so stuck for now. Changed out TPS, Coil, MAP, Dis cap and rotor. Cleaned up all the connections I could find. This is where I'm at now.

Problems as of now: Idle is horrible. Starts at 1k drops down and bounces between 500 and 700 then up to 1000 and back down etc etc. Get the RPMs up to around 3k and let go it backfires and sticks at 1250 to 1500 RPMs until I turn it off and restart. It has almost no throttle response when driving and the transmission is shifting harder than it did when I first picked it up. The CEL is still on but wasn't able to have it ran because apparently Hawaii thinks the holidays last for a week or so longer than the rest of the U.S.

Anyone that can give me some insight on where to go next would be great. I'm going to have the codes ran again tomorrow and will post an update. Thanks again.
 
I had this exact same issue. Changed the plugs, rotor, cap, wires, TPS cleaned the throttle body, new air filter, etc etc. I even had a misfire on 6 that was rectified by the new plugs.

What fixed the idle/bogging issues for me was a new CPS. I know a bad CPS is usually diagnosed by stalling and hard starts, but once i swapped it out for a new one, it idles right at 750 RPM and runs great.

Just an idea. The CPS on these are known to go bad. They're easy enough to replace (essentially) but you'll need a buttload of patience, a rachet with 18" of extensions, a universal joint, and an 11/16 socket. It's a $@@^ to get to, but isn't impossible to do.

Edited to add:

The idle seemed to get worse with everything I did. It was hunting like yours was. Some may say to check the IAC valve, but that won't account for your issues while driving (intermittent bog down/ back fire) and mine had these exact symptoms.

Do yourself a favor, change out the CPS. They're like 65 bucks at Autozone/Advance Auto, and if you order them online you can get like a 15-20% discount around this time of year.

http://www.naxja.org/forum/showthread.php?t=1093905 - my thread, detailing the oddessy it was to fix this. Sound familiar? lol
 
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Were all the parts new, like the TPS?
Sounds like the vacuum line from the throttle body to the Map is loose or leaking to me. What size injectors did you buy, what spark plugs?

And yes, the CPS could be going bad.
 
Were all the parts new, like the TPS?
Sounds like the vacuum line from the throttle body to the Map is loose or leaking to me. What size injectors did you buy, what spark plugs?

And yes, the CPS could be going bad.

It wouldn't surprise me. It seems he's going through the same rounds that I did, with the exception of the injectors.

Have the CEL checked. Ecomike is right, it could be something he said as well. I just know my CPS issue became noticably worse within 60 miles of driving, to the point where when I test drove it after doing the tb cleaning, it would sputter and bog so badly I couldn't make it around my block.
 
I have no solution to your issue, but wanted to say thank you. I see your name is red and this was your first post. Thank you for being a paying member from the get-go.

Once this issue gets solved, keep asking questions. Lots of knowledge on the boards!!!
 
It wouldn't surprise me. It seems he's going through the same rounds that I did, with the exception of the injectors.

Have the CEL checked. Ecomike is right, it could be something he said as well. I just know my CPS issue became noticably worse within 60 miles of driving, to the point where when I test drove it after doing the tb cleaning, it would sputter and bog so badly I couldn't make it around my block.


Not sure on the injector size. I bought some nice ones from precision injectors dot com and I ended up buying the wrong year. So I used some crap ones I got off ebay while back before I did my research.

http://www.ebay.com/itm/30-Bosch-In...EANED-REBUILT-FLOWED-0280150756-/230877249339

Not sure if I can post the link so I apologize ahead of time if I'm not supposed to. Anyway I'm going to run down and get the codes ran again then probably pick up the CPS. Pretty much the ONLY part I didnt grab yesterday when I went thru my checklist. I'll let you know
 
The new injectors are perfect... for 99 to 01'. The connection on them for the computer wasn't the same type. Chrysler changed their injectors when the new emissions came out apparently. No luck on getting the code ran today. Its illegal for any company to run the code unless their a legit mechanic shop in Hawaii and the place on base told me they wouldnt be able to do it until tomorrow. I ordered a cheapo one off amazon and it'll be here tomorrow so hopefully more info then.

Just took it out for a spin and while its in drive / driving the thing is great. Still getting a CEL and a bit more throttle loss than when I first picked it up. Gonna replace the CPS just for sh%ts and giggles today. Hopefully I can get this code ran and post it up if it doesnt tell me something I can figure out.
 
Injectors that have dried out at some time tend to get gummed up. I would run a can of BG44K through the gas. It can't hurt and it will remove carbon as well. Don't bother with STP injector cleaner and the rest.

CPS is a possible culprit as well, but your symptoms are not typical for a failure.

If you can get the codes, that would help a ton. Good Luck.
 
Check out post #11 here:

http://naxja.org/forum/showthread.php?t=1085574&highlight=neon+injectors&page=10

You need 19#/hr fuel injectors for 98, not 30#/hr injectors. Little doubt that is part of your problem.

What year were the new ones? They might be OK. Part number? Flow rate on them? Why didn't try them?

http://www.precisionautoinjectors.com/product.sc?productId=32&categoryId=3

Those were the ones I purchased

http://www.precisionautoinjectors.com/product.sc?productId=11

are the ones I meant to get
 
don't forget about the battery.

if it was shipped it probably went flat.

a bad or weak battery will do all sorts of weird things to a modern FI computer.
 
don't forget about the battery.

if it was shipped it probably went flat.

a bad or weak battery will do all sorts of weird things to a modern FI computer.

You think so? Its a fairly new red top but I know optimum has gone down the drain the past few years when contracted out of country.
 
Just want to throw something out there--your FUEL.

What blend they are running in AK when the Cherokee was there may NOT work well in the Hawaiian temperatures.
 
Just want to throw something out there--your FUEL.

What blend they are running in AK when the Cherokee was there may NOT work well in the Hawaiian temperatures.

Joe thanks for the reply. When I picked up the vehicle it didnt have enough gas to even make it down to the gas station. Stalled out so I ended up having a friend bring a jerry can with 5 gallons of the Hawaiian good stuff (sarcasm). You would think about the fuel filter being clogged from sucking the nasty crap out of the bottom of the tank but the tank is brand new and fuel filter was better than some of the crap they put in the new vehicles.
 
Ok got the CPS in and returned some power to the throttle. Still getting a bouncing engine / RPM's until its driven around a bit then it levels out just under or at 1k. CEL is still on. Hopefully my scanner gets here tomorrow and I'll be able to check the code. Also noticed there was a giant hole cut out of the air filter box on the back so taped that up.
 
If the CEL is a missfire code for a cylinder again, the PCM shuts down the fuel to that cylinder making the idle lousy as hell, Limp mode.

If you still have 30#/hr injectors in there, they need to go, that is part of the problem. I can't tell from your last links what injectors you have in the jeep or what their flow rate is.
 
Sorry folks finally went back to work. Update is pretty bad. CEL has popped back on and now its starting to blink when I'm accelerating at main road / highway speeds. Stays on for a few seconds then goes solid again once I let the RPMs go down. My new injectors will be here tomorrow hopefully.

I went to Midas today to have my cat checked out. Said nothing was wrong with the exhaust but I'm getting a backfire and the floor boards were melting my sandal. Didnt think not having a carpet in would heat it up like that but I got some patching to do on the floorboards.
 
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